Organs that regenerate. Physiological and reparative regeneration. Types, methods of reparative regeneration

Badertdinov R.R.

The work provides short review achievements of regenerative medicine. What is regenerative medicine, and how realistic is it to apply its developments in our lives? How soon can we use them? An attempt is made to answer these and other questions in this work.

regeneration

regenerative medicine

stem cells

cytogenes

recovery

genetics

nanomedicine

gerontology

What do we know about regenerative medicine? For most of us, the theme of regeneration and everything connected with it is strongly associated with fantastic plots of feature films. Indeed, due to the low awareness of the population, which is very strange, given the constant relevance and vital importance this issue, people have a fairly strong opinion: reparative regeneration is an invention of screenwriters and science fiction writers. But is it? Is the possibility of human regeneration really someone's invention in order to create a more sophisticated plot?

Until recently, it was believed that the possibility of reparative regeneration of the body, which occurs after damage or loss of any part of the body, was lost by almost all living organisms during the process of evolution and, as a consequence, the complication of the structure of the body, except for some creatures, including amphibians. One of the discoveries that greatly shook this dogma was the discovery of the p21 gene and its specific properties: blocking the regenerative capabilities of the body, by a group of researchers from the Wistar Institute, Philadelphia, USA (The Wistar Institute, Philadelphia).

Experiments on mice have shown that rodents lacking the p21 gene can regenerate lost or damaged tissue. Unlike ordinary mammals, in which wounds heal by forming scars, genetically modified mice with damaged ears form a blastema at the site of the wound - a structure associated with rapid cell growth. At the entrance of regeneration, tissues of the recovering organ are formed from the blastema.

According to scientists, in the absence of the p21 gene, rodent cells behave like regenerating embryonic stem cells. Ane like mature mammalian cells. That is, they grow new tissue rather than repair damaged tissue. Here it would be appropriate to remember that the same regeneration scheme is also present in salamanders, which have the ability to regrow not only the tail, but also lost limbs, or uplanaria, eyelash worms, which can be cut into several parts, and a new planaria will grow from each piece.

According to the cautious remarks of the researchers themselves, it follows that theoretically, disabling the p21 gene can trigger a similar process and in the human body. Of course, it is worth noting that the p21 gene is closely related to another gene, p53. which controls cell division and prevents the formation of tumors. In normal adult cells, p21 blocks cell division in the event of DNA damage, so mice in which it has been disabled are at greater risk of cancer.

But although the researchers did find large amounts of DNA damage in the experiment, they found no traces of cancer: on the contrary, the mice intensified the mechanism of apoptosis, the programmed “suicide” of cells that also protects against the formation of tumors. This combination may allow cells to divide faster without turning cancerous.

Avoiding far-reaching conclusions, we note that the researchers themselves only talk about temporarily disabling this gene in order to accelerate regeneration: “While we are just beginning to understand the repercussions of these findings, perhaps, one day we’ll be able to accelerate healing in humans by temporarily inactivating the p21 gene". Translation: “We are just now beginning to understand the full implications of our discoveries, and perhaps one day we will be able to speed up healing in people by temporarily inactivating the p21 gene.”

And this is just one of many possible ways. Let's consider other options. For example, one of the most famous and promoted, partly for the purpose of making large profits by various pharmaceutical, cosmetic and other companies, is stem cells (SC). The most frequently mentioned are embryonic stem cells. Many people have heard about these cells; they help earn a lot of money; many attribute truly fantastic properties to them. So what are they? Let's try to bring some clarity to this issue.

Embryonic stem cells (ESCs) refer to the continuously proliferating stem cell niches of the inner cell mass, or embryoplast, of the mammalian blastocyst. Any type of specialized cell can develop from these cells, but not an independent organism. Embryonic stem cells are functionally equivalent to embryonic germ cell lines derived from primary embryonic cells. The distinctive properties of embryonic stem cells are the ability to maintain them in an undifferentiated state in culture for an unlimited time and their ability to develop into any cells of the body. The ability of ESCs to give rise to a large number of different cell types makes them a useful tool for basic scientific research a new source of cell populations for new therapies. The term “embryonic stem cell line” refers to ESCs that have been maintained in culture for a long time (months or years) under laboratory conditions in which they proliferate without differentiation. There are several good sources of basic information about stem cells, although published review articles quickly become outdated. One useful source of information is the website of the US National Institutes of Health ( National Institutes of Health (NIH), USA).

Characteristics of different stem cell populations and molecular mechanisms, which support their unique status are still being studied. At the moment, there are two main types of stem cells: adult and embryonic stem cells. Let us highlight three important features that distinguish ESCs from other types of cells:

1.ESCs express spluripotent cell-associated factors such as Oct4, Sox2, Tert, Utfl and Rex1 (Carpenter and Bhatia 2004).

2.ESCs are unspecialized cells that can differentiate into cells with special functions.

3.ESCs can self-renew through multiple divisions.

ESCs are maintained in vitro in an undifferentiated state by strictly adhering to certain culture conditions, which include the presence of the leukemia inhibitory factor (LIF), which prevents differentiation. If LIF is removed from the environment, ESCs begin to differentiate and form complex structures called embryonic bodies and composed of various types of cells, including endothelial, nerve, muscle and hematopoietic progenitor cells.

Let us separately dwell on the mechanisms of operation and regulation of stem cells. The special characteristics of stem cells are determined not by one gene, but by a whole set of them. The possibility of identifying these genes is directly related to the development of a method for culturing embryonic stem cells in vitro, as well as the possibility of using modern methods of molecular biology (in particular, the use of the leukemia inhibitory factor LIF).

As a result of joint research by Geron Corporation and Celera Genomics, cDNA libraries of undifferentiated ESCs and partially differentiated cells were created (cDNA is obtained by synthesis based on an mRNA molecule complementary to a DNA molecule using the enzyme reverse transcriptase). When analyzing data on sequencing nucleotide sequences and gene expression, more than 600 genes were identified, the inclusion or switching off of which distinguishes undifferentiated cells, and a picture of the molecular pathways along which differentiation of these cells occurs was compiled.

Currently, it is customary to distinguish stem cells by their behavior in culture and by chemical markers on the cell surface. However, the genes responsible for the manifestation of these features remain unknown in most cases. However, research has made it possible to identify two groups of genes that give stem cells their wonderful properties. On the one hand, the properties of stem cells are manifested in a specific microenvironment known as the stem cell niche. By studying these cells, which surround, nourish and maintain stem cells in an undifferentiated state, about 4,000 genes were discovered. Moreover, these genes were active in the cells of the microenvironment, and inactive in all others.
cells.

In a study of Drosophila ovarian embryonic stem cells, a signaling system between stem cells and specialized “niche” cells was identified. This signaling system determines the self-renewal of stem cells and the direction of their differentiation. Regulatory genes in niche cells provide instructions to stem cell genes that determine further path their development. These and other genes produce proteins that act as switches that start or stop stem cells from dividing. It was found that the interaction between niche cells and stem cells, which determines their fate, is mediated by three different genes - piwi, pumilio (pum) and bam (bag of marbles). It has been shown that for successful self-renewal of embryonic stem cells, the piwi and pum genes must be activated, while the bam gene is necessary for differentiation. Further studies showed that the piwi gene is part of a group of genes involved in the development of stem cells of various organisms belonging to both the animal and plant kingdoms. Genes similar to piwi (they are called, in this case, MIWI and MILI), pum and bam are also found in mammals, including humans. Based on these discoveries, the authors suggest that the niche cell gene piwi ensures the division of germ cells and maintains them in an undifferentiated state by suppressing the expression of the bum gene.

It should be noted that the database of genes that determine the properties of stem cells is constantly updated. A complete catalog of stem cell genes could improve their identification and clarify the mechanisms by which these cells function, which would provide differentiated cells needed for therapeutic applications and also provide new opportunities for drug development. The importance of these genes is great, since they provide the body with the ability to preserve itself and regenerate tissue.

Here the teacher may ask: “How far have scientists advanced in the practical application of this knowledge?” Are they used in medicine? Are there prospects for further development in these areas? To answer these questions, we will conduct a short review of scientific developments in this vein, both old, which should not be surprising, because research in the field of regenerative medicine has been going on for a long time, at least the beginning of the 20th century, as well as completely new, sometimes very unusual and exotic.

To begin with, we note that back in the 80s of the 20th century in the USSR at the Institute of Evolutionary Ecology and Animal Morphology named after. Severtsev Academy of Sciences of the USSR, in the laboratory of A.N. Studitsky conducted experiments: crushed muscle fiber the damaged area was transplanted, which subsequently recovered and forced the regeneration of nerve tissue. Hundreds of successful operations have been performed on humans.

At the same time, at the Institute of Cybernetics. Glushkov in the laboratory of Professor L.S. Aleev created an electrical muscle stimulator - Meoton: the movement impulse of a healthy person is amplified by the device and directed to the affected muscle of an immobile patient. The muscle receives a command from the muscle and causes the immobile one to contract: this program is recorded in the memory of the device and the patient can then work on his own. It should be noted that these developments were made several decades ago. Apparently, it is these processes that underlie the program, independently developed and applied to this day by V.I. Dikulem. More information about these developments can be found in the documentary film “The Hundredth Mystery of the Muscle” by Yuri Senchukov, Tsentrnauchfilm, 1988.

Separately, we note that in the middle of the 20th century, a group of Soviet scientists, under the leadership of L.V. Polezhaev conducted research with successful practical application of their results on the regeneration of the bones of the cranial vault of animals and humans; The defect area reached up to 20 square centimeters. The edges of the hole were filled with crushed bone tissue, which caused a regeneration process, during which the damaged areas were restored.

In this regard, it would be appropriate to recall the so-called “Spivak Case” - the formation of the histol phalanx of the finger of a sixty-year-old man, when the stump was treated with components of the extracellular matrix (a cocktail of molecules), which was powder from the pig bladder (this was mentioned in the weekly analytical program “In the Center of Events” on the state television channel TV Center).

Also, I would like to focus on such an everyday and familiar object as salt (NaCl). The healing properties of the marine climate, places, with high content salt in the air and in the air, like Dead Sea in Israel or Sol-Iletsk in Russia, salt mines, widely used in hospitals, sanatoriums and resorts around the world. Athletes and people leading an active lifestyle are also familiar with salt baths used in the treatment of injuries to the musculoskeletal system. What is the secret of these amazing properties? regular salt? As scientists from Tufts University (USA) discovered, for the process of restoring a cut or bitten off tail, tadpoles need salt. If you sprinkle it on a wound, the tail will grow back faster, even if scar tissue (scar) has already formed. In the presence of salt, the amputated tail grows back, but the absence of sodium ions blocks this process. Of course, it should be recommended to refrain from unrestrained salt consumption, in the hope of speeding up the healing process. Numerous studies clearly demonstrate the harm that excessive salt intake causes to the body. Apparently, to initiate and accelerate the regeneration process, sodium ions must reach the damaged areas through other routes.

Speaking about modern regenerative medicine, there are usually two main directions. Adherents of the first path are engaged in growing organs and tissues separately from the patient or on the patient himself, but in a different place (for example, on the back), and then transplanting them to the damaged area. The initial stage in the development of this direction can be considered the solution to the skin issue. Traditionally, new skin tissue was taken from patients or dead bodies, but today skin can be grown in large quantities. The raw material of unwanted skin is taken from newborn babies. If an infant boy is circumcised, then this piece can be used to make great amount living tissue. It is extremely important to take skin to grow newborns; the cells should be as young as possible. A natural question may arise here: why is this so important? The fact is that in order to double DNA during cell division, the enzymes occupied by these enzymes in higher organisms require specially designed end sections of chromosomes, telomeres. It is to this that the RNA primer is attached, with which the synthesis of the second strand begins on each strand of the DNA double helix. However, in this case, the second strand is shorter than the first by the area that was occupied by the RNA primer. The telomere shortens until it becomes so small that the RNA primer can no longer attach to it, and cell division cycles stop. In other words, the younger the cell, the large quantity divisions will occur before the very possibility of these divisions disappears. In particular, back in 1961, the American gerontologist L. Hayflick established that “in vitro” skin cells - fibroblasts - can divide no more than 50 times. From one foreskin you can grow 6 football fields of skin tissue (approximate area - 42840 square meters).

Subsequently, a special plastic was developed that was biodegradable. It was used to make an implant on the back of a mouse: a plastic frame molded in the shape of a human ear, covered with living cells. During the growth process, cells adhere to the fibers and take the required shape. Over time, cells begin to dominate and form new tissue (for example, cartilage auricle). Another version of this method: an implant on the patient’s back, which is a frame of the required shape, is seeded with stem cells of a certain tissue. After some time, this fragment is removed from the back and implanted in place.

In the case of internal organs consisting of several layers of cells different types, we have to use slightly different methods. First internal organ was grown and subsequently successfully implanted with a bladder. This is an organ that experiences enormous mechanical stress: about 40 thousand liters of urine passes through the bladder during a lifetime. It consists of three layers: outer - connective tissue, middle - muscular, internal - mucous membrane. A full bladder contains approximately 1 liter of urine and has the shape of an inflated hot air balloon. To grow it, a frame of a complete bladder was made, onto which living cells were seeded layer by layer. It was the first organ grown entirely from living tissue.

The same plastic mentioned just above was used to restore the damaged spinal cord laboratory mice. The principle here was the same: plastic fibers were rolled into a bundle and embryonic cells were seeded onto it. nerve cells. As a result, the gap was closed with new tissue, and all motor functions were completely restored. Enough full review quoted in the BBC documentary “Superman. Self-healing."

To be fair, we note that the very fact of possibility full recovery motor functions after severe injuries, up to a complete break of the spinal cord, in addition to single enthusiasts like V.I. Dikul, was proven by Russian scientists. They also proposed effective method rehabilitation of such people. Despite the fantastic nature of such a statement, I would like to note that by analyzing the statements of the luminaries of scientific thought, we can conclude that in science there are no and cannot be any axioms, there are only theories that can always be changed or refuted. If a theory contradicts facts, then the theory is wrong and needs to be changed. This simple truth, unfortunately, is very often ignored, and the basic principle of science: “Doubt everything” acquires a purely one-sided character - only in relation to the new. As a result, the latest techniques, who can help thousands and hundreds of thousands of people, are forced to break through a blank wall for years: “This is impossible, because it is impossible in principle.” To illustrate the above and show how far and how long ago science has come, I will give a short excerpt from the book by N.P. Bekhtereva “The Magic of the Brain and the Labyrinths of Life”, one of those specialists who pioneered the development of this method. “In front of me on the gurney lay a blue-eyed guy, 18-20 years old (Ch-ko), with a mass of dark brown, almost black hair. “Bend your leg, pull yourself up. Now straighten it up. The other was commanded by the head of the spinal cord stimulation group, an informal leader. How difficult, how slowly the legs moved! What enormous stress this cost the patient! We all wanted to help so much! And yet the legs moved, they moved according to orders: the doctor, the patient himself - it doesn’t matter, it’s important - according to orders. Ana operations on the spinal cord in the D9-D11 area were literally scooped out with spoons. After the Afghan bullet went through the patient's spinal cord, it was a mess. Afghanistan turned the handsome young man into an embittered animal. Still, after stimulation carried out according to the method proposed by the same informal leader S.V. Medvedev, a lot has changed in visceral functions.

What can't you do? You cannot give up on a patient just because textbooks have not yet included everything that specialists can do today. The same doctors who saw the patient and saw everything were surprised: “Well, for mercy’s sake, comrade scientists, of course, you have science there, but there is a complete break in the spinal cord, what can you say?!” Like this. We saw and did not see. There is a scientific film, everything is filmed.

The sooner stimulation begins after brain damage, the more likely the effect is. However, even in cases of long-standing injuries, much can be learned and done.

In another patient, electrodes were inserted into the superior and inferior portions of the spinal cord. The injury was long-standing, and none of us were surprised that the electromyelogram (electrical activity of the spinal cord) of the electrodes below the break was not recorded, the lines were completely straight, as if the device had not been turned on. And suddenly (!) - no, not quite suddenly, but it looks like “suddenly”, since it happened after several sessions electrical stimulation, - the electromyelogram of the electrodes below the complete, long-standing (6 years) break began to appear, intensify and finally reached the characteristics of electrical activity above the break! This coincided with a clinical improvement in the state of pelvic functions, which, naturally, greatly pleased not only the doctors, but the patient, who otherwise had psychologically and physically adapted well to his tragic present and future. It was difficult to expect more. The leg muscles atrophied, the patient moved on a gurney, and his hands took over everything they could. But here, in the development of positive and negative events, the matter was not without changes in the cerebrospinal fluid. Taken from the patient's area below the break, it poisoned the cells in culture and was cytotoxic. After stimulation, cytotoxicity disappeared. What happened to the spinal cord below the break before stimulation? Judging by the above revival, he (the brain) did not die. More likely, he was sleeping, but he slept as if under anesthesia of toxins, he slept in a “dead” sleep - there was no wakefulness or sleep activity in the electroencephalogram.”

In the same direction, there are the most exotic ways, such as a three-dimensional bioprinter created in Australia, which is already printing skin, and in the near future, according to the developers, will be able to print entire organs. His work is based on the same principle as in the described case of creating a bladder: seeding living cells layer by layer.

The second direction of regenerative medicine can be roughly described in one phrase: “Why grow new things if you can fix the old ones?” The main task of adherents of this direction is the restoration of damaged areas by the body itself, using its reserves, hidden capabilities (it is worth remembering the beginning of this article) and certain interventions from the outside, mainly in the form of the supply of additional resources and building material for reparation.

There are also a large number of possible options here. To begin with, it should be noted that according to some estimates, each organ from birth has a reserve of reserve stem cells of approximately 30%, which are consumed during life. Accordingly, according to some gerontologists, the species limit of human life is 110-120 years. Consequently, the biological reserve of human life is 30-40 years, taking into account Russian realities, these figures can be increased to 50-60 years. Another question is that modern living conditions do not contribute to this: the extremely deplorable, and every year worsening, state of the environment; strong, and more importantly, constant stress; enormous mental, intellectual and physical stress; the depressing state of medicine locally, in particular Russian; The focus of pharmaceuticals not on helping people, but on obtaining super profits and much more, completely wears out the human body at the moment when, in theory, the peak of our strength and capabilities should begin. However, this reserve can greatly help in recovering from injuries and treating serious illnesses, especially in infancy.

Evan Snyder, a neurologist at Boston Children's Hospital (USA), has long been studying the process of recovery of children and infants after various injuries brain. As a result of his research, he noted the most powerful possibilities for healing the nerve tissue of his young patients. As an example, let us give a case of an eight-month-old baby who suffered a massive stroke. Already three weeks after the incident, he experienced only slight weakness of the left limbs, and three months later, a complete absence of any pathologies was recorded. The specific cells Snyder discovered while studying brain tissue were called neural stem cells or embryonic brain cells (ECM). Subsequently, successful experiments were carried out on the introduction of ECM to mice suffering from tremor. After the injections, cells spread throughout the brain tissue and complete healing occurred.

Relatively recently, in the USA, at the Institute of Regenerative Medicine, in the state of North Carolina, a group of researchers led by Jeremy Laurence managed to make the heart of a mouse that had died 4 days earlier beat. Other scientists in different countries All over the world, they are trying, sometimes quite successfully, to launch regeneration mechanisms using cells isolated from a cancerous tumor. It should be noted here that telomeres, already mentioned above, are sexually cancer cells During the division process they are not shortened (to be more precise, this is due to a special enzyme - telomerase, which completes the shortened telomeres), which makes them practically immortal. That's why it's so unexpected turn in the history of sleep diseases has an absolutely rational beginning (this was mentioned in the weekly analytical program “In the Center of Events” on the state television channel TV Center).

Let us separately highlight the creation of hemobanks for the collection of umbilical cord blood of newborns, which is one of the most promising sources of stem cells. Umbilical cord blood is known to be rich in hematopoietic stem cells (HSCs). A characteristic feature of SCs obtained from umbilical cord blood is that they are much more similar than adult SCs to cells from embryonic tissues in such parameters as biological age and the ability to reproduce. Umbilical cord blood obtained from the placenta immediately after the birth of a child is rich in SCs with greater proliferative capabilities than cells obtained from bone marrow or peripheral blood. Like any blood product, cord blood stem cells require an infrastructure to collect, store and determine suitability for transplantation. The umbilical cord is clamped 30 seconds after the birth of the child, the placenta and umbilical cord are separated, and the cord blood is collected in a special bag. The sample must be at least 40ml to be used. The blood is HLA typed and cultured. Immature human cord blood cells with a high ability to proliferate, multiply outside the body and survive after transplantation can be stored frozen for more than 45 years, then after thawing they with high probability remain effective in clinical transplantation. Cord blood banks exist all over the world, with more than 30 in the United States alone and many more private banks. The US National Institutes of Health sponsors a program to study umbilical cord blood transplantation. The New York Blood Center has a placental blood program, and the National Bone Marrow Donor Registry has its own research program.

Mainly, this area is actively developing in the USA, Western Europe, Japan and Australia. In Russia, this is only gaining momentum; the most famous is the hemobank of the Institute of General Genetics (Moscow). The number of transplants increases every year, and about a third of patients are now adults. About two-thirds of transplants are performed on patients with leukemia, and about a quarter on patients genetic diseases. Private cord blood banks offer their services to couples expecting the birth of a child. They store cord blood for future use by the donor or his family. Community cord blood banks provide resources for transplants from unrelated donors. Umbilical cord blood and mother's blood are typed according to HLA antigens and tested for the absence infectious diseases, the blood type is determined and this information is stored in the medical history of the mother and family.

Currently, active research is being conducted in the field of propagation of stem cells contained in a unit of umbilical cord blood, which will allow it to be used for larger patients and allow for faster engraftment of stem cells. Reproduction of umbilical cord blood stem cells occurs using growth factors and nutrition. Developed by ViaCell Inc. a technology called Selective Amplification makes it possible to increase the population of SCs in umbilical cord blood by an average of 43 times. Scientists from ViaCell and the University of Duesseldorf in Germany described a new, truly pluripotent population of human cord blood cells, which they called USSCs - unrestricted somatic stem cells (Kogler et al 2004). Both in vitro and in vivo, USSCs showed homogeneous differentiation into osteoblasts, chondroblasts, adipocytes, and neurons expressing neurofilaments, sodium channel proteins, and distinct neurotransmitter phenotypes. Although these cells have not yet been used in human cell therapy, USSCs from umbilical cord blood can regenerate various organs, including the brain, bone, cartilage, liver and heart.

Another important area of ​​research is the study of the ability of umbilical cord blood SCs to differentiate into cells of various tissues, in addition to hematopoietic ones, and the establishment of appropriate SC lines. Researchers at the University of South Florida (USF, Tampa, FL) used retinoic acid to induce cord blood stem cells to differentiate into nerve cells, which was demonstrated at the genetic level by analyzing DNA structure. These results showed the possibility of using these cells to treat neurodegenerative diseases. Cord blood for this work was provided by the child's parents; It was processed by the state-of-the-art CRYO-CELL laboratory and the fractionated frozen cells were transferred to USF scientists. Umbilical cord blood has proven to be a source of much more diverse progenitor cells than previously thought. It can be used to treat neurodegenerative diseases, including in combination with gene therapy, trauma and genetic diseases. In the near future it will be possible when children are born genetic defects collect their umbilical cord blood, use genetic engineering to correct the defect and return this blood to the child.

In addition to the umbilical cord blood itself, it is possible to use umbilical cord and perivascular cells as a source of mesenchymal stem cells. Scientists from the Institute of Biomaterials and Biomedical Engineering of the University of Toronto (Toronto, Canada) have discovered that the jelly-like connective tissue surrounding the blood vessels of the umbilical cord is rich in mesenchymal stem cells - precursors and can be used to produce there are a lot of them for a short time. Perivascular (surrounding blood vessels) cells are often discarded because the focus is usually on umbilical cord blood, in which mesenchymal cells occur at an incidence of only one in 200 million. But this source of progenitor cells, allowing them to multiply, could greatly improve bone marrow transplants.

In parallel, research is underway on those already found and the search for new ways to obtain adult human SCs. Their number includes: milk teeth, brain, mammary glands, fat, liver, pancreas, skin, spleen or a more exotic source - SC of the neural cross from adults hair follicles. Each of these sources has its own advantages and disadvantages.

While debate continues about the ethical and therapeutic potential of embryonic and adult SCs, a third group of cells has been discovered that play a role in key role in the development of the body and cells capable of differentiation in all major types of tissues. VENT (ventrally emigrating neural tube) cells are unique multipotent cells that separate from the neural tube early in embryonic development, after the tube closes to form the brain (Dickinson et al 2004). VENT cells then move along the nerve pathways, eventually ending up in front of the nerves and scattering throughout the body. They move together with the cranial nerves to certain tissues and are dispersed in these tissues, differentiating into cells of the main four types of tissues - nervous, muscle, connective epithelium. If VENT cells play a role in the formation of all tissues, perhaps most notably in the formation of connections between the central nervous system and other tissues - given how these cells move in front of nerves, as if showing them the way. Nerves can be guided by certain signs left after the differentiation of VENT cells. This work was carried out on embryos of chickens, ducks and quails, and it is planned to repeat it in a mouse model that allows for detailed genetic studies. These cells can be used to isolate human cell lines.

Other, advanced and most promising direction is nanomedicine. Despite the fact that politicians paid close attention to everything that has the particle “nano” in their names only a few years ago, this direction has appeared quite a long time ago and certain successes have already been achieved. Most experts believe that these methods will become fundamental in the 21st century. The American National Institute of Health has included nanomedicine in the top five priority areas for the development of medicine in the 21st century, and the US National Cancer Institute is going to apply the achievements of nanomedicine in the treatment of cancer. Robert Freitos (USA), one of the founders of the theory of nanomedicine, gives the following definition: “Nanomedicine is the science and technology of diagnosing, treating and preventing diseases and injuries, reducing pain, as well as preserving and improving human health using molecular technical means and scientific knowledge omolecular structure of the human body." Eric Drexler, a classic in the field of nanotechnological developments and predictions, names the main postulates of nanomedicine:

1) do not injure tissue mechanically;

2) do not damage healthy cells;

3) do not cause side effects;

4) medications must be taken independently:

Feel;

To plan;

Act.

The most exotic option are the so-called nanorobots. Among the projects of future medical nanorobots there already exists internal classification for macrophagocytes, respirocytes, clottocytes, vasculoids and others. All of them are essentially artificial cells, mainly human immunity or blood. Accordingly, their functional purpose directly depends on what cells they replace. In addition to medical nanorobots, which currently exist only in the minds of scientists and individual projects, a number of technologies for the nanomedicine industry have already been created around the world. These include: targeted delivery of drugs to diseased cells, diagnosis of diseases using quantum dots, laboratories on a chip, new bactericidal agents.

As an example, let us cite the developments of Israeli scientists in the field of treatment autoimmune diseases. The object of their research was the protein matrix metallopeptidase 9 (MMP9), which is involved in the formation and maintenance of the extracellular matrix - tissue structures that serve as a framework on which cells develop. This matrix ensures the transport of various chemicals - from nutrients to signaling molecules. It stimulates the growth and proliferation of cells at the site of damage. But the proteins that form it, primarily MMP9, when they escape from the control of proteins inhibiting their activity - endogenous inhibitors of metalloproteinases (TIMPS), can become the causes of the development of some autoimmune disorders.

Researchers have taken up the question of how these proteins can be “pacified” in order to stop autoimmune processes right at the source. Until now, when solving this problem, scientists have concentrated on searching chemicals, selectively blocking the operation of MMPS. However, this approach has serious limitations and severe side effects- and biologists from the Irit Sagi group decided to approach the problem from the blue side. They decided to synthesize a molecule that, when introduced into the body, would stimulate the immune system to produce antibodies similar to TIMPS proteins. This significantly more subtle approach provides the highest precision: antibodies will attack MMPS many orders of magnitude more selectively and efficiently than any chemical compounds.

And the scientists succeeded: they synthesized an artificial analogue of the active site of the MMPS9 protein: a zinc ion coordinated by three histidine residues. Its injection into laboratory mice resulted in the production of antibodies that act in exactly the same manner in which TIMPS proteins work: by blocking entry into the active site.

The world is experiencing a boom in investment in the nanoindustry. Most of the investments in nanotechnology come from the USA, EU, Japan and China. The number of scientific publications, patents and journals is constantly growing. There are forecasts for the creation of $1 trillion worth of goods and services by 2015, including the creation of up to 2 million jobs.

In Russia, the Ministry of Education and Science has created an Interdepartmental Scientific and Technical Council on the problem of nanotechnology and nanomaterials, whose activities are aimed at maintaining technological parity in the future world. For the development of nanotechnology in general and nanomedicine in particular. The adoption of a federal target program for their development is being prepared. This program will include the training of a number of specialists in the long term.

Advances in nanomedicine will become available via different estimates only in 40-50 years. Eric Drexler himself puts the figure at 20-30 years. But given the scale of work in this area and the amount of money invested in it, more and more analysts are shifting their initial estimates downwards by 10-15 years.

The most interesting thing is that such drugs already exist; they were created more than 30 years ago in the USSR. The impetus for research in this direction was the discovery of the effect premature aging an organism that was widely observed by military personnel, especially strategic missile forces, crews of nuclear-powered missile submarines, and combat aviation pilots. This effect is expressed through the premature destruction of the immune, endocrine, nervous, cardiovascular, reproductive systems, and vision. It is based on the process of suppressing protein synthesis. The main question facing Soviet scientists was: “How to restore a full synthesis?” Initially, the drug “Tymolin” was created, made on the basis of peptides isolated from the thymus of young animals. It was the world's first immune system drug. Here we see the same principle that was the basis for the process of producing insulin in the initial stages of developing methods for treating diabetes. But the researchers from the Department of Structural Biology of the Institute of Bioorganic Chemistry, headed by Vladimir Khavinson, did not stop there. At the nuclear magnetic resonance laboratory, the spatial and chemical structures of the peptide molecule from the thymus were determined. Based on the information obtained, a method was developed for the synthesis of short peptides that have specified properties similar to natural ones. The result is the creation of a series of drugs called cytogenes (others possible names: bioregulators or synthetic peptides; indicated in the table).

List of cytogenes

When the St. Petersburg Institute of Bioregulation and Gerontology conducted experiments on mice and rats (cytogen intake began in the second half of life), an increase in life by 30-40 % was observed. Subsequently, an examination and constant monitoring of the health status of 300 elderly people, residents of Kiev and St. Petersburg, who took cytogenes in courses twice a year, were carried out. Data on their well-being was compared with regional statistics. They observed a 2-fold decrease in mortality and a general improvement in well-being and quality of life. In general, over 20 years of using bioregulators, more than 15 million people have undergone therapeutic measures. The effectiveness of the use of synthetic peptides was consistently high, and, more importantly, there was not a single case of adverse or allergic reaction. The laboratory received Prizes from the Council of Ministers of the USSR, the authors received extraordinary scientific titles, Doctor of Science degrees and carte blanche in scientific work. All work done was protected by patents, both in the USSR and abroad. The results obtained by Soviet scientists published in foreign scientific journals were refuted worldwide recognized standards and limits, which inevitably raised doubts among experts. Checks at the US National Institute of Aging confirmed high efficiency cytogens. In experiments, an increase in the number of cell divisions was observed with the addition of synthetic peptides compared to the control by 42.5 %. Why has this line of drugs not yet been introduced to the international sales market, given the lack of foreign analogues, and this priority is temporary, big question. Perhaps this should be asked to the management of RosNano, which at present oversees all developments in the field of nanotechnology. You can learn more about these developments in the documentary film “Epiphany. Nanomedicine and the human species limit” by Vladislav Bykov, Prosvet film studio, Russia, 2009.

To sum up, we can be convinced that human regeneration is a reality of our days. A lot of data has already been obtained that destroys the deep-rooted stereotypes that have become established in public opinion. Many different techniques have been developed to provide healing from diseases previously considered incurable due to their degenerative properties, as well as successful and complete restoration of damaged or even completely lost organs and tissues. The previous ones are constantly being “polished” and new ways and means of solving are being searched for. the most complex tasks regenerative medicine. Everything that has already been developed now sometimes amazes our imagination, sweeping away all our usual ideas about the world, about ourselves, about our possibilities. At the same time, it is worth realizing that what is described in this article is only small part scientific knowledge accumulated to date. The work is ongoing, and it is quite possible that any facts presented here, at the time the article is published, will already be outdated or completely irrelevant and even erroneous, as has often happened in the history of science: what at some point was considered immutable In truth, within a year it could turn out to be a delusion. In any case, the facts presented in the article inspire hope for a bright, happy future.

Bibliography

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Bibliographic link

Regeneration

Regeneration(restoration) - the ability of living organisms to restore damaged tissues, and sometimes entire lost organs, over time. Regeneration is also called the restoration of a whole organism from its artificially separated fragment (for example, the restoration of a hydra from a small fragment of the body or dissociated cells). In protists, regeneration can manifest itself in the restoration of lost organelles or cell parts.

Regeneration is the restoration by the body of lost parts at one or another stage of the life cycle. Regeneration that occurs in the event of damage or loss of any organ or part of the body is called reparative. Regeneration in the process of normal functioning of the body, usually not associated with damage or loss, is called physiological.

Physiological regeneration

In every organism, throughout its life, processes of restoration and renewal constantly occur. In humans, for example, the outer layer of skin is constantly renewed. Birds periodically shed their feathers and grow new ones, and mammals change their fur. Deciduous trees lose leaves every year and are replaced with fresh ones. Such processes are called physiological regeneration.

Reparative regeneration

Reparative is the regeneration that occurs after damage or loss of any part of the body. There are typical and atypical reparative regeneration.

In typical regeneration, the lost part is replaced by the development of exactly the same part. The reason for the loss may be external influence(for example, amputation), or the animal deliberately tears off part of its body (autotomy), like a lizard breaking off part of its tail to escape from an enemy.

With atypical regeneration, the lost part is replaced by a structure that differs from the original quantitatively or qualitatively. The regenerated limb of a tadpole may have fewer toes than the original one, and a shrimp may grow an antenna instead of an amputated eye.

Regeneration in animals

Chameleon

The ability to regenerate is widespread among animals. Lower animals, as a rule, are more often capable of regeneration than more complex, highly organized forms. Thus, among invertebrates there are many more species capable of restoring lost organs than among vertebrates, but only in some of them is it possible to regenerate an entire individual from a small fragment. Nevertheless general rule the decrease in the ability to regenerate with increasing complexity of the organism cannot be considered absolute. Such primitive animals as roundworms and rotifers are practically incapable of regeneration, but in much more complex crustaceans and amphibians this ability is well expressed; Other exceptions are known. Some relatively closely related animals differ greatly in this respect. Thus, in many species of earthworms, only a new individual can completely regenerate from the front half of the body, while leeches are not able to restore even individual lost organs. In tailed amphibians, a new limb is formed in place of the amputated limb, but in the frog, the stump simply heals and no new growth occurs. There is also no clear connection between the nature of embryonic development and the ability to regenerate. Thus, in some animals with strictly determined development (comb jellies, polychaetes) in adulthood, regeneration is well developed (in crawling ctenophores and some polychaetes, a whole individual can be restored from a small area of ​​the body), and in some animals with regulatory development (sea urchins, mammals) - quite weak.

Many invertebrates are capable of regenerating large parts of their body. In most species of sponges, hydroid polyps, many species of flatworms, tapeworms and annelids, bryozoans, echinoderms and tunicates, an entire organism can regenerate from a small fragment of the body. Particularly noteworthy is the ability to regenerate in sponges. If the body of an adult sponge is pressed through mesh fabric, then all the cells will separate from each other, as if sifted through a sieve. If you then place all these individual cells in water and carefully, thoroughly mix, completely destroying all the connections between them, then after some time they begin to gradually come closer together and reunite, forming a whole sponge, similar to the previous one. This involves a kind of “recognition” at the cellular level, as evidenced by the following experiment: three different types of sponges were divided into individual cells in the described manner and mixed thoroughly. At the same time, it was discovered that the cells of each species are able to “recognize” the cells of their own species in the total mass and reunite only with them, so that as a result, not one, but three new sponges were formed, similar to the original three. Of other animals, only hydra is capable of restoring a whole organism from a suspension of cells.

Regeneration in humans

In humans, the epidermis regenerates well; its derivatives, such as hair and nails, are also capable of regeneration. Also has the ability to regenerate bone(bones heal after fractures). With the loss of part of the liver (up to 75%), the remaining fragments begin to rapidly divide and restore the original size of the organ. Under certain conditions, fingertips can regenerate. In connection with the detection of weak electrical voltages on regenerating tissues, it can be assumed that weak electrophoresis currents accelerate regeneration.

see also

• Morphallaxis

Notes

Literature

1. Dolmatov I. Yu., Mashanov V. S. Regeneration in holothurians. - Vladivostok: Dalnauka, 2007. - 208 p.
2. Tanaka E.M. Cell differentiation and cell fate during urodele tail and limb regeneration. Curr Opin Genet Dev. 2003 Oct;13(5):497-501. PMID 14550415
3. Nye HL, Cameron JA, Chernoff EA, Stocum DL. Regeneration of the urodele limb: a review. Dev Dyn. 2003 Feb;226(2):280-94. PMID 12557206
4. Gardiner DM, Blumberg B, Komine Y, Bryant SV. Regulation of HoxA expression in developing and regenerating axolotl limbs. Development. 1995 Jun;121(6):1731-41. PMID 7600989
5. Putta S, Smith JJ, Walker JA, Rondet M, Weisrock DW, Monaghan J, Samuels AK, Kump K, King DC, Maness NJ, Habermann B, Tanaka E, Bryant SV, Gardiner DM, Parichy DM, Voss SR, From biomedicine to natural history research: EST resources for ambystomatid salamanders. BMC Genomics. 2004 Aug 13;5(1):54. PMID 15310388
6. Andrews, Wyatt. Medicine's Cutting Edge: Re-Growing Organs, Sunday Morning, CBS News(March 23, 2008).

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• Proverb
• Galkin, Alexander Abramovich

See what “Regeneration” is in other dictionaries:

REGENERATION- REGENERATION, the process of formation of a new organ or tissue in place of a part of the body that was removed in one way or another. Very often R. is defined as the process of restoring what has been lost, that is, the formation of an organ similar to the removed one. This... ... Great Medical Encyclopedia

REGENERATION- (late lat., from lat. re again, again, and genus, eris genus, generation). Revival, renewal, restoration of what was destroyed. In a figurative sense: a change for the better. Dictionary foreign words, included in the Russian language.... ... Dictionary of foreign words of the Russian language

REGENERATION- REGENERATION, in biology, the body’s ability to replace one of the lost parts. The term regeneration also refers to a form of Asexual Reproduction in which a new individual arises from a separated part of the mother's body... Scientific and technical encyclopedic dictionary

regeneration- restoration, recovery; compensation, regeneration, renewal, heteromorphosis, pettencoferation, revival, morphallaxis Dictionary of Russian synonyms. regeneration noun, number of synonyms: 11 compensation (20) ... Synonym dictionary

Regeneration- 1) restoration, using certain physicochemical processes, of the original composition and properties of waste products for their reuse. In military affairs, air regeneration has become widespread (especially on underwater... ... Marine Dictionary

Regeneration- – returning the used product to its original properties. [Terminological dictionary of concrete and reinforced concrete. FSUE "Research Center "Construction" NIIZHB named after. A. A. Gvozdeva, Moscow, 2007, 110 pp.] Regeneration - restoration of waste... ... Encyclopedia of terms, definitions and explanations of building materials

REGENERATION- (1) restoration of the original properties and composition of waste materials (water, air, oils, rubber, etc.) for their reuse. It is carried out with the help of certain physical chem. processes in special regenerator devices. Wide... ... Big Polytechnic Encyclopedia

REGENERATION- (from Late Lat. regeneratio rebirth renewal), in biology, the restoration by the body of lost or damaged organs and tissues, as well as the restoration of the whole organism from its part. Mostly characteristic of plants and invertebrates... ...

REGENERATION- in technology, 1) returning the spent product to its original qualities, for example. restoration of the properties of spent molding sand in foundries, purification of used lubricating oil, transformation of worn rubber products into plastic... ... Big Encyclopedic Dictionary

People have always been amazed at the incredible properties of the animal body. Such properties of the body as organ regeneration, restoration of lost body parts, the ability to change color and do without water and food for a long time, acute vision, existence in incredibly difficult conditions, and so on. Compared to animals, it seems that they are not our “smaller brothers,” but we are theirs.

But it turns out that the human body is not as primitive as it might seem to us at first glance.

Regeneration of the human body

The cells in our body are also renewed. But how does cell renewal in the human body occur? And if cells are constantly renewed, then why does old age set in, and not eternal youth last?

Swedish neurologist Jonas Friesen established: every adult is on average fifteen and a half years old.

But if many parts of our body are constantly renewed, and as a result they turn out to be much younger than their owner, then some questions arise:

• For example, why doesn't the skin remain smooth and pink all its life, like a baby's, if the top layer of skin is always two weeks old?
• If muscles are approximately 15 years old, then why is a 60-year-old woman not as flexible and mobile as a 15-year-old girl?

Friesen saw the answers to these questions in the DNA of mitochondria (this is part of every cell). She quickly accumulates various damage. This is why the skin ages over time: mutations in mitochondria lead to a deterioration in the quality of such an important component of the skin as collagen. According to many psychologists, aging occurs due to the mental programs that have been embedded in us since childhood.

Today we will look at the timing of renewal of specific human organs and tissues:

Body regeneration: Brain

Brain cells live with a person throughout his life. But if the cells were renewed, the information that was embedded in them would go with them - our thoughts, emotions, memories, skills, experience.

A lifestyle such as smoking, drugs, alcohol - to one degree or another destroys the brain, killing some of the cells.

And yet, in two areas of the brain, cells are renewed:

• The olfactory bulb is responsible for the perception of smells.
• The hippocampus, which controls the ability to assimilate new information in order to then transfer it to the “storage center”, as well as the ability to navigate in space.

It became known quite recently that heart cells also have the ability to renew. According to researchers, this only happens once or twice in a lifetime, so it is extremely important to preserve this organ.

Body regeneration: Lungs

For each type of lung tissue, cell renewal occurs at different rates. For example, the air sacs that are located at the ends of the bronchi (alveoli) are reborn every 11 to 12 months. But the cells located on the surface of the lungs are renewed every 14-21 days. This part respiratory organ takes on most of the harmful substances coming from the air we breathe.

Bad habits (primarily smoking), as well as a polluted atmosphere, slow down the renewal of the alveoli, destroy them and, in the worst case, can lead to emphysema.

Regeneration of the body: Liver

The liver is the champion of regeneration among the organs of the human body. Liver cells are renewed approximately every 150 days, that is, the liver is “born” again once every five months. It is able to recover completely, even if as a result of the operation a person has lost up to two-thirds of this organ.

The liver is the only organ in our body that has such a high regenerative function.

Of course, detailed endurance of the liver is possible only with your help to this organ: the liver does not like fatty, spicy, fried and smoked foods. In addition, alcohol and most medications make the liver’s work very difficult.

And if you don’t pay attention to this organ, it will cruelly take revenge on its owner with terrible diseases - cirrhosis or cancer. By the way, if you stop drinking alcohol for eight weeks, the liver can completely cleanse itself.

Regeneration of the body: Intestines

The intestinal walls are covered from the inside with tiny villi, which ensure the absorption of nutrients. But they are under constant influence gastric juice, which dissolves food, so they do not live long. The time frame for updating them is 3-5 days.

Body regeneration: Skeleton

The bones of the skeleton are renewed continuously, that is, at any given moment in the same bone there are both old and new cells. It takes about ten years to completely update the skeleton.

This process slows down with age, when bones become thinner and more fragile.

Body regeneration: Hair

Hair grows on average one centimeter per month, but hair can completely change in a few years, depending on the length. For women, this process takes up to six years, for men – up to three. Eyebrow and eyelash hairs grow back in six to eight weeks.

Body regeneration: Eyes

In such a very important and fragile organ as the eye, only the cells of the cornea are capable of renewal. Its top layer is replaced every 7 to 10 days. If the cornea is damaged, the process occurs even faster - it can recover within a day.

Body regeneration: Tongue

10,000 receptors are located on the surface of the tongue. They are able to distinguish the tastes of food: sweet, sour, bitter, spicy, salty. Tongue cells have a fairly short life cycle - ten days.

Smoking and oral infections weaken and inhibit this ability, and also reduce the sensitivity of taste buds.

Body regeneration: Skin and Nails

The surface layer of skin is renewed every two to four weeks. But only if the skin is provided with proper care and does not receive excess ultraviolet radiation.

Smoking negatively affects the skin - this bad habit accelerates skin aging by two to four years.

The most famous example of organ renewal is nails. They grow 3–4 mm every month. But this is on the hands; on the toes, nails grow twice as slow. A fingernail is completely renewed on average in six months, and a toenail in ten.

Moreover, nails on the little fingers grow much slower than others, and the reason for this still remains a mystery to doctors. The use of medications slows down the recovery of cells throughout the body.

Now you know a little more about your body and its properties. It becomes obvious that man is very complex and not fully understood. How much do we still have to find out?

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Regeneration of organs and tissues, its types

Regeneration is the process of restoring lost or damaged tissues or organs.

There are two types of regeneration:

Physiological

Reparative

Physiological regeneration is manifested in the restoration of cells and tissues that die during the normal functioning of the body.

For example, the formed elements of blood - red blood cells, white blood cells - continuously die off, and the loss of these cells is replenished in the hematopoietic organs.

All the time, keratinized epidermal cells are rejected from the surface of the skin, and their restoration continuously occurs.

Physiological regeneration includes hair change and replacement of baby teeth with permanent ones.

Reparative regeneration (Greek - repair) manifests itself in the restoration of tissues or organs lost due to damage.

Reparative regeneration underlies wound healing and bone healing after fractures. Reparative regeneration occurs after burns.

The following methods of reparative regeneration exist:

1. Epithelization

2. Epimorphosis

3. Morphallaxis

4. Endomorphosis (or hypertrophy)

Epithelialization– healing of epithelial wounds. Regeneration comes from the wound surface.

The wound surface dries out to form a crust. The epithelium along the edge of the wound thickens due to an increase in cell volume and expansion of intercellular spaces. A fibrin clot forms. Epithelial cells with phagocytic activity migrate deep into the wound. An outbreak of mitoses is observed. Epithelial cells from the sides of the wound grows under non-living necrotic tissue, separating the crust covering the wound.

Epimorphosis– a method of regeneration, which consists in the growth of a new organ from the amputated surface. Regeneration comes from the wound surface.

Epimorphic regeneration may be typical if the organ restored after amputation does not differ from the undamaged one. Atypical when the restored organ differs in shape or structure from normal. An example of a typical regeneration is the restoration of a limb in an axolotl after amputation. Axolotl (class amphibians) – Ambystoma larva – an object of experimental biology.

An example of atypical regeneration is the regeneration of a limb in some species of lizards. As a result, a tail-like appendage is formed instead of a limb.

Atypical regeneration includes heteromorphosis. For example, when the eye is removed along with the nerve ganglion at the base of the eye, a jointed limb is regenerated.

Morphallaxis– regeneration by restructuring the regenerating area – after amputation, an organ or organism regenerates, but of a smaller size.

An example is the regeneration of a hydra from a ring cut from the middle of its body or the restoration of one tenth or twentieth part.

Typically, regeneration processes occur in the area of ​​the wound surface.

But there is special forms regeneration is endomorphosis (hypertrophy), which has two forms:

Regenerative hypertrophy,

Compensatory hypertrophy.

Regenerative hypertrophy - an increase in the size of the remnant of an organ without restoring its original shape (the size increases, but not the shape)

If a significant portion of a rat's liver or spleen is removed, the wound surface heals. Inside the remaining area, intensive cell proliferation begins. Liver volume increases and liver function returns to normal.

Compensatory hypertrophy is a change in one organ with a violation in another belonging to the same organ system.

If one kidney is removed from a rabbit, the second one receives an increased load. This causes it to grow, and its volume doubles.

Compensatory hypertrophy is not reparative regeneration, because the intact organ grows. However, it is considered as a restorative process of the excretory organ system as a whole.

Regeneration cannot be considered as a local reaction. It is a process in which the organism as a whole participates. Nervous regulation is especially important. Regeneration occurs if the innervation is not disrupted. Alone external factors inhibit, others stimulate recovery processes.

Every organ and tissue has special conditions and patterns of regeneration. In some cases, regeneration is successful when using special prostheses of glass, plastic, and metal. Using prostheses, it was possible to obtain regeneration of the trachea, bronchi, large blood vessels. The prosthesis serves as a framework along which the vascular endothelium grows. There are many unresolved issues in the regeneration problem. For example, the ear and tongue do not regenerate in case of marginal damage, but in case of damage through the thickness of the organ, recovery is successful.

Transplantation

Transplantation is the engraftment and development of transplanted tissues in a new location.

The organism from which the material for transplantation is taken is called the donor, and the one to which the transplant is performed is called the recipient. The tissue or organ that is transplanted is called a graft.

There are:

1. Autotransplantation.

2. Homotransplantation (allotransplantation).

3. Heterotransplantation (xenotransplantation)

At autotransplantation the donor and recipient are the same organism; the graft is taken from one place and transplanted to another. This type of transplant is widely used in reconstructive surgery. For example, for extensive facial injuries, the skin of the arm or abdomen of the same patient is used. An artificial esophagus and rectum are created through autotransplantation.

At allo- or homotransplantation donor and recipient are different individuals of the same species. In humans and higher animals, the success of homotransplantation depends on the antigenic compatibility of donor and recipient tissues. If the donor's tissues contain substances foreign to the recipient - antigens, then they cause the formation of immune antibodies in the recipient's body. The recipient's antibodies react with transplant antigens and cause changes in the structure and function of the antigen and foreign tissue, rejection, which means that the tissues are immunologically incompatible. An example of allotransplantation in humans is blood transfusion.

At heterotransplantation donor and recipient are animals different types. In invertebrates, engraftment is possible. In higher animals, during transplantations of this kind, the graft, as a rule, is resorbed.

Currently, scientists and doctors are working on the problem of suppressing the immune reaction of rejection and overcoming immunological incompatibility. Immunological tolerance (tolerance) to foreign cells is of great importance.

Currently, there are several ways to prevent transplant rejection:

Selection of the most compatible donor

Irradiation x-rays immune system of bone marrow and lymphatic tissues. Irradiation suppresses the formation of lymphocytes and thus slows down the rejection process.

Use of immunosuppressants, e.g. substances that not only suppressed immunity, but selectively and specifically suppressed transplantation immunity, while maintaining the function of protection against infections. The search for specific immunosuppressants is currently underway. There are examples of the lives of patients with transplanted kidneys, liver, and pancreas.

Nowadays there is a lot of talk about growing individual organs outside the body and replacing them with lost ones. But maybe there is a better way - simply restore or, to put it scientifically, regenerate your organs?

In principle, a person is partly endowed with this gift. Our cuts heal thanks to skin regeneration. The blood is also regenerated. But I want more. Moreover, not only ordinary people, but also scientists dream about this.

For example, employees of the Laboratory of Regeneration Problems of the Institute of Developmental Biology of the Russian Academy of Sciences, headed by Doctor of Biological Sciences Viktor Mitashov, have long been developing various methods for restoring human bone and nerve tissue, and recently the retina. Actually lower organisms are more often capable of regeneration than more highly organized ones.

Thus, among invertebrates there are many more species capable of restoring lost organs than among vertebrates, but only in some of them is it possible to regenerate an entire individual from a small fragment. Such primitive animals as ctenophores and rotifers are practically incapable of regeneration, but in much more complex crustaceans and amphibians this ability is well expressed.

Many would like to get regeneration like Wolverine, the hero of American comics. He can heal even the most terrible wounds in a matter of minutes.

The ability to regenerate in sponges is especially amazing. Scientists performed an unusual experiment; pressed the body of an adult sponge through the mesh fabric and separated all the resulting fragments from each other. It turned out that if you then place these small pieces in water and mix them thoroughly, completely destroying all the connections between them, then some time later they will gradually begin to come closer together and eventually reunite, forming a whole sponge, similar to the previous one. This involves a kind of “recognition” at the cellular level.

Another champion of regeneration is the tapeworm, which is able to recreate an entire individual from any part of its body. It is theoretically possible, by cutting one worm into 200,000 pieces, to obtain the same number of new worms as a result of regeneration. And from one ray of a starfish a whole star can be reborn.

But another example that is much better known is lizards that grow their own tails, and newts that can regenerate their eyes, paws and tail up to six times.

Alas, man is deprived of this invaluable property. Couldn't modern science help us master the corresponding mechanisms?

When recalculated for a person’s life, a restoration process similar to Triton’s could take us only six months. However, it is very difficult to fully understand how Triton restores the eye in a month. Scientists cannot yet repeat his feats. But it has already become clear how he and others like him do it.

Let's start from the very beginning - with the birth of the organism. It is known that during embryonic development, the cells of any multicellular organism undergo specialization. Some make, for example, legs, others, say, muscles, gills or eyes. The so-called Dox genes give the command to both the entire body and specific organs to develop according to a certain plan - so that it does not happen that an eye grows where a leg should be.

The Drosophila fly has 8 Dox genes, the frog has 6, and humans have 38. And it turned out that during regeneration, the newt “remembers” its embryonic past, including a genetic program that activates Dox genes and restores deleted or damaged tissues and organs .

But an eye or a tail must arise from something - it cannot be regenerated from thin air. The body has two ways - to produce new cells, new construction material or use what is left after the loss of an organ.

It turned out that nature uses both of these methods. Embryonic stem cells serve as the “building blocks” for regeneration. This is the name given to embryonic cells that in their development simply have not reached the stage of specialization and, therefore, are capable, under the influence of certain factors, of turning into cells of various tissues and organs of more than two hundred types.

Moreover, during regeneration, “old” newt cells, through complex manipulations, turn into ones similar to embryonic ones. There has been a lot of controversy surrounding them lately. The fact is that for scientists the main source of embryonic stem cells is human embryos. Biologists are studying the properties of embryonic stem cells with great enthusiasm: after all, if successful, these cells will open up completely new possibilities in surgery and ensure the restoration of certain organs. If, as a result of the disease, some groups of cells, even highly specialized ones, fail, then it will be possible to replace them.

And our biologists are not in the last role in these works. For example, Academician of the Russian Academy of Natural Sciences Leonid Polezhaev has been studying the problem of regeneration of the bones of the cranial vault for decades. First, he managed to achieve regeneration of skull bones in dogs and rats. Then, together with doctors from the Institute of Neurosurgery named after N.N. Burdenko of the USSR Academy of Medical Sciences tried to restore skull bones in patients with head injuries.

In this case, bone filings were used, which “encouraged” the bones of the human skull to regenerate. As a result, the injury area was completely covered with new bone. More than 250 operations have been performed using this technique.

Recently, a group of scientists from the University of Tokyo, led by Makoto Asashima, cultured thousands of embryonic stem cells in a special solution of vitamin A, varying the concentration of the vitamin. A low concentration activates genes that control the development of eye tissue, while a high concentration triggers the work of genes responsible for the formation of the hearing organ.

Makoto Asashima stated that this way a whole frog's eye can be obtained in five days. Similar, but more simple method First, new kidneys were grown and successfully transplanted into the frog. The recipient animal lived for a month after this operation.

And specialists from Tokyo's Keio University published a report on a successful experiment using human embryonic stem cells to restore damaged spinal cord tissue in monkeys. According to the head of the work, Professor Hideyuki Okano, the original stem cells were taken from a deceased human embryo with the consent of the parents and the approval of the university ethics council.

These cells were then multiplied in a nutrient medium and given to five monkeys (10 million cells each) whose forelimbs were immobilized as a result of a spinal injury. In one primate, all musculoskeletal functions returned to normal after two months, while in the rest the recovery process continues.

In the laboratory of Viktor Mitashov, experiments were successfully carried out to restore the newt's eye. And now researchers are preparing for experiments on growing human retinas.

But experts are cautious about the possibility of growing a whole eye. They can be understood: the evolutionary gap between newt and man is too great. On the other hand, the mechanisms of organ development are similar, so there is hope that someday biologists will be able to force a traumatized person, “falling into childhood,” to grow necessary organs- teeth, to replace the ones that have fallen out, new cells of the liver, kidneys, pancreas, new muscle tissue for the heart affected by myocardial infarction.