Regeneration (biology)
Encyclopedia
In biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
, regeneration is the process of renewal, restoration, and growth that makes genomes, cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s, organs, organisms, and ecosystems resilient
Resilience (ecology)
In ecology, resilience is the capacity of an ecosystem to respond to a perturbation or disturbance by resisting damage and recovering quickly. Such perturbations and disturbances can include stochastic events such as fires, flooding, windstorms, insect population explosions, and human activities...
to natural fluctuations or events that cause disturbance or damage. Every species is capable of regeneration, from bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
to humans. At its most elementary level, regeneration is mediated by the molecular processes of DNA synthesis
DNA replication
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for biological inheritance. The process starts with one double-stranded DNA molecule and produces two identical copies of the molecule...
. Regeneration in biology, however, mainly refers to the morphogenic
Morphogenesis
Morphogenesis , is the biological process that causes an organism to develop its shape...
processes that characterizes the phenotypic plasticity
Phenotypic plasticity
Phenotypic plasticity is the ability of an organism to change its phenotype in response to changes in the environment. Such plasticity in some cases expresses as several highly morphologically distinct results; in other cases, a continuous norm of reaction describes the functional interrelationship...
of traits allowing multi-cellular organisms to repair and maintain the integrity of their physiological and morphological states. Above the genetic level, regeneration is fundamentally regulated by asexual cellular processes. It is important to note that regeneration is different from reproduction. For example, hydra
Hydra (genus)
Hydra is a genus of simple fresh-water animal possessing radial symmetry. Hydras are predatory animals belonging to the phylum Cnidaria and the class Hydrozoa. They can be found in most unpolluted fresh-water ponds, lakes, and streams in the temperate and tropical regions and can be found by...
performs regeneration but it reproduces by the method of budding
Budding
Budding is a form of asexual reproduction in which a new organism grows on another one. The new organism remains attached as it grows, separating from the parent organism only when it is mature. Since the reproduction is asexual, the newly created organism is a clone and is genetically identical...
.
The hydra
Hydra (genus)
Hydra is a genus of simple fresh-water animal possessing radial symmetry. Hydras are predatory animals belonging to the phylum Cnidaria and the class Hydrozoa. They can be found in most unpolluted fresh-water ponds, lakes, and streams in the temperate and tropical regions and can be found by...
and the planarian flatworm have long served as model organisms for their highly adaptive
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
regenerative capabilities. Once wounded, their cells become activated and start to remodel tissues and organs back to the pre-existing state. The urodele (salamander), an amphibian, is possibly the most adept vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
for their capability of regenerating limbs, tails, jaws, eyes and a variety of internal structures. The regeneration of organs is a common and widespread adaptive capability among metazoan creatures. In a related context, some animals are able to reproduce asexually
Asexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
through fragmentation, budding
Budding
Budding is a form of asexual reproduction in which a new organism grows on another one. The new organism remains attached as it grows, separating from the parent organism only when it is mature. Since the reproduction is asexual, the newly created organism is a clone and is genetically identical...
, or fission
Fission (biology)
In biology, fission is the subdivision of a cell into two or more parts and the regeneration of those parts into separate cells...
. A planarian parent, for example, will constrict, split in the middle, and each half generates a new end to form two clones
Clone (cell biology)
A clone is a group of identical cells that share a common ancestry, meaning they are derived from the same mother cell.Clonality implies the state of a cell or a substance being derived from one source or the other...
of the original. Echinoderms (such as the starfish), crayfish, many reptiles, and amphibians exhibit remarkable examples of tissue regeneration. The case of autotomy
Autotomy
Autotomy or self amputation is the act whereby an animal severs one or more of its own appendages, usually as a self-defense mechanism designed to elude a predator's grasp...
, for example, serves as a defensive function as the animal detaches a limb or tail to avoid capture. After the limb or tail has been autotomized, cells move into action and tissues regenerate. Ecosystems are regenerative as well. Following a disturbance, such as a fire or pest outbreak in a forest, pioneering species
Pioneer species
Pioneer species are species which colonize previously uncolonized land, usually leading to ecological succession. They are the first organisms to start the chain of events leading to a livable biosphere or ecosystem...
will occupy, compete for space, and establish themselves in the newly opened habitat. The new growth of seedlings and community assembly
Assembly rules
Community assembly rules are a set of controversial rules first proposed by Jared Diamond. The rules were developed after more than a decade of research into the avian assemblages on islands near New Guinea and assert that competition is responsible for determining the patterns of assemblage...
process is known as regeneration in ecology
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
.
Cellular molecular fundamentals
Pattern formation in the morphogenesis of an animal is regulated by genetic induction factorsRegulation of gene expression
Gene modulation redirects here. For information on therapeutic regulation of gene expression, see therapeutic gene modulation.Regulation of gene expression includes the processes that cells and viruses use to regulate the way that the information in genes is turned into gene products...
that put cells to work after damage has occurred. Neural cells, for example, express growth-associated proteins, such as GAP-43, tubulin
Tubulin
Tubulin is one of several members of a small family of globular proteins. The most common members of the tubulin family are α-tubulin and β-tubulin, the proteins that make up microtubules. Each has a molecular weight of approximately 55 kiloDaltons. Microtubules are assembled from dimers of α- and...
, actin
Actin
Actin is a globular, roughly 42-kDa moonlighting protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans...
, an array of novel neuroptides
Neuropeptide
Neuropeptides are small protein-like molecules used by neurons to communicate with each other. They are neuronal signaling molecules, influence the activity of the brain in specific ways and are thus involved in particular brain functions, like analgesia, reward, food intake, learning and...
, and cytokines that induce a cellular physiological response to regenerate from the damage. Many of the genes that are involved in the original development of tissues are reinitialized during the regenerative process. Cells in the primordia
Primordium
A primordium , in embryology, is defined as an organ or tissue in its earliest recognizable stage of development. Cells of the primordium are called primordial cells...
of zebrafish fins, for example, express four genes from the homeobox
Homeobox
A homeobox is a DNA sequence found within genes that are involved in the regulation of patterns of anatomical development in animals, fungi and plants.- Discovery :...
msx family during development and regeneration.
Tissues and organs
"Regenerative strategies include the rearrangement of pre-existing tissue, the use of adult somaticSomatic cell
A somatic cell is any biological cell forming the body of an organism; that is, in a multicellular organism, any cell other than a gamete, germ cell, gametocyte or undifferentiated stem cell...
stem cells and the dedifferentiation and/or transdifferentiation of cells, and more than one mode can operate in different tissues of the same animal. All these strategies result in the re-establishment of appropriate tissue polarity, structure and form." During the developmental process genes are activated that serve to modify the properties of cell
Cell potency
The potency of a cell specifies its differentiation potential, or potential to differentiate into different cell types.-Totipotency:Totipotency is the ability of a single cell to divide and produce all the differentiated cells in an organism, including extraembryonic tissues.Totipotent cells...
as they differentiate into different tissues. Development and regeneration involves the coordination and organization of populations cells into a blastema
Blastema
A blastema is a mass of cells capable of growth and regeneration into organs or body parts. Historically blastema have been thought to be composed of undifferentiated pluripotent cells, but recent research indicates that in some organisms blastema may retain memory of tissue origin...
, which is "a mound of stem cells from which regeneration begins." The dedifferentiation of cells means that they lose their tissue specific characteristics as tissues remodel during the regeneration process. The transdifferentiation of cells means that they lose their tissue specific characteristics during the regeneration process and then re-differentiate to a different kind of cell.
Planaria (Platyhelminthes)
Planaria exhibit an extraordinary ability to regenerate lost body parts. For example, a planarian split lengthwise or crosswise will regenerate into two separate individuals. In one experiment, T. H. Morgan found that a piece corresponding to 1⁄279th of a planarian could successfully regenerate into a new worm. This size (about 10,000 cells) is typically accepted as the smallest fragment that can regrow into a new planarian. Regeneration of planaria is epimorphic regeneration. After amputation, stump cells form blastema.Amphibians
Limb regeneration in newts occurs in two major steps, first de-differentiationCellular differentiation
In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a simple zygote to a complex system of...
of adult cells into a stem cell
Stem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
state similar to embryonic cells and second, development
Developmental biology
Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and "morphogenesis", which is the process that gives rise to tissues, organs and anatomy.- Related fields of study...
of these cells into new tissue more or less the same way it developed the first time. Simpler animals like planarian have an enhanced capacity to regenerate because the adults retain clusters of stem cells (neoblast) within their bodies which migrate to the parts that need healing. They then divide and differentiate to grow the missing tissue and organs back.
In salamander
Salamander
Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...
s, the regeneration process begins immediately after amputation. Limb regeneration in the axolotl
Axolotl
The axolotl , Ambystoma mexicanum, is a neotenic salamander, closely related to the Tiger Salamander. Larvae of this species fail to undergo metamorphosis, so the adults remain aquatic and gilled. It is also called ajolote...
and newt
Newt
A newt is an aquatic amphibian of the family Salamandridae, although not all aquatic salamanders are considered newts. Newts are classified in the subfamily Pleurodelinae of the family Salamandridae, and are found in North America, Europe and Asia...
have been extensively studied. After amputation, the epidermis migrates to cover the stump in less than 12 hours, forming a structure called the apical epidermal cap (AEC). Over the next several days there are changes in the underlying stump tissues that result in the formation of a blastema
Blastema
A blastema is a mass of cells capable of growth and regeneration into organs or body parts. Historically blastema have been thought to be composed of undifferentiated pluripotent cells, but recent research indicates that in some organisms blastema may retain memory of tissue origin...
(a mass of dedifferentiated proliferating cells). As the blastema forms, pattern formation genes – such as Hox
Homeobox
A homeobox is a DNA sequence found within genes that are involved in the regulation of patterns of anatomical development in animals, fungi and plants.- Discovery :...
A and HoxD – are activated as they were when the limb was formed in the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
. The distal
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
tip of the limb (the autopod, which is the hand or foot) is formed first in the blastema. The intermediate portions of the pattern are filled in during growth of the blastema by the process of intercalation. Motor neuron
Motor neuron
In vertebrates, the term motor neuron classically applies to neurons located in the central nervous system that project their axons outside the CNS and directly or indirectly control muscles...
s, muscle, and blood vessels grow with the regenerated limb, and reestablish the connections that were present prior to amputation. The time that this entire process takes varies according to the age of the animal, ranging from about a month to around three months in the adult and then the limb becomes fully functional.
In spite of the historically few researchers studying limb regeneration, remarkable progress has been made recently in establishing the neotenous amphibian the axolotl (Ambystoma mexicanum) as a model genetic organism. This progress has been facilitated by advances in genomics
Genomics
Genomics is a discipline in genetics concerning the study of the genomes of organisms. The field includes intensive efforts to determine the entire DNA sequence of organisms and fine-scale genetic mapping efforts. The field also includes studies of intragenomic phenomena such as heterosis,...
, bioinformatics
Bioinformatics
Bioinformatics is the application of computer science and information technology to the field of biology and medicine. Bioinformatics deals with algorithms, databases and information systems, web technologies, artificial intelligence and soft computing, information and computation theory, software...
, and somatic cell
Somatic cell
A somatic cell is any biological cell forming the body of an organism; that is, in a multicellular organism, any cell other than a gamete, germ cell, gametocyte or undifferentiated stem cell...
transgenesis
Transgenesis
thumb|300px|right|A diagram comparing the genetic changes achieved through conventional plant breeding, transgenesis and cisgenesisTransgenesis is the process of introducing an exogenous gene – called a transgene – into a living organism so that the organism will exhibit a new property and transmit...
in other fields, that have created the opportunity to investigate the mechanisms of important biological properties, such as limb regeneration, in the axolotl. The Ambystoma Genetic Stock Center (AGSC) is a self-sustaining, breeding colony of the axolotl supported by the National Science Foundation
National Science Foundation
The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...
as a Living Stock Collection. Located at the University of Kentucky, the AGSC is dedicated to supplying genetically well-characterized axolotl embryos, larvae, and adults to laboratories throughout the United States and abroad. An NIH
National Institutes of Health
The National Institutes of Health are an agency of the United States Department of Health and Human Services and are the primary agency of the United States government responsible for biomedical and health-related research. Its science and engineering counterpart is the National Science Foundation...
-funded NCRR grant has led to the establishment of the Ambystoma EST database, the Salamander Genome Project (SGP) that has led to the creation of the first amphibian gene map and several annotated molecular data bases, and the creation of the research community web portal.
Mice
The mechanism for regeneration in Murphy Roths LargeMurphy Roths Large
Murphy Roths Large, a strain of mouse, was found in 1999 to have remarkable tissue regeneration abilities.-External links:* * *...
(MRL) mice has been found and it is related to the deactivation of the p21 gene.
Adult mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s have limited regenerative capacity compared to most vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
embryos/larvae, adult salamanders and fish. The MRL mouse
Murphy Roths Large
Murphy Roths Large, a strain of mouse, was found in 1999 to have remarkable tissue regeneration abilities.-External links:* * *...
is a strain of mouse
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
that exhibits remarkable regenerative abilities for a mammal. Study of the regenerative process in these animals is aimed at discovering how to duplicate them in humans.
By comparing the differential gene expression
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
of scarless healing MRL mice and poor healing C57BL/6 mice strain, 36 gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s have been identified that are good candidates for studying how the healing process differs in MRL mice and other mice.
The regenerative abilities of MRL mice does not, however, protect them against myocardial infarction
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
, as heart regeneration in adult mammals (neocardiogenesis
Neocardiogenesis
In cardiology neocardiogenesis is the homeostatic regeneration, repair and renewal of sections of malfunctioning adult cardiovascular tissue. This includes a combination of cardiomyogenesis and angiogenesis .- Definition and Scope :The term neocardiogenesis comes from cardiogenesis, which refers...
) is limited because heart muscle cells are nearly all terminally differentiated
G0 phase
The G0 phase is a period in the cell cycle in which cells exist in a quiescent state. G0 phase is viewed as either an extended G1 phase, where the cell is neither dividing nor preparing to divide, or a distinct quiescent stage that occurs outside of the cell cycle...
. MRL mice show the same amount of cardiac injury and scar formation as normal mice after a heart attack. Though recent studies provide evidence that this may not be the case, and that MRL mice do regenerate from heart damage. http://www.eurekalert.org/pub_releases/2001-08/wi-rit080201.php
Fingers
In May 1932, L.H. McKim published a report in The Canadian Medical Association Journal, that described the regeneration of an adult digit-tip following amputation. A house surgeon in the Montreal General Hospital underwent amputation of the distal phalanx
Phalanx bones
In anatomy, phalanx bones are those that form the fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones.The phalanges do not have individual names...
to stop the spread of an infection. In less than one month following surgery, x-ray analysis showed the regrowth of bone while macroscopic observation showed the regrowth of nail and skin. This is one of the earliest recorded examples of adult human digit-tip regeneration.
Studies in the 1970s showed that children up to the age of 10 or so who lose fingertips in accidents can regrow the tip of the digit within a month provided their wounds are not sealed up with flaps of skin – the de facto treatment in such emergencies. They normally won't have a finger print, and if there is any piece of the finger nail left it will grow back as well, usually in a square shape rather than round.
In August 2005, Lee Spievack, then in his early sixties, accidentally sliced off the tip of his right middle finger just above the first phalanx
Phalanx bones
In anatomy, phalanx bones are those that form the fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones.The phalanges do not have individual names...
. His brother, Dr. Alan Spievack, was researching regeneration and provided him with powdered extracellular matrix
Extracellular matrix
In biology, the extracellular matrix is the extracellular part of animal tissue that usually provides structural support to the animal cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.Extracellular...
, developed by Dr. Stephen Badylak of the McGowan Institute of Regenerative Medicine
Regenerative medicine
Regenerative medicine is the "process of replacing or regenerating human cells, tissues or organs to restore orestablish normal function". This field holds the promise of regenerating damaged tissues and organs in the body by replacing damaged tissue and/or by stimulating the body's own repair...
. Mr. Spievack covered the wound with the powder, and the tip of his finger re-grew in four weeks. The news was released in 2007. Lee Spievack is the first documented case of an adult human regenerating fingertips; however, Ben Goldacre
Ben Goldacre
Ben Michael Goldacre born 1974 is a British science writer, doctor and psychiatrist. He is the author of The Guardian newspaper's weekly Bad Science column and a book of the same title, published by Fourth Estate in September 2008....
has described this as "the missing finger that never was", claiming that fingertips regrow and quoted Simon Kay, professor of hand surgery
Hand surgery
The field of hand surgery deals with both surgical and non-surgical treatment of conditions and problems that may take place in the hand or upper extremity including injury and infection. Hand surgery may be practiced by graduates of general surgery, orthopedic surgery and plastic surgery...
at the University of Leeds
University of Leeds
The University of Leeds is a British Redbrick university located in the city of Leeds, West Yorkshire, England...
, who from the picture provided by Goldacre described the case as seemingly "an ordinary fingertip injury with quite unremarkable healing"
A similar story was reported by CNN. A woman named Deepa Kulkarni lost the tip of her little finger and was initially told by doctors that nothing could be done. Her personal research and consultation with several specialists including Badylak eventually resulted in her undergoing regenerative therapy and regaining her fingertip.
Ribs
There have appeared claims that human rib
Rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...
s could regenerate if the periosteum
Periosteum
Periosteum is a membrane that lines the outer surface of all bones, except at the joints of long bones. Endosteum lines the inner surface of all bones....
, the membrane surrounding the rib, were left intact. In one study rib material was used for skull reconstruction and all 12 patients had complete regeneration of the resected rib.
Liver
The human liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
is one of the few glands in the body that has the ability to regenerate from as little as 25% of its tissue. This is largely due to the unipotency
Cell potency
The potency of a cell specifies its differentiation potential, or potential to differentiate into different cell types.-Totipotency:Totipotency is the ability of a single cell to divide and produce all the differentiated cells in an organism, including extraembryonic tissues.Totipotent cells...
of hepatocyte
Hepatocyte
A hepatocyte is a cell of the main tissue of the liver. Hepatocytes make up 70-80% of the liver's cytoplasmic mass.These cells are involved in:* Protein synthesis* Protein storage* Transformation of carbohydrates...
s. Resection of liver can induce the proliferation of the remained hepatocytes until the lost mass is restored, where the intensity of the liver’s response is directly proportional to the mass resected. For almost 80 years surgical resection of the liver in rodents has been a very useful model to the study of cell proliferation.
Kidney
Regenerative capacity of the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
remains largely unexplored. The basic functional and structural unit of the kidney is nephron
Nephron
The renal tubule is the portion of the nephron containing the tubular fluid filtered through the glomerulus. After passing through the renal tubule, the filtrate continues to the collecting duct system, which is not part of the nephron....
, which is mainly composed of four components: the glomerulus, tubules, the collecting duct and peritubular capillaries. The regenerative capacity of the mammalian kidney is limited compared to that of lower vertebrates.
In the mammalian kidney, the regeneration of the tubular component following an acute injury is well known. Recently regeneration of the glomerulus has also been documented. Following an acute injury, the proximal tubule is damaged more, and the injured epithelial cells slough off the basement membrane of the nephron. The surviving epithelial cells, however, undergo migration, dedifferentiation, proliferation, and redifferentiation to replenish the epithelial lining of the proximal tubule after injury. Recently, the presence and participation of kidney stem cell
Stem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
s in the tubular regeneration has been shown. However, the concept of kidney stem cells is currently emerging. In addition to the surviving tubular epithelial cells and kidney stem cells, the bone marrow stem cells have also been shown to participate in regeneration of the proximal tubule, however, the mechanisms remain controversial. Recently, studies examining the capacity of bone marrow stem cells to differentiate into renal cells are emerging.
Like other organs, the kidney is also known to regenerate completely in lower vertebrates such as fish. Some of the known fish that show remarkable capacity of kidney regeneration are goldfish, skates, rays, and sharks. In these fish, the entire nephron regenerates following injury or partial removal of the kidney.
Heart
Several animals can regenerate heart damage, but in mammals cardiomyocytes (heart muscle cells) cannot proliferate (multiply) and heart damage causes scarring and fibrosis.
The long held view was that mammalian cardiomyocytes are terminally differentiated and cannot divide. However inhibition of p38 MAP kinase was found to induce mitosis in adult mammalian cardiomyocytes. Treatment with FGF1 and p38 MAP kinase inhibitors regenerates the heart, reduces scarring, and improves cardiac function in rats with cardiac injury.
Sources
- Tanaka EM. Cell differentiation and cell fate during urodele tail and limb regeneration. Curr Opin Genet Dev. 2003 Oct;13(5):497-501. PMID 14550415
- 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
- Yu H, Mohan S, Masinde GL, Baylink DJ. Mapping the dominant wound healing and soft tissue regeneration QTL in MRL x CAST. Mamm Genome. 2005 Dec;16(12):918-24. PMID 16341671
- 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
- Torok MA, Gardiner DM, Shubin NH, Bryant SV. Expression of HoxD genes in developing and regenerating axolotl limbs. Dev Biol. 1998 Aug 15;200(2):225-33. PMID 9705229
- 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
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External links
- Spallanzani's mouse: a model of restoration and regeneration
- Mice that regrow hearts in the news
- DARPA Grant Supports Research Toward Realizing Tissue Regeneration
- The Geniuses Of Regeneration in BusinessWeekBusinessWeekBloomberg Businessweek, commonly and formerly known as BusinessWeek, is a weekly business magazine published by Bloomberg L.P. It is currently headquartered in New York City.- History :...
, May 24, 2004 - UCI Limb Regeneration Lab