Compensatory growth aimed to replace loss of tissue in an organ.
Liver Regeneration. Transplant surgeons, hepatologists and other researchers are developing liver cell-based regenerative therapies for patients who'd otherwise need whole-liver transplants. The liver has the greatest regenerative capacity of any organ in the body. Liver regeneration has been recognized for many years, dating all the way back to Prometheus in ancient Greek mythology. When the liver is injured beyond its ability to regenerate itself, a liver transplant is the treatment of choice Regeneration and humans. Regeneration means the regrowth of a damaged or missing organ part from the remaining tissue. As adults, humans can regenerate some organs, such as the liver. If part of the liver is lost by disease or injury, the liver grows back to its original size, though not its original shape. And our skin is constantly being renewed and repaired. In these animals, each tissue – such as muscle, nerve, or skin – has its own set of stem cells that just make the different types of cells in that particular tissue. In other words, a muscle stem cell cannot make skin and skin stem cells can’t make muscle. About the liver. The liver is the largest organ of the human body. It does many jobs, including removing toxins from the blood, helping to digest food and fighting infections. It is the only organ in the body that can regenerate itself after damage. The cells that do the work in the liver are called hepatocytes. On average, each hepatocyte lives for around 200 to 300 days. In a healthy liver, hepatocytes can divide to make copies of themselves. This means they can replace the cells that die and can even repair some kinds of damage. The liver is a gland and plays a major role in metabolism with numerous functions in the human body, including regulation of glycogen storage, decomposition of red blood cells, plasma protein synthesis, hormone production, and detoxification. The liver is the only human internal organ capable of natural regeneration of lost tissue; as little as 25% of a liver can regenerate into a whole liver. This is, however, not true regeneration but rather compensatory growth in mammals. Liver regeneration is perhaps the most studied example of compensatory growth aimed to replace loss of tissue in an organ. Hepatocytes, the main functional cells of the liver, manage to proliferate to restore mass and to simultaneously deliver all functions hepatic functions necessary to maintain body homeostasis. Termination of liver regeneration is a complex process affected by integrin mediated signaling and it restores the organ to its original mass as determined by the needs of the body (hepatostat function). 1 Regeneration. 2  Regeneration involves delivering specific types of cells or cell products to diseased tissues or organs, where they will ultimately restore tissue and organ function. 3  This can be done through cell-based therapy or by using cell products, such as growth factors.  Dwarf yellow-headed gecko with regenerating tail. In biology, regeneration is the process of renewal, restoration, and growth that makes genomes, cells, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Every species is capable of regeneration, from bacteria to humans. For example, hydra perform regeneration but reproduce by the method of budding. The hydra and the planarian flatworm have long served as model organisms for their highly adaptive regenerative capabilities. Once wounded, their cells become activated and start to remodel tissues and organs back to the pre-existing state. The Dynamics of Liver Regeneration. Partial hepatectomy leads to proliferation of all populations of cells within the liver, including hepatocytes, biliary epithelial cells and endothelial cells. DNA synthesis is initiated in these cells within 10 to 12 hours after surgery and essentially ceases in about 3 days. These types of observations have prompted considerable research into the mechanisms responsible for hepatic regeneration, because understanding the processes involved will likely assist in treatment of a variety of serious liver diseases and may have important implications for certain types of gene therapy. A new model of liver regeneration. When the Hippo pathway is inactivated, mature liver cells revert back to a stem cell-like state. Picture shows a group of cells transitioning from a mature cell type (green) to a stem cell type (red). White cells are the cells where Hippo is being inactivated. (Credit: Dean Yimlamai/Boston Children's Hospital). This means the cells turn back the clock to become stem-cell like again, thus allowing them to give rise to functional progenitor cells that can regenerate a diseased liver. The liver has been a model of regeneration for decades, and it’s well known that mature liver cells can duplicate in response to injury.
http://www.mayo.edu/research/centers-programs/center-regenerative-medicine/focus-areas/liver-regeneration http://www.eurostemcell.org/factsheet/regeneration-what-does-it-mean-and-how-does-it-work http://www.eurostemcell.org/factsheet/chronic-liver-disease-how-could-regenerative-medicine-help https://en.wikipedia.org/wiki/Liver http://www.ncbi.nlm.nih.gov/pubmed/23720294 http://www.mayo.edu/research/centers-programs/center-regenerative-medicine/patient-care/about-regenerative-medicine https://en.wikipedia.org/wiki/Regeneration_%28biology%29 http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/liver/regen.html http://hsci.harvard.edu/news/new-model-liver-regeneration
regeneration of liver cells is an example of