After cellular or tissue damage, the resident stem cells present in the human body can locally repair and regenerate the damaged tissue or organ. However, even though some tissues do not have stem cells, they can repair and regenerate with the help of pre-existing cells. For example, beta cells of the pancreas and hepatocytes of the liver can divide to renew and regenerate the tissue. Here, both cell division and cell death are well regulated by homeostasis.

However, failure of such a system may result in life threatening diseases. Dysfunction in insulin-secreting cells, as well as the target cells’ responsiveness to insulin, can lead to a condition called diabetes mellitus. Interestingly, a recent study also found that as a backup, both the liver and pancreas have a few stem cells which are activated under extreme conditions to produce differentiated cell types. In this case, both the liver and pancreas revert back to their normal mechanisms of repair and renewal.