Organ repair and regeneration: an overview

A number of organs have the intrinsic ability to regenerate, a distinctive feature that varies among organisms. Organ regeneration is a process not fully yet understood. However, when its underlying mechanisms are unraveled, it holds tremendous therapeutic potential for humans. In this review, we chose to summarize the repair and regenerative potential of the following organs and organ systems: thymus, adrenal gland, thyroid gland, intestine, lungs, heart, liver, blood vessels, germ cells, nervous system, eye tissues, hair cells, kidney and bladder, skin, hair follicles, pancreas, bone, and cartilage. For each organ, a review of the following is presented: (a) factors, pathways, and cells that are involved in the organ's intrinsic regenerative ability, (b) contribution of exogenous cells - such as progenitor cells, embryonic stem cells, induced pluripotent stem cells, and bone marrow-, adipose- and umbilical cord blood-derived stem cells - in repairing and regenerating organs in the absence of an innate intrinsic regenerative capability, (c) and the progress made in engineering bio-artificial scaffolds, tissues, and organs. Organ regeneration is a promising therapy that can alleviate humans from diseases that have not been yet cured. It is also superior to already existing treatments that utilize exogenous sources to substitute for the organ's lost structure and/or function(s).