Generation of functional organs from stem cells

Stem cells are undifferentiated cells found in the body which have the ability to continuously divide, self-renew themselves and differentiate into various kinds of cells. With the capability of self-renewal, pluripotency and differentiation, stem cells have been believed to be useful for treatment of a wide variety of diseases in the future, including stroke, traumatic brain injury, Alzheimer’s disease, Parkinson’s disease, spinal cord injury, baldness, blindness, deafness, wound healing, amyotrophic lateral-sclerosis, myocardial infarction, muscular dystrophy, osteoarthritis rheumatoid arthritis, Crohn’s disease, and diabetes. Amongst the applications, a number of adult stem cell therapies have already been practiced clinically. As an example, hematopoietic stem cell transplantation has been successfully applied to treat leukemia.In addition to cell replacement therapy using stem cells, organ transplantation has been successfully practiced in clinics for organ failure of the liver or kidney. However, the severe shortage of donor organs has become the main obstacle to expand the organ transplant program. Generation of biological or semi-biological organs could be an alternative approach to solve the problem of the donor organ shortage. Notably, researchers have been hunting for ways to establish a whole organ using stem cells.In recent years encouraging approaches for functional organ generation have emerged. The present manuscript provides an overview of organ generation using a single adult tissue stem cell, a blastocyst complementation system coupled with a specific stem cell niche, a method of decellularization and recellularization of bio-scaffold, and a combinatorial approach of tissue engineering and stem cells.To demonstrate whether there are true stem cells in a given tissue, one needs to show that a single stem cell purified from the tissue has the capability of generating the entire organ. Up to present, it has been elegantly shown by independent groups