Foreword

The last decade has witnessed an explosion of new knowledge regarding cellular homeostasis throughout life. This new information essentially requires a revision of fundamental paradigms regarding the life cycle of the higher organism. Importantly these new insights have therapeutic implications

The traditional paradigm has held that most (but importantly not all) of our crucial organ systems are terminally differentiated - in essence the cells that throughout life comprise the heart, central nervous system, islets of Langerhans, kidney are the ones that we are born with. The inevitable loss of these cells throughout life leads to permanent diminution in the function of the organ. Moreover, with widespread destruction of tissue such as due to myocardial infarction, stroke, or type I diabetes, tissue recovery does not occur.

We now know that all of our organs have greater plasticity than the initial paradigm held. The central discovery is that of adult stem cells - reservoirs of stem and precursor cells that underlie a cellular homeostatic process. In the heart, estimates range that throughout adult life there is a turnover rate that ranges between 1 and 7 percent per year. Importantly this rate declines with age. Thus, endogenous repair pathways are operative and disease processes must now be viewed within the context of a homeostatic balance between cell loss and replacement.

Not only do these cells exist, but they can be accessed and amplified ex vivo, offering a major new therapeutic avenue. The book edited by Professor Herman Cheung offers a state of the art examination of this exciting new area of biology and therapeutics. The contributions cover important areas ranging from the ethics and considerations of justice in stem cell therapeutics to evaluations of crucial areas of the biology of endogenous tissue homeostasis.

The field of adult stem cells builds upon the discovery of pluripotent stem cells - embryonic and inducible. The discovery of these cells has initiated a field based upon the idea that tissue and cell loss can be replaced by exogenous cells. Work in the area of pluripotency has lead to the exciting insight that the adult mammal possesses a greater degree of plasticity than previously appreciated. The book Stem Cell and Regenerative Medicine offers a comprehensive and state of the art review of this exciting new area of biology and medicine.