Potential and pitfalls of stem cell therapy in old age.

Our increasing understanding of resident stem cell populations in various tissues of the adult body provides promise for the development of cell-based therapies to treat trauma and disease. With the sharp rise in the aging population, the need for effective regenerative medicine strategies for the aged is more important then ever. Yet, the vast majority of research fuelling our understanding of the mechanisms that control stem cell behaviour, and their role in tissue regeneration, is conducted in young animals. Evidence collected in the last several years indicates that, although stem cells remain active into old age, changes in the stem cells and their microenvironments inhibit their regenerative potential. An understanding of both the cell-intrinsic stem cell changes, as well as concomitant changes to the stem cell niche and the systemic environment, are crucial for the development of regenerative medicine strategies that might be successful in aged patients.