Adult stem cells, also known as somatic stem cells, are found throughout the body in every tissues and organs after development and function as self-renewing cell pools to replenish dying cells and regenerate damaged tissues throughout life[
16]. However, adult stem cells appear to age with the person. As stem cells age, their functional ability also deteriorates[
12,
17]. Specifically, this regenerative power appears to decline with age, as injuries in older individuals heal more slowly than in childhood. For example, healing of a fractured bone takes much longer time in elderly than in young individuals[
18-
21]. There is a substantial amount of evidence showing that deterioration of adult stem cells in the adult phase can become an important player in the initiation of several diseases in aging[
22,
23]. The following is some of the examples of aging-associated effects on stem cells.