Aging of tissue-resident adult stem/progenitor cells and their pathological consequences.

The fascinating discovery of tissue-resident adult stem/progenitor cells in recent years led to an explosion of interest in the development of novel stem cell-based therapies for improving the regenerative capacity of these endogenous immature cells or transplanted cells for the repair of damaged and diseased tissues. In counterbalance, a growing body of evidence has revealed that the changes in phenotypic and functional properties of human adult stem/progenitor cells may occur during chronological aging and have severe pathological consequences. Especially, intense oxidative and metabolic stress and chronic inflammation, enhanced telomere attrition and defects in DNA repair mechanisms may lead to severe DNA damages and genomic instability in adult stem/progenitor cells with advancing age that may in turn trigger their replicative senescence and/or programmed cell death. Moreover, the changes in the intrinsic and extrinsic factors involved in the stringent control of self-renewal and multilineage differentiation capacities of these regenerative cells, including deregulated signals from the aged niche, may also contribute to their dysfunctions or loss during chronological aging. This age-associated decline in the regenerative capacity and number of functional adult stem/progenitor cells may increase the risk to develop certain diseases. At opposed end, the telomerase reactivation and accumulation of genetic alterations leading to a down-regulation of numerous tumor suppressor genes concomitant with the enhanced expression of diverse oncogenic products may result in their malignant transformation into cancer-initiating cells. Therefore, the rescue or replacement of aged and dysfunctional endogenous adult stem/progenitor cells or molecular targeting of their malignant counterpart, cancer stem/progenitor cells may constitute potential anti-aging and cancer therapies. These therapeutic strategies could be used for treating diverse devastating premature aging and age-related disorders including hematopoietic and immune disorders, heart failure and cardiovascular diseases, neurodegenerative, muscular and gastrointestinal diseases, atherosclerosis and aggressive and lethal cancers.