Stem cells and aging

Abstract

Aging is a steady alteration in genetic, biochemical, molecular, and physiological dynamism over time, leading to development of multiple human pathologies, including cardio-cerebro vascular disorders, diabetes, cancer, and neurodegeneration, among others. The underlying holistic mechanisms leading to irreversible changes and the consequent diseases are yet to be completely deciphered and understood in light of ever-emerging scientific evidences. Among multiple mechanisms underlying aging process, stem cell exhaustion, cellular senescence, genetic and chromosomal instability, altered cellular communications, telomere attrition, mitochondrial dysfunction, epigenetic changes, immunosenescence, and loss of proteostasis are few of them. Such degenerative changes are biologically pervasive, occurring in various types of somatic, germinal, and stem cells, thereby leading to cellular malfunctioning with eventual onset of aging process. Such changes, invariably occurring in all the tissues and organs, are thought to be primarily driven by aging resident stem cells. Stem cells are cells with immense self-renewal, differentiation, and trans-differentiation potential, located in almost every tissues and organs with varying abundance and biological functions. Aforementioned potential intrinsically inherent to stem cells makes them capable of serving organs in multiple ways such as providing appropriate niches and secreting myriad of growth factors for tissue-damage repair, among others, throughout an individual’s life. However, over the time as the aging process sets in and microenvironment starts deteriorating, stem cells, just like their non-stem cell counterpart, undergo molecular and genetic senescence, compromising the homeostatic and regenerative potential of organs, in particular, and body, in general. Therefore, decline in the stem cell function is thought to play a very crucial, if not primary, role in organismal aging. Stem cell exhaustion/decline is dependent on both the extrinsic and intrinsic factors. Besides, stem cells are also thought to recalibrate and reset their cellular and molecular properties so as to keep them functionally aligned with changing growth, homeostasis, and regenerative demands of various tissues and organs. Any disparity and imbalance may result into various degenerative diseases, on the one hand, and abnormal growth and cancers, on the other. These chronological and molecular regulations in stem cells reflect precise regulation of heterochronic genes, causing temporal shift in the stem cell functions. Therefore, developing translational understanding of existing relationship between stem cells and aging may help in clinical intervention of age-related pathologies, delay the onset and pace of aging, live longer in health, and add many more years of disease-free life to one’s lifespan.