Reduction, proliferation, and differentiation defects of stem cells over time: a consequence of selective accumulation of old centrioles in the stem cells?

Abstract

All molecules, structures, cells in organisms are subjected to destruction during the process of vital activities. In the organisms of most multicellular animals and humans, the regeneration process always takes place: destruction of old cells and their replacement with the new. The replacement of cells happens even if the cells are in perfect condition. The sooner the organism destroys the cells that emerged a certain time ago and replaces them with the new (i.e., the higher is the regeneration tempo), the younger the organism is. Stem cells are progenitor cells of the substituting young cells. Asymmetric division of a mother stem cell gives rise to one, analogous to the mother, daughter cell, and to a second daughter cell that takes the path of further differentiation. Despite such asymmetric divisions, the pool of stem cells diminishes in its quantity over time. Moreover, intervals between stem cell divisions increase. The combination of these two processes causes the decline of regeneration tempo and aging of the organism. During asymmetric stem cell divisions daughter cells, with preserved potency of the stem cell, selectively conserve mother (old) centrioles. In contrast with molecules of nuclear DNA, reparations do not take place in centrioles. Hypothetically, old centrioles are more subjected to destruction than other structures of a cell-which makes centrioles potentially the main structure of aging.