In aging societies, it is crucial to understand the mechanisms of physiological aging and the basis for aging-associated diseases. Stem cell systems play fundamental roles in the homeostatic maintenance of many tissues and organs. I did my dermatology residency at Kyoto University Hospital and earned my Ph.D. at Kyoto University, studying melanocyte (pigment cell) development. We subsequently identified melanocyte stem cells as reservoirs for melanocytes in skin and hair follicles (1), and then revealed that aging-associated depletion of the population results in graying hair (2). The study clearly indicated that the aging of stem cells is a key to understanding tissue and organ aging.

Since establishing my own research team as a Professor at Kanazawa University in 2006 and then at TMDU in 2009, we started working on the niche microenvironment of stem cells and have revealed that hair follicle stem cells function as “niche cells” for melanocyte stem cells (3). We also have found the existence of a “stemness checkpoint”, which determines the fate of somatic stem cells, namely whether stem cells stay in an immature state as stem cells or commit to differentiation, during aging and under genomic stress (4).

More recently, we have been focusing on the in vivo cellular dynamics and exact changes that occur in somatic stem cells during aging and the eventual fate of those stem cells in tissues and organs. Our approach has revealed the existence of a “stem cell-centric aging program” that governs tissue aging characterized by miniaturization of hair follicle, the mini-organ to grow hair and hair loss (senescent alopecia) (5). This helps explain why and how organs in our bodies become smaller (miniaturize) and/or thinner, with associated functional decline, due to aging. We are devising new strategies for tissue regeneration and rejuvenation by focusing on somatic stem cells. We welcome international collaboration to realize the therapeutic potential in this area.