The Bald Truth: Altered Cell Divisions Cause Hair Thinning
upstart writes in with an IRC submission:
The bald truth: Altered cell divisions cause hair thinning:
The basis for new hair growth is the proper function of hair follicle stem cells (HFSCs). HFSCs undergo cyclic symmetric and asymmetric cell divisions (SCDs and ACDs). SCDs generate two identical cells that go on to have the same fate, while ACDs generate a differentiating cell and a self-renewing stem cell. The combination ensures that the stem cell population continues to exist, yet how those contribute to the loss of HFSC function due to aging is not yet completely understood.
"For proper tissue function, symmetric and asymmetric cell divisions have to be in balance," says corresponding author of the study Emi Nishimura. "Once stem cells preferentially undergo one of either or, worse yet, deviate from the typical process of either type of cell division, the organ suffers. In this study, we wanted to understand how stem cell division plays into hair grows during aging."
[...] But why does the mode of cell division change so drastically during aging? To answer this question, the researchers focused on hemidesmosomes, a class of protein that connect the cells to the extracellular matrix (ECM; proteins surrounding cells). Cell-ECM have long been known to confer polarity to cells, i.e., that the cells can sense their localization within a given space through the action of specific proteins. The researchers found that during aging both hemidesmosomal and cell polarity proteins become destabilized, resulting in the generation of aberrantly differentiating cells during division of HFSCs. As a result, HFSCs become exhausted and lost (leading to hair thinning and hair loss) over time.
Journal Reference:
Hiroyuki Matsumura, Nan Liu, Daisuke Nanba, et al. Distinct types of stem cell divisions determine organ regeneration and aging in hair follicles, Nature Aging (DOI: 10.1038/s43587-021-00033-7)
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