A Niche Above: A Novel Modality of Stem Cell Regulation in Mammalian Skin Epidermis

The study demonstrated that contractility in differentiating keratinocytes in the upper layers of the epidermis regulated the replication and differentiation of stem/progenitor keratinocytes in the basal layer. This finding expanded the understanding of the stem cell niche in skin, highlighting actomyosin contractility as a key component. Using transgenic mouse models, the researchers showed that increased contractility in differentiating keratinocytes led to increased proliferation in basal keratinocytes and altered lineage selection, diverting cells away from the hair follicle lineage. These effects were reversible with pharmacological inhibitors of non-muscle myosin, suggesting that mechanical forces from the upper layers influence stem cell behavior in the basal layer. This research provided significant insights into the regulation of stem cells in the epidermis and raised new questions about the specific mechanisms involved.