Defining the role of cell mechanics in regulating hair follicle stem cells across homeostasis and aging

About This Grant

Project Summary: The overarching goal of this application is to investigate cell mechanics-mediated regulation of hair follicle stem cells (HFSCs) during homeostasis and aging. We propose to study microRNA-205- mediated regulation of extracellular matrix (ECM) and actin cytoskeleton for HFSC quiescence and activation and leverage the ability of microRNA-205 (miR-205) to stimulate HFSC activation to enhance HFSC aging. MicroRNA (miRNA) is a class of small noncoding, regulatory RNAs that play important roles in mammalian development, stem cells, diseases and aging. In our preliminary studies, we have determined mechanical properties of HFSCs during homeostasis and aging. We have revealed that bulge HFSCs reside in a stiff microenvironment with high actomyosin contraction forces. In contrast, hair germ progenitors are relatively soft and undergo periodic enlargement and contraction. Notably, induction of miR-205, one of the most highly expressed miRNAs in HFSCs, downregulates many bona fide targets, which are enriched in the function of ECM, actomyosin cytoskeleton and mechanosensing. And this leads to rapid activation of HFSC cell division and promotes hair regeneration in both young and aged mice. Mechanistically, we have identified Piezo1 as a novel target of miR-205, which functions downstream of miR-205 and translates mechanical cues into a gene expression program to reinforce the mechanical properties and maintain cellular states of quiescent HFSCs. To examine the role of PIEZO1-mediated calcium influx in HFSCs, we have further developed a high-resolution intravital imaging system to accurately record calcium influx in HFSCs over an extended period of time during quiescence and activation. This allows us to quantify cumulative calcium levels and further identify transcription factors, NFATC1 and JUN (AP1), which function downstream of PIEZO1-mediated calcium influx to promote the expression of the ECM and actin cytoskeleton genes. Based on these exciting findings and promising preliminary data, we propose to further elucidate the mechanism of miR-205-mediated HFSC activation and aging through the regulation of ECM and actomyosin contraction forces (Aim 1), determine the regulation of PIEZO1-mediated mechanosensing by miR-205 (Aim 2), and leverage miR-205-induced HFSC activation to improve HFSC functions and hair growth during aging (Aim 3). Together, this application will provide new insights into the mechanisms orchestrating the mechanical properties and stem cell functions of HFSCs. By harnessing the powerful combination of live imaging, cell biology, mouse genetics, and single-cell genomics, we will establish a new paradigm for studying tissue architecture, cell mechanics and underlying mechanisms. These results will lay the foundation for leveraging noncoding, regulatory RNAs to enhance HFSC functions during aging.