Do human dermal adipocytes switch from lipogenesis in anagen to lipophagy and lipolysis during catagen in the human hair cycle

: In murine skin, dermal white adipose tissue (DWAT) undergoes fluctuations in size across the hair cycle, whereas changes in size, function and metabolism of dermal adipocytes (DAs) during the human scalp hair cycle remain unexplored. Transmission electron microscopy results suggest that during anagen-catagen transition, human DAs co-opt the autophagy machinery to undergo lipophagy within their lipid droplets. Whole-mount staining of hair follicles (HFs) and surrounding DWAT for the autophagy marker LC3B confirms the increased presence of LC3B+ lipid droplets adjacent to catagen HFs; moreover, DWAT around catagen HFs engages in greater glycerol release compared to DWAT surrounding anagen HFs. Thus, we hypothesize that human DAs switch from lipogenesis during anagen to lipophagy together with lipolysis during catagen. We propose various experiments to further prove this hypothesis, whose systematic exploration should help to better characterize the functions of human DWAT and its communication with the HF.