Plucking during telogen induces apoptosis in the lower part of hair follicles

Highly synchronized anagen development is achieved by depilation, which contrasts with spontaneous anagen development. The precise mechanism responsible for plucking-induced synchronization has not been explained. Plucking appears to mechanically injure or wound the follicle. We hypothesized that the injured hair follicle cells are removed by apoptosis, with an associated induction of synchronized anagen development. Female C57 BL/6 mice in which all the hair follicles of the back skin were in telogen were induced to enter anagen by depilation. Skin specimens from the back at 0 to 72 h after plucking were examined, and TUNEL staining and electrophoresis of isolated DNA were applied to substantiate the presence of apoptosis. Simultaneously, cell proliferation was also examined by bromodeoxyuridine (BrdU) incorporation. All methods of analysis revealed that plucking induced apoptosis of hair follicle cells in the dermal remnant, and there was a subsequent associated proliferative response that resulted in a highly synchronized anagen phase. From 12 to 36 h after plucking, hair follicle cells with weakly BrdU-positive nuclei were detected around the holes in the lower part of the follicle, which were induced by plucking. At 48 and 72 h, many cells with BrdU-positive nuclei were seen in the entire follicle, mainly in the bulb, as well as in the epidermis. Cell proliferation and apoptosis appeared to occur simultaneously after plucking. These findings mirror the events noted during the development of other organs in which the coordination of cell proliferation and apoptosis is essential for orderly restructuring events.