Effects of hypertrichotic agents on follicular and nonfollicular cells in vitro

Our previous studies revealed that topical minoxidil induced an increased rate of DNA synthesis in both dermal papilla and follicular germinal cells in early anagen and bulbar matrix as well as outer root sheath and perifollicular fibrocytic cells in mid and late anagen follicles in the bald scalp of the stump-tailed macaque. However, the epidermis and dermal fibrocytes showed no response. To determine the specific action of hypertrichotic agents on follicular cells, we examined the effects of two potent hypertrichotic agents, minoxidil and cyclosporin, on the DNA synthesis of cultured cells derived from either follicular cells (dermal papillar, perifollicular fibrocytic and outer root sheath cells) obtained from human and macaque scalps or nonfollicular cells (fibrocytes and epidermal keratinocytes) from human and macaque foreskin, palm and sole regions and the 3T3 cell line. Cultured subconfluent cells from the above follicular and nonfollicular specimens were incubated with either minoxidil (0.01-2 mM) or cyclosporin (0.01-100 mM) in medium (serum-free DMEM) for 48 h, then 3H-thymidine was added for the final 6 h. Minoxidil induced a significant increase in DNA synthesis in all follicular cells in a dose-specific manner (maximum rate at 0.5 mM for dermal papilla and perifollicular fibrocytic cells and 0.1 mM for outer root sheath cells). The perifollicular fibrocytic cells appeared to have a potentiality similar to that of the dermal papilla cells. Nonfollicular cells showed no response to minoxidil; 3T3 cells were rather suppressed. Cyclosporin appeared to have rather suppressive effects on both follicular and nonfollicular cells. These results suggest that minoxidil has a specific affinity to hair follicular cells and induced their cell proliferation. Although cyclosporin is known as a potent hypertrichotic agent, our studies on cultured follicular cells showed no direct proliferative effect. The hypertrichotic mechanism of cyclosporin appeared to be different from that of minoxidil.