Anticancer drugs induce apoptosis in mouse hair follicles

Apoptosis represents an important mode of cell death induced by chemotherapeutic drugs. It is plausible that apoptosis may also play an important role in alopecia caused by anticancer drugs. C57 BL/6 mice were induced to enter into anagen by hair shaft depilation and a single intraperitoneal injection of cyclophosphamide (150 mg/kg) was given. Skin specimens were taken from the backs of mice at day 9, 10, 11, 12 and 13 postdepilation (p.d.). Specimens were stained with TUNEL method, and DNA was isolated from the plucked hair follicles and was electrophoresed. Many TUNEL-positive cells were observed in hair bulbs in the cyclophosphamide group at days 10-13. At day 13 p.d., most follicles were damaged and extensive hair loss was observed. Fragmented DNA, but not so distinct, were observed in a DNA ladder pattern corresponding to the in situ results. This study suggests that anticancer drugs can induce apoptosis-related damage to the hair follicles in mice. Control mice when treated with saline also showed apoptosis when they spontaneously entered into catagen, but they never showed hair loss. Consequently, hair loss induced by anticancer drugs may result from a wave of induced apoptotic death.