Apoptosis of hair follicle cells during doxorubicin-induced alopecia in rats

Alopecia is a common side effect of cancer chemotherapy, and to date, little progress has been made in alopecia prevention or treatment. The present studies were undertaken to topographically localize the site of injury in the hair follicle after doxorubicin (DXR) administration and to investigate the mechanism of DXR-induced alopecia. Tissue samples of head and proximal neck skin obtained from newborn rats treated with DXR were histologically examined by light and electron microscopy and stained by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method. Light microscopy revealed pyknotic cells in the matrix and in the upper bulb and a decrease in the number of mitotic cells. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick-end labeling analysis evidenced cells with nuclear staining indicative of apoptosis, as confirmed by ultrastructural analysis. Kinetics studies indicated that even a single DXR treatment induced apoptosis and a decrease in mitotically active cells. Our data show that DXR treatment induces injury in a cell subset localized in the hair matrix. The successful prevention of drug-induced alopecia in patients may depend on the selective protection of these cells of the hair follicle.