Investigation of germinative cells in generating and renewed anagen hair apparatus in mice using anti-bromodeoxyuridine monoclonal antibody.

To elucidate the cell kinetics in generating and renewed anagen hair apparatus in mice, S-phase cells in dorsal skin of new-born and 14 to 25-day-old mice were labeled with bromodeoxyuridine (BrdU) and stained immunohistochemically using anti-BrdU monoclonal antibody. In primary hair germ, lower and outer cells were positively stained. In hair peg, the positive cells were divided into upper and lower portions. In bulbous hair peg, the lower positive cells gathered at the suprapapillary area, whereas the upper positive cells were located in the outer part of the hair apparatus. The latter positive cells were further divided in the middle and upper parts of the epithelial cord. The upper cells were going to form a sebaceous gland. From the suprapapillary group of germinative cells, hair cortex through the innermost cell layer of the outer root sheath were considered to be produced. The positive cells of the outer middle group may be important for elongation of hair apparatus and produce outer root sheath cells. At the end of anagen phase, first the suprapapillary cells became negative and then the outer root sheath cells became negative. BrdU-positive cells reappeared at the bottom of telogen hair apparatus and formed a secondary hair germ. Then, a similar cell kinetics was repeated in the renewed anagen hair apparatus. The germinative cells were separated into a few groups during the generation and cyclic changes of hair apparatus. Each cell group formed the individual part of the hair apparatus in a coordinate fashion, resulting in dynamic changes of the hair apparatus.