Further immunocytochemical characterization of cultured hair apparatus cells

In immunocytochemical studies of cultured hair apparatus cells we employed anti-hair keratin monoclonal antibodies (HKN-2, HKN-4, HKN-5, HKN-6 and HKN-7) and compared the results with electron microscopic studies. On day 1, the cultured cells positively stained with HKN-2 (52%), HKN-4 (50%), HKN-5 (43%), HKN-6 (33%), or HKN-7 (37%). On day 3, more than 88% of the cells showed no reaction to any antibody. On day 6, most of the cells stained with all of the antibodies: HKN-2 (96%), HKN-4 (92%), HKN-5 (80%), HKN-6 (72%) and HKN-7 (74%). These reactivities were maintained until day 13. Electron microscopic studies revealed that, on day 1, half of the observed cells were immature and 47% of them were already differentiated. Most (88%) of the cells showed immature features and the percentage of differentiated cells had decreased by day 3. The differentiated cells (87%) reappeared by day 6, and degenerated cells (63%) increased by day 13. These immunocytochemical results were consistent with those of simultaneous electron microscopic studies, demonstrating that immature cells proliferated and differentiated into subpopulations of each hair apparatus layer type, including the outer root sheath cells, in this culture system.