Cell Proliferation Kinetics in the Human Hair Root

• Published in: Journal of investigative dermatology Vol. 74; no. 1; pp. 43 - 46
• Main Authors: Weinstein, Gerald D., Mooney, Kathryne Mason
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-01-1980
• Subjects: Autoradiography; Cell Division; Hair - cytology; Humans; Mitotic Index
• ISSN: 0022-202X; 1523-1747
• DOI: 10.1111/1523-1747.ep12514601

The kinetics of cell proliferation in the matrix cells of human scalp hair were determined in vivo. Autoradiographic analysis was employed on biopsy specimens taken at specific time intervals after intradermal injection of tritiated thymidine (3H-TdR) into the scalps of volunteer subjects. The durations of the S and G2 phases (Ts and Tg2) were 11.1 and 3.6hr respectively, obtained from the composite percent labeled mitosis curve. The labeling index of the hair matrix cells was 28.6% ± 2.2%. The durations of mitosis and of the total cell cycle (Tm and Tgc) were calculated to be 0.8hr and 38.8hr respectively. The growth fraction of hair root germinative cells was estimated as 75–100% on the basis of “continuous” 3H-TdR exposure over the duration of the cell cycle.
It is noted that the kinetics of human hair root cells are quite similar to the kinetics of psoriatic epidermal cells, suggesting that both tissues are approaching the maximum proliferative rate of keratinogenic epithelial cells.