HUMAN SCALP HAIR FOLLICLE DEVELOPMENT FROM BIRTH TO ADULTHOOD - STATISTICAL STUDY WITH SPECIAL REGARD TO PUTATIVE STEM-CELLS IN THE BULGE AND PROLIFERATING CELLS IN THE MATRIX

The depths of hair follicle compartments, and in particular of the bul ge, the putative site of hair follicle stem cells, have not yet been d etermined in human scalp skin from infants, children or adolescents. T his information is necessary in order to use the scalp safely as a don or site for skin grafts. We therefore investigated the development of the infundibulum, the bulge, Adamson's fringe, the B-fringe and the ma trix by measuring the depths of these five follicular compartments in parietal scalp biopsy specimens from 100 patients ranging in age from 2 weeks to 21 years. The thickness of the epidermis and the dermis wer e also assessed. The correlations of these measurements with age were determined by regression analysis. The regression equation for the bul ge was found to be b (mu m) = 683.3 + 30.8y (r = 0.73; SEM = 145.5) wh ere y is the age in gears, and for the matrix it was m (mu m) = 1616.2 + 90.4y (r = 0.76; SEM = 406.5); P < 0.0001 for the null hypothesis. The growth of the inferior portion below the bulge was not parallel bu t proportional to that of the superior portion. The relative position of the bulge in the dermis was stable, whereas the inferior portion mo ved progressively more deeply into the subcutis. These findings provid e evidence for the postulated biologically advantageous localization o f the bulge, and thus is a further argument in favour of the bulge as the site of follicular stem cells.