Analyses of changes on skin by aging

Background This study aimed to evaluate the histological changes occurring in rat skin with increasing age, starting from the intrauterine period. Methods Thirty‐two healthy female Sprague–Dawley rats were evaluated in four groups: group 1 – intrauterine day 19, group 2 – postpartum day 21, group 3 – postpartum day 60, and group 4 – postpartum month 19. Skin samples from the back, abdomen, head, and upper and lower limbs were obtained from each subject under anesthesia. Tissue specimens were evaluated statistically and morphologically for the thicknesses of the epidermis, dermis, and basement membrane; the number, height, and width of dermal papillae; and the mast cell and pilosebaceous counts per group. The changes in collagen/elastic fibers and glycosaminoglycans were also assessed. Results Epidermal thickness was the highest in the intrauterine group; it decreased in the postpartum period and increased again in the aged group. Basal membrane thickness increased steadily with age. The number, height, and width of dermal papillae and dermal thickness increased up to day 60 after birth although these decreased in the aged group. Mast cell count also reached the maximum in the intrauterine group and gradually decreased with age. Pilosebaceous units of the dermis were fewer in intrauterine specimens; they showed an increase during the postpartum period and a decrease in the aged group. Conclusion Skin specimens obtained from rats showed striking differences between the intrauterine and postpartum groups. Moreover, the postpartum group showed considerable intra‐group differences.