Histological and immunohistochemical studies of excisional wounds in the rat with special reference to the involvement of the hair follicles in the wound healing process

Abstract

It is well known amongst surgeons that scalp skin heals better than non-hairy skin and is used for repeated split thickness skin graft harvesting in patients with severe bums. In biology literature it is well established that the skin of hairy animals heals relatively quickly. The contribution of the epithelial components of the hair follicle to skin wound healing has been studied to some extent however little or no attention has been given to the possible contribution of the hair follicle dermal components especially in view of the morphological similarities between dermal sheath cells and wound fibroblasts and myofibroblasts. Moreover little is known about any possible differences in the wound healing process between anagen and telogen hairy skin. The PVG rat model was used to look for any differences in wound healing between anagen and telogen skin and to study the contribution of the dermal components of the hair follicle to skin wound healing. The reparative process of the basement membrane of the hair follicle and the wound epithelium were also studied. Excisional punch biopsy wounds were analysed macroscopically and microscopically. The latter involved Weigerts' Haematoxylin staiiming of paraffin sections and alpha smooth muscle actin (a SMA), collagen IV and laminin indirect immunoflourescenee staining. Light microscopy, UV light microscopy and confocal microscopy were used. Anagen skin was found to have a statistically significant smaller wound diameter than telogen skin at 7 and 8 days post wounding. Epithelial basement membrane was observed to start regenerating in the central part of the wound epithelium as well as in the periphery. The dermal sheath of the hair follicles in the wound merged with the wound fibroblast network, a SMA staining showed concentric spiral patterns of marking around anagen follicles in the wound highly suggestive of dermal sheath cell migration into the wound. The implications of these findings with regards to improvements in living skin equivalents and to further the scope for the use of the scalp as a split thickness skin donor site are discussed.