HYPERPIGMENTATION OF HUMAN SKIN GRAFTED ON TO ATHYMIC NUDE-MICE - IMMUNOHISTOCHEMICAL STUDY

Human skin grafted on to athymic nude mice (BALB/C-nu/nu) spontaneousl y hyperpigments. We wished to identify the morphological and molecular bases for the hyperpigmentation for this phenomenon. We present data on the relationship of healing, regeneration of melanocytes and produc tion of some melanogenic stimuli. Biopsies were taken at preset times post-graft and studied by histological and immunohistochemical methods . DOPA-positive melanocytes first became visible 120 h post-graft and melanin deposition became visible along the basal cell layer 2 weeks p ost-graft and increased in quantity with lime. By immunochemical stain s the quantity of three melanocyte specific enzymes, i.e, tyrosinase, tyrosinase-related protein-1 (TRP-1) and DOPA-chrome tautomerase (TRP- 2), was markedly enhanced 1 week after grafting and persisted until 4 weeks post-graft. alpha-Melanocyte-stimulating hormone and adrenocorti cotrophic hormone were clearly detected in the epidermis soon after gr afting. They were still strongly detected in the epidermis and in the dermis 2-4 weeks post-graft. We conclude that hyperpigmentation in the grafted skin accompanies a marked increase in the quantity of melanog enic enzymes and melanogenic peptides. The neuropeptides might be one of many factors which stimulate melanogenesis.