Apoptosis, necrosis, and proliferation: possible implications in the etiology of keloids

Keloids are collagenous lesions acquired as a result of abnormal wound heating. In this study we have assessed the potential role of proliferation, apoptosis, and necrosis in keloids. Samples were immunolabeled for proliferating cell nuclear antigen or DNA strand breaks or stained with acridine orange. Proliferating cells were observed in the basal layer of the epidermis and fibroblasts in the dermis, the numbers of the latter being increased in comparison with normal skin. No proliferating cells were observed in the central region of the keloid. In normal skin, apoptotic cells were restricted to the basal layer of the epidermis. In keloid samples, numerous apoptotic cells were observed in the epidermis and dermis; the number and distribution of positive cells decreased more distal to the keloid lesion. Apoptotic endothelial cells of a small proportion of blood vessels in the dermis were also observed. Evidence of necrosis was also seen in the dermis. These results suggest that, with maturity, progressive cell degeneration primarily by apoptosis results in clearance of certain cellular populations resulting in the typical keloid lesion. However, the persistence of fibroblast proliferation at the dermal/keloid interface propagates the fibrosis.