Proliferating activity of dermal fibroblasts in keloids and hypertrophic scars

Monoclonal antibodies were used to demonstrate proliferating cell nuclear antigen (PCNA) and Ki-67 antigen of dermal fibroblasts in formalin-fixed, paraffin-embedded tissue sections of keloids, hypertrophic scars and normal skin. PCNA-stained fibroblasts were more pronounced than Ki-67, which showed only scanty Ki-67-positive fibroblasts. The mean density of dermal fibroblasts was significantly higher in keloids and hypertrophic scars than in normal skin (p < 0.01). The proliferating activity of fibroblasts detected by PCNA was significantly higher in keloids than in hypertrophic scars or normal skin (p < 0.01). The mean densities and the proliferating activities were apparently not correlated with the age of the patient. This indicates that keloids, with higher density and proliferating activity of dermal fibroblasts, continue to increase their volume and invade the surrounding tissue, while hypertrophic scars, with higher density and lower proliferating activity, show a tendency towards spontaneous regression.