Deep and superficial keloid fibroblasts contribute differentially to tissue phenotype in a novel in vivo model of keloid scar.

BACKGROUND Keloids are thick fibrous scars that are refractory to treatment and unique to humans. The lack of keloid animal models has hampered development of effective therapies. The authors' goal was to develop an animal model of keloids using grafted engineered skin substitutes composed of keloid-derived cells. To demonstrate the model's utility, differences between deep and superficial keloid fibroblasts were investigated. METHODS Engineered skin substitutes were prepared using six combinations of cells: 1, normal keratinocytes and normal fibroblasts; 2, normal keratinocytes and deep keloid fibroblasts; 3, normal keratinocytes and superficial keloid fibroblasts; 4, keloid keratinocytes and normal fibroblasts; 5, keloid keratinocytes and deep keloid fibroblasts; and 6, keloid keratinocytes and superficial keloid fibroblasts. Engineered skin substitutes stably grafted to athymic mice were evaluated for wound area, thickness, and gene expression. RESULTS Deep keloid fibroblasts displayed elevated expression of type 1 collagen alpha 1 (COL1A1), transforming growth factor β-1, periostin, plasminogen activator inhibitor 2, and inhibin beta A compared with superficial keloid fibroblasts and normal fibroblasts. After grafting, engineered skin substitutes in group 5 were significantly thicker than controls and had increased COL1A1 expression. Engineered skin substitutes in group 6 showed significantly increased area. Histologic analysis revealed abnormal collagen organization in engineered skin substitutes containing deep keloid fibroblasts or superficial keloid fibroblasts. CONCLUSIONS Aspects of the phenotypes of engineered skin substitutes prepared with keloid cells are analogous to thickening and spreading of human keloid scars. Therefore, use of keloid engineered skin substitutes is a valuable new tool for the study of keloid scarring.