Expression of transforming growth factor beta 1, 2, and 3 proteins in keloids

Keloids represent a pathological response to cutaneous injury, creating disfiguring scars with no known satisfactory treatment. They are characterized by an excessive accumulation of extracellular matrix, especially collagen. Transforming growth factor beta (TGF-beta) has been implicated in the pathogenesis of keloids. The three TGF-beta isoforms identified in mammals (TGF-beta1, -beta2, and -beta3), are thought to have different biological activities in wound healing. TGF-beta1 and TGF-beta2 are believed to promote fibrosis and scar formation, whereas TGF-beta3 has been shown to be either scar inducing or reducing, depending on the study. The aim of this study was to characterize expression of TGF-beta isoforms in keloids at the protein level using Western blot analysis. The authors found that TGF-beta1 and -beta2 proteins were at higher levels in keloid fibroblast cultures compared with normal human dermal fibroblast cultures. In contrast, the expression of TGF-beta3 protein was comparable in both the normal (N = 3) and keloid (N = 3) cell lines. These findings, demonstrating increased TGF-beta1 and -beta2 protein expression in keloids relative to normal human dermal fibroblasts further support the roles of TGF-beta1 and -beta2 as fibrosis-inducing cytokines.