High temperature requirement factor A1 (HTRA1) regulates the activation of latent TGF-β1 in keloid fibroblasts

Scar treatments are considered a major issue in the plastic surgery field. Activation of the transforming growth factor-β (TGF-β)-mediated signaling pathway plays a key role in the scar pathogeneses, and high temperature requirement factor A1 (HTRA1) inhibits TGF-β1 activation in tumor cells. Our study aims to investigate the role of HTRA1 in the pathogenesis of scars. The mRNA levels of HTRA1 was evaluated by real time PCR, HTRA1 protein expression was determined using western blot and immunohistochemistry, and a luciferase assay was applied to measure dynamic changes of TGF-β1 activity. We found that the expression of HTRA1 was significantly elevated in keloid tissues, compared to normal skin, and TGF-β1 mRNA levels slightly increase in the keloid tissue. Furthermore, active TGF-β1 protein levels and Smad2 phosphorylation significantly increased in the keloid tissue. Treatment with the latent TGF-β1 or recombinant human HTRA1 (rhHTRA1), alone or in combination, increased Smad2 phosphorylation levels in keloid fibroblasts and active TGF-β1 contents of associated supernatants. Our results suggest that HTRA1 is involved in the pathogenesis of scars through regulating activation of latent TGF-β1 in keloid fibroblasts, and our study reveals that HTRA1 is a novel target that regulates scar formation.