Mechanical compression upregulates MMP9 through SMAD3 but not SMAD2 modulation in hypertrophic scar fibroblasts.

PURPOSE: Activation of transforming growth factor-ß (TGF-ß) signaling and matrix metalloproteinases are involved in hypertrophic scar (HS) formation. Compression therapy is known to be an effective approach for the treatment of hypertrophic scarring; however, the underlying molecular mechanisms remain poorly understood. We investigated the relationship between TGF-ß signaling activation and matrix metalloproteinases in HS fibroblasts during mechanical compressive stress. MATERIALS AND METHODS: Two groups of skin tissue from HS and the nearby normal tissue were obtained from surgical patients and analyzed. Primary fibroblasts from the HS tissue and normal fibroblasts were isolated. Pressure therapy was recapitulated in an in vitro three-dimensional culture model, using mechanical stress produced with the Flexcell FX-4000C Compression Plus System. Quantitative real-time PCR (qPCR) was used to analyze the gene expression profiles in skin tissue and cultured primary cells exposed to compressive stress. Knockdown of SMAD2 and SMAD3 was performed using their specific siRNA in HS and normal fibroblasts subjected to compressive stress, and gene expression was examined by qPCR and Western blot. RESULTS: There was a significant upregulation of the mRNA expression of matrix metalloproteinase-2 (MMP2) and MMP9 in primary HS fibroblasts in response to mechanical stress. In contrast, the mRNA levels of collagen I and collagen III were downregulated in primary HS fibroblasts compared with those in the control cells. SiRNA-mediated knockdown of SMAD3 in the primary fibroblasts exposed to mechanical stress resulted in a decrease in the expression of MMP9 compared to control cells. CONCLUSION: These results demonstrate that compressive stress upregulates MMP9 by SMAD3 but not by SMAD2.

Pressure therapy upregulates matrix metalloproteinase expression and downregulates collagen expression in hypertrophic scar tissue.

BACKGROUND: Pressure therapy improves hypertrophic scar healing, but the mechanisms for this process are not well understood. We sought to investigate the differential expression of matrix metalloproteinases (Mmps) and collagen in posttraumatic hypertrophic scar tissue with mechanical pressure and delineate the molecular mechanisms of pressure therapy for hypertrophic scars. METHODS: Fibroblast lines of normal skin and scar tissue were established and a mechanical pressure system was devised to simulate pressure therapy. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting assays were used to compare differences in the mRNA and protein expression of Mmps and collagen in scar fibroblasts before and after pressure therapy. RESULTS: The expression differed between the hypertrophic scar cell line and the normal cell line. RT-PCR assays showed that Collagen I, highly expressed in the hypertrophic scar cell line, decreased significantly after pressure therapy. Mmp2, Mmp9, and Mmp12 expression in the hypertrophic scar tissue increased significantly after pressure therapy (P < 0.05). Western blotting assays further revealed that Mmp9 and Mmp12 expression increased significantly in the hypertrophic scar tissue after pressure therapy (P < 0.05) but not Mmp2 expression (P > 0.05). CONCLUSION: Mechanical pressure induces degradation of Collagen I in hypertrophic scar tissue by affecting the expression of Mmp9 and Mmp12.