Blocking fibrotic signaling in fibroblasts from patients with carpal tunnel syndrome

Fibrosis of the subsynovial connective tissue (SSCT) in carpal tunnel syndrome (CTS) patients is increasingly recognized as an important aspect of CTS pathophysiology. In this study, we evaluated the effect of blocking profibrotic pathways in fibroblasts from the SSCT in CTS patients. Fibroblasts were stimulated with transforming growth factor beta 1 (TGF-beta 1), and then treated either with a specific fibrosis pathway inhibitor targeting TGF-beta receptor type 1 (T beta RI), platelet-derived growth factor receptor (PDGFR), epidermal growth factor receptor (EGFR), or vascular endothelial growth factor receptor (VEGFR). Fibrosis array and quantitative real-time polymerase chain reaction of fibrotic genes were evaluated. Array gene expression analysis revealed significant down-regulation of multiple fibrotic genes after treatment with T beta RI, PDGFR, and VEGFR inhibitors. No array fibrotic genes were significantly down-regulated with EGFR inhibition. Further gene expression analysis of known CTS fibrosis markers collagen type I A2 (Col1), collagen type III A1 (Col3), connective tissue growth factor (CTGF), and SERPINE1 showed significantly down-regulation after T beta RI inhibition. In contrast, VEGFR inhibition significantly down-regulated CTGF and SERPINE1, whereas, PDGFR and EGFR inhibition significantly down-regulated Col3. Taken together the inhibition of T beta RI appears to be the primary mediator of fibrotic gene expression in fibroblasts from CTS patients. TGF-beta/Smad activity was further evaluated, and as expected inhibition of Smad activity was significantly down-regulated after inhibition of T beta RI, but not with PDGFR, VEGFR, or EGFR inhibition. These results indicate that local therapies specifically targeting TGF-beta signaling alone or in combination offer the potential of a novel local antifibrosis therapy for patients with CTS.