Silibinin inhibits myofibroblast transdifferentiation in human tenon fibroblasts and reduces fibrosis in a rabbit trabeculectomy model

Purpose: To investigate the effect of silibinin in myofibroblast transdifferentiation and in animal trabeculectomy models. Methods: The effect of silibinin on the expression of -smooth muscle actin (-SMA) and vimentin in response to transforming growth factor-1 (TGF-1) was determined in human tenon fibroblasts (HTFs). Cell migration and collagen contraction arrays were used to demonstrate the functionality of silibinin-modulated HTFs. ELISA analysis was used to determine the effect of silibinin on the release of type 1 collagen and connective tissue growth factor (CTGF). The effect of silibinin on the activation of the TGF- receptor-related pathway was evaluated by Western blotting. A rabbit model of trabeculectomy was established to assess the effect of silibinin in vivo. Results: TGF-1 elevated the expression of -SMA and vimentin in HTFs; this elevation was inhibited by silibinin. TGF-1 increased cell migration and collagen contraction of HTFs, which were also suppressed by silibinin. The production of both CTGF and type 1 collagen in TGF-1-treated HTFs was inhibited by silibinin. The effects of silibinin on TGF-1-stimulated HTFs were mediated via the down-regulation of TGF- receptor-related SMAD signalling pathways. In the rabbit model of trabeculectomy, silibinin increased the period of decreasing intraocular pressure after trabeculectomy and reduced the production of collagen and -SMA at the site of blebs in vivo. Conclusion: Silibinin inhibited the TGF- receptor-related signalling pathway in TGF--treated HTFs and several of the downstream events associated with myofibroblast transdifferentiation. Silibinin also improved the outcome of trabeculectomies by reducing the fibrotic response in the bleb tissue in vivo.