Secreted protein, acidic and rich in cysteine is crucial for the vascular endothelial growth factor-stimulated fibrotic process in human Tenon’s fibroblasts

Abstract

Background Aberrant post-surgical scarring is responsible for failure of glaucoma filtration surgery (GFS) and is attributed to strong fibrotic process of human Tenon’s fibroblasts (HTFs). Vascular endothelial growth factor (VEGF) and secreted protein, acidic and rich in cysteine (SPARC) contribute to angiogenesis and fibrosis. However, whether SPARC can regulate the VEGF-mediated fibrotic process in HTFs has not been clarified. This study aimed to examine how SPARC and VEGF crosstalk to regulate the expression of Collagen-I and matrix metalloproteinase 9 (MMP9) as well as the ERK signalling in HTFs. Methods Human Tenon's capsule tissues were cultured for preparation of HTFs, which were characterized by immunofluorescence. The effects of VEGF treatment on SPARC, Collagen-I and MMP9 expression and ERK phosphorylation were determined by Western blot, quantitative RT-PCR and immunofluorescence. The proliferation and wound healing induced by VEGF were examined in HTFs and SPARC-silenced HTFs. Results Following successful passages, immunofluorescent assays indicated that HTFs at passages 3-9 displayed unique characters of fibroblasts with Vimentin, but not keratin, expression. Treatment with VEGF significantly up-regulated SPARC, Collagen-I and MMP9 expression and ERK phosphorylation, and promoted the proliferation and wound healing of HTFs. The stimulatory effects of VEGF were significantly mitigated by SPARC silencing in HTFs. Conclusions Our data provided novel evidence that SPARC was crucial for the VEGF-stimulated fibrotic process in HTFs and may be a novel target for anti-fibrotic therapies post GFS.