Knocking down FSTL1 reduces TGF-β2–induced trabecular meshwork fibrosis and ocular hypertension via inhibition of the Smad3 signaling pathway

Background Excessive accumulation of extracellular matrix (ECM) in the trabecular meshwork (TM) increases aqueous humor outflow resistance, leading to elevated intraocular pressure (IOP) and the development of primary open-angle glaucoma (POAG). Transforming growth factor-β2 (TGF-β2) is a well-established profibrotic mediator implicated in TM fibrosis. Despite its recognized role in promoting ECM deposition, the downstream regulatory mechanisms remain incompletely understood. Follistatin-like 1 (FSTL1), a secreted glycoprotein involved in various fibrotic diseases, has recently drawn attention, yet its role in TM fibrosis and IOP regulation in POAG remains unclear.Methods TGF-β2-induced human trabecular meshwork (HTM) cells and a murine model of TGF-β2-induced ocular hypertension were employed. Proteomic analysis, Western blotting, quantitative real-time PCR, and immunofluorescence were used to assess ECM expression and TGF-β2/Smad3 signaling. Loss-of-function approaches were applied to examine the role of FSTL1 in trabecular meshwork fibrosis and intraocular pressure regulation.Results FSTL1 was induced by TGF-β2 and associated with enhanced ECM accumulation and Smad3 activation in HTM cells. Silencing FSTL1 reduced TGF-β2 induced ECM deposition and p-Smad3 accumulation in vitro, and intraocular FSTL1 knockdown mitigated TM fibrosis and lowered TGF-β2-induced ocular hypertension in mice.Conclusion These findings identify FSTL1 as an important regulator of TGF-β2-induced TM fibrosis. FSTL1 contributes to ECM accumulation and IOP elevation with Smad3 signaling under profibrotic conditions. Targeting FSTL1 may represent a potential therapeutic strategy for limiting TM fibrosis and IOP elevation in POAG.