EFFECTS OF TGF-BETA2, FOLLISTATIN AND ACTIVIN A ON EXTRACELLULAR MATRIX IN NORMAL HUMAN TRABECULAR MESHWORK CELLS AND TISSUES.

Purpose: Primary open angle glaucoma (POAG) is characterized as a group of eye diseases resulting in optic nerve head damage and irreversible blindness. A major risk factor for developing POAG is increased intraocular pressure (IOP) leading to decreased outflow of aqueous humor (AH) through the trabecular meshwork (TM). Transforming growth factor-beta2 (TGF-β2) is increased in the AH of glaucoma patients, and causes increased extracellular matrix (ECM) protein synthesis in the TM. Bone morphogenetic protein-4 (BMP-4) has been shown to inhibit TGF-β2 actions. Follistatin (FST) is an antagonist of BMP-4 and is elevated in the glaucomatous TM. Elevated levels of FST in the TM may block BMP-4 ability to attenuate TGF-β2 induction of ECM proteins. FST may also have a direct role in regulating ECM protein expression in human TM (HTM) cells. HTM cells also express Activin A (Act A). The purpose of this study was to assess the role of FST and Act A in HTM cells as related to TGF-β2/BMP-4 signaling. Understanding these interactions may provide possible new therapeutic targets for the treatment of glaucoma. Methods: Normal HTM cell lines were cultured and treated with TGF-β2 (5ng/ml), FST-315, FST-288, or Act A (each at 50ng/ml) alone and/or simultaneously for 24 and 48 hrs. Western blot analysis was used to evaluate the effects of FST-315/288, Act A, and TGF-β2 on ECM protein synthesis including fibronectin (FN), PAI-1, and collagen1A. Results: TGF-β2 induced expression of PAI-1 and FN.. ACT-A mildly induced PAI-1 and FN proteins as compared to TGF-β2. TGF-β2 and Act A treatment appeared to have a synergistic effect on the expression of PAI-1 and FN protein as compared to individual treatment (Tx) of TGF-β2 or Act A. FST 288 does not seem to change the Act A + TGF-β2 synergism. FST 315 inhibits the synergism of Act A + TGF-β2 showing a decrease in PAI-1 and FN protein. Conclusions: FST-315 decreased the induction of ECM proteins by TGF-β2 and Act-A. FST-288 increased induction of ECM proteins in cells treated with TGF-β2 and Act A. FST-288 treatment for 24 hours induced increased ECM proteins PAI-1 and FN, but there was no induction at 48 hours. FST-315 treatment for 24 hours slightly induced ECM PAI-1 and FN, but there was no induction at 48 hours. Act A treatment for 24 and 48 hours increased induction of PAI-1 or FN. These results further our knowledge of the potential role of BMP antagonists in the human TM and their potential roles in the pathogenesis of glaucoma.