Trabecular cells express the TGF-beta 2 gene and secrete the cytokine

We investigated whether trabecular cells contain TGF-beta 2 mRNA and whether they synthesize this cytokine. By using a primer pair for TGF-beta 2 and the highly specific and sensitive techniques of reverse transcriptase-polymerase chain reaction, a single amplified sequence was obtained from cultured trabecular cells and tissue samples of trabecular meshwork, corneal epithelium, iris and ciliary body ex vivo from fresh porcine eyes. Regression analysis with standard DNA size markers indicated that the products were of the anticipated size of 310 base pairs. Southern hybridization further confirmed that all of the products were specific for TGF-beta 2. Enzyme-linked immunosorbent assay (ELISA) with a specific antibody against TGF-beta 2 revealed that this cytokine was secreted by cultured trabecular cells in the conditioned medium. The TGF-beta 2 produced by trabecular cells was in a latent form, and no intrinsically active protein was detected. The results suggest that TGF-beta 2 has an autocrine and/or paracrine action in the trabecular meshwork system, and that trabecular cells could contribute to the presence of TGF-beta 2 in their microenvironment as well as in aqueous humor. It is hypothesized that abnormal changes in the production of TGF-beta s by trabecular cells and/or in the activation of these growth modulators contribute to the excess accumulation of extracellular matrix components in the aqueous outflow system as observed in aging and glaucomatous eyes.