Cultured human trabecular meshwork cells express functional growth factor receptors

Purpose; Growth factors may be involved in maintaining the microenviorment of the trabecular meshwork (TM) since they are present in aqueous humor and are synthesized by human trabecular meshwork cells (HTM). However, the role growth factor receptors play in the normal function of the TM has not be extensively studied. The purpose of this study was to determine which growth factor receptors are expressed by cultured HTM cells and determine if the receptors are functional. Methods: Growth factor receptor mRNA expression was examined by total cellular RNA isolation, RT-PCR, and agarose gel electrophoresis using well characterized HTM cell lines from 6 day, 6 month, 2 year, 18 year, 54 year and 80 year old donors. PCR primers for specific growth factor receptors were designed using Oligo 4.0 (National Biosciences Inc., Plymouth, MN.). The functionality of expressed receptors was studied by (a) cell proliferation assays using growth factors at 5-10 ng/ml concentrations and by (b) the cytosensor microphysiometer which measures extracellular acidification in response to ligand. Results; We detected mRNA's for the following growth factor receptors: HGFR, KGFR, EGFR, FCFR-l(flg), TGFβ-RI, TGFβ -RII, and TGFβ -Rill. Cell proliferation in low serum medium was stimulated by HGF (5 ng/ml), EGF (10 ng/ml), FGF-1, FGF-2, and TGF-a but not by any of the TGF-β isoforms (β1-β3) nor by KGF. Positive extracellular acidification data correlated with positive cellular proliferation data with the exception of FGF-2. Conclusion; These results indicate that cultured human trabecular meshwork cells express functional growth factor receptors which may be involved in maintaining the normal microenvironment of the trabecular meshwork.