SHORT COMMUNICATION : Expression of transforming growth factor-ßs and their receptors by human retinal glial cells

Abstract

PURPOSE. To help test the hypothesis that transforming growth factor beta (TGF-ß) may serve an autocrine function in the retina, we asked whether human Müller (glial) cells in culture express TGF-ß receptors, contain transcripts for various isoforms of this cytokine, and release TGF-ßs into the medium. METHODS. Using the reverse transcriptase-polymerase chain reaction (RT-PCR) technique with specific primers for TGF-ß1, -ß2 and -ß3 precursors and for TGF-ß type I and type II receptors, we searched for mRNA transcripts expressed by cultured human Müller cells. Also, an ELISA assay allowed quantification of the levels of various TGF-ßs in medium exposed to these glial cells. RESULTS. Human Müller cells in culture express transcripts for both type I and type II TGF-ß receptors and also for TGF-ß1 and TGF-ß2. In conditioned medium, the concentration of TGF-ß1 in the mature form was below detectable levels, and the total TGF-ß1 was relatively low (mean = 252 pg/ml in confluent cultures). In contrast, the mean levels of mature (55 pg/ml) and total (2530 pg/ml) TGF-ß2 were markedly higher. CONCLUSIONS. Our observations that cultured Müller cells contain mRNA coding for the TGF-ß2 precursor, release TGF-ß2 into the medium and express transcripts for both type I and type II TGF-ß receptors are consistent with the idea that this cytokine serves an autocrine function for these glia in the retina.