EXPRESSION OF TRANSFORMING GROWTH FACTOR-BETA-S AND THEIR RECEPTORS BY HUMAN RETINAL GLIAL-CELLS

Purpose. To help test the hypothesis that transforming growth factor b eta (TGF-beta) may serve an autocrine function in the retina, we asked whether human Muller (glial) cells in culture express TGF-beta recept ors, contain transcripts for various isoforms of this cytokine, and re lease TGF-beta s into the medium. Methods. Using the reverse transcrip tase-polymerase chain reaction (RT-PCR) technique with specific primer s for TGF-beta 1, -beta 2 and -beta 3 precursors and for TGF-beta type I and type II receptors, we searched for mRNA transcripts expressed b y cultured human Muller cells. Also, an ELISA assay allowed quantifica tion of the levels of various TGF-beta s in medium exposed to these gl ial cells. Results. Human Muller cells in culture express transcripts for both type I and type II TGF-beta receptors and also for TGF-beta 1 and TGF-beta 2. In conditioned medium, the concentration of TGF-beta 1 in the mature form was below detectable levels, and the total TGF-be ta 1 was relatively low (mean = 252 pg/ml in confluent cultures). In c ontrast, the mean levels of mature (55 pg/ml) and total (2530 pg/ml) T GF-beta 2 were markedly higher. Conclusions. Our observations that cul tured Muller cells contain mRNA coding for the TGF-beta 2 precursor, r elease TGF-beta 2 into the medium and express transcripts for both typ e I and type II TGF-beta receptors are consistent with the idea that t his cytokine serves an autocrine function for these glia in the retina .