Identification of transforming growth factor-beta expressed in cultured human retinal pigment epithelial cells.

PURPOSE This study examined whether retinal pigment epithelial (RPE) cells have the capacity to express transforming growth factor-beta (TGF-beta). Also examined were TGF-beta isoform genes expressed in the RPE cells. METHODS Complementary DNA (cDNA) was generated from polyA+ RNA extracted from human RPE cells in culture, and polymerase chain reaction (PCR) using degenerate and specific primers of the known TGF-beta isoforms was carried out by using the cDNAs as templates. Sequencing and Southern blot analysis of the PCR products, and Northern blot analysis were performed to identify which isoforms are expressed in RPE cells. RESULTS PCR using degenerate primers showed that most of the amplified sequences were derived from TGF-beta 2, although TGF-beta 1 expression was shown by using specific primers. Northern blot analyses confirmed not only the expression of the TGF-beta gene, but also suggested that alternative splicing of TGF-beta mRNA in the RPE cells occurred. CONCLUSION Cultured human RPE cells expressed TGF-beta 1 and beta 2 genes, whereas gene expression of TGF-beta 3 was not confirmed. Our data suggest that RPE cell are intraocular origin of TGF-beta production.