| Research Abstract |
We asked whether human Muller (glial) cells in culture express some growth factors (transforming growth factor-beta1, -beta2, -beta3, nerve growth factor, brain-derived neurotrophic factor, neurotropin-3, vascular endothelial growth factor, and hepatocyte growth factor) and their receptors (transforming growth factor type I receptor, type II receptor, trkA,trkB,and trkC). Using the reverse transcriptase-polymerase chain reaction (RT-PCR) technique with specific promers for TGF-beta1, -beta2, -beta3, NGF,BDNF,NT-3, VEGF,HGF,TGF-beta type I,type II receptors, trkA,trkB,and trkC,we searched for mRNA transcripts expressed by cultured human Muller cells. Also, an ELISA assay allowed quantification of the levels of various TGF-betas and VEGF in medium exposed to these glial cells. Human Muller cells in culture express transcripts for TGF-beta1, -beta2, NGF,BDNF,NT-3, VEGF,HGF,TGF-beta type I,type II receptors, trkB and trkC but not express TGF-beta3 and trkA.In conditioned medium, the concentration of TGF-beta1 in the mature from was below detectable levels, and the total TGF-beta1 was relatively low. In contrast, the mean levels of mature and total TGF-beta2 were markedly higher. Advanced glycation end product enhanced the expression of VEGF in these cells. Our observations that cultured Muller cells contain mRNA coding for many growth factors and their receptors, release TGF-beta2 and VEGF into the medium are consistent with the idea that these cytokines serve an autocrine function for these glia in the retina. These growth factors mays a important role in some intraocular proliferative diseases, such as proliferative vitreoretinopathy or proliferative diabetic retinopathy.
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