Abstract
Abstract: :
Purpose: The selective loss of capillary pericytes is the first lesion of diabetic retinopathy. Since retinal capillaries are surrounded by glial cells (Mueller cells), these cells may play an important role in maintaining the viability of capillary pericytes under various stress environments such as diabetes. In this study, we have examined whether the conditioned media of astrocytoma cells can rescue serum starvation induced pericyte death. Methods: Both dog retinal capillary pericytes and human brain astrocytoma cells U118MG are maintained in DMEM media supplemented with 10% FCS. Conditioned media of U118MG were prepared by concentrating the media with 10,000 MW cut membrane after cultured in serum-free DMEM media for 12 hours. Cell viability was expressed with the viable cell number after cultured for 7 days. FGF and PDGF mRNA expression, MAPK assay and quantitation of FGF and PDGF were conducted by RT-PCR, Western blot and ELISA assay, respectively. Results: When cultured in serum-free media, the viable cell number of pericytes was significantly decreased. The addition of concentrated conditioned medium form U118MG rescued this pericyte death by serum starvation with the activation of MAPK. The mixture of two well-known growth factors FGF and PDGF also protected pericytes from serum starvation. However, although the expression of FGF and PDGF mRNAs in U118 MG was detectable, the concentration of these two growth factors in conditioned media of U118MG was extremely low (picomolar range). When considered the general working condition required the nanomolar range of concentration, the protective effect of conditioned media on pericytes from serum starvation cannot be explained with these growth factors produced by U118MG. Conclusion: Astrocytoma cell line, U118MG expresses two growth factors FGF and PDGF. The cells also produce another growth factor(s) that activate MAPK and enhance the viability of capillary pericytes. The evidence also suggests that glial cells may contribute in maintaining pericyte viability by producing various growth factors.
Keywords: 388 diabetic retinopathy • 341 cell death/apoptosis • 560 retinal culture