RESUMO
PURPOSE: Müller cells are dedifferentiated after retinal injuries and are transformed into nestin-positive progenitor cells that play crucial roles in remodeling. The purpose of this study was to determine the changes in the expression of nestin, CD44 (a receptor of hyaluronan), vascular endothelial growth factor (VEGF), and glutamine sythetase in cultured Müller cells after dedifferentiation by basic fibroblast growth factor (bFGF) and insulin. METHODS: Cells from a rat retinal Müller cell line (TR-MUL5) and from primary rat retinal Müller cells were grown in culture. The cells were incubated in various concentrations of bFGF (1.0, 10, 100 ng/mL) with or without insulin (5 µM) for 48 h. Changes in the expression of nestin, CD44, VEGF, and glutamine synthetase were determined by immunoblot and immunohistochemistry. RESULTS: Exposure of TR-MUL5 cells to 10 ng/mL of bFGF led to the maximum increase in nestin by 1.5-fold, whereas the exposure had no effects on the expression of CD44. Addition of insulin (5 µM) to the bFGF significantly increased the CD44 level in TR-MUL5 cells by 1.4-fold. Immunohistochemistry showed that the combined treatments also upregulated the expression of nestin and CD44 in primary retinal Müller cells. Immunoblot analyses showed that exposure to bFGF and insulin caused significant increases of nestin (4.9-fold), CD44 (3.4-fold), and VEGF (1.44-fold) and decreases in glutamine synthetase (0.7-fold). CONCLUSIONS: The inflammation and angiogenesis that develop after retinal injuries may be due to an upregulation of CD44 and VEGF by the dedifferentiated Müller cells.
