Critical role and involvement of vascular endothelial growth factor and transforming growth factor-β2 in collagen gel contraction induced by retinal pigment epithelial cells

Abstract

To investigate the influence of vascular endothelial growth factor(VEGF) and transforming growth factor (TGF)-β(2) to human retinal pigment epithelium(RPE) cell differentiation, and the mechanism of collagen gel contraction mediated by RPE cells. Experiment study. An in vitro collagen gel contraction assay was performed to evaluate the effect of cultured human RPE in addition of VEGF and TGF-β(2) at indicated time points (24 h, 48 h and 72 h). Three groups were established in the experiment:control group, 50 µg/L VEGF group and 5 µg/L TGF-β(2) group. The effects of both cytokines on the collagen gel contraction were analyzed by the reduced diameter of the collagen gel. And the changes of cell morphology and their transdifferentiation were assessed to estimate the possible connection between RPE transdifferentiation and collagen gel contraction. One-way ANOVA was used in conjunction with SNK-q test to assess statistical significance at different time periods within groups. There were differences on collagen gel contraction rates among VEGF group [(34.7 ± 3.1)%, (44.3 ± 6.0)%, (44.0 ± 7.2)%], TGF-β(2) group [(29.3 ± 3.1)%, (31.7 ± 3.5)%, (29.0 ± 3.6)%] and control group [(20.0 ± 0.5)%, (17.3 ± 3.6)%, (19.1 ± 0.8)%] at 24 h, 48 h and 72 h after cultured (24 h: F = 26.220, P = 0.001; 48 h: F = 26.796, P = 0.001; 72 h: F = 21.522, P = 0.002), and on each time point two two comparison in the three groups (SNK-q test, P < 0.05). There were differences on protein expression level of α-smooth muscle actin (α-SMA) in 50 µg/L VEGF group and 5 µg/L TGF-β(2) group at difference time points, respectively (TGF-β(2) group: F = 1.134, P = 0.000; each time point: SNK-q test, P < 0.05; VEGF group: F = 279.179, P = 0.000; each time point: SNK-q test, P < 0.05). Moreover, TGF-β(2) (5 µg/L) demonstrated stronger and more permanent gel contraction than VEGF (50 µg/L) (6 h: F = 3.646, P = 0.000; 24 h: F = 18.706, P = 0.003; 48 h: F = 124.195, P = 0.000; 72 h: F = 76.811, P = 0.000). RPE cells' form happened fibroblasts sample transformation in both VEGF group and TGF-β(2) group. Both VEGF and TGF-β(2) can induce the collagen gel contraction, partly by means of inducing the expression of α-SMA and RPE contraction, which may thus contribute to the explanations of vitro-retinal diseases.