Effect of growth factors on the activation of human Tenon's capsule fibroblasts

Purpose. To investigate stimulatory effects of PDGF-AA, PDGF-AB, PDGF-BB, bFGF, IL-1beta, TGF-beta1 and TGF-beta2 on the proliferation and myofibroblast transformation of cultured human Tenon's capsule fibroblasts and to characterize expression of PDGF- and TGF-beta-receptors in these cells. Methods. To determine cell proliferation, cell number of 2nd passage cultured human Tenon's capsule fibroblasts was measured before and after addition of growth factors using a computer-based cell counter system. Immunoblotting was used to detect and quantitate alpha-smooth-muscle actin (alpha-SMA) expression. Expression of PDGF- and TGF-beta-receptor mRNA was detected by RT-PCR, expression of the corresponding protein was demonstrated using Western blot. Results. A significant increase in proliferation (p less than or equal to 0.05) was detected after exogenous stimulation with PDGF-AA (10 ng/ml and 100 ng/ml), PDGF-AB (10 ng/ml and 100 ng/ml), PDGF-BB (10 ng/ml and 100 ng/ml), bFGF (100 ng/ml), IL-1beta (1 ng/ml and 10 ng/ml), TGF-beta1 (0.5 ng/ml) and TGF-beta2 (0.5 ng/ml). Both TGF-1 and TGF-2 stimulated expression of alpha-SMA in a dose dependent manner with peak activity at a concentration of 50 ng/ml (TGF-beta1) and 500 ng/ml (TGF-beta2). Protein and mRNA of PDGF-receptor type alpha and type beta and TGF-beta-receptors type I, II and III are expressed in cultured human Tenon's capsule fibroblasts. Conclusions. The present investigation strongly supports the hypothesis that PDGF-isoforms are major stimulators of proliferation of Tenon's capsule fibroblasts after glaucoma filtering surgery while TGF-beta-isoforms are essential for the transformation of Tenon's capsule fibroblasts into myofibroblasts.