Abstract
Purpose: :
Pathologic proliferation of vascular endothelial cells and retinal pigment epithelial cells in the eye caused by various angiogenic growth factors contribute to the development of blinding proliferative vitreoretinopathy. As previous studies have demonstrated that insulin-like growth factor-1 (IGF-1) induces the production of angiogenic factors such as VEGF, and as pigment epithelium-derived factor (PEDF) inhibits glucose-stimulated production of erythropoietin (Epo), this study investigated the effect of IGF-1 and PEDF on Epo production in in vitro human retinal pigment epithelial (hRPE) cells.
Methods: :
Human RPE specimens were obtained from postmortem non-pathological eyes and cultured in vitro. Cellular proliferation in the presence of increasing concentrations of FBS, IGF-1, and IGF-1 with PEDF was measured by 3H-thymidine incorporation; trypan blue exclusion studies verified cell viability. Under the same experimental conditions, synthesis of Epo was measured utilizing 14C-methionine incorporation using immunoprecipitation and immuno-cytochemical methods.
Results: :
FBS stimulated hRPE cell proliferation in a dose-dependent manner, as measured by trypan blue exclusion and 3H-thymidine incorporation in hRPE cells. IGF-1 showed a further stimulatory effect on hRPE cell proliferation. IGF-1 also stimulated 14C-Epo synthesis in hRPE cells in a dose-dependent manner, as demonstrated by 14C-methionine immunoprecipitation. PEDF (10 ng/mL) suppressed the stimulatory effect of IGF-1 (50 ng/mL) on hRPE cell number (112,500±11,500 vs. 68,750±10,200, CPM±SEM, p<0.05,N=8) and immunoprecipitated 14C-Epo (394.66±42.52 vs. 316.07±20.30, CPM±SEM, p<0.05,N=16). This data was qualitatively confirmed by immuno-cytochemical studies.
Conclusions: :
PEDF inhibits IGF-1 stimulation of Epo synthesis and hRPE cell proliferation and may have therapeutic value in treating proliferative eye diseases.
Keywords: retinal pigment epithelium • diabetic retinopathy