Abstract
Abstract: :
Purpose: Previously, we have shown that Fibroblast Growth Factor 2 (FGF2), a potent stimulator of human retinal pigment epithelial (hRPE) cell proliferation, also stimulates c–Myc protein synthesis by two fold. The purpose of this project was to establish the role of adrenomedullin (ADM) and c–Myc protein in the proliferation of hRPE cells, since abnormal proliferation is seen in the proliferative vitreoretinopathy (PVR). Methods: To measure the effect of ADM on the proliferation of cultured hRPE cells, we incubated hRPE cells in the presence of increasing concentrations of ADM and then quantified cell proliferation by using the trypan blue exclusion method (TBE) and tritiated thymidine incorporation (3H–thy) in hRPE cells. The immunoprecipitation method was used to evaluate the expression of the c–Myc protein using 14C radiolabeled hRPE cells, increasing concentrations of ADM and anti–c–Myc antibody. Immunocytochemistry was also performed using anti–c–Myc and ADM. Statistical analysis was done using the student "t" test. ADM response was compared with Ham's F12 medium alone as a control. Results: ADM stimulated hPRE cell proliferation as measured by TBE in a dose dependent manner with a maximum increase at 10–7 M ADM (30.1±2.71 VS.26.91±2.71, mean cell number x 10,000±SEM, p<0.05,n=4). ADM also stimulated 3H–thy in a dose dependent manner with a maximum increase also at 10–7 M ADM (3868±300 vs.3109±113, mean CPM ±SEM, n=9, p< 0.005). The studies of c–Myc synthesis showed that c–Myc synthesis was mildly increased by 10–7 M ADM (161.2±14.3 vs. 117.8 ±9.7 CPM±SEM, n=12, p< 0.04). Of interest, it appears that the newly synthesized c–Myc is not translocated to nucleus since the c–Myc protein was localized to the cytoplasm in the presence of ADM. Conclusions: : Adrenomedullin is a mild stimulator of hRPE cell proliferation and c–Myc synthesis. This data and our previous work suggest that c–Myc may be a growth regulator of hRPE cells and may play a role in the pathophysiology of PVR.
Keywords: retinal pigment epithelium • growth factors/growth factor receptors • proliferative vitreoretinopathy