ABILITY OF RETROVIRAL TRANSDUCTION TO MODIFY THE ANGIOGENIC CHARACTERISTICS OF RPE CELLS

Background: Retinal pigment epithelial (RPE) cells play an important r ole in the modulation of ocular angiogenesis. Transduction of RPE cell s with retroviral vectors bearing modulating genes can result in long- term transgene expression and may alter the angiogenic characteristics of RPE cells. This study was designed to determine whether changes in angiogenic characteristics of RPE cells result from transduction with retroviral vectors bearing modulating genes, using in vitro angiogeni c assays, including analysis of endothelial proliferation and wound he aling, Methods: Human RPE cells were transduced with retroviral vector s bearing either a urokinase-type plasminogen activator (u-PA) or a ti ssue-type plasminogen activator (t-PA) cDNA. Ten weeks after gene tran sfer, RPE cells transduced with the u-PA (u-PA-RPE cells) or the t-PA cDNA (t-PA-RPE cells), or untransduced (control) RPE cells, were cocul tured with human umbilical vein endothelial cells (HUVECs) by contacti ng and noncontacting coculture methods. The effects of these cells on proliferation and in vitro ''wound healing'' of HUVECs were evaluated. Results: Over 18 weeks, u-PA-RPE cells released large amounts of biol ogically active u-PA (total amount, 50.2 +/- 9.7 ng/10(6) cells/24 h), while t-PA-RPE cells released large amounts of functional t-PA (15.4 +/- 3.2 ng/10(6) cells/24 h). Control RPE cells did not release any de tectable t-PA or u-PA. In the proliferation assay, u-PA-RPE cells stim ulated HUVEC proliferation in contacting cell cultures, but not in non -contacting cell cultures. In contrast, t-PA-RPE cells, normal RPE cel ls or exogenous u-PA had no effect on HUVEC proliferation. Ln the woun d healing assay, u-PA-RPE cells in contacting coculture and exogenous u-PA stimulated wound healing of HUVECs, while non-contacting u-PA-RPE cells, t-PA-RPE cells and normal RPE cells had no effect on HUVEC wou nd healing. RPE cells transduced with u-PA secreted large amounts of u -PA for as long as 18 weeks, and these cells stimulate HUVEC prolifera tion and in vitro wound healing. As a result, the angiogenic character istics of RPE cells can undergo long-term changes. Conclusions: These results suggest that genetically modified RPE cells can be used to mod ulate ocular angiogenesis and may have potential for gene therapy of o cular diseases.