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C Wong, M Wilson, MW Berns; Bioengineering Retinal Blood Vessels with Pro-Angiogenic Polymeric Scaffolds . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1286.
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Purpose: To evaluate the in vitro release kinetics of both VEGF and bFGF that are encapsulated in a non-biodegradable polymeric implant, which intravitreally produces growth of sustained retinal blood vessels, subsequent hemorrhage, and traction retinal detachment in the avascular rabbit retina over a 4-week period (Wong et al., CER 22:240, 2001). Methods: Both VEGF (20 ug or 4 ug) and bFGF (15 ug or 3 ug) either together or separately are incorporated in a Hydron solution of 95% ethanol/water, formed into 1.5 mm diameter pellets, air-dried overnight, and then placed in sterile plastic wells containing 1 ml phosphate-buffered saline with penicillin-streptomycin-amphotericin. At various times over a 7-day period at room temperature, 100 ul aliquots were collected, frozen at -70 C, and subsequently analyzed by ELISA for both VEGF and bFGF. Results: At timepoints of 2, 4, 6, 24 hours, and 3 days after placement of polymeric pellets in wells containing PBS, levels of VEGF were constant at 3.5 pmoles/day while levels of bFGF varied between 1.5 pmoles/day and 3.5 pmoles/day over a 3-day period. When either bFGF or VEGF was incorporated separately in the Hydron polymeric matrix, the release rates were similar to their combination within the matrices. Conclusion: In vitro release studies indicate that levels of either bFGF or VEGF are sustained within a 1-week period. Additional in vivo studies will define both the release kinetics of the pro-angiogenic growth factors and retention of biologic activities in correlation with pathologic retinal neovascularization and hemorrhage. Thus, defining the sequential and synergistic nature of various growth factors that lead to functional blood vessel growth in the retina ultimately will provide insight on novel therapeutic approaches for anti-angiogenic control of posterior segment NV. Finally, this approach may have potential application for engineering tissue regeneration where sequential cytokine modulation of stem cell signalling within biodegradable polymeric scaffold can lead to the in situ growth of functional adult retinal cells.
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