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F.–Q. Liang, C. Wang, K. Locke, Y.–Z. Wang, D.G. Birch, B.F. Godley; Heparin Enhances AAV2–mediated Transduction Efficiency In The Mouse Retina . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4772.
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Purpose: Rapid binding of adeno–associated virus type 2 (AAV2) to heparan sulfate proteoglycans on the cell surface limits the viral distribution. Co–infusion of AAV2 with heparin increases vector distribution and transgene expression in the brain. This study examined whether heparin co–injection can augment transduction efficiency of AAV2 in the retina.Methods:AAV2–EGFP (3.1x10e7 iu/ml) were mixed with either heparin (1000 U/ml) or PBS (as a control) in a volume ratio 3:1 and incubated at room temperature for 30 min before injection. We injected 1 µl of these mixtures into the subretinal space of wild–type adult mice (C57Bl/6J, n=8), with AAV2+heparin in one eye and AAV2+PBS in the contralateral eye. Full–field rod and cone ERGs were obtained to evaluate retinal function. Animals were sacrificed 8 weeks post–injection and their eyes were dissected, examined under a dissecting microscope for any sign of hemorrhage, and processed for either cryostat sectioning or flat–mounting of the retina. GFP expression in the retina was examined under a Nikon epi–fluorescent microscope and quantified using image analysis software written in Matlab program.Results: Co–injection of AAV with heparin or PBS resulted in robust GFP expression in the photoreceptor and RPE cells. The areas showing GFP fluorescence were markedly expanded in the eyes injected with heparin+AAV2, covering 3–4 quadrants of the retina vs 1–2 quadrants in the eyes injected with PBS+AAV2. The total numbers of GFP–expressing cells were significantly greater (p=0.001) in heparin+AAV2 injected eyes compared to those in PBS+AAV2 eyes. No hemorrhages and no visible tissue damage were evident apart from the needle track in all eyes. Analysis of ERGs revealed no differences between eyes in rod or cone amplitude implicit times or rod a–wave parameters.Conclusions:Heparin facilitates AAV2 spread and transgene expression in the retina and may be considered for application in retinal gene therapy studies.
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