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M. Sapieha, M. Peltier, W.C. Manning, A. Di Polo; Fibroblast Growth Factor-2 Gene Delivery Stimulates Extensive Axonal Regeneration of Adult Retinal Ganglion Cells In Vivo . Invest. Ophthalmol. Vis. Sci. 2003;44(13):129.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Fibroblast Growth Factor-2 (FGF-2) is a potent stimulator of retinal ganglion cell (RGC) axon growth during development. We tested if FGF-2 upregulation in adult RGCs promoted axonal regeneration in vivo after acute optic nerve injury. Methods: Recombinant adeno-associated virus (AAV) containing the FGF-2 gene was injected into the vitreous chamber of adult rats followed by micro-crush lesion of the optic nerve. RGC axons were visualized using the anterograde tracer cholera toxin ß-subunit and the extent of axonal regeneration was quantified at 14 days post-injury. Alternatively, surviving injured neurons were quantified in retinal whole-mounts following retrograde labeling with FluoroGold. The cellular localization of endogenous and AAV-mediated FGF-2, FGF receptor-1 (FGFR1) and cell surface heparan sulfate (HS) was investigated by immunocytochemistry on retinal and optic nerve cryosections. Results: FGF-2 upregulation in RGCs led to a striking increase in the number and length of axons that crossed over the glial scar, into the distal optic nerve. For example, AAV.FGF-2 injection led to a 10-fold increase in the number of axons growing past 500 µm from the lesion site compared to optic nerves from eyes treated with a control virus. We found a tight correlation between AAV-mediated FGF-2 expression in injured RGCs and their ability to regrow. All regenerating axons were immunopositive for GAP-43, a growth associated protein expressed in RGCs only during active axon growth. The capacity of RGCs to respond to FGF-2 was supported by our finding that FGFR-1 and HS, key molecules involved in FGF-2 binding and signaling, were abundantly expressed by adult rat RGCs. AAV.FGF-2 produced only transient neuroprotection of axotomized RGCs, thus its regenerative effect could not be solely attributed to an increase in cell survival. Conclusion: Our data indicate that selective upregulation of FGF-2 in adult RGCs is an effective strategy to stimulate axon regeneration within the growth inhibitory optic nerve environment.
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