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R.E. Blanco, I. Soto, M. Duprey–Diaz, J.M. Blagburn; Application of FGF–2 to the Optic Nerve After Axotomy Increases the Long–Term Survival of Ganglion Cells Expressing BDNF and TrkB . Invest. Ophthalmol. Vis. Sci. 2006;47(13):161.
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© ARVO (1962-2015); The Authors (2016-present)
We have previously shown that application of basic fibroblast growth factor (FGF–2) to the optic nerve after axotomy promotes the survival of retinal ganglion cells (RGCs) in the frog, Rana pipiens. We have also shown that, while axotomy alone increases the synthesis of BDNF and TrkB mRNAs in RGCs, FGF–2 treatment to the nerve accelerates and augments this upregulation of both BDNF and TrkB expression in the retina up to one week after application. The purpose of this study was to investigate if FGF–2 application to the optic nerve has long term effects on BDNF and TrkB expression that could account for its survival effect after axotomy.
BDNF and TrkB immunoreactive ganglion cells were counted and intensities measured 6 weeks after axotomy, from retinas with FGF–2– or PBS–treated nerves. Western blot analysis was performed to measured changes in total protein content. In situ hybridization and real time PCR were performed to assess the changes in expression of BDNF and TrkB mRNAs over this long–term survival period.
In retinas the optic nerves of which were treated with FGF–2, a large increase in the number of BDNF–immunopositive retinal ganglion cells was observed 6 weeks after axotomy compared to the retinas with PBS–treated nerves. The number of TrkB–immunoreactive ganglion cells was not significantly altered. However, FGF–2 treatment to the nerve increased the staining intensity of both BDNF and TrkB in retinal ganglion cells. In situ hybridization of the retinas showed that the changes in BDNF mRNA were mainly observed in RGCs and that the intensity of staining was increased in retinas with FGF–2–treated nerves. Frog RGCs expressed high levels of TrkB mRNA 6 weeks after axotomy, but no major difference was observed between retinas with FGF–2– or PBS– treated nerves.
FGF–2 treatment to the optic nerve after axotomy increases long term survival of BDNF–expressing ganglion cells. Our results suggest that FGF–2 treatment prolongs the upregulation of BDNF in frog RGCs after axotomy during the period of optic nerve regeneration. This upregulation of BDNF could make an essential contribution to the survival and regenerative capabilities of frog RGCs.
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