Abstract
Purpose: :
Retinal ganglion cells (RGCs) die in glaucoma and a number of other optic neuropathies. Recently, novel TrkB monoclonal antibodies have been shown to be able to activate TrkB receptors and exert neuroprotective and neurotrophic effects (Qian et al., 2006). In previous study, we examined the ability of one of these, 29D7, on RGC survival in culture. In the present study, we examined the ability of 29D7 on RGC survival and neurite growth both in culture and in vivo.
Methods: :
RGCs from postnatal day (P)3-4 Sprague-Dawley rats were isolated to over 99% homogeneity by sequential immunopanning using a monoclonal antibody to Thy1. RGCs were cultured in 96 well plates pre-coated with poly-D-lysine and laminin at a density of 2x103 cells/well, in serum-free defined medium. RGC viability was assessed after 1-3 days by an MTT assay. The activation of TrkB downstream signals was confirmed by immunofluorescence and Western blot. Intravitreal injections of 29D7 were performed after ON axotomy, RGC survival was quantified using ß-III tubulin immunostaining. Regeneration was assessed using retrograde flurogold (FG) tracing in ON-peripheral nerve (PN) graft model.
Results: :
Similar to brain-derived neurotrophic factor (BDNF), the 29D7 antibody strongly promoted RGC survival and neurite growth in vitro compared with medium alone or control IgG at 24 hours in culture. Forskolin, which weakly supported RGC survival on its own, potentiated the effect of 29D7. Intravitreal injection of 29D7 enhanced RGC survival but not regeneration in vivo 2 weeks after injury.
Keywords: neuroprotection • retina • regeneration