Purpose
Transient retinal ischemic-reperfusion injury is a popular mouse model to be used for the study of mechanisms of ischemia-induced neuron death. Our recent study showed that retinal ischemia induced interferon gamma (IFN-γ), suggesting that IFN-γ may contribute to the death of retinal neurons. We thus propose to test if suppression of IFN-γ protects retinal ischemia-induced neuron death.
Methods
Acute retinal ischemia was induced in C57BL6/J mice. Briefly, the anterior chamber of right eye was cannulated with a glass needle connected to a sterile saline bag via plastic tubing. The intraocular pressure was elevated to 110 mmHg for 60 min by raising the saline bag to 120 cm high. In sham-operated group, same procedure of cannulation was performed without infusing saline into the anterior chamber. Two μg of anti-IFN-γ IgG or vehicle control solution (saline or IgG isotype) was administrated to the vitreous cavity at day 3, 7, 10 and 14 post-induction of retinal ischemia. At 3 weeks post injury, electroretinographic (ERG) response was recorded in mice. The mice were sacrificed at 4 weeks post injury. Whole-mount retinas were collected and incubated with Tuj1 antibody which recognizes a marker for retinal ganglion cells (RGC). Tuj1+ RGC were visualized by incubating with Cy3 conjugated secondary antibody, and Tuj1+ RGC were quantified. The percentage of RGC loss was calculated by comparing with that in normal retina. To determine the T cell-mediated responses potentially involved in the ischemia induced pathological process, cells from cervical lymph nodes of the mice were stimulated with phorbol 12-myristate 13-acetate and ionomycin for 4 hr in culture and analyzed by FACS.
Results
Significantly less number of Tuj1+ RGC loss was observed in the ischemic retina that received anti-IFN-γ treatments than that were treated with saline or IgG isotype (p<0.01). However, we did not observe significant improvement of ERG response in the ischemic retina that were treated with anti-IFN-γ if compared with saline or IgG isotype-treated groups, of which all have shown significant reduction of ERG a- and b-wave amplitudes comparing to the normal retina. Nor did administration of anti-IFN-γ altered the population of CD4+IFN-γ+ cells in the cervical lymph node as compared to the saline treated group
Conclusions
Suppression of IFN-γ by administration of neutralizing IFN-γ antibody improves RGC survival following retinal ischemia.
Keywords: 572 ischemia •
557 inflammation •
531 ganglion cells