Purpose: In the current study, a non-histological approach, namely semi-quantitative RT-PCR, was used to provide information on retinal ganglion cell (RGC) injury and survival after optic nerve transection (ONT). The levels of mRNAs synthesized by RGCs and glial components were initially measured at defined time points after ONT. Subsequently, a comparison was made between the levels of these mRNAs in the ONT retinas of rats treated with the neuroprotectant BDNF and in rats which received vehicle.
Methods: Wistar rats received an ONT in one eye, while the fellow eye served as a control. ONT was performed 1-2 mm from the optic disc without damaging the retinal blood supply. In the first experiment, rats were killed at 1, 3, 5, 7, and 21 days after ONT. In the second experiment, brain derived neurotrophic factor (BDNF; 5 microg) or vehicle was injected intravitreally at the same time as the ONT and animals were killed after 7 days.
Results: After ONT, mRNA levels of RGC markers (NF-L and Thy-1) decreased substantially, while levels of GFAP and certain trophic factors mRNAs increased significantly. Administration of BDNF resulted in a substantial, but not complete, preservation of the levels of the RGC specific mRNAs, while ONT induced increases in GFAP and trophic factor mRNAs were not reduced to any great extent by BDNF.
Conclusions: The present studies show that measurement of NF-L and Thy-1 mRNAs provides a sensitive and reliable index of RGC injury after ONT, while measurement of GFAP and trophic factors mRNAs provides more general information on the effect of the injury on the retina.