Abstract
Aims Glaucoma is a common neurodegenerative disease that affects retinal ganglion cells (RGCs) and their axons. Little is known of the synaptic degeneration involved in the pathophysiology of glaucoma. Here we used an experimental ocular hypertension model in rats to investigate this issue. Methods Elevated intraocular pressure (IOP) was induced by laser coagulation of the episcleral and limbal veins. RGCs were retrogradely labeled with Fluoro-Gold (FG). The c-fos protein was used as a neuronal connectivity marker. Expression of c-fos in the retinas was investigated by immunohistochemistry at 5 days and 2 weeks after the induction of ocular hypertension. Both surviving RGCs as revealed by retrograde FG-labeled and c-fos-labeled RGCs were counted. Results The c-fos protein was mainly expressed in the nuclei and nucleoli of cells in the ganglion cell layer and inner nuclear layer in the normal retina. We also confirmed that c-fos was also expressed in the nuclei and nucleoli of RGCs retrogradely labeled with FG. There was no significant RGC loss at 5 days but about 13% RGC loss at 2 weeks after the induction of ocular hypertension. The number of RGCs expressing c-fos was significantly lower in the experimental animals at both 5 days and 2 weeks than normal. Conclusion Our study suggests that there is synaptic disconnection for RGCs after ocular hypertension and it may precede the cell death in the early stage. It may provide insight into novel therapeutic strategies to slow the progress of glaucoma.
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Acknowledgments
This study was supported by funding from the Jessie Ho Professorship in Neuroscience (The University of Hong Kong Foundation for Educational Development and Research Limited, and donation from Mr. George Ho), and donations from Madame Tung Shai Yun, and Madame Annie Tsao Wen Wei. Part of this research is supported by the Grants of Guangdong National Science Foundation, China (8451008901000852) and National Science Foundation of China (30801272).
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Qing-ling Fu and **n Li contributed equally to this work.
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Fu, Ql., Li, X., Shi, J. et al. Synaptic Degeneration of Retinal Ganglion Cells in a Rat Ocular Hypertension Glaucoma Model. Cell Mol Neurobiol 29, 575–581 (2009). https://doi.org/10.1007/s10571-009-9349-7
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DOI: https://doi.org/10.1007/s10571-009-9349-7