Changes of mitochondrial dynamics related genes expression in a glaucoma rat model

Objective To investigate the ultrastructural changes of mitochondria and dynamic changes of mitochondrial dynamics related genes in chronic ocular hypertension rat models. Methods Forty Sprague-Dawley (SD) rats were randomized into normal control group, modeling 3 day-group, modeling 7 day-group and modeling 14 day-group.Glaucoma models were induced by translimbal laser photocoagulation of trabecular meshwork in rats.The number of survival retinal ganglion cells was evaluated by retrogradely labeling of FluoroGold.The morphological change of mitochondria in optical nerve was observed under the transmission microscope.The dynamic changes of mitochondrial dynamic-related gene expression in the retina in gene and protein levels were detected by real-time fluorescence quantitative PCR and Western blot assay, respectively.The experiment complied ARVO Statement for the Use of Animals in Ophthalmic and Vision Research and approved by the Animal Experimentation Ethics Committee of the Eye and ENT Hospital of Fudan University. Results The intraocular pressure was significantly higher in the modeling 3-day group, modeling 7-day group and modeling 14-day group than that in the normal control group (all at P<0.01). Compared with the normal control group, the immunoreactivity of glial fibrillary acidic protein (GFAP) was increased in the Muller cells in all modeling retinas, and the relative expressing levels of GFAP protein were significantly mcreased in all modeling groups (F=91.47, 17.58, both at P<0.01). Compared to the normal control group, the number of mitochondria was increased, and the mitochondrial health degree in the optic nerve and the nearest neighbor distance between adjacent mitochondria were decreased in the modeling 3- day group and 14-day group (all at P<0.05). The expression levels of dynamics-related protein 1(Drp1), parkin protein, PINK1, KIF5B and Miro1 mRNA in the retina were significantly elevated in the modeling 3-day group (all at P<0.05). In addition, the expression levels of optineurin, parkin and OPA1 proteins were higher in the modeling 3-, 7- and 14-day groups than those in the normal control group (all at P<0.05). Conclusions Dysfunction of mitochondria and changes of mitochondrial dynamics exist in RGCs of glaucomatous rats, including increased mitochondrial fission and fusion as well as the activation of mitophagy pathway, which probably are the mechanism of RGC damage in glaucoma. Key words: Mitochondria; Glaucoma; Fission; Fusion; Mitophagy; Retinal ganglion cells; Animal models; SD rats