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Jihong Wu, Shenghai Zhang; Accumulated Increase of mtDNA Damage Contribute to Progressive Loss of RGC in a Rat Model of Glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):284.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the molecular mechanisms for the progressive RGCs loss even after IOP elevation return to normal in a glaucomatous rat model.
Wistar rat was used to induce glaucomatous model through episcleral vein cauterization (EVC). IOP elevation sustained for 6 weeks and we continued the experiment till 6 months when IOP had already returned to normal to mimic the clinical feature of glaucoma. RGC loss was detected by retrograde labeling of FG. Fresh RGCs was isolated with magnetic beads coated by CD 11b/c and Thy-1 antibodies. Mitochondria isolation, DNA and RNA isolation were carried out in order to detect mtDNA damage or mutations, mtDNA copies, expression of mtDNA repair enzymes, and mitochondrial function. Cultured astrocytes were given 30 mmHg to study the whether pressure induce mitochondria dysfunction and possible mechanisms.
We have reported that there was a significant loss of RGCs at 2 and 4 weeks (15.26±1.57% and 22.35±2.01%) after EVC. Here, we found that the number of RGCs in the EVC- eyes was 32.3±1.24% (p< 0.01) and 41.7±2.26% (p< 0.01) lower than in the contralateral control eyes at 2, and 6 months, indicating the progressive RGCs loss in the EVC-eyes even after IOP elevation reversal. mtDNA damage and mutations occurred as early as 2 week after EVC and continued to increase in the EVC-RGCs even when the IOP elevation return to normal and up to 17.8-folds than the control at 6 months. mtDNA copies of RGC continued to decrease(by 49% at 6 months compared to control) and mtDNA repair enzyme decreased during all the observation period. ATP production rate of mitochondria in RGC was reduced by 47% and ROS increased by 38% at 6 months after EVC. In vitro results shown that pressure resulted in mtDNA damage, mtDNA copies decreased, expression of mtDNA repair enzyme decreased, mitochondrial membrane potential decreased and eventually cell death. Interestingly, we found mitochondrial fission was induced as early as 2h pressure-treated and fission itself leaded to mtDNA abnormalities.
Progressive RGCs loss in glaucomatous rat model even after IOP elevation reversal. Accumulated increase of mtDNA damage contributed to the progressive loss of RGCs in the glaucomatous model. Pressure induced mitochondria abnormality at least partly by inhibited mitochondria fusion.
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