|Session Assignment: 713|
|COMPLEMENT AND GLIAL ACTIVITY IN THE RETINOCOLLICULAR PATHWAY OF MICE USING A NOVEL MODEL OF GLAUCOMA|
|Author: Sean Silverman||Presenter: Sean Silverman|
|Department: North Texas Eye Research Institute|
|Research Area: Eye/Vision|
|(1) Complement , (2) Microglia, (3) Glaucoma|
|Silverman SM, McDowell CM, Kim B-J, Wordinger RJ, & Clark AF North Texas Eye Research Institute, UNT Health Science Center, Fort Worth, TX 76107|
|Short Description: Using a mutation in a human gene associated with glaucoma, we were able to simulate this disease in mice through a viral injection. The mouse eye is remarkably similar to the human eye, which makes them a popular choice when studying glaucoma. One of the leading risk factors of glaucoma is increased pressure within the eye, which can be easily measured through tonometry. Following viral injections we observed increased pressure in the eye similar to that in human patients. Following treatments times that varied from 3 day to 8 weeks tissues from these mice were harvested for molecular techniques in order to identify the activity of an immune protein, c1q, in the retina and area of the brain directly connected to the retina, the superior colliculus. Additionally, we observed two different cell types in the retina we speculated were responsible for the increased production of c1q.|
Purpose: Glaucoma is a leading cause of irreversible visual impairment and blindness throughout the world. C1q is responsible for axonal pruning in early ocular development and is upregulated in glaucomatous eyes of mice, non-human primates, and humans. We used an inducible mouse model of human primary open angle glaucoma with elevated intraocular pressure (IOP) to examine expression levels of C1q in the retina and superior colliculus (SC), as well as identify changes in cellular homeostasis.
Methods: Anesthetized A/J mice were given a single intravitreal injection of Ad5.MYOC.Y437H (5x107 pfu), a mutant glaucoma gene, or Ad5.null control virus. Following injections, conscious IOPs were measured weekly, using a TonoLab tonometer (iCare). Mice were sacrificed at time points between 3 days and 8 weeks. Brains and retinas were harvested for immunofluorescence or immunoblotting studies. Microglia and astrocytes cells were identified using Iba1 and GFAP, respectively. All quantifications were performed using ImageJ Analysis software(NIH).
Results: IOPs were significantly increased in the Ad5.MYOC.Y437H eyes (p<0.01) compared to the contralateral un-injected eye and eyes receiving Ad5.null. C1q expression was significantly upregulated in retinas receiving Ad5.MYOC.Y437H (2.69-fold±0.38, p<0.0001) compared to contralateral control retinas (0.7-fold±0.29). C1q upregulation was additionally observed in SC hemispheres receiving neural connections from injected eyes. Mice given Ad5.null vector displayed no elevation of C1q in the visual axis. Additionally, colocalization studies demonstrated significant increases of inner retinal microglia density beginning 2 weeks post injection (0.61%±0.07, p<0.001) and continuing at 4 weeks (0.87%±0.09, p<0.0001) compared to untreated retinas (0.41%±0.03 and 0.44%±0.03, respectively). No signs of astrogliosis were detected.
Conclusions: C1q is actively upregulated in the retina and SC, following mutant myocilin induced ocular hypertention, whereas adenovirus alone had no effect. An increased microglial population in the retina accompanied these changes. This suggests that microglia may sense the increased IOP and play a role in upregulating endogenous C1q. Early glaucoma pathogenesis may result from the reactivation of the ocular developmental roles of C1q and microglia, suggesting new therapeutic targets for future neuroprotective studies.
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