Purchase this article with an account.
Cathy Nguyen, Frances Cone, Justin Hanes, Anthony Kim, Thao Nguyen, Gulgun Tezel, Mary Ellen Pease, Matthew Steinhart, Harry Quigley; Studies of Scleral Microstructure, Proteomic Analysis, and Biomechanical Behavior Suggest Mechanisms of Susceptibility to Experimental Glaucoma in Mice. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3187.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To study features of the sclera that contribute to greater susceptibility to experimental glaucoma damage in CD1 compared to C57BL/6 mice.
Chronic experimental glaucoma for 6 weeks was produced in 2-4 month old CD1 and C57BL/6 mice (n=100), using polystyrene bead injection into the anterior chamber (Cone et al, Exp Eye Res 2010). Measurements were made of baseline and elevated IOP (TonoLab), axial length (ex vivo), scleral thickness and collagen fibril lamellar orientation and size distribution (electron microscopy), proteomic content of digested sclera (Tezel et al, IOVS 2010), inflation testing of sclera ex vivo (Myers et al Exp Eye Res 2010), and scleral mesh size by fluorescence recovery after photobleaching (FRAP).
CD1 mice lost more retinal ganglion cells (RGC) than C57BL/6 mice at similar intraocular pressure (IOP) exposure (40+35% vs 22+15%, p=0.03, n=21, 50 mice). Axial length and width increased after glaucoma (in comparison to fellow eyes) by 6% in CD1 and 10% in C57BL/6 (all p<0.03 or less). Using inflation test data, we fitted an orthotropic model to the circumferential and meridional stress-strain responses. Comparison of the material parameters for posterior sclera showed that CD1 controls were more anisotropic, with a significantly more compliant meridional direction, than the C57BL/6 controls (p=0.006, n=20 each strain). In both CD1 and C57BL/6 strains, exposure to chronic IOP elevation resulted in a stiffer response in both the circumferential (p=0.04, n=20; p=0.0007, n=12 respectively) and the meridional (p=0.05, n=20; p=0.02, n=12 respectively) directions. There were no consistent differences in scleral thickness by strain or after glaucoma exposure. By FRAP, the normal peripapillary sclera had slower diffusion than mid-posterior and equatorial sclera, and after glaucoma, FRAP was 9% faster than control, suggesting an increase in connective tissue mesh size (p=0.04, n=9 mice). Proteomic analysis of scleral digests showed that sclera of glaucoma eyes had 2-3 fold increases in thrombospondins 1,4 (activators of transforming growth factor β), as well as several other proteins involved in myofibroblast activation (n=37 mice, 74 eyes).
Initial studies of susceptibility to glaucoma damage in mice suggest that lower scleral stiffness at baseline is associated with increased RGC loss, and that scleral stiffness increases after chronic IOP elevation, as in monkey and human eyes. The scleral composition and its response to chronically elevated IOP, particularly in the peripapillary zone, can be studied biochemically, mechanically, and in terms of connective tissue macrostructure in mouse models.
This PDF is available to Subscribers Only