PURPOSE The role of Spy1 inDNA damage has been well established, but now Spy1 may be a critical determinant of its ability to regulate both cell growth and death processes. In many CNS diseases, proliferation becomes dysregulated and gliosis is a fundamental CNS response disease in which cell hypertrophy and proliferation play prominent roles. In the DBA/2J chronic model of glaucoma, gliosis concomitant with raised intraocular pressure (IOP) that leads to a slow and progressive retinal ganglion cell axonopathy. The present study used this model to investigate the role of retinal expression of Spy1 inthe development of glaucoma.

METHODS  Different approaches, including slit-lamp biomicroscopy, ophthalmoscopic examination and IOP measurement were used to examine and classify the eyes of D2 mice at different ages. Two groups of C57/BL6 (B6) mice were served as controls. Then, the retinas were either removed for Western blot or fixed for immunohistochemistry (IHC).

RESULTS IOPs of B6 mice were stable with age,whereas increased with age in most, but not all, D2 mice.(This increase reached its peak at age 9 months). Dramatic iris atrophy and atrophic excavation of the optic nerve in 9-month-old DBA/2J mice was observed in comparison to that of age-matched B6 mice from a clinical and histologic analysis of aging D2 mice. (We performed these examinations to determine whether they develop glaucoma.) Temporally, Spy1 was up-regulated in D2 mice retina compared with the control B6 mice retina, and peaked at the stage of no glaucoma. Spatially, Spy1 was diffusely expressed in the D2 mice retina, while increased predominantly in Iba1⁺ microglia, suggesting that microglia contribute to the increase in Spy1 seen in D2 mice.

CONCLUSIONS Findings of this data identify that genetic predisposition of D2 mice induced a general upregulation of Spy1 inthe mouse glaucomatous retina. Spy1 was increased predominantly in microglia, which were largely proliferated. Collectively, we hypothesized an up-regulation of Spy1 was associated with microglia proliferation.