ScholarWorks at WMU ScholarWorks at WMU Retinal Regeneration in a Genetic Mouse Model of Glaucoma Retinal Regeneration in a Genetic Mouse Model of Glaucoma

Glaucoma is a degenerative retinal disease characterized by progressive loss of retinal ganglion cells (RGCs). Previous studies have shown that application of a specific α7 nicotinic acetylcholine receptor agonist, PNU-282987 (PNU), onto the murine retina induces neurogenesis of numerous retinal cell types, including RGCs. The aim of this study is to characterize the short-term and long-term effects of PNU in a glaucoma model. The effects of PNU were analyzed in a DBA/2J mouse model that auto-induces a glaucoma-like condition in adulthood. These mice manifest an elevated intraocular pressure (IOP) starting at 6 months, followed by loss of RGCs. To assess short-term regenerative effects, PNU treatment was applied daily as eye drops for 2 weeks to DBA/2J mice at various ages (3, 6, and 10 months). To assess the effects of early treatment, a chronic early treatment group began receiving PNU at either 3 or 6 months and received weekly treatment until the animals reached 10 months. An acute early treatment group received two-week daily treatment at either 3 or 6 months, then no further treatment until they reached 10 months. Following treatment, retinas were removed, fixed, processed using IHC procedures, and RGC regeneration was assessed and compared. Results showed a 29% loss of RGCs by 10 months of age in this DBA/2J colony. Two-week application of PNU induced a significant 21% increase in RGCs across all time points. Chronic early treatment produced a similarly significant increase in RGCs while acute early treatment had no effect on RGC numbers. 2-week treatment with PNU, as well as chronic long-term treatment, induced a significant increase in the number of RGCs in the DBA/2J retina, counteracting the effects of the DBA/2J genetic glaucoma-like condition. These results suggest the future clinical potential of PNU in the treatment of degenerative retinal diseases. Abstract Previous studies have shown that eye drop application of the selective α7 nicotinic acetylcholine receptor agonist, PNU-282987, induces neurogenesis of RGCs in adult wild-type rodents. This study was designed to test the hypothesis that PNU-282987 reverses the loss of RGCs associated with glaucoma. A DBA/2J mouse model that auto-induces a glaucoma-like condition in adulthood was used for these studies. Short-term effects using PNU-282987 and BrdU eye drop treatments were examined, as well as the effects of early treatment and the effects in a chronic early treatment group in DBA/2J mice aged 3, 6 and 10 months. With and without treatment, retinas were removed, fixed, immunostained and RGC counts were assessed. IOP measurements were obtained weekly using a Tonolab tonometer. Results showed an average typical loss of BrdU positive RGCs by 29% by 10 months of age in this DBA/2J colony corresponding with a significant increase in IOP. However, the two-week short-term application of PNU-282987 and BrdU induced a significant 21% increase in RGCs for DBA/2J mice at all ages. Chronic early PNU-282987 treatment produced a similarly significant increase in RGCs, while acute early treatment had no effect on RGC numbers. IOP measurements were not affected with PNU-282987 treatment. These studies demonstrated that 2-week treatment with PNU-282987, as well as chronic long-term treatment, induced a significant increase in the number of RGCs in the DBA/2J retina, counteracting the effects of the DBA/2J genetic glaucoma-like condition. These results suggest a potential future treatment of degenerative retinal diseases with PNU-282987.