Improved Retinal Ganglion Cell Survival through Retinal Microglia Suppression by a Chinese Herb Extract, Triptolide, in the DBA/2J Mouse Model of Glaucoma

To investigate the changes in retinal microglia and retinal ganglion cell (RGC) survival after long-term administration of a Chinese herb extract, triptolide, in a DBA/2J mice. DBA/2J mice (n = 96) were administered triptolide (n = 48) 25 mg/kg or vehicle (n = 48) and were judged at 7, 9, 11 months of age. Long-term triptolide treatment tended to attenuate the anterior segment pathology in experimental group, though intraocular pressure was not significantly different between the two groups. In the experimental group, RGC survival was improved (7, 9, 11 months: p = 0.035, 0.004, 0.014), and microglia activation was suppressed based on a more ramified appearance (9, 11 months: p = 0.024, 0.013) and a lower total microglial cell count (7, 9, 11 months: p = 0.028, 0.025, 0.014). Double-immunofluorescence staining revealed TNF? localized to microglia, TNFR1 localized to the RGCs and nerve fiber layer. These findings indicate that long-term triptolide administration suppressed microglia activation and improved RGC survival in DBA/2J mice.