Abstract
Purpose :
Myeloid cells including microglia and macrophages are the major immune cells contributing to retinal disease. The objective of this study was to investigate the activation of myeloid cells after retinal ischemia-reperfusion injury (I/R) and to determine the effect of myeloid cell depletion on blood-retinal barrier breakdown induced by retinal I/R.
Methods :
To induce the retinal ischemia-reperfusion injury, 8-10 week-old C57BL/6J mice were anesthetized with a cocktail of ketamine, xylazine, and acepromazine. The anterior chamber of one eye was cannulated with a 30-gauge needle attached to a line infused with sterile saline. The intraocular pressure was raised to 110 mmHg by elevating the saline reservoir for 90 mins. Inflammatory cell populations were evaluated with flow cytometry at 3 days after I/R injury. To deplete the myeloid cells in the retina, C56BL/6J mice received the CSF1R inhibitor PLX5622 in their diet for one week before I/R injury. Inflammatory gene expression was evaluated one day after I/R injury. Inflammatory cell population and leukocytosis were examined three days after I/R injury. To evaluate the effect of myeloid cell depletion on blood-retinal barrier breakdown in the I/R injury model, leakage of H3-mannitol tracer was measured in the retina after 1 hour of circulation.
Results :
There was a significant increase in cell number and activation of myeloid cells in I/R retinas three days after injury compared with control retinas (n=9; p=0.014). PLX5622 treatment significantly reduced myeloid cell numbers in I/R retinas (n=; p<0.0001). There was a significant reduction in the expression of retinal inflammatory cytokines including as Il-1b, Tnf-a, and Il6, and chemokines including Ccl2, Cxcl2, and Cxcl10 one day after I/R injury in the PLX5622-treated mice. PLX5622 treatment significantly reduced retinal vascular leakage induced by I/R injury (n=10; p=0.01).
Conclusions :
Myeloid cell proliferation and activation were observed at an early stage following retinal ischemia/reperfusion injury. Depletion of myeloid cells with PLX5622 ameliorated inflammatory cytokine and chemokine expression and blood-retinal barrier breakdown induced by I/R injury. These results indicate an important role for myeloid cells in regulation of retinal inflammation and blood-retinal barrier breakdown.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.