Abstract
Purpose :
Subretinal macular fibrosis occurs in up to 50% of neovascular age-related macular degeneration (nAMD) eyes and is a major cause of anti-VEGF resistance in nAMD. Currently, there are no medications to prevent or treat macular fibrosis secondary to nAMD. The aim of this study was to investigate the role of CC-chemokine receptor 2 (CCR2) expressing monocytes in the development of the fibrovascular phenotype of nAMD.
Methods :
Subretinal fibrosis was induced in C57BL/6J mice using the two-stage laser-induced protocol previously described by Little et al (2020). The dynamics of the fibrotic lesion and infiltrating macrophages were assessed by immunofluorescence staining of collagen-1, F4/80 and CCR2, respectively at days 0, 1, 3, 6 and 10 post-second laser. Circulating CCR2+ monocytes were depleted using the CCR2 depleting antibody, MC-21, from day 1 to day 5 (acute stage depletion) or from day 5 to day 10 (chronic stage depletion). The level of depletion was confirmed by flow cytometry. Vascular and fibrotic components of the fibrovascular membrane were examined at day 10 post-second laser by immunofluorescence staining of isolectin B4 and collagen-1, respectively.
Results :
The fibrotic lesion size reaches its peak 3 days after the second laser. CCR2+F4/80+ macrophages were detected in and around the fibrotic lesion and their number increased from day 3 to 10 post-second laser. Depletion of CCR2+ monocytes at the acute stage of disease did not affect the size of subretinal fibrosis. However, depletion of CCR2+ monocytes at the chronic stage of the disease significantly reduced the vascular and fibrotic components of the fibrovascular membrane.
Conclusions :
Our results suggest that CCR2+ monocytes play a critical role in the development of the fibrovascular phenotype of nAMD during the chronic stage of inflammation. The underlying mechanism of CCR2+monocytes in promoting subretinal fibrosis warrants further investigation.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.