Abstract
Purpose :
Neovascular age-related macular degeneration (nAMD) is amongst the leading causes of blindness worldwide and characterized through development of choroidal neovascularization (CNV). We recently showed that developmental deletion of endothelial transforming growth factor receptor 2 (Tgfbr2) in mice promotes formation of CNV concomitant with an accumulation of myeloid cells. Here, we used a mouse model of nAMD to investigate the role of microglia cells and Tgf-β signaling in endothelial cells and interaction of both cell types during CNV development.
Methods :
Adult B6.Cdh5-Cre-ERT2.Tgfbr2fl/fl mice (Tgfbr2ΔEC) and Tgfbr2fl/fl littermates (controls) were treated with tamoxifen eye drops. Activation of cre and subsequent deletion of Tgfbr2 was monitored via cre reporter mice and PCR. Microglia were depleted in a subset of Tgfbr2ΔEC and control animals by feeding PLX5622 chow. CNV development was induced via a NdYAG-Laser (150 mW, 100 ms, 100 µm). CNV formation was documented by funduscopy and fluorescein angiography. CNV area and the number of accumulating microglia was determined using immunohistochemical staining against Collagen IV and IBA-1. RNA Sequencing was used to determine differentially expressed genes between all four groups.
Results :
Tamoxifen treatment reliably activated Cdh5-Cre and led to deletion of Tgfbr2 in choroidal endothelial cells. Following laser treatment, Tgfbr2ΔEC mice developed significantly larger CNVs compared to controls with similar numbers of accumulating microglia between both groups. Additional depletion of microglia in Tgfbr2ΔEC resulted in significantly less microglia cells near CNV lesions, concomitant with a significantly reduced CNV area. RNA-Seq analyses revealed a clear clustering between all four experimental groups with significant changes in the transcriptional profile depending on both endothelial TGF-β signaling and PLX treatment.
Conclusions :
Deletion of endothelial TGF-β signaling did not alter recruitment of CNV-associated microglia cells indicating no targeted communication from endothelial cells towards microglia in our experimental setup. However, deletion of endothelial Tgf-β signaling had pro-angiogenic effects that could be neutralized through PLX-mediated microglia depletion, clearly suggesting a targeted angiogenic communication from microglia towards endothelial cells.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.