Normal Retina Contains Resident Plasmacytoid Dendritic Cells That Increase in a Mouse Model of Retinopathy of Prematurity

Abstract

Purpose : We have recently demonstrated that plasmacytoid dendritic cells (pDCs) in the cornea possess angiostatic properties. This study aims to determine the presence and distribution and density of resident retinal pDCs during steady state and their alterations during pathologic retinal angiogenesis.

Methods : Six-8-week old DPE-GFP×RAG1^-/- (pDC-GFP) transgenic mice (pDCs express GFP⁺) were perfused with FITC-dextran (FITC-D). Retinal whole-mounts and sections were subjected to immunofluorescence staining with AlexaFlour-594 anti-GFP antibody and were visualized by confocal microscopy. GFP⁺ pDCs from collagenase-digested retinal single cell suspensions were assessed by flow cytometry. In oxygen-induced retinopathy (OIR), a murine model of retinopathy of prematurity, C57BL/6 wild-type mice were exposed to 75% oxygen for five days beginning at postnatal day seven (P7), followed by return to room air for additional five days. Age- and gender-matched control mice were housed at room air. At P17, retinas were collected for assessment of pDC density by flow cytometry for CD45, Ly6C, CD11b, P2Y12R, CD45R/B220, and PDCA-1. Unpaired t-test was used to assess differences between groups. P < 0.05 was considered significant.

Results : In whole-mounted retinas of pDC-GFP mice, the vasculature was clearly visualized by FITC-D and GFP⁺ pDCs were found throughout the retina adjacent to the microvasculature and at higher densities in the peripheral retina (18.33 ± 3.51 cells/mm²), compared to the central retina (4.33 ± 1.52/mm²; p=0.003). On retinal cross-sections, GFP⁺ pDCs were mainly localized along the inner nuclear layer (9.33 ± 3.05 cells/mm²), adjacent to the deep retinal microvasculature, and were 6-fold higher than in the ganglion cell layer (1.67 ± 0.58 cells/mm², p = 0.013). Flow cytometry showed that CD11b^negP2Y12R^negLy6C⁺B220⁺PDCA-1⁺pDCs, as percentage of CD45⁺ cells, were increased by 1.81-fold in the retina undergoing OIR (2.07 ± 0.43%), compared to control mice (1.10 ± 0.36%; p = 0.04) at P17, the time point with the maximal of angiogenesis.

Conclusions : This study demonstrates that the retina contains with resident retinal pDCs that reside in close proximity to retinal deep layer vasculature in the inner nuclear layer, and increase during the development of retinal angiogenesis.

This is a 2020 ARVO Annual Meeting abstract.