The role of microglial cells in the development of retinal angiomatous proliferation in the Vldlr knockout mouse

ABSTRACT: Objective: Retinal angiomatous proliferation (RAP) represents a special form of neovascular age-related macular degeneration. Immune cells accumulate at RAP, but so far it is unclear whether these cells are resident retinal microglial cells (MG) or blood infiltrating monocytes (MO) and whether these cells can influence RAP formation. The aim of this study is to determine the relative contribution of MG and MO to RAP and to define the transcriptional profile of the dominant cell population. Methods: Vldlr -/- Knockout mice were crossed with MG-specific Cx3cr1CreER/+:Rosa26-Tomfl/+ re-porter mice (MG-Tom). The resulting Vldlr-/-:MG-Tom mice received tamoxifen injection at day 1 after birth (P1), leading to expression of Tomato fluorochrome (Tom) in myeloid cells. Myeloid cells were examined at P17, P31, and P42 by immunohistochemical Iba1 staining and retinal Tom expression. In addition, Tom-positive MG were isolated at P17 by fluorescence-activated cell sorting, and the transcriptional profile of MG was analyzed by RNA sequencing. MG Tom mice, also injected at P1 with tamoxifen, served as controls for RNA-Seq. Results: Our data show that at the beginning of RAP formation (P17), hardly any MO migrates from blood into tissues (0.2±0.5 MO/RAP, 2.0±0.8 MG/RAP). During the course of RAP formation, this changes only slightly (P31: 0.6±2.2 MO/RAP, 10.3±12.8 MG/RAP; P42: 0.6±2.4 MO/RAP, 14.3±9.4 MG/RAP). RNA sequencing of the isolated MG identified 140 differentially expressed genes (DEG), of which 67 were upregulated and 73 were downregulated upon RAP formation. Gene ontology enrichment analysis of the 140 DEGs revealed that they contribute primarily to immune-associated processes, such as leukocyte migration and chemotaxis, regulation of the immune system and immune response, and wound responses. Retinal MG thereby express the pro-angiogenic soluble factor Spp1 (log2FC 1.8) in addition to Ccl2 and Cxcl14 during RAP formation. Conclusion: Our data indicate that resident MG represent the dominant immune cell population during retinal angiomatous proliferation in the Vldlr knockout mouse. RNA sequencing of MG reveals upregulation of immune-associated processes and of pro-angiogenic factors, such as Spp1. Cell-specific modulation of MG may thus form the basis of a future therapeutic option for the treatment of RAP.

ORGANISM(S): Mus musculus

PROVIDER: GSE163642 | GEO | 2022/06/30

REPOSITORIES: GEO