Single-cell transcriptomics reveals novel role of microglia in fibrovascular membrane of proliferative diabetic retinopathy.

Vitreous fibrovascular membranes (FVMs), the hallmark of proliferative diabetic retinopathy (PDR), cause retinal hemorrhage, detachment and eventually blindness. However, little is known about the pathophysiology of FVM. In this study, we employed single-cell RNA sequencing on surgically harvested PDR-FVMs and generated a comprehensive cell atlas of FVM. A total of 8 cellular compositions were identified, with microglia as the major cell population. We identified a GPNMB+ subpopulation of microglia, which presented both profibrotic and fibrogenic properties. Pseudotime analysis further revealed the profibrotic microglia was uniquely differentiated from retina-resident microglia and expanded in PDR setting. Ligand-receptor interactions between the profibrotic microglia and cytokines upregulated in PDR vitreous implicated the involvement of several pathways, including CCR5, IFNGR1 and CD44 signaling, in the microglial activation within PDR microenvironment. Collectively, our description of the novel microglia phenotypes in PDR-FVM may offer new insight into the cellular and molecular mechanism underlying the pathogenesis of DR, as well as potential signaling pathways amenable to disease-specific intervention.