Preliminary results of the RETINAL study: Effect of SARS-CoV-2 infection on retinal structure in patients with diabetes meliitus

DESIGN. Prospective cross-sectional study. PURPOSE. SARS-CoV-2 infection has long-term consequences on body homeostasis mostly through an imbalance of the inflammatory response and endothelial cell (EC) damage. Here we studied the association between COVID-19 and retinal microvasculature in subjects with diabetes and to collect data on inflammatory microRNAs. METHODS. We conducted a study on consecutive subjects of >18 years of age with diabetes with or without non-proliferative diabetic retinopathy (NPDR) referring to the eye department for retinopathy evaluation. The study involved complete ophthalmological evaluation, macular OCT/angio-OCT with Zeiss AngioPlex Cirrus 5000. Central macular thickness (CMT), foveal avascular zone (FAZ) area, perimeter and circularity index (CI), vessel density (VD%), and perfusion density (PD%) were automatically calculated on a 3 × 3  mm fovea scan on the superficial capillary plexus. In addition, we collected information on COVID-19 occurrence and a sample of peripheral blood (PB) to measure circulating mononuclear cells (MCs) and levels of microRNAs known to be associated with COVID-19, inflammation, and angiogenesis (miR-21, miR-210, miR-20b, miR-27b, miR-15a, miR-144, miR-146, miR150, and miR126). In addition, PBMC conditioned medium (CCM) proteomic analysis based on proximity extension assay was conducted. We studied the crosstalk between PBMCs and EC via in vitro Matrigel assay. RESULTS. We enrolled N = 64 patients with diabetes into 2 groups age and sex-matched: patients that have had COVID-19 (N = 24) or not (N = 40). Although OCT and angio-OCT analysis showed no significant changes associated with post-COVID-19 in relevant parameters, the levels of PBMC miR-21, miR-210, miR15a, miR27b, miR144, miR146a, and miR-20b significantly decreased in post-COVID-19. A subsequent analysis in 4 groups considering NPDR confirmed a significant decrease of hypoxia-miR miR-210 associated with both NPDR and COVID-19. Functional studies showed that PBMC-CCM from patients with NPDR and COVID-19 significantly inhibited EC network formation on Matrigel. Secretome analysis evidenced significant changes COVID-19-associated in several inflammatory cytokines including IL-1β, IL-6, TNF-α, IL-17A, and IL-17F. CONCLUSIONS. In patients with diabetes, we observed dramatic changes in PBMCs inflammatory miRNA levels and released cytokines that may contribute to EC impairment post-COVID-19. A larger cohort of patients will be required to assess associated microvascular alterations.