Abstract
Purpose :
Retinal inflammation is associated with vascular degeneration in oxygen-induced-retinopathy (OIR). micro-RNAs (miRs) have been identified as key regulators of genes expression. miR-125 is reported as strongly expressed in the retina, implicated in retinal development and in inflammatory processes. This study aimed to investigate the potential anti-inflammatory properties of miR-125 in a rat model of OIR.
Methods :
qRT-PCR and western blot were performed to evaluate the expression of miR-125 and inflammatory cytokines. In vitro: miR-125 function was investigated using a miR-125 mimic on activated microglial cells (SIM-A9) by hyperoxia or LPS. The angiogenic effects were analyzed by Matrigel assay and qRT-PCR. In vivo: OIR rat pups were intravitreally injected with miR-125 mimic (10 nmol/kg) or a control-miR at P5 during the cycling OIR model. Retinal tissues were collected at P10 and P14 and the vascular density was analysed by retinal lectin-immunostaining. Apoptosis was analyzed in vitro and in vivo.
Results :
miR-125 expression is significantly reduced in the retina of OIR rats compared to control rats, and in SIM-A9 subjected to hyperoxia or LPS. This is correlated with an upregulation of key proinflammatory cytokines including TNF-a, IL-6 and IL-16. Interestingly, we found a significant decrease of TNF-a, IL-6 and IL-16 expression, associated with decreased apoptosis in SIM-A9 transfected with miR-125 before hyperoxic or LPS treatment. Retinal endothelial cells (HRMEC) exposed with the culture medium of SIM-A9 pre-subjected to hyperoxia display a decrease in their angiogenic capacity associated with an increase of apoptosis. Interestingly, overexpression of miR-125 in SIM-A9 reverses the deleterious effects of hyperoxia on their secretome to rescue vasculogenic function of HRMEC. In vivo, OIR rat pups intravitreally supplemented with miR-125 mimic display a significantly decrease of TNF-a, IL-6, IL-16 and activated Caspase-3, associated with lower vasoobliteration area compared to the miR-control group at P10 and P14.
Conclusions :
This study suggests that miR-125 acts as an inflammatory and apoptotic suppressor of activated-microglial cells protecting microvascular density during OIR. miR-125-based therapy could potentially constitute a novel anti-inflammatory therapeutic strategy to limit vascular degeneration in the initial step of ischemic retinopathies.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.