miR-15a/16 reduces retinal leukostasis through decreased pro-inflammatory signaling

Background: Hyperglycemia is a significant risk factor for diabetic retinopathy and induces increased inflammatory responses and retinal leukostasis, as well as vascular damage. Although there is an increasing amount of evidence that miRNA may be involved in the regulation in the pathology of diabetic retinopathy, the mechanisms by which miRNA mediate cellular responses to control onset and progression of diabetic retinopathy are still unclear. The purpose of our study was to investigate the hypothesis that miR-15a/16 inhibit pro-inflammatory signaling to reduce retinal leukostasis. Methods: We generated conditional knockout mice in which miR-15a/16 are eliminated in vascular endothelial cells. For the in vitro work, human retinal endothelial cells (REC) were cultured in normal (5 mM) glucose or transferred to high glucose medium (25 mM) for 3 days. Transfection was performed on REC in high glucose with miRNA mimic (hsa-miR-15a-5p, hsa-miR-16-5p). Statistical analyses were done using unpaired Student t test with two-tailed p value. p < 0.05 was considered significant. Data are presented as mean ± SEM. Results: We demonstrated that high glucose conditions decreased expression of miR-15a/16 in cultured REC. Overexpression of miR-15a/16 with the mimic significantly decreased pro-inflammatory signaling of IL-1β, TNFα, and NF-ΚB in REC. In vivo data demonstrated that the loss of miR-15a/16 in vascular cells led to increased retinal leukostasis and CD45 levels, together with upregulated levels of IL-1β, TNFα, and NF-ΚB. Conclusions: The data indicate that miR-15a/16 play significant roles in reducing retinal leukostasis, potentially through inhibition of inflammatory cellular signaling. Therefore, we suggest that miR-15a/16 offer a novel potential target for the inhibition of inflammatory mediators in diabetic retinopathy.