Exosomal miR-29b found in aqueous humour mediates calcium signaling in diabetic patients with cataract

Abstract

Background: Ca2+ was supposed to play an important role in the cataract formation. Exosomal miR-29b from aqueous humour may play an important role in the mechanism of diabetes and cataracts. The purpose of this study was to investigate the role of exosomal miR-29b and Ca2+ in regulating the function of human lens epithelial cells. Methods: Exosomes were isolated from human aqueous humour by ultracentrifugation, and visualized by nanoparticle tracking and transmission electron microscopy. Exosomal miRNA sequencing was performed to identify differentially expressed miRNAs between diabetes and cataracts group (DMC) and age-related cataracts group (ARC). TargetScan was used to predict potential target of certain miRNA. The expression of CACNA1C mRNA was determined by quantitative real-time PCR and CACNA1C protein was determined by Western blotting. Concentration of Ca2+ in human aqueous humour and the culture supernatant of cells was detected by the Calcium Assay Kit. Cell Counting Kit-8 was used to determine cell viability. Results: Exosomes were isolated from human aqueous humour, which had a typical cup-shaped phenotype and a particle size distribution in accordance with micro extracellular vesicles. Exosomal miRNA sequencing revealed that miR-29b was significantly downregulated in diabetes and cataracts group (DMC) compared with age-related cataracts group (ARC). Ca2+ concentration of human aqueous humour in DMC was higher than that in ARC. The culture supernatant of cells transfected with miR-29b inhibitors had a higher concentration of Ca2+ than that transfected with miR-29b mimics. miR-29b reduced the viability of human lens epithelium cells (HLECs) by upregulating CACNA1C expression.Conclusions: Exosomes isolated from human aqueous humour contained abundant miRNAs. A significantly expressed miRNA, miR-29b, could affect the concentration of Ca2+ and regulate HLEC processes by upregulating CACNA1C.