Mesenchymal stromal cell-derived extracellular vesicles improve islet β-cell metabolic function via miRNA-mediated...

Mesenchymal stromal-cell-derived extracellular vesicles (MSC-EVs) improve islet function, which may be mediated in part through the delivery of microRNAs (miRNAs) to β-cells. To investigate the underlying mechanisms, we identified the most abundant MSC-EV miRNAs, their relative transfer to β-cells and the extent to which Ankyrin-B (Ank2) may represent a downstream target mediating the beneficial effects of EVs on islet function.

Mouse islets were treated with MSC-EVs, and changes in islet miRNAs were assessed using small RNAseq. miR-21a-5p showed the highest content, and subsequent bioinformatic analysis identified Ank2 as one of its predicted target genes. Expression levels of Ank2 mRNA were assessed by bulkRNA sequencing, while Ank2 protein was quantified by immunoblotting. Knockdown of Ank2 by siRNA was used to evaluate its role in islet function. Cell viability was measured using live/dead staining, oxygen consumption was quantified with a Seahorse analyser, and glucose-stimulated insulin secretion was determined by radioimmunoassay.

MSC-EV treatment of islets was associated with elevated β-cell miR-21a-5p mRNA levels. Bioinformatic and experimental analyses identified Ank2 as a predicted downstream target of miR-21a-5p. Treatment of mouse islets with MSC-EVs was associated with increased Ank2 mRNA and protein expression, which was accompanied by improved β-cell metabolic function and enhanced glucose-stimulated insulin secretion. Ank2 knockdown caused a significant reduction in β-cell ATP-coupled respiration.

These findings identify a novel miRNA-mediated mechanism underlying the beneficial effects of MSC-EVs on islet function and support the development of MSC-EV-based cell-free strategies to enhance islet function for diabetes therapies.