Insulin secretory granules release exosomal miR-503 to promote insulin resistance and ß-cell senescence.

Since ß cell specific miR-503 transgenic (ßTG) mice showed metabolic stress induced insulin resistance and ß cell dysfunction, we applied single cell sequencing (scSeq) technology to distinguish different cell type in ß TG islets and define different phases of ß cell subtypes through pseudotime analysis. Islets were isolated and digested at 37?for 5 min by 0.08 % trypsin containing 0.006 % EDTA to generate islet single cell, cell suspension was centrifuged and resuspended in cold PBS buffer with 0.4% of BSA at the concentration of ~1000/µl, which then was loaded onto the 10X Chromium Controller using Chromium Single Cell 3' v2 reagents. Sequencing library was prepared following the manufacturer's instructions (10X Genomics), and sequenced via a Illumina HiSeq PE150 instrument. 8698 cells were detected from 10-week old wild type (WT, n = 4540 cells) and ßTG (n = 4158 cells) mice islets, cells were split to 12 subtypes by using cell ranger software and k-means algorithm. According to specific gene profile we found that ßTG islets was infiltrated with Ccr6/Ccr7 positive immune cells, and most ß cells in ßTG mice islets were defined senescent cells by using GO enrichment and pseudotime analysis. Our study represents the analysis of islet single cell transcriptomes, the results showed that miR-503 highly expression in ß cells promotes ß cell senescence and diabetes onset. Overall design: Single-cell RNA-sequencing (scSeq) profiles of 10-week old wild type (WT) and ßTG mice islets.