miRNAs are released in exosomes of beta-cells. RNA was isolated from exosomes purified from the culture media of MIN6B1 cells (A) and human islets (B). The amount of miR-7, miR-29a and miR-146a recovered in exosomes was measured by qPCR and is expressed as percentage of the corresponding miRNA present inside MIN6B1 cells (A) or human islets (B). C) Exosomes isolated from MIN6B1 culture media were spiked with an oligonucleotide corresponding to the sequence of miR-142-3p (oligo-m142-3p) and incubated with (+ RNase) or without (Ctl) RNAse A and T1. D) MIN6B1 cells were transfected with a control pMSCV plasmid (pMSCV-ctl) or with a plasmid coding for miR-146a (pMSCV-m146a). Media were collected 24 h, 48 h, 72 h and 96 h after transfection. Exosomes were isolated and analyzed for their miRNA content.