Confluence does not affect the expression of miR-375 and its direct targets in rat and human insulin-secreting cell lines

MicroRNAs are small non-coding RNAs, which negatively regulate the expression oftarget genes. They have emerged as important modulators in beta cell compensationupon increased metabolic demand, failure of which leads to reduced insulin secretionand type 2 diabetes. To elucidate the function of miRNAs in beta cells, insulin-secretingcell lines, such as the rat insulinoma INS-1 832/13 and the human EndoC-βH1, arewidely used. Previous studies in the cancer field have suggested that miRNA expressionis influenced by confluency of adherent cells. We therefore aimed to investigate whetherone of the most enriched miRNAs in the pancreatic endocrine cells, miR-375, andtwo of its validated targets in mouse, Cav1 and Aifm1, were differentially-expressed incell cultures with different confluences. Additionally, we measured the expression ofother miRNAs, such as miR-152, miR-130a, miR-132, miR-212 and miR-200a, withknown roles in beta cell function. We did not see any significant expression changesof miR-375 nor any of the two targets, in both the rat and human beta cell lines atdifferent confluences. Interestingly, among the other miRNAs measured, the expressionof miR-132 and miR-212 positively correlated with confluence, but only in the INS-1832/13 cells. Our results show that the expression of miR-375 and other miRNAs withknown roles in beta cell function is independent of, or at least minimally influencedby the density of proliferating adherent cells, especially within the confluence rangeoptimal for functional assays to elucidate miRNA-dependent regulatory mechanismsin the beta cell. © 2017 Ofori et al.publishersversionpublishe