MicroRNA miR-183-5p regulates β-cell protection from apoptosis and is associated to a dedifferentiation signature in NOD mouse and T1D patients pancreatic islets

Background: MicroRNAs are a class of small non-coding RNAs that regulate gene expression, which are involved in β-cell function and differentiation; their alteration may contribute to the development of type 1 diabetes(T1D). The aim of this study was to analyze their expression profile in pancreatic islets of diabetic NOD mice and T1D patients, in order to understand their possible role in β cell damage.

Methods: MicroRNAs expression profile was evaluated using TaqMan Array Microfluidic Cards in pancreatic endocrine tissue collected using Laser Capture Microdissection(LCM) from 3 NOD.SCID, 3 NOD normoglycemic and 3 NOD diabetic mice. Individual RT-PCR validation of differentially expressed microRNAs was performed in an additional cohort of NOD mice, where islets were separately captured based on the degree of infiltration. LCM analysis was also performed on pancreatic-endocrine tissue from 3 non-diabetic organ donors (nPOD cohort) and 3 T1D recent-diabetic patients (DiViD study cohort). Differentially expressed microRNAs were modulated in MIN6 murine β-cell line treated or not with a cytokines mix (IFNγ+IL-1β+TNFα) in order to evaluate apoptosis and microRNA target genes expression.

Results: miR-183-5p was downregulated (p<0.05) in LCM captured islets from NOD diabetic mice vs normoglycemics and its expression was inversely correlated to the degree of islets infiltration. Moreover, miR-183-5p downregulation was associated to higher expression of dedifferentiation marker Aldh3a1 and a decreased expression of Foxo1 in NOD diabetic mice vs normoglycemic. Additionally, miR-183-5p was found significantly reduced in LCM islets from T1D patients vs non-diabetic(p<0.05).In MIN6, miR-183-5p inhibition prevents cytokines-induced apoptosis (p<0.001), indicating that miR-183-5p could modulate apoptosis under cytokine stress. MiR-183-5p target genes analysis highlighted Bach2 apoptosis regulator, whose expression resulted higher in MIN6 transfected with miR-183-5p inhibitor vs CTR. In T1D, islet miR-183-5p reduction is associated to dedifferentiation signature and contributes to ?-cell protection from apoptosis through the modulation of anti-apoptotic factor Bach2.