MiR-34a Protects Mesenchymal Stem Cells From Hyperglycaemic Injury Through The Activation of The Sirt1/FoxO3a Autophagy Pathway

Abstract BackgroundAutologous mesenchymal stem cells (MSCs) are favourable treatments for ischaemic diseases; however, MSCs from diabetic patients are not useful for this purpose. Recent studies have shown that the expression of miR-34a is significantly increased in patients with hyperglycaemia, the precise role of miR-34a in MSCs in diabetes need to be clarified.ObjectiveThe aim of this study is to determine the precise role of miR-34a in MSCs exposed to hyperglycaemia and in healing the heart after myocardial infarction in diabetes mellitus (DM) rats.MethodsDM rats were established by STZ injection. MSCs were isolated from the bone marrow of donor rats. Chronic culture of MSCs under high glucose was used to mimic the DM microenvironment. The role of miR-34a in regulating cell viability, senescence and paracrine effects were investigated using a cell counting kit-8 (CCK-8) assay, senescence-associated β-galactosidase (SA-β-gal) staining, and VEGF and bFGF ELISA, respectively. The expression of autophagy- and senescence-associated proteins in MSCs and silent information regulator 1 (SIRT1) and forkhead box class O 3a (FOXO3a) were analysed by western blotting. Autophagic bodies were analysed by transmission electron microscopy (TEM). The MI model was established by left anterior descending coronary artery (LAD) ligation, and then the mice were transplanted with differentially treated MSCs intramuscularly at sites around the border zone of the infarcted heart. Thereafter, cardiac function in mice in each group was detected via cardiac ultrasonography at 1 week and 3 weeks after surgery. The infarct size was determined through a 2,3,5-triphenyltetrazolium chloride (TTC) staining assay, while myocardial fibrosis was assessed by Masson staining.ResultsThe results of the current study showed that miR-34a was significantly upregulated under chronic hyperglycaemia exposure. Overexpression of miR-34a was significantly associated with impaired cell viability, exacerbated senescence and disrupted cell paracrine capacity. Moreover, we found that the mechanism underlying miR-34a-mediated deterioration of MSCs exposed to high glucose involves the activation of the Sirt1/Foxo3a autophagy pathway. Further analysis showed that miR-34a inhibitor-treated MSC transplantation could improve cardiac function and decrease the scar area in DM rats.ConclusionsOur study demonstrates for the first time that miR-34a mediates the deterioration of MSC functions under hyperglycaemia. The underlying mechanism may involve the Sirt1/Foxo3a autophagy signalling pathway. Thus, inhibition of miR-34a might have important therapeutic implications in MSC-based therapies for myocardial infarction in DM patients.