Abstract
Mesangial cell (MC) phenotypic transition is crucial for the progression of diabetic nephropathy. A major stimulus mediating high glucose-induced MC phenotypic transition is TGF-β1. Our current study focuses on microRNA-215 (miR-215) and investigates its role in TGF-β1-mediated MC phenotypic transition. Using real-time quantitative PCR (qRT-PCR) and northern blotting, we determined that the miR-192/215 family is dramatically upregulated under diabetic conditions both in vitro and in vivo. Gain- and loss-of-function approaches demonstrated that miR-215 inhibition significantly inhibited TGF-β1-induced mouse mesangial cell (MMC) phenotypic transition, whereas miR-215 upregulation promoted MMC phenotypic transition. Interestingly, these changes were not detected in cells that were treated with TGF-β1 and miR-192 mimics or inhibitors. These results suggest that miR-215 participates in TGF-β1-induced MMC phenotypic transition. Luciferase reporter assays were used to identify whether catenin-beta interacting protein 1 (CTNNBIP1) is a direct target of miR-215, which was predicted by bioinformatic analysis. Mechanistic studies revealed that CTNNBIP1 suppresses Wnt/β-catenin signaling and that miR-215 promotes β-catenin activation and upregulates α-SMA and fibronectin expression in TGF-β1-treated MMCs by targeting CTNNBIP1. In addition, in vivo miR-215 silencing with a specific antagomir significantly increased CTNNBIP1 protein expression, resulting in reduced β-catenin activity and decreased α-SMA and fibronectin expression in db/db mouse kidney glomeruli. Taken together, our findings indicate that miR-215 plays an essential role in MC phenotypic transition by regulating the CTNNBIP1/β-catenin pathway, which is related to the pathogenesis of diabetic nephropathy.
Highlights
Diabetic nephropathy (DN) is a major microvascular diabetic complication that is characterized by glomerular hypertrophy, extracellular matrix (ECM) accumulation, glomerulosclerosis, and end-stage kidney disease (ESKD) [1,2,3]
A and B, there was a significant increase in both miR-192 and miR-215 expression in mouse mesangial cell (MMC) that were treated with 30 mM glucose for 48 hours
We demonstrated for the first time that miR-215 plays a positive regulatory role in Mesangial cell (MC) activation, which is associated with DN pathology
Summary
Diabetic nephropathy (DN) is a major microvascular diabetic complication that is characterized by glomerular hypertrophy, extracellular matrix (ECM) accumulation, glomerulosclerosis, and end-stage kidney disease (ESKD) [1,2,3]. Central to the pathophysiology of DN are mesangial cells (MCs), which undergo glomerular injury-induced programmed myofibroblast transdifferentiation, termed ‘activation’ or ‘phenotypic transition,’ into myofibroblasts under diabetic conditions [4,5,6]. Increasing evidence [7,8,9,10] indicates that hyperglycemia initiates MC phenotypic transition. Numerous reports [11,12,13] have demonstrated that high glucose increases TGF-b1 levels in glomerular MCs, whereas neutralizing anti-TGF-b1 antibodies prevent these changes [14], suggesting that TGF-b1 is necessary for regulating high glucose-induced MC activation. The mechanisms by which TGF-b1 induces MC phenotypic changes during the diabetic nephropathy progressive fibrosis phase are not fully defined
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