Pericyte specific MDM2 knockout alleviates kidney injury in diabetic mice

Background: Diabetic nephropathy (DN) is one of the most severe microvascular complications of diabetes. Interstitial fibrosis/tubular atrophy and renal function decline are typical hallmarks of advanced DN. Pericytes play an important role in kidney vascular function and fibrosis. Murine double minute 2 (MDM2) is an E3 ubiquitin ligase of p53. MDM2 is expressed in glomeruli and involved in podocyte injury. MDM2-inhibition reduces inflammation and fibrosis. However, whether MDM2 affects diabetic renal injury is unclear. This study aims to investigate the effects of pericyte conditional MDM2-KO on renal function and morphology.

Methods: We generated the pericyte specific MDM2 knockout (MDM2-KO) mice using the Cre-loxP system. Animals were divided into four groups: wildtype (C57BL/6) non-diabetes (WT-NC), WT-diabetes (WT-DC), KO-NC and KO-DC. Mice at seven weeks (7W) old were intraperitoneally injected with tamoxifen (10 mg/kg BW) for 5 consecutive days and at eight weeks diabetes was induced using streptozotocin (STZ, 140mg/kg BW). After three months diabetes duration, renal function and morphologic changes were assessed. Fibrosis related protein expression was evaluated by Western blot, immunofluorescence and immunohistochemistry.

Results: MDM2-KO reduced urinary albumin to creatinine ratio (uACR), mitigated the occurrence of renal epithelial-mesenchymal transition (EMT), reduced the deposition of fibrotic proteins (collagen and fibronectin) and decreased expression of alpha smooth muscle actin (α-SMA) in diabetic kidneys. TGF-β signaling and connective tissue growth factor (CTGF) expression were induced in diabetes, whereas MDM2-KO significantly reduced the secretion of CTGF and TGF-β1 and inhibited phosphorylation of SMAD3 (P-SMAD3) in the kidney. MDM2 improved renal fibrosis in diabetes through the regulation of the TGF-β1/SMAD3 and CTGF-related pathways.

Conclusions: Pericyte specific MDM2-KO alleviates glomerular fibrosis and kidney injury in diabetes, and further rescues renal function by lowering uACR. MDM2 seems to play an important role in the development of DN by regulating CTGF, and TGF-β1/P-SMAD3 pathways. Therefore, MDM2 inhibition may provide a new approach for the treatment of diabetic kidney diseases.

Acknowledgement: This study was funded by German Research Foundation (DFG)

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Artikel online veröffentlicht:
18. April 2024