In Vivo Knockdown of I-mfa Using The Targeted Nanoparticle Delivery System Ameliorated Renal Injury in Diabetic Mice

Abstract

Accumulation of extracellular matrix (ECM) proteins in glomerulus is one of early features of diabetic nephropathy. Glomerular mesangial cell (MC) is the major source of ECM. Inhibitor of Myogenic Family isoform a (I-mfa) is a cytosolic protein interacting with components of Wnt/β-catenin pathway and of store-operated Ca^(2+) signaling pathway, both of which are involved in the development of diabetic nephropathy. The present study was carried out to determine if I-mfa in MCs contributed to renal injury in diabetic mice. Twelve male mice were randomly divided into 4 groups (3 mice each group): non-diabetes, diabetes, diabetes treated with scramble siRNA, and diabetes treated with siRNA against I-mfa. Diabetes was generated by multiple low-dose streptozotocin (STZ, 50 mg/kg) injections (intraperitoneal, once one day for 5 days) at an age of 6 weeks. Mice in group of non diabetes were injected with 10 mM citrate buffer (vehicle). Diabetes was indicated by a fasting blood glucose level of > 300 mg/dl. Scramble or I-mfa siRNA treatment started 24 weeks after STZ injection and the treatment lasted 2 weeks. All siRNAs (10 mg/kg body weight) were delivered by our recently established-targeted nanoparticle/siRNA delivery system which is glomerular mesangial cell specific. We found that STZ treatment significantly increased blood glucose level after 4 weeks of injection and reduced body weight 26 weeks after treatment. I-mfa siRNA treatment did not improve hyperglycemia, but lessened renal hypertrophy in STZ mice. Furthermore, diabetic mice showed significantly greater 24 hour urine output and this diabetic uresis was compromised by I-mfa siRNA treatment. Although knocking down I-mfa did not mitigate albuminuria, it lowered the level of blood urea nitrogen in diabetic mice. Consistent with the functional data, histological examination showed improved mesangial expansion and glomerular fibrosis in I-mfa siRNA-treated STZ mice. Immunohistochemical examination showed a significant reduction of protein abundance of glomerular fibronectin and collagen IV in the siRNA-treated diabetic mice. Taken together, our data indicate that I-mfa in MCs is involved in the development of diabetic kidney disease and thus, could be a potential therapeutic target for diabetic nephropathy.

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