Delivery of megsin siRNA plasmid reveals therapeutic potential against diabetic nephropathy by down-regulating p27(kip1) level.

BACKGROUND: Diabetic nephropathy is a complex disease with poor outcomes, and our current treatment measures are limited. It is urgent to search for novel therapeutic targets. Recently, a mesangium-predominant gene, megsin, has emerged as a participant in mesangial cell proliferation and/or mesangial matrix expansion. This study investigated the effect of megsin down-regulation on the progression of diabetic nephropathy.

METHODS: Streptozotocin (STZ)-induced diabetic CD-1 mice after uninephrectomy received a pBAsi mU6 Neo megsin siRNA plasmid for 12 weeks and were compared with age-matched nondiabetic mice. In vitro mouse mesangial cells were transfected with pBAsi mU6 Neo megsin siRNA plasmid using Lipofectamine 2000 reagent and further cultured in DMEM containing high glucose for up to 48 hours. All of the cells were collected for protein extraction and the supernatant for type IV collagen measurement. The expression of megsin, matrix metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteases-2 (TIMP-2) and p27(Kip1) was determined by Western blotting.

RESULTS: The megsin siRNA plasmid alleviated proteinuria and glomerular type IV collagen accumulation 12 weeks after the STZ injection, down-regulated renal cell proliferation and normalized the imbalance between MMP-2 and TIMP-2. Also, in vitro experiments showed that the glomerular mesangial cellular proliferation and type IV collagen production induced by high glucose were relieved after the transfection of megsin siRNA plasmid. The level of p27(kip1) was down-regulated in transfected mesangial cells significantly.

CONCLUSIONS: The study suggests that the down-regulation of megsin might exert beneficial effects on the diabetic kidney partly through down-regulation of p27(kip1) level and that megsin may serve as a novel therapeutic target in the management of diabetic nephropathy.