MicroRNA-21 in glomerular injury

Area of Science:

• Molecular Biology
• Nephrology
• Genetics

Background:

• Transforming growth factor-beta 1 (TGF-β1) drives glomerulosclerosis and podocyte apoptosis, key features of kidney disease.
• MicroRNA-21 (miR-21) expression is regulated by TGF-β1 and inhibits apoptosis in cancer cells.
• TGF-β1-transgenic mice show accelerated podocyte loss and glomerulosclerosis.

Purpose of the Study:

• To investigate the role of miR-21 in TGF-β1-induced and hyperglycemia-induced glomerular injury.
• To determine if miR-21 functions as a protective factor against podocyte loss and glomerulosclerosis.

Main Methods:

• Assessed miR-21 expression in cultured murine podocytes exposed to TGF-β1.
• Examined kidney tissues from TGF-β1-transgenic mice and streptozotocin-induced diabetic mice, with and without miR-21 deficiency.
• Analyzed glomerular and tubulointerstitial fractions from American-Indian patients with diabetic nephropathy for miR-21 expression and albumin-to-creatinine ratio.

Main Results:

• miR-21 expression increased in podocytes upon TGF-β1 exposure and was elevated in TGF-β1-transgenic mouse kidneys.
• miR-21 deficiency exacerbated proteinuria, extracellular matrix deposition, and podocyte loss in TGF-β1-transgenic mice and diabetic mice.
• Inhibition of miR-21 in cultured podocytes increased cell death and TGF-β/Smad3 signaling.
• Albumin-to-creatinine ratio positively correlated with glomerular miR-21 expression in patients with diabetic nephropathy.

Conclusions:

• miR-21 ameliorates TGF-β1 and hyperglycemia-induced glomerular injury by suppressing proapoptotic signals, thus preventing podocyte loss.
• miR-21 acts as a feedback inhibitor of TGF-β signaling in the context of glomerular disease.
• Findings in glomerular injury contrast with tubulointerstitial injury models but align with cancer models.