Long noncoding RNA-GAS5 retards renal fibrosis through repressing miR-21 activity

Abstract Background/aims Long noncoding RNA (lncRNA) is a large and diverse class of RNA molecules, and has received widespread attention for its role in the regulation of various biological processes, including stem cell transformation, neurological disease, and tumorigenesis. However, the role of lncRNA in renal fibrosis remains unclear. Methods We investigated the expression of lncRNA-GAS5 by quantitative real-time polymerase chain reaction (PCR) or fluorescence in situ hybridization in chronic kidney disease (CKD) by designing both in vivo and in vitro experiments. With over-expression of GAS5 or knockdown GAS5, miR-21 and its downstream target genes were tested using quantitative real-time PCR or western blots. Mutants of miR-21 were designed and transfected in cells. GAS5 in the plasma and urine of patients with CKD was measured by quantitative real-time PCR. Results In normal rats, GAS5 was predominantly expressed in renal tubular epithelial cells. GAS5 induction was significantly reduced in obstructive kidneys at 7 days after unilateral ureteral obstruction. In vitro, GAS5 was inhibited in cultured normal rat renal proximal tubular cells (NRK-52E) after incubation with transforming growth factor β at 24 h. Ectopic over-expression of GAS5 repressed extracellular matrix (ECM) levels such as collagen type III and fibronectin 1. Conversely, knockdown GAS5 augmented ECM accumulation in NRK-52E cells. GAS5 suppressed miR-21 activity in a direct and mechanistic manner. It subsequently turned off the expression of miR-21 downstream target genes, matrix metallopeptidase 2 and 9, which resulted in excessive ECM synthesis and deposition. Of note, plasma GAS5 was positively correlated with estimated glomerular filtration rate levels in CKD patients with different etiologies while urine GAS5 was negatively correlated. Conclusion Activation of lncRNA-GAS5 attenuates kidney fibrosis by modulating miR-21 activity and may serve as a surrogate biomarker in monitoring CKD progression.