Elevated Levels of miR-146a and miR-155 in Kidney Biopsy and Urine from Patients with IgA Nephropathy

Background: Previous studies suggested miR-146a and miR-155 play important roles in innate and adaptive immune responses. We studied intra-renal and urinary levels of miR-146a and miR-155 in patients with immunoglobulin A nephropathy (IgAN). Methods: Intra-renal and urinary levels of miR-146a and miR-155 are quantified in 43 patients with IgAN; the result was compared to 20 nephrectomy specimens and urine sediment of 13 healthy volunteers. Results: The levels of intra-renal and urinary levels of miR-146a and miR-155 of IgAN are significantly higher than controls. Estimated glomerular filtration rate inversely correlates with intra-renal level of miR-146a and miR-155; proteinuria positively correlates with intra-renal level of miR-146a and miR-155, as well as urinary level of miR-146a and miR-155. Intra-renal level of miR-155 significantly correlates with tubulointerstitial scarring. Urinary level of miR-146a inversely correlates with urinary expression of interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α and positively correlates with urinary expression of regulated upon activation, normal T-cell expressed, and secreted (RANTES). Urinary level of miR-155 inversely correlates with urinary expression of IL-1β and TNF-α and positively correlates with urinary expression of forkhead box P3 (FOXP3) and RANTES. Conclusion: We conclude that intra-renal and urinary levels of miR-146a and miR-155 were significantly elevated in IgAN, and the degree of upregulation correlates with clinical and histological severity of the disease. Our results suggested miR-146a and miR-155 might play an important role in the pathophysiology of IgAN.