Effects of microRNA-346 on epithelial-mesenchymal transition in mouse podocytes.

Recent studies have shown that microRNA (miR)-346 regulates the expression of glycogen synthase kinase (GSK)-3β and activates the Wnt/β-catenin pathway, which regulates the differentiation of human bone marrow mesenchymal stem cells. Here, we explored whether miR-346 was involved in high glucose-induced epithelial-mesenchymal transition in mouse podocytes and examined the relationship between miR-346 and GSK-3β expression. The expression of miR-346 in podocytes was measured in the presence of different concentrations of glucose. Podocytes were transfected with miR-346 mimic or miR-346 inhibitor to test whether miR-346 affected the expression of nephrin, α-smooth muscle actin (α-SMA), and GSK-3β. Luciferase assays were performed to determine whether miR-346 directly regulated GSK-3β expression. The expression of miR-346 was significantly higher in podocytes cultured in the presence of 12.5mM glucose than in podocytes cultured in the presence of physiological glucose (5.6mM). However, culture in 25 mM glucose resulted in decreased miR-346 expression compared with culture in 12.5mM glucose. Cells transfected with miR-346 mimic showed reduced expression of α-SMA and increased expression of nephrin. Luciferase assays showed that miR-346 did not directly bind to the 3'-untranslated region of GSK-3β mRNA in mouse podocytes. The production of GSK-3β protein was markedly lower in podocytes transfected with the miR-346 mimic than in untransfected podocytes but was not altered in podocytes transfected with miR-346 inhibitor. Thus, these data demonstrated that miR-346 participated in the epithelial-mesenchymal transition in mouse podocytes under high-glucose conditions and that miR-346 could indirectly regulate the expression of GSK-3β in mouse podocytes.