MiR‐29 mediates TGFβ1‐induced extracellular matrix synthesis through activation of PI3K‐AKT pathway in human lung fibroblasts

TGFβ1 is very important in the synthesis and degradation of extracellular matrix, and also in the mediation of human lung fibroblasts proliferation, and miR‐29 plays an important role in this process. To explore the interactions of miR‐29 family members and TGFβ1, the effects of transforming growth factor TGFβ1 on the expression of miR‐29 and whether miR‐29 is involved in pro‐survival signaling pathways mediated by TGFβ1 were examined in human lung fibroblasts. Treatment of the human embryonic lung fibroblast cell line IMR90 with TGFβ1 caused a decrease in expression of miR‐29a/b/c by real‐time PCR analysis. TGFβ1 stimulation increased cell proliferation, colony formation and up‐regulated expression of COL1A1; transfecting with miR‐29a/b/c mimics reverse TGFβ1‐induced phenotype changes in IMR90 cells. Western blot analyses showed that TGFβ1 treatment unchanged total protein expression levels of PI3K or AKT, but the expression levels of p‐PI3K, p‐AKT, and COL1A1 were increased; and miR‐19a/b/c mimics interfering blocked phosphorylation of PI3K or AKT and decreased expression of COL1A1 after TGFβ1 treatment. The results indicate that TGFβ1 beta uses the PI3k‐Akt pathway in these embryonic fibroblasts and miR29 blocks this activation pathway. It indicates a novel biological function of the PI3K‐Akt pathway in IMR90. Elevated expression of miR‐29 may play an important role in the pathogenesis of diseases related to fibrogenic reactions in human lung fibroblasts. J. Cell. Biochem. 114: 1336–1342, 2013. © 2013 Wiley Periodicals, Inc.