Tissue inhibitor of metalloproteinase-1 (TIMP-1) regulates mesenchymal stem cells through let-7f microRNA and Wnt/?-catenin signaling.
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ABSTRACT: Tissue inhibitor of metalloproteinases 1 (TIMP-1) is a matrix metalloproteinase (MMP)-independent regulator of growth and apoptosis in various cell types. The receptors and signaling pathways that are involved in the growth factor activities of TIMP-1, however, remain controversial. RNA interference of TIMP-1 has revealed that endogenous TIMP-1 suppresses the proliferation, metabolic activity, and osteogenic differentiation capacity of human mesenchymal stem cells (hMSCs). The knockdown of TIMP-1 in hMSCs activated the Wnt/?-catenin signaling pathway as indicated by the increased stability and nuclear localization of ?-catenin in TIMP-1-deficient hMSCs. Moreover, TIMP-1 knockdown cells exhibited enhanced ?-catenin transcriptional activity, determined by Wnt/?-catenin target gene expression analysis and a luciferase-based ?-catenin-activated reporter assay. An analysis of a mutant form of TIMP-1 that cannot inhibit MMP indicated that the effect of TIMP-1 on ?-catenin signaling is MMP independent. Furthermore, the binding of CD63 to TIMP-1 on the surface of hMSCs is essential for the TIMP-1-mediated effects on Wnt/?-catenin signaling. An array analysis of microRNAs (miRNAs) and transfection studies with specific miRNA inhibitors and mimics showed that let-7f miRNA is crucial for the regulation of ?-catenin activity and osteogenic differentiation by TIMP-1. Let-7f was up-regulated in TIMP-1-depleted hMSCs and demonstrably reduced axin 2, an antagonist of ?-catenin stability. Our results demonstrate that TIMP-1 is a direct regulator of hMSC functions and reveal a regulatory network in which let-7f modulates Wnt/?-catenin activity.
SUBMITTER: Egea V
PROVIDER: S-EPMC3277529 | biostudies-literature | 2012 Feb
REPOSITORIES: biostudies-literature
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