Tissue inhibitor of metalloproteinase-1 (TIMP-1) regulates mesenchymal stem cells through let-7f microRNA and Wnt/β-catenin signaling.
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/β-catenin signaling pathway as indicated by the increased stability and nuclear localization of β-catenin in TIMP-1-deficient hMSCs. Moreover, TIMP-1 knockdown cells exhibited enhanced β-catenin transcriptional activity, determined by Wnt/β-catenin target gene expression analysis and a luciferase-based β-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 β-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/β-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 β-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 β-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/β-catenin activity.
Division of Clinical Chemistry and Clinical Biochemistry, Surgical Department, Ludwig-Maximilians-University, 80336 Munich, Germany.
Virginia
V
Egea
Stefan
S
Zahler
Nicole
N
Rieth
Peter
P
Neth
Tanja
T
Popp
Kai
K
Kehe
Marianne
M
Jochum
Christian
C
Ries
D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D055785:Gene Knockdown Techniques; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000201:enzymology*; D035683:MicroRNAs / Q000378:metabolism*; D010012:Osteogenesis; D011485:Protein Binding; D060149:Tetraspanin 30 / Q000378:metabolism; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism*; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000378:metabolism
D035683:MicroRNAs; D060149:Tetraspanin 30; D019715:Tissue Inhibitor of Metalloproteinase-1; D051176:beta Catenin; C487931:mirnlet7 microRNA, human