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- Title
Runx2 deletion in smoothmuscle cells inhibits vascular osteochondrogenesis and calcification but not atherosclerotic lesion formation.
- Authors
Mu-En Lin; Chen, Theodore M.; Wallingford, Mary C.; Nguyen, Ngoc B.; Shunsuke Yamada; Chenphop Sawangmake; Jaimei Zhang; Speer, Mei Y.; Giachelli, Cecilia M.
- Abstract
Aims Vascular smooth muscle cells (SMCs) are major precursors contributing to osteochondrogenesis and calcification in atherosclerosis. Runt-related transcription factor-2 (Runx2) has been found essential for SMC differentiation to an osteochondrogenic phenotype and subsequent calcification in vitro. A recent study using a conditional targeting allele that produced a truncated Runx2 protein in SMCs of ApoE−/− mice showed reduced vascular calcification, likely occurring via reduction of receptor activator of nuclear factor-κB ligand (RANKL), macrophage infiltration, and atherosclerotic lesion formation. Using an improved conditional Runx2 knockout mouse model, we have elucidated new roles for SMC-specific Runx2 in arterial intimal calcification (AIC) without effects on atherosclerotic lesion size. Methods and results We used an improved targeting construct to generate LDLr−/− mice with floxed-Runx2 alleles ( LDLr−/− :Runx2 f/f ) such that Cre-mediated recombination ( LDLr−/− :Runx2 ΔSM ) does not produce functional truncated Runx2 protein, thereby avoiding off-target effects. We found that both LDLr−/− :Runx2 f/f and LDLr−/− :Runx2 ΔSM mice fed with a high fat diet developed atherosclerosis. SMC-specific Runx2 deletion did not significantly reduce atherosclerotic lesion size, macrophage number, or expression of RANKL, MCP-1, and CCR2. However, it significantly reduced AIC by 50%. Mechanistically, Sox9 and type II collagen were unaltered in vessels of LDLr−/− :Runx2 ΔSM mice compared to LDLr−/− :Runx2 f/f counterparts, while type X collagen, MMP13 and the osteoblastic marker osteocalcin were significantly reduced. Conclusions SMC autonomous Runx2 is required for SMC differentiation towards osteoblast-like cells, SMC-derived chondrocyte maturation and AIC in atherosclerotic mice. These effects were independent of systemic lipid metabolism, RANKL expression, macrophage infiltration, and atheromatous lesion progression.
- Subjects
DELETION mutation; VASCULAR smooth muscle; CHONDROGENESIS; ATHEROSCLEROSIS treatment; CALCIFICATION
- Publication
Cardiovascular Research, 2016, Vol 112, Issue 2, p606
- ISSN
0008-6363
- Publication type
Article
- DOI
10.1093/cvr/cvw205