title: Runx2 Expression in Smooth Muscle Cells Is Required for Arterial Medial Calcification in Mice.
abstract: Arterial medial calcification (AMC) is a hallmark of aging, diabetes, and chronic kidney disease. Smooth muscle cell (SMC) transition to an osteogenic phenotype is a common feature of AMC, and is preceded by expression of runt-related transcription factor 2 (Runx2), a master regulator of bone development. Whether SMC-specific Runx2 expression is required for osteogenic phenotype change and AMC remains unknown. We therefore created an improved targeting construct to generate mice with floxed Runx2 alleles (Runx2(f/f)) that do not produce truncated Runx2 proteins after Cre recombination, thereby preventing potential off-target effects. SMC-specific deletion using SM22-recombinase transgenic allele mice (Runx2(ΔSM)) led to viable mice with normal bone and arterial morphology. After vitamin D overload, arterial SMCs in Runx2(f/f) mice expressed Runx2, underwent osteogenic phenotype change, and developed severe AMC. In contrast, vitamin D-treated Runx2(ΔSM) mice had no Runx2 in blood vessels, maintained SMC phenotype, and did not develop AMC. Runx2 deletion did not affect serum calcium, phosphate, fibroblast growth factor-23, or alkaline phosphatase levels. In vitro, Runx2(f/f) SMCs calcified to a much greater extent than those derived from Runx2(ΔSM) mice. These data indicate a critical role of Runx2 in SMC osteogenic phenotype change and mineral deposition in a mouse model of AMC, suggesting that Runx2 and downstream osteogenic pathways in SMCs may be useful therapeutic targets for treating or preventing AMC in high-risk patients.
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington.
authors.forename: Mu-En
authors.initials: ME
authors.lastname: Lin
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington.
authors.forename: Theodore
authors.initials: T
authors.lastname: Chen
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Leaf
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington. Electronic address: yfwang@u.washington.edu.
authors.forename: Mei Y
authors.initials: MY
authors.lastname: Speer
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington. Electronic address: ceci@u.washington.edu.
authors.forename: Cecilia M
authors.initials: CM
authors.lastname: Giachelli
mesh_terms: D000818:Animals; D001846:Bone Development; D002118:Calcium / Q000378:metabolism*; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D032389:Myocytes, Smooth Muscle / Q000378:metabolism* / Q000473:pathology; D010012:Osteogenesis / Q000187:drug effects; D010641:Phenotype; D010710:Phosphates / Q000378:metabolism; D017384:Sequence Deletion; D061205:Vascular Calcification / Q000378:metabolism* / Q000473:pathology; D014807:Vitamin D / Q000009:adverse effects
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D010710:Phosphates; C493716:Runx2 protein, mouse; D014807:Vitamin D; D002118:Calcium