MSX2-Wnt Signaling in Cardiovascular Calcification

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DESCRIPTION (provided by applicant): Cardiovascular calcification is a common consequence of aging, diabetes, hypercholesterolemia, hypertension, abnormal valve mechanics & inflammation, & chronic renal insufficiency. Once thought benign, the deleterious clinical consequences of calcific vasculopathy are now becoming clear; it is a key component of pathophysiology leading to CVA, Ml, and PVD -- with amputation and cardiovascular mortality portended by the anatomy and extent of calcific vasculopathy. The ability to cure or substantially reverse macrovascular calcification (MVC) represents an unmet clinical need. A better understanding of MVC initiation and progression is required. Osteogenic & inflammatory gene regulatory programs are activated in MVC-- variably involving adventitial, medial, intimal, and valvular tissues -- via mechanisms overlapping those that control bone physiology. We've shown that a pro-osteogenic program -- a "feed-forward" BMP2-Msx2-Wnt signaling cascade -- is activated in aortic myofibroblasts by diabetes and dyslipidemia. By contrast, PTH/PTHrP receptor agonists (e.g., teriparatide) suppress vascular myofibroblast calcification and aortic Msx2-Wnt gene expression. We now study the role and regulation of myofibroblast Msx2-Wnt signaling in MVC. In Aim 1, we use LDLR-/-.TOPGAL+ reporter mice (LacZ transgene under control of Wnt-responsive TCF/LEF element) to relate spatial activation of aortic Wnt signaling to diet-induced Msx2-Wnt expression and recruitment of osteoprogenitors from adventitial, medial, & valvular myofibroblasts. We also test if the enhanced aortic calcification and Wnt expression we observe in CMV-Msx2 transgenic mice activates aortic LacZ expression. Co-culture studies of primary aortic myofibroblasts will test if Msx2--activated paracrine Writ signaling is inhibited by PTH (1-34). In Aim 2, using TOPGAL mice, we test if PTH(1-34) inhibits canonical Wnt signaling in vivo. In Aim 3, we map Msx2 promoter protein-DNA interactions that convey transcriptional suppression to PTH(1-34) in myofibroblasts, emphasizing elements that mediate BMP2 and Wnt activation.