Abstract P1112: Inhibition Of Wnt Signaling Protects Against Myxomatous Valve Disease In A Mouse Model Of Marfan Syndrome

Abstract

Introduction: Myxomatous valve disease (MVD) is the most common cause of mitral regurgitation, characterized by valve leaflet thickening and progressive valve degeneration, leading to impaired cardiac function and heart failure. MVD in a mouse model of Marfan syndrome (MFS) includes valve leaflet thickening and increased immune cell infiltration. However, the underlying mechanisms by which immune cells are recruited in MFS valves remain undefined. Hypothesis: Inhibition of Wnt signaling prevents immune cell recruitment and MVD progression in MFS valves. Methods: Mice with the mutation of Fibrillin 1 ( Fbn1 C1039G/+ ) recapitulate histopathological features of MFS and Wnt signaling activity was detected in TCF/Lef-lacZ reporter mice. Inhibition of Wnt signaling was achieved by conditional induction of the soluble Wnt inhibitor Dkk1 in periostin-expressing valve interstitial cells of Periostin-Cre; tetO-Dkk1; R26rtTA; TCF/Lef-lacZ; Fbn1 C1039G/+ mice. Dietary doxycycline was administered for one month beginning with MVD initiation (1-month-old) or MVD progression (2-month-old). Histological evaluation and immunofluorescence for immune cells were performed. Results: Wnt signaling as detected by TCF/Lef-reporters is activated early in mitral valve disease progression, prior to immune cell infiltration in Fbn1 C1039G/+ mice. Inhibition of Wnt signaling by Dkk1 induction at 1-month of age reduced valve leaflet thickness with decreased CD45+ leukocytes in Fbn1 C1039G/+ mice. However, later Wnt inhibition starting at 2 months did not alter valve leaflet thickness. Conclusions: Inhibition of early Wnt signaling ameliorates myxomatous valve degeneration and immune cell infiltration previously demonstrated to be required for progression of MVD.