Wnt Signaling Inhibition Prevents Postnatal Inflammation and Disease Progression in Mouse Congenital Myxomatous Valve Disease.

BACKGROUND

Myxomatous valve disease (MVD) is the most common cause of mitral regurgitation, leading to impaired cardiac function and heart failure. MVD in a mouse model of Marfan syndrome includes valve leaflet thickening and progressive valve degeneration. However, the underlying mechanisms by which the disease progresses remain undefined.

METHODS

Mice with gene variant recapitulate histopathologic features of Marfan syndrome, and Wnt (Wingless-related integration site) signaling activity was detected in (T-cell factor/lymphoid enhancer factor-β-galactosidase) reporter mice. Single-cell RNA sequencing was performed from mitral valves of wild-type and mice at 1 month of age. Inhibition of Wnt signaling was achieved by conditional induction of the secreted Wnt inhibitor Dkk1 (Dickkopf-1) expression in periostin-expressing valve interstitial cells of -Cre; mice. Dietary doxycycline was administered for 1 month beginning with MVD initiation (1-month-old) or MVD progression (2-month-old). Histological evaluation and immunofluorescence for ECM (extracellular matrix) and immune cells were performed.

RESULTS

Wnt signaling is activated early in mitral valve disease progression, before immune cell infiltration in mice. Single-cell transcriptomics revealed similar mitral valve cell heterogeneity between wild-type and mice at 1 month of age. Wnt pathway genes were predominantly expressed in valve interstitial cells and valve endothelial cells of mice. Inhibition of Wnt signaling in mice at 1 month of age prevented the initiation of MVD as indicated by improved ECM remodeling and reduced valve leaflet thickness with decreased infiltrating macrophages. However, later, Wnt inhibition starting at 2 months did not prevent the progression of MVD.

CONCLUSIONS

Wnt signaling is involved in the initiation of mitral valve abnormalities and inflammation but is not responsible for later-stage valve disease progression once it has been initiated. Thus, Wnt signaling contributes to MVD progression in a time-dependent manner and provides a promising therapeutic target for the early treatment of congenital MVD in Marfan syndrome.