Lymphatic dysfunction and ZFP36 deficiency contribute to myxomatous valve degeneration in Marfan syndrome mice
Can Tan, Ziyou Ren, Shreya Kurup, Xianpeng Liu, Zhi-Dong Ge, Shodai Suzuki, Pritika Jakka, Cheryl Tang, M. Luisa Iruela-Arispe, Tsutomu Kume
Can Tan, Ziyou Ren, Shreya Kurup, Xianpeng Liu, Zhi-Dong Ge, Shodai Suzuki, Pritika Jakka, Cheryl Tang, M. Luisa Iruela-Arispe, Tsutomu Kume
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Research Article Cardiology Development Vascular biology

Lymphatic dysfunction and ZFP36 deficiency contribute to myxomatous valve degeneration in Marfan syndrome mice

Abstract

Enhanced TGF-β signaling caused by mutations in Fibrillin-1 (FBN1) in patients with Marfan syndrome (MFS) leads to myxomatous degeneration of the mitral valve (MDMV). MDMV can result in mitral valve prolapse, severe regurgitation, and sudden cardiac death. However, it remains unknown whether lymphatic vessel (LV) dysfunction contributes to MDMV development in MFS. Here, we show that lymphangiogenesis in murine mitral valves (MVs) begins postnatally. However, this process is inhibited in a mouse MFS model, Fbn1 mutant (Fbn1C1039G/+) mice, accompanied by disrupted lymphatic cell-cell junctions, impaired lymphatic drainage, and an abnormally widespread distribution of MHCII+ infiltrating macrophages. Treatment of Fbn1 mutant mice with VEGF-C156S, a selective VEGFR3 agonist, stimulates the ERK and Akt pathways, increases LV density in MVs, and ameliorates MDMV. Fbn1 mutant MVs display disorganized valvular endothelial cells (VECs) and decreased expression of the antiinflammatory modulator Zfp36 (zinc finger protein 36) in VECs and immune cells. Treatment with FTY720 (fingolimod), a ZFP36 activator and S1P antagonist, rescues MDMV phenotypes in Fbn1 mutant mice by reducing immune cell infiltration and restoring lymphatic cell junctions and drainage. These findings suggest that the Fbn1 mutation causes LV hypoplasia and defective lymphatic drainage in MVs, driven in part by proinflammatory VECs, leading to MFS-related MDMV.

Authors

Can Tan, Ziyou Ren, Shreya Kurup, Xianpeng Liu, Zhi-Dong Ge, Shodai Suzuki, Pritika Jakka, Cheryl Tang, M. Luisa Iruela-Arispe, Tsutomu Kume

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Figure 1

Development of LVs is inhibited in Fbn1 mutant MVs.

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Development of LVs is inhibited in Fbn1 mutant MVs. Whole-mount immunost...
Whole-mount immunostaining followed by confocal imaging was performed on hearts and MV samples. (A) Z-stack (left) and optical section (right) images show vasculatures near MV leaflets in WT mouse at E12.5. White and black scale bars: 100 and 50 μm, respectively. (B) Development of LVs in MVs of WT mice at early stages. LVs (VEGFR3+, indicated by arrows) appear in the anterior triangle (AT; outlined by a white dashed line) above the anterior commissure (AC) at P0 before sprouting and penetrating the mitral annulus (MA) at P3. The asterisk indicates the left ventricular wall at the fibrosa side of the pL. Scale bars: 200 μm. (C) Lymphatic sprouting in the aL at P7. White and green arrows indicate lymphatic sprouts from the sides of the anterior (AC) and posterior commissure, respectively. Scale bars: 200 μm. (D) Lymphatic sprouting in aLs at P14. Arrows indicate the EdU+ LECs. Yellow lines outline the proximal edge of MV leaflets. White and yellow scale bars: 200 and 50 μm, respectively. (E–H) Quantification of MV leaflet area (E), LV area (F), LV density (G), and number of EdU+ LECs (H) based on D and Supplemental Figure 2B. Data are mean ± SEM, unpaired 2-tailed Student’s t test, each symbol represents 1 mouse. N = 6–7 in E–G (male/female = 3–4:3 per group), N = 4 in H (male/female = 3:1 and 1:3 in WT and mutant, respectively), *P < 0.05, **P < 0.01, ***P < 0.001.