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
View: Text | PDF
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

×

Figure 2

Lymphatic defects in Fbn1 mutant MVs.

Options: View larger image (or click on image) Download as PowerPoint
Lymphatic defects in Fbn1 mutant MVs. (A) Representative confocal images...
(A) Representative confocal images of whole-mount leaflets at 6 weeks. Arrows indicate LVs. Scale bars: 200 μm. (B) Quantification of lymphatic density in the total leaflet area (both aL and pL) (N = 8-9 per group; 5 males, 3-4 females), LV diameter (N = 6-8; 3-5 males, 3 females), and number of lymphatic branching points/0.01 mm2 of LVs (N = 7-8; 3-5 males, 3–4 females). Data are mean ± SEM, unpaired 2-tailed Student’s t test, *P < 0.05, ***P < 0.001. (C) Representative confocal images of lymphatic capillaries in MVs showing impaired lymphatic cell-cell junctions in Fbn1 mutant MVs at 6 weeks. Boxed regions are shown at higher magnification in insets a–e. Blue and red boxes represent the tip and proximal segment, respectively, of the LV. Arrows indicate disrupted cell-cell junctions in the mutant compared with the continuous junctions in WT. Pink and blue scale bars: 20 and 10 μm, respectively. (D–G) Evans blue permeability assay at P14 using mice with Prox1-eGFP reporter. N = 6–8; 4–5 males, 2–3 females. (D) Representative Z-stack images of MV leaflets. Prox1-eGFP is expressed not only in LECs but also in VECs in the MV leaflet. Arrows indicate LVs. White dashed lines show the proximal edge of the MV leaflets. EC-Z1, EC zone 1. Scale bars: 200 μm. (F) Representative optical section images showing Evans blue outside and inside LVs (outlined by dashed lines). Scale bars: 20 μm. Quantification was performed for the fluorescence intensity (FI) of Evans blue (EB) in the interstitium beneath EC zone 1 for both aLs and pLs (E), and outside/inside LVs (G). Data are mean ± SEM, unpaired 2-tailed Student’s t test, each symbol represents 1 mouse, ***P < 0.001, ****P < 0.0001.