Abstract：
UNASSIGNED: Mitral valve (MV) disease including myxomatous degeneration is the most common form of valvular heart disease with an age-dependent frequency. Genetic evidence indicates that mutations of the transcription factor FOXC1 are associated with MV defects, including MV regurgitation. In this study, we sought to determine whether murine Foxc1 and its closely related factor, Foxc2, are required in valvular endothelial cells (VECs) for the maintenance of MV leaflets, including VEC junctions and the stratified trilaminar ECM (extracellular matrix).
UNASSIGNED: Adult mice carrying tamoxifen-inducible, vascular endothelial cell (EC), and lymphatic EC-specific, compound Foxc1;Foxc2 mutations (ie, EC-Foxc-DKO and lymphatic EC-Foxc-DKO mice, respectively) were used to study the function of Foxc1 and Foxc2 in the maintenance of MVs. The EC and lymphatic EC mutations of Foxc1/c2 were induced at 7 to 8 weeks of age by tamoxifen treatment, and abnormalities in the MVs of these mutant mice were assessed via whole-mount immunostaining, immunohistochemistry/RNAscope, Movat pentachrome/Masson Trichrome staining, and Evans blue injection.
UNASSIGNED: EC deletions of Foxc1 and Foxc2 in mice resulted in abnormally extended and thicker MVs by causing defects in the regulation of ECM organization with increased proteoglycan and decreased collagen. Notably, reticular adherens junctions were found in VECs of control MV leaflets, and these reticular structures were severely disrupted in EC-Foxc-DKO mice. PROX1 (prospero homeobox protein 1), a key regulator in a subset of VECs on the fibrosa side of MVs, was downregulated in EC-Foxc1/c2 mutant VECs. Furthermore, we determined the precise location of lymphatic vessels in murine MVs, and these lymphatic vessels were aberrantly expanded and dysfunctional in EC-Foxc1/c2 mutant MVs. Lymphatic EC deletion of Foxc1/c2 also resulted in similar structural/ECM abnormalities as seen in EC-Foxc1/c2 mutant MVs.
UNASSIGNED: Our results indicate that Foxc1 and Foxc2 are required for maintaining the integrity of the MV, including VEC junctions, ECM organization, and lymphatic vessel formation/function to prevent myxomatous MV degeneration.
UNASSIGNED: Adult mice carrying tamoxifen-inducible, vascular endothelial cell (EC), and lymphatic EC-specific, compound Foxc1;Foxc2 mutations (ie, EC-Foxc-DKO and lymphatic EC-Foxc-DKO mice, respectively) were used to study the function of Foxc1 and Foxc2 in the maintenance of MVs. The EC and lymphatic EC mutations of Foxc1/c2 were induced at 7 to 8 weeks of age by tamoxifen treatment, and abnormalities in the MVs of these mutant mice were assessed via whole-mount immunostaining, immunohistochemistry/RNAscope, Movat pentachrome/Masson Trichrome staining, and Evans blue injection.
UNASSIGNED: EC deletions of Foxc1 and Foxc2 in mice resulted in abnormally extended and thicker MVs by causing defects in the regulation of ECM organization with increased proteoglycan and decreased collagen. Notably, reticular adherens junctions were found in VECs of control MV leaflets, and these reticular structures were severely disrupted in EC-Foxc-DKO mice. PROX1 (prospero homeobox protein 1), a key regulator in a subset of VECs on the fibrosa side of MVs, was downregulated in EC-Foxc1/c2 mutant VECs. Furthermore, we determined the precise location of lymphatic vessels in murine MVs, and these lymphatic vessels were aberrantly expanded and dysfunctional in EC-Foxc1/c2 mutant MVs. Lymphatic EC deletion of Foxc1/c2 also resulted in similar structural/ECM abnormalities as seen in EC-Foxc1/c2 mutant MVs.
UNASSIGNED: Our results indicate that Foxc1 and Foxc2 are required for maintaining the integrity of the MV, including VEC junctions, ECM organization, and lymphatic vessel formation/function to prevent myxomatous MV degeneration.
摘要：
■包括粘液瘤变性的二尖瓣（MV）疾病是瓣膜性心脏病的最常见形式，其频率与年龄有关。遗传证据表明，转录因子FOXC1的突变与MV缺陷有关，包括MV返流。在这项研究中,我们试图确定小鼠Foxc1及其密切相关的因子，Foxc2是瓣膜内皮细胞(VECs)维持MV小叶所必需的,包括VEC连接和分层三层ECM(细胞外基质)。
■携带他莫昔芬诱导的成年小鼠，血管内皮细胞（EC），和淋巴EC特异性，化合物Foxc1；Foxc2突变(即，EC-Foxc-DKO和淋巴EC-Foxc-DKO小鼠，分别）用于研究Foxc1和Foxc2在维护MV中的功能。在7~8周龄时,通过他莫昔芬治疗诱导Foxc1/c2的EC和淋巴EC突变,并通过整装免疫染色评估这些突变小鼠的MV异常，免疫组织化学/RNA检查，Movatpentachrome/Masson三色染色，还有伊文思蓝注射液.
■小鼠中Foxc1和Foxc2的EC缺失导致ECM组织的调节缺陷，蛋白聚糖增加，胶原蛋白减少，导致MV异常延长和增厚。值得注意的是,在对照MV小叶的VEC中发现了网状粘附连接，这些网状结构在EC-Foxc-DKO小鼠中被严重破坏。PROX1（prosprohomeobox蛋白1），MV纤维侧VEC子集中的关键调节因子，在EC-Foxc1/c2突变型VEC中下调。此外，我们确定了小鼠MV中淋巴管的精确位置，在EC-Foxc1/c2突变体MV中，这些淋巴管异常扩张和功能障碍。Foxc1/c2的淋巴EC缺失也导致类似的结构/ECM异常,如在EC-Foxc1/c2突变体MV中所见。
■我们的结果表明，Foxc1和Foxc2是维持MV完整性所必需的，包括VEC接头，ECM组织，和淋巴管形成/功能，以防止粘液瘤MV变性。
■携带他莫昔芬诱导的成年小鼠，血管内皮细胞（EC），和淋巴EC特异性，化合物Foxc1；Foxc2突变(即，EC-Foxc-DKO和淋巴EC-Foxc-DKO小鼠，分别）用于研究Foxc1和Foxc2在维护MV中的功能。在7~8周龄时,通过他莫昔芬治疗诱导Foxc1/c2的EC和淋巴EC突变,并通过整装免疫染色评估这些突变小鼠的MV异常，免疫组织化学/RNA检查，Movatpentachrome/Masson三色染色，还有伊文思蓝注射液.
■小鼠中Foxc1和Foxc2的EC缺失导致ECM组织的调节缺陷，蛋白聚糖增加，胶原蛋白减少，导致MV异常延长和增厚。值得注意的是,在对照MV小叶的VEC中发现了网状粘附连接，这些网状结构在EC-Foxc-DKO小鼠中被严重破坏。PROX1（prosprohomeobox蛋白1），MV纤维侧VEC子集中的关键调节因子，在EC-Foxc1/c2突变型VEC中下调。此外，我们确定了小鼠MV中淋巴管的精确位置，在EC-Foxc1/c2突变体MV中，这些淋巴管异常扩张和功能障碍。Foxc1/c2的淋巴EC缺失也导致类似的结构/ECM异常,如在EC-Foxc1/c2突变体MV中所见。
■我们的结果表明，Foxc1和Foxc2是维持MV完整性所必需的，包括VEC接头，ECM组织，和淋巴管形成/功能，以防止粘液瘤MV变性。
