Effect of Mitral Regurgitation on Ischemic LV Remodeling

描述（由申请人提供）：本补充材料将使用人胚胎干细胞（ESC）来解决心肌梗死（MI）后左心室（LV）重塑对心室大小和功能的不良影响，特别关注这种重塑如何通过引起二尖瓣返流（MR）来增加容量超负荷。这些是母研究R 01（二尖瓣返流对缺血性LV重塑的影响）和相关研究R21（缺血性MR的主动补片治疗）中的科学问题。MI后，心脏壁的局部扭曲限制了附着的二尖瓣瓣叶闭合的能力，导致MR，从而加剧LV重塑并使晚期死亡率加倍。我们的初步研究表明，被动的外部约束施加到MI区可以扭转其形状变化，消除MR，但是，整个区域的心肌仍然是固定的。与合作的研究人员一起，我们一直在研究将自体骨骼成肌细胞注射到梗死壁中以使其重新成形并重新成形可以逆转MR的可能性，同时也有可能增强收缩。然而，使用骨骼肌成肌细胞用于此目的可能存在一些限制，包括缺乏协调收缩所需的移植细胞和宿主细胞之间的连接间隙连接。因此，下一个合乎逻辑的步骤将是测试我们是否可以减少LV重塑和缺血性MR，同时，通过在梗死后MR模型中使用人胚胎干细胞代替骨骼肌成肌细胞来提供功能组织的额外益处。我们的同事已经表明，这种未分化的细胞，在组织生长因子的影响下，可以致力于心脏谱系，有证据表明肌节条纹和间隙连接蛋白的表达，允许与周围心肌整合。因此，来自胚胎干细胞的细胞将是用真正的肌细胞替代受损肌肉的最佳候选者，具有实际增加收缩力的最大潜力。具体目标包括：1）建立简单的人胚胎干细胞心脏定向移植方案，并了解其分子机制 2）研究肿瘤细胞的命运和免疫相容性， 移植到MI后和衰竭的绵羊心脏中的心脏定向ESC;和3）评估 在患有MR. NIH细胞登记号TE 03恶化的心力衰竭的绵羊中植入心脏定向ESC后心脏功能的改善（培训可用）。该补充汇集了独特的资源和专业知识来应对这一挑战，包括在细胞移植到梗死区域，在其他物种中成功的ESC心脏分化以及心脏功能的定量三维评估方面具有丰富经验的团队。

DESCRIPTION (provided by applicant): This supplement will use human embryonic stem cells (ESCs) to address the adverse effects of left ventricular (LV) remodeling following myocardial infarction (MI) on ventricular size and function, with particular focus on how such remodeling augments volume overload by causing mitral regurgitation (MR). These are the scientific questions in the parent R01, Effect of Mitral Regurgitation on Ischemic LV Remodeling, and the related R21, Active Patch Therapy of Ischemic MR. Following MI, localized distortion of the heart wall restricts the ability of the attached mitral leaflets to close, causing MR that exacerbates LV remodeling and doubles late mortality. Our initial studies have shown that passive external constraints applied to the MI zone can reverse its shape change and eliminate MR; however, an entire region of myocardium remains immobilized. With collaborating investigators, we have been studying the possibility that injecting autologous skeletal myoblasts into the infarcted wall to thicken and re-shape it can reverse MR, with potential for augmenting contraction as well. However, there may be some limitations of using skeletal myoblasts for this purpose, including absence of connecting gap junctions between grafted and host cells needed for concerted contraction. The next logical step would therefore be to test whether we can reduce LV remodeling and ischemic MR and, at the same time, provide the added benefit of functional tissue by using human embryonic stem cells instead of skeletal myoblasts in a post-infarct MR model. Our colleagues have shown that such undifferentiated cells, under the influence of tissue growth factors, can be committed to a cardiac lineage, with evidence for sarcomeric striations and expression of gap junction protein, allowing integration with surrounding myocardium. Cells derived from embryonic stem cells would therefore be the best candidates to replace damaged muscle with true myocytes, with the greatest potential for actually increasing contractility. Specific aims include: 1) To establish simple protocols for cardiac commitment of human ESCs and to understand the molecular mechanisms underlying this process to prevent tumor formation; 2) To investigate the fate and immunocompatibility of cardiac-committed ESCs transplanted into post-MI and failing sheep hearts; and 3) To evaluate the improvement of cardiac function after engraftment of cardiac-committed ESCs in sheep with heart failure worsened by MR. NIH cell registry number TE03 (training available). This supplement brings together unique resources and expertise to address this challenge, including groups with extensive experience in cell transplantation into infarcted regions, successful cardiac differentiation of ESCs in other species, and quantitative three-dimensional evaluation of cardiac function.