Immunology of xenogeneic extracellular matrix scaffolds for heart valve tissue engineering

摘要： 美国心脏协会估计，美国心脏瓣膜疾病的患病率为2.5%，需要超过 每年更换10万个瓣膜。目前的心脏瓣膜置换远非理想，领先于NHLBI 心脏外科工作组建议增加对心脏瓣膜生物材料研究的支持。虽然 戊二醛固定的异种组织瓣膜(例如牛心包(BP))改善短期存活率， 慢性移植物特异性免疫反应持续存在，导致长期的生物材料损伤、钙化和 最终失败(约2-10岁，取决于植入时的年龄)。事实上，NHLBI异种移植工作组 注意到生物材料的抗原性是扩大异种生物材料使用的主要翻译障碍 临床实践中的组织。消除人类相关抗原的未固定BP有可能作为 一种免疫可接受的细胞外基质(ECM)支架，用于心脏瓣膜生物假体。然而， 识别与人类相关的BP抗原并促进其从候选ECM支架中移除代表 这类生物材料开发的关键翻译障碍。我们假设人类的灭绝- 相关抗原可以通过在BP ECM支架过程中采用靶向抗原溶解步骤来获得 制作。这项提议试图定义负责启动移植物特异性免疫的主要BP抗原。 人类患者的反应(目标1，阶段1)、量化消除(目标1，阶段2)和靶向消除 来自BP ECM支架的人类相关抗原(目标1，阶段3)。不固定的ECM脚手架，避免破坏性 移植物特异性获得性免疫反应有可能调节建设性的促再生受体 先天免疫反应。我们的团队之前已经证明了天然组织ECM利基在 BP支架对促进体内促再生受体反应至关重要。然而，在多大程度上 暴露天然的基质结合部位可以进一步增强促再生的先天免疫极化 完整的BP ECM支架仍不清楚。我们假设ECM利基和矩阵解密信号暴露是 调节人巨噬细胞极化和体内最终支架命运的关键因素。这项建议 目的是确定不同的机制(即细胞外基质生态位成分和巨噬细胞受体) 基质解密信号暴露的来源调制人巨噬细胞极化(目标2，阶段1)并结合 每个矩阵解密曝光源的最佳水平朝向最大化促进再生极化(目标2， 阶段2)。目的1和2被确定为具有积极调节人体体内支架命运的潜在因素 将使用活体绵羊心脏瓣膜置换模型进行验证(AIM 3)。完成这项提案将 提供对负责启动移植物特异性免疫的人类相关抗原的机械性见解 对当前临床使用的异种生物材料的反应，定义基质解密的机制 信号调节人巨噬细胞极化并利用这些发现促进NEXT的发展 生成免疫学上可接受的支持再生的非固定BP ECM支架，用于心脏瓣膜置换。

ABSTRACT: American Heart Association estimates a 2.5% prevalence of valvular heart disease in the US, requiring over 100,000 valve replacements annually. Current replacement heart valves are far from ideal, leading the NHLBI cardiac surgery working group to recommend increased support for heart valve biomaterial research. Although glutaraldehyde fixed xenogeneic tissue valves (e.g., bovine pericardium (BP)) improve short-term survival, chronic graft-specific immune responses persist, resulting in long-term biomaterial damage, calcification and ultimately failure (~2-10 yr depending on age at implantation). Indeed, NHLBI xenotransplantation working group noted that biomaterial antigenicity represents the primary translational barrier to expanding the use of xenogeneic tissues in clinical practice. Unfixed BP in which human-relevant antigens are eliminated has potential to serve as an immunologically-acceptable extracellular matrix (ECM) scaffold for heart valve bioprostheses. However, identifying human-relevant BP antigens and facilitating their removal from candidate ECM scaffolds represent critical translational barriers for development of such biomaterials. We hypothesize that elimination of human- relevant antigens can be achieved by employing targeted antigen solubilization steps during BP ECM scaffold production. This proposal seeks to define primary BP antigens responsible for initiating graft-specific immune responses in human patients (Aim 1, Phase 1), quantify removal (Aim 1, Phase 2) and target elimination of such human-relevant antigens from BP ECM scaffolds (Aim 1, Phase 3). Unfixed ECM scaffolds that avoid destructive graft-specific adaptive immune responses have potential to modulate constructive pro-regenerative recipient innate immune responses. Our group has previously demonstrated that retention of native tissue ECM niche in BP scaffolds is critical to promoting pro-regenerative in vivo recipient responses. However, extent to which exposure of natural matricryptic sites can further enhance pro-regenerative innate immune polarization towards intact BP ECM scaffolds remains unknown. We hypothesize that ECM niche and matricryptic signal exposure are critical factors in modulating human macrophage polarization and ultimate in vivo scaffold fate. This proposal aims to determine mechanisms (i.e., ECM niche component and macrophage receptor) by which differing sources of matricryptic signal exposure modulate human macrophage polarization (Aim 2, Phase 1) and combine optimal levels of each matricryptic exposure source toward maximizing pro-regenerative polarization (Aim 2, Phase 2). Aim 1 and 2 factors identified as having potential to positively modulate in vivo scaffold fate in humans will be validated using an in vivo ovine heart valve replacement model (Aim 3). Completion of this proposal will provide mechanistic insights into human-relevant antigens responsible for initiating graft-specific immune response towards current clinically-utilized xenogeneic biomaterials, define mechanisms by which matricryptic signaling modulates human macrophage polarization and leverage these findings towards development of next generation immunologically-acceptable pro-regenerative unfixed BP ECM scaffolds for heart valve replacements.