Xenogeneic Scaffolds for Heart Valve Tissue Engineering

描述(由申请人提供)：美国心脏协会估计，瓣膜心脏病在美国的患病率为2.5%，每年导致20,000人死亡。虽然用异种戊二醛固定的瓣膜(例如牛心包)替换病变的瓣膜可以显著改善短期结果，但长期免疫介导的攻击会导致钙化，并最终导致瓣膜衰竭(约10年寿命)。目前瓣膜置换的不足导致国家心肺血液研究所(NHLBI)心脏外科工作组建议支持心脏瓣膜假体生物材料的研究。一种组织工程心脏瓣膜，利用未固定的BP作为支架，患者的细胞在其上生长(重新细胞化)，有可能制造出潜在的理想心脏瓣膜。然而，NHLBI异种移植工作组指出，刺激受体免疫反应的成分(异种抗原)是扩大异种生物材料临床应用的关键障碍。我们提出了一种组合方法(我们的新的抗原去除方法结合间充质干细胞(MSC)介导的免疫调节)来生产一种免疫可接受的异种生物材料，用于心脏瓣膜组织工程。抗原去除的目的是去除生物材料中的异种抗原，同时保持细胞外基质(ECM)的完整性，并与再细胞化兼容。我们假设异种抗原的增溶作用是促进其从生物材料中去除的关键。因此，我们建议逐步应用蛋白质化学原理来增溶并去除BP异种抗原。目的1：从完整的BP中去除水溶性异种抗原，同时保持天然的ECM结构/功能关系和再细胞化潜力。目标1将分两个阶段进行。第一阶段将评估两种新因素对从BP中去除水溶性抗原的影响。第二阶段将确保生成的支架保留与心脏瓣膜组织工程兼容的细胞外基质特性。目的2：在保留天然ECM结构/功能关系和再细胞化潜能的同时，逐步去除完整BP中的脂溶性异种抗原。AIM 2将使用相同的2阶段方法进行，不同的是AIM 2中使用的因子旨在去除脂溶抗原。所得到的BP支架(有或没有MSC再细胞化)在植入具有免疫能力的受者体内后，必须是免疫可接受的。因此，我们建议：目标3：评估在逐步去除水溶和脂溶异种抗原后BP的体内免疫反应。评估同种异体骨髓间充质干细胞去除抗原后的BP再细胞化(BP-AR)对生物材料体内免疫反应的影响。目的利用免疫活性兔模型评价BP-AR和MSC再细胞BP-AR的免疫应答。这项提议的完成将产生一种结构完整、机械性能良好、免疫学上可接受的异种支架，与心脏瓣膜组织工程的再细胞化兼容。

DESCRIPTION (provided by applicant): American Heart Association estimates that valvular heart disease has a US prevalence of 2.5% and accounts for 20,000 deaths annually. Although replacement of the diseased valve with a xenogeneic glutaraldehyde- fixed valve (e.g., bovine pericardium (BP)) dramatically improves short term outcome, long term immune mediated attack results in calcification and ultimately valve failure (~10 yr lifespan). Deficiencies of curent valve replacements led the National Heart Lung and Blood Institute (NHLBI) cardiac surgery working group to recommend support for heart valve prosthesis biomaterial research. A tissue engineered heart valve utilizing un-fixed BP as a scaffold onto which patients' cells are grown (recellularization), has the potential to produce a potentially ideal heart valve. However, as noted by the NHLBI xenotransplantation working group, components which stimulate a recipient immune response (xenoantigens) represent the critical barrier to expanding clinical use of xenogeneic biomaterials. We propose a combinatorial approach (our novel antigen removal methodology combined with mesenchymal stem cell (MSC) mediated immunomodulation) for production of an immunologically-acceptable xenogeneic biomaterial for heart valve tissue engineering. Antigen removal aims to remove biomaterial xenoantigens, while leaving the extracellular matrix (ECM) intact and compatible with recellularization. We hypothesize that solubilization of xenoantigens is critical to facilitate their removal from the biomaterial. We therefore propose stepwise application of protein chemistry principles to solubilize and consequently removal BP xenoantigens. Aim 1: Remove water-soluble xenoantigens from intact BP while maintaining native ECM structure/function relationships and recellularization potential. Aim 1 will be conducted in two phases. Phase 1 will assess the effect of two novel factors on removal of water-soluble antigens from BP. Phase 2 will ensure that the resulting scaffold retains ECM properties compatible with heart valve tissue engineering. Aim 2: Remove lipid-soluble xenoantigens from intact BP in a stepwise manner after initial removal of water-soluble xenoantigens, while maintaining native ECM structure/function relationships and recellularization potential. Aim 2 will be conducted using the same 2 phased approach, with the exception that factors used in aim 2 are designed to remove lipid-soluble antigens. The resulting BP scaffold (with or without MSC recellularization) must be immunologically-acceptable following implantation in an immunocompetent recipient. We therefore propose: Aim 3: Assess the in vivo immune response to BP following stepwise antigen removal of water- and lipid-soluble xenoantigens. Assess effect of allogeneic MSC recellularization of BP following antigen removal (BP-AR) on in vivo immune response towards the biomaterial. Aim 3 utilizes an immunocompetent rabbit model for assessment of immune response to both BP-AR and MSC recellularized BP-AR. Completion of this proposal will result in a structurally integral, mechanically sound, immunologically- acceptable xenogeneic scaffold compatible with recellularization for heart valve tissue engineering.