Failure mechanisms in collagen of heart valves and tissue engineered replacements

组织工程旨在用完全天然的再生结构替换受损或患病的组织。该企业的许多目标是机械关键结构（例如心脏瓣膜，动脉置换，心脏壁），其中失败可能意味着患者的严重疾病或死亡。由于心脏每年跳动3500万次，因此迫切需要了解天然组织和工程替代物对与重复负荷相关的机械疲劳的反应机制。此外，组织工程替代品在结构和功能上往往是幼稚的，在立即接管成熟的成年组织的职责方面面临真实的挑战。在这项研究计划中，我们正在寻求了解生物力学失败的基本结构根源，及其预防，在天然心脏瓣膜和组织工程替代品。因此，我们希望降低患者置换瓣膜和设计中具有确定安全性的生物工程瓣膜失效的可能性。项目一将使用同步加速器X射线衍射和小角散射来研究胶原蛋白分子的包装（i）在完整组织和过载组织中失败，以及（ii）在不同年龄的组织中，从新生儿到老年。通过这种方法，我们希望了解组织结构的这种分子水平特征如何定义胶原蛋白的稳定性，从而抵抗解卷和降解。项目二将使用两种新的共聚焦激光显微镜技术（二次谐波产生和CNA 35结合），以检查单轴和双轴载荷失效过程中胶原纤维和纤维束结构的变化。这种方法将允许直接可视化胶原结构被破坏的机制，以及老化、交联和机械疲劳对这些机制的影响。最后，在项目三中，我们将使用宿主炎症细胞（巨噬细胞）来观察胶原蛋白的变化（疲劳损伤、酶分解和交联）如何影响宿主对植入组织器械的反应。

Tissue engineering seeks to replace damaged or diseased tissues with fully natural, regenerated structures. Many of the targets for this enterprise are mechanically critical structures (e.g. heart valves, artery replacements, heart wall) where failure can mean severe illness or death for the patient. Since the heart beats 35 million times a year, there is a strong need to understand the mechanisms by which both native tissues and engineered replacements respond to the mechanical fatigue associated with repeated loading. Moreover, tissue-engineered replacements are often juvenile in structure and function and face real challenges in immediately taking over the duties of mature, adult tissues. In this research program, we are seeking to understand the fundamental structural roots of biomechanical failure, and its prevention, in natural heart valves and tissue engineered replacements. Thereby, we hope to decrease the likelihood of failure of a replacement valve in a patient and bioengineer valves that have a defined safety in their design. Project one will use synchrotron x-ray diffraction and small angle scattering to study the packing of collagen molecules (i) in intact tissues and tissues overloaded to failure, and (ii) in tissues of varying age, from neonatal life to old age. By this means we hope to understand how this molecule-level characteristic of tissue architecture defines the stability of collagen and thereby its resistance to uncoiling and degradation. Project two will use two new confocal laser microscopy techniques (2nd harmonic generation and CNA35 binding) to examine changes in collagen fibre and bundle structure during uniaxial and biaxial loading to failure. This approach will allow direct visualization of the mechanisms by which the collagen architecture is disrupted, and the influence that age, crosslinking, and mechanical fatigue has on those mechanisms. Finally, in Project three, we will use host inflammatory cells (macrophages) to look at how changes in collagen (fatigue damage, enzyme breakdown, and crosslinking) influence the host reaction to implanted tissue devices.