Role of Collagen In Hierarchical Structure, Composition, And Biomechanics Of Bone

骨骼是由矿物质和胶原蛋白组成的复杂组织。骨脆性是一种重大的社会负担，通常通过骨量和结构的变化来诊断，但并不完全。在纳米结构水平上了解胶原和矿物质的贡献和相互作用，对于了解骨量以外的因素如何控制骨脆性至关重要。骨胶原的形成和整合受到高度调控，胶原蛋白或胶原相关蛋白的变化导致骨病成骨不全(OI)，表现为极高的骨脆性和脆性。了解胶原蛋白和矿物质相互作用的变化如何导致骨脆性，将有助于更好地理解骨含量、结构和机械性能在多个长度尺度上是如何相互作用的。本项目介绍了原子力显微镜红外光谱(AFMIR)和正电子湮没寿命光谱(PALS)的新用途，以检测骨胶原-矿物质相互作用的变化。通过了解这些过程如何在OI模型中分解，这项研究将通过确定在更常见的疾病(如骨质疏松症)中与骨脆性和脆性最密切相关的关键因素，产生更广泛的影响。这项研究将确定胶原如何在不同大小的尺度上控制骨材料的特性。我们假设，骨脆性是通过在胶原-矿物质相互作用水平上跨骨的层级组织的变化来调节的。为了验证这一假设，将通过AFM-IR和PALS成像对具有胶原螺旋结构、前胶原加工或翻译后羟化缺陷的小鼠进行研究。分级表型分析将在多个长度尺度上进行，并将识别因素与在这些小鼠中发现的轻度、中度和重度骨脆性最密切相关。通过AFM-IR，胶原纤维结构将直接在其周围的基质化学、组织硬度和局部纤维组织的背景下可视化。PALS将在相同的尺度下描述空洞的大小和分布。这些技术将通过组织学、纳米CT和纳米压痕技术与更高层次的上下文信息相结合，包括组织组织(编织-片层图案)、孔隙度(血管和细胞来源)、组织矿物质和硬度。该项目的学术意义源于了解胶原蛋白如何在不同大小的尺度上控制骨材料的特性，并将提供关于骨形成、生长和成熟背后的基本生物学原理的基础性理解。

Bone is a complex tissue composed of mineral and collagen. Bone fragility represents a significant societal burden, and is commonly, but incompletely diagnosed through changes in bone mass and structure. Understanding the contributions and interactions of collagen and mineral at the nanostructural level is critical for understanding how factors beyond bone mass govern bone fragility. Collagen formation and incorporation into bone is highly regulated, and changes in collagen or collagen-related proteins leads to the bone disease osteogenesis imperfecta (OI), exemplified by extremely high bone brittleness and fragility. Understanding how changes in collagen and mineral interactions lead to bone brittleness will provide a greater understanding of how bone content, structure, and mechanical properties interact at multiple length scales. This project introduces a novel use of atomic force microscopy-based infrared spectroscopy (AFMIR) and positron annihilation lifetime spectroscopy (PALS) to detect changes in collagen-mineral interactions in bone. By understanding how these processes break down in models of OI, this research will have a broader impact by identifying key factors that are most closely correlated with bone brittleness and fragility in more common diseases such as osteoporosis.This research will determine how collagen governs bone material properties across multiple size scales. We hypothesize that bone brittleness is regulated through changes across the hierarchical organization of bone originating at the level of the collagen-mineral interaction. To test the hypothesis, mice with defects in collagen helical structure, pro-collagen processing, or post-translational hydroxylation will be studied by AFM-IR and PALS imaging. Hierarchical phenotype analysis will be performed across multiple length scales and will identity factors most closely correlated with the mild, moderate, and severe bone brittleness found in these mice. Collagen fibril structure will be directly visualized in the context of its surrounding matrix chemistry, tissue stiffness, and local fibril organization by AFM-IR. PALS will describe void size and distribution at this same size scale. Together, these techniques will be integrated with higher order contextual information including tissue organization (woven-lamellar patterns), porosity (of vascular and cellular origin), tissue mineral, and stiffness through histologic, nanoCT, and nanoindentation techniques. The intellectual significance of this project arises from understanding how collagen governs bone material properties across multiple size scales and will provide foundational understanding regarding the basic biological principles behind bone formation, growth, and maturation.