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

骨是由矿物质和胶原蛋白组成的复杂组织。骨脆弱性是一种重大的社会负担，通过骨量和结构的变化通常但不完全地被诊断出来。了解胶原蛋白和矿物质在纳米结构水平上的作用和相互作用对于理解骨量以外的因素如何影响骨脆弱性至关重要。胶原蛋白的形成和并入骨骼受到高度调控，胶原蛋白或胶原蛋白相关蛋白的变化导致骨病成骨不全症（OI），其典型表现为极高的骨脆性和易碎性。了解胶原蛋白和矿物质相互作用的变化如何导致骨脆性，将有助于更好地了解骨含量、结构和力学性能在多个长度尺度上的相互作用。本项目介绍了一种基于原子力显微镜的红外光谱（AFMIR）和正电子湮灭寿命光谱（PALS）的新应用，以检测骨中胶原-矿物质相互作用的变化。通过了解这些过程在成骨不全模型中是如何分解的，本研究将通过确定与骨质疏松症等更常见疾病中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蛋白如何在多个尺寸尺度上控制骨材料的特性。我们假设骨脆性是通过在胶原蛋白-矿物质相互作用水平上产生的骨分层组织的变化来调节的。为了验证这一假设，将对胶原螺旋结构、前胶原加工或翻译后羟基化缺陷的小鼠进行AFM-IR和PALS成像研究。分层表型分析将在多个长度尺度上进行，并将确定与这些小鼠中发现的轻度、中度和重度骨脆性最密切相关的因素。通过AFM-IR，胶原原纤维结构将在其周围基质化学，组织刚度和局部原纤维组织的背景下直接可视化。PALS将描述相同尺寸尺度下的空隙大小和分布。总之，这些技术将通过组织学、纳米oct和纳米压痕技术与高阶上下文信息集成，包括组织组织（编织层状图案）、孔隙度（血管和细胞起源）、组织矿物质和硬度。该项目的知识意义在于了解胶原蛋白如何在多个尺寸尺度上控制骨材料的特性，并将为了解骨形成、生长和成熟背后的基本生物学原理提供基础。

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.