An Integrated Investigation of Cartilage as a Skeletal Material

本研究项目是对软骨作为骨骼材料的性能、生物力学和生物化学进行多层次、跨学科的研究。软骨通常被认为是一种关节材料，是骨元素之间的支撑面，或者是鼻子和耳朵的轮廓填充物——然而鲨鱼和它们的近亲使用软骨作为它们的骨骼材料。骨骼系统是脊椎动物成功的基础，提供支持、保护和重要的生理作用。因此，骨这种典型的骨骼材料的生物学特性被很好地理解也就不足为奇了。同样，软骨作为关节表面的“通常”作用也得到了很好的研究，因为这种类型的软骨的损伤和畸形是主要的健康问题。可以毫不夸张地说，作为骨骼材料的软骨几乎完全不为人所知。事实上，对于鲨鱼软骨的硬度或强度，并没有一个单一的公布值。尽管有软骨骨骼，鲨鱼和它们的近亲至少进化了四次，完全以硬猎物为食。本项目从四个方面比较了硬猎物碎碎兽和密切相关的通才兽的软骨骨骼：全畜性能；结构力学;材料性质和生物化学。初步数据表明，硬猎物专门型的软骨在结构、材料和生物化学上都与通才型不同，也与哺乳动物的软骨不同。初步数据表明，四种鲨鱼的软骨比所有四足动物的软骨变化更大，这可能是因为对软骨骨骼组织的需求比对关节软骨的需求变化更大。性能将通过确定硬猎物破碎机和通才的咬合力来评估，而结构力学将通过分析颌骨的三维CT扫描来确定。用固体和粘弹性试验测量了软骨块的材料性能。生物化学组成的三个方面——胶原蛋白含量和交联，聚集蛋白含量和富含亮氨酸的蛋白聚糖含量（decorin, biglycan）将被评估并与四足动物的值进行比较。此外，成分和材料性质之间的相关性将使我们更清楚地了解软骨成分与其对载荷的响应之间的因果关系。

This research project is a multi-level, interdisciplinary investigation of the performance, biomechanics, and biochemistry of cartilage as a skeletal material. Cartilage is usually perceived as an articular material, a bearing surface between bony elements, or as contour-filler in the nose and ears - yet sharks and their relatives use cartilage as their skeletal material. The skeletal system is fundamental to the success of vertebrates, providing support, protection, and serving vital physiological roles. It is therefore unsurprising that the biology of bone, the typical skeletal material, is quite well understood. Similarly, cartilage, in its 'usual' role as an articular surface has been well studied because damage and malformations of this type of cartilage are major health issues. It would not be an exaggeration to say that cartilage, in its role as a skeletal material, is almost completely unknown. In fact, there is not a single published value for the stiffness or strength of cartilage from a shark.Despite a cartilaginous skeleton sharks and their relatives evolved an exclusively hard prey diet at least four times. This project compares the cartilaginous skeleton of hard prey crushers and closely related generalists at four levels: whole animal performance; structural mechanics; material properties and biochemistry. Preliminary data indicate that the cartilage of hard prey specialists is different in structure, material, and biochemistry than that of generalists, and also varies from mammalian cartilage. Preliminary data indicate that cartilage is more varied among four species of shark than among all tetrapods, perhaps because the demands placed on a cartilaginous skeletal tissue are more variable than the demands placed on articular cartilage. Performance will be assessed by determining the bite forces in hard prey crushers and generalists, while structural mechanics will be determined through analysis of 3-d CT scans of jaws. The material properties of blocks of cartilage are measured with solid and viscoelastic tests. Three aspects of the biochemical composition - collagen content and cross linking, aggrecan content, and leucine-rich proteoglycan content (decorin, biglycan) will be assessed and compared to values for tetrapods. In addition, correlations between composition and material properties will lead to a clearer understanding of the causal relationship between the constituents of cartilage and its response to load.