Klein Travis J, Chaudhry Manu, Bae Won C, Sah Robert L
Department of Bioengineering, 9500 Gilman Dr., Mail Code 0412, University of California, San Diego, La Jolla, CA 92093-0412, USA.
J Biomech. 2007;40(1):182-90. doi: 10.1016/j.jbiomech.2005.11.002. Epub 2006 Jan 4.
Adult articular cartilage has depth-dependent mechanical and biochemical properties which contribute to zone-specific functions. The compressive moduli of immature cartilage and tissue-engineered cartilage are known to be lower than those of adult cartilage. The objective of this study was to determine if such tissues exhibit depth-dependent compressive properties, and how these depth-varying properties were correlated with cell and matrix composition of the tissue. The compressive moduli of fetal and newborn bovine articular cartilage increased with depth (p<0.05) by a factor of 4-5 from the top 0.1 mm (28+/-13 kPa, 141+/-10 kPa, respectively) to 1 mm deep into the tissue. Likewise, the glycosaminoglycan and collagen content increased with depth (both p<0.001), and correlated with the modulus (both p<0.01). In contrast, tissue-engineered cartilage formed by either layering or mixing cells from the superficial and middle zone of articular cartilage exhibited similarly soft regions at both construct surfaces, as exemplified by large equilibrium strains. The properties of immature cartilage may provide a template for developing tissue-engineered cartilage which aims to repair cartilage defects by recapitulating the natural development and growth processes. These results suggest that while depth-dependent properties may be important to engineer into cartilage constructs, issues other than cell heterogeneity must be addressed to generate such tissues.
成人关节软骨具有深度依赖性的力学和生化特性,这些特性有助于特定区域的功能。已知未成熟软骨和组织工程软骨的压缩模量低于成人软骨。本研究的目的是确定这些组织是否表现出深度依赖性的压缩特性,以及这些随深度变化的特性如何与组织的细胞和基质组成相关。胎儿和新生牛关节软骨的压缩模量随深度增加(p<0.05),从组织顶部0.1毫米处(分别为28±13千帕、141±10千帕)到组织内1毫米深处增加了4至5倍。同样,糖胺聚糖和胶原蛋白含量随深度增加(均为p<0.001),并与模量相关(均为p<0.01)。相比之下,通过分层或混合来自关节软骨表层和中层的细胞形成的组织工程软骨在构建体的两个表面都表现出类似的柔软区域,如大的平衡应变所示。未成熟软骨的特性可能为开发组织工程软骨提供一个模板,该组织工程软骨旨在通过重现自然发育和生长过程来修复软骨缺陷。这些结果表明,虽然深度依赖性特性对于构建软骨构建体可能很重要,但要生成这样的组织,除了细胞异质性之外,还必须解决其他问题。