MECHANISMS & ENHANCEMENT OF INTEGRATIVE CARTILAGE REPAIR

修复或再生关节软骨的组织工程疗法通常包括单独移植细胞、工程支架内的细胞或含有细胞的组织。一个尚未解决的主要问题是植入物和宿主关节软骨之间的整合不一致。该项目的长期目标是对导致综合软骨修复的细胞和分子过程进行量化了解，并将这些信息应用于改善内科、外科和物理治疗，以刺激成功的软骨愈合。我们工作的一般假设是：功能性的整体性修复可以由软骨表面的一系列局部事件引起，其中包括：(A)胶原纤维分子成分的细胞生物合成和调节纤维形成的分子，(B)这些分子在细胞外的协调沉积和相关的胶原纤维网络的重塑。这一假设的推论是：移植的软骨细胞可以调节和加速这一过程，如果这些细胞保持在缺损处的黏附并贡献适当的分子产物。我们最近的研究(I)表明内源性软骨细胞的胶原生物合成以及随后的胶原沉积和交联性是牛软骨相对表面之间发生适度生物力学整合的关键因素，(2)开发了一种将软骨细胞定量移植到软骨表面从而在软骨-软骨界面提供代谢活性细胞的方法，以及(3)开发了一种系统来表征软骨细胞与关节软骨(例如，周围的宿主组织)的粘附性。我们现在建议检验两个具体的假设。(I)移植的软骨细胞附着于关节软骨的能力取决于软骨基质基质与移植细胞的表面受体或预先形成的细胞周基质之间的相互作用的程度。(2)内源性软骨细胞和移植软骨细胞在体外促进关节软骨整体修复的能力依赖于其局部沉积促进胶原网络重塑的分子的能力。建议的方法包括(A)将生物力学功能与特定分子的新陈代谢联系起来，(B)进行定量测量以表征胶原的合成、扩散和交联性，以及(C)调查具有潜在临床实用价值并提供潜在分子机制的操作。

Tissue engineering therapies for repair or regeneration of articular cartilage typically involve grafting cells alone, cells within engineered scaffolds, or tissues containing cells. A major unresolved problem is the inconsistent integration between the implant and the host articular cartilage. The long- term goal of this project is to develop a quantitative understanding of cellular and molecular processes leading to integrative cartilage repair and to apply this information to improve medical, surgical, and physical therapies for stimulating successful cartilage healing. Our working general hypothesis is: functional integrative repair can result from a local sequence of events at a cartilage surface that includes: (a) cellular biosynthesis of molecular components of collagen fibrils and molecules that regulate fibrillogenesis, (b) coordinated extracellular deposition of these molecules and associated remodeling of the fibrillar collagen meshwork. A corollary of this hypothesis is: transplanted chondrocytes can mediate and accelerate this process if these cells remain adherent at the defect site and contribute appropriate molecular products. Our recent studies (i) implicated collagen biosynthesis by endogenous chondrocytes, and subsequent deposition and crosslinking of collagen, as critical factors for the modest biomechanical integration that occurs between apposing surfaces of bovine cartilage in vitro, (2) developed a method to transplant chondrocytes quantitatively onto a cartilage surface and thereby provide metabolically active cells at a cartilage-cartilage interface, and (3) developed a system to characterize adhesiveness of chondrocytes to articular cartilage (e.g., the surrounding host tissue). We now propose to test two specific hypotheses. (i) The ability of transplanted chondrocytes to adhere to articular cartilage depends on the extent of interactions between the cartilage matrix substrate and the surface receptors or pre-formed pericellular matrix of the transplanted cells. (2) The ability of endogenous and transplanted chondrocytes to promote integrative repair of articular cartilage in vitro depends on their ability to locally deposit molecules that contribute to remodeling of the collagen meshwork. The approaches proposed include (a) relating biomechanical function to the metabolism of specific molecules, (b) making quantitative measurements to characterize collagen synthesis, diffusion, and crosslinking, and (c) investigating manipulations that are of potential clinical utility and provide insight into underlying molecular mechanisms.