MECHANISMS & ENHANCEMENT OF INTEGRATIVE CARTILAGE REPAIR

用于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与宿主关节软骨之间的不一致整合。该项目的长期目标是对导致软骨综合修复的细胞和分子过程进行定量理解，并将这些信息应用于改善医学、外科和物理疗法，以刺激软骨成功愈合。我们工作的一般假设是：功能性整合修复可以由软骨表面的局部事件序列引起，包括：(a)胶原原纤维分子成分和调节纤维形成的分子的细胞生物合成，(b)这些分子的细胞外沉积和纤维胶原网络的相关重塑。这一假设的一个推论是：移植的软骨细胞可以介导和加速这一过程，如果这些细胞在缺陷部位保持粘附并提供适当的分子产物。我们最近的研究(i)涉及内源性软骨细胞的胶原生物合成，以及随后胶原的沉积和交联，作为体外牛软骨相对表面之间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的方法，从而在软骨-软骨界面提供代谢活跃的细胞。(3)开发了表征软骨细胞对关节软骨（例如周围宿主组织）粘附性的系统。我们现在提议检验两个具体的假设。(1)移植软骨细胞粘附关节软骨的能力取决于软骨基质基质与移植细胞表面受体或预先形成的细胞周基质之间相互作用的程度。(2)内源性和移植软骨细胞在体外促进关节软骨整体修复的能力取决于它们在局部沉积有助于胶原网重塑的分子的能力。提出的方法包括(a)将生物力学功能与特定分子的代谢联系起来，(b)进行定量测量以表征胶原合成，扩散和交联，以及(c)研究具有潜在临床实用性的操作方法并提供潜在分子机制的见解。

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.