Maturational changes in superficial zone chondrocytes

描述(由申请人提供)： 成人的关节内损伤在临床上是有问题的，因为软骨的愈合能力有限。虽然软骨愈合与年龄有关，但骨骼未成熟个体具有更好的愈合能力的因素尚不清楚。在此之前，我们已经使用高表达骨形态发生蛋白-7(BMP-7)的转基因软骨细胞来测试增加软骨细胞基质合成是否可以促进软骨修复。虽然基因改造确实增加了软骨细胞中II型胶原和蛋白多糖的合成，但在体内，它们无法与宿主软骨结合，因此没有发现长期的益处。在我们研究的最后时间点，观察到来自宿主细胞的纤维软骨修复。深部组织呈透明状，上部和关节表面严重异常，纤维组织与周围组织不整合。以往的研究表明，靠近软骨关节表面的软骨细胞具有不同的表型，而不是更深层的软骨细胞。浅层(S)软骨细胞通过深层(D)软骨细胞调节基质合成，并产生更高水平的基质降解酶。我们在初步研究中表明，S软骨细胞也比D软骨细胞具有更大的迁移能力。本研究的目的是测试S软骨细胞是否比D软骨细胞更能支持软骨的整体修复。为了验证这一假设，我们将首先优化S软骨细胞的培养和增殖。迁移和表达基质金属蛋白酶的能力将被用作重塑能力的替代指标。S和D软骨细胞的软骨修复将使用本课题组先前建立的体外模型进行。由于骨骼未成熟个体的软骨修复比成人更容易，S和来自未成熟或老年牛的D软骨细胞将被比较。在建立优化的S软骨细胞培养条件下，将测试未成熟和老化的S和D软骨细胞在基质附着和生长因子敏感性方面的差异。尽管大多数基于细胞的软骨修复策略，包括我们团队之前的研究，都集中在增加软骨细胞基质的合成上，这些研究将探讨软骨细胞增强重塑是否对综合软骨修复更重要。

DESCRIPTION (provided by applicant): Intra-articular injuries in adults are clinically problematic, as cartilage has a limited capacity to heal. While cartilage healing is age-related the factors contributing to the superior healing capacities in skeletally immature individuals is unknown. Previously, we have used genetically modified chondrocytes over expressing bone morphogenetic protein-7 (BMP-7) to test whether increasing chondrocyte matrix synthesis could enhance cartilage repair. While genetic modification did increase type II collagen and proteoglycan synthesis in the chondrocytes, in vivo, they were unable to integrate to the host cartilage so that no long-term benefit was found. At the terminal time point of our study, fibro-cartilage repair, derived from host cells was observed. While this tissue had hyaline-like qualities in the deep zone, the upper zone and articular surface were severely abnormal with fibrous tissue that was not integrated to the surrounding tissue. Previous studies have shown that chondrocytes from close to the articular surface of cartilage have a distinct phenotype versus those in the deeper zones. Superficial (S) chondrocytes modulate matrix synthesis by deep zone (D) chondrocytes and produce higher levels of matrix degrading enzymes. We have shown in preliminary studies that S chondrocytes also have a greater capacity to migrate than D chondrocytes. The purpose of this investigation is to test whether S chondrocytes may be better than D chondrocytes in supporting integrative cartilage repair. To test this hypothesis, we will first optimize the culture and propagation of S chondrocytes. Ability to migrate and express matrix metallo-proteases will be used as surrogate indicators of remodeling capacity. Cartilage repair by S versus D chondrocytes will be performed using an in vitro model previously established by our group. As cartilage repair occurs more readily in skeletally immature individuals than in adults, S and D chondrocytes from immature or aged steers will be compared. In developing optimized culture conditions for S chondrocytes, differences in matrix attachment and growth factor sensitivity between immature and aged S and D chondrocytes will be tested. Whereas most cell based cartilage repair strategies, including previous studies by our group, have focused on increasing chondrocyte matrix synthesis, these studies will investigate whether enhanced remodeling by chondrocytes may be more important for integrative cartilage repair.