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，但导致未成熟个体上级愈合能力的因素尚不清楚。以前，我们使用过表达骨形态发生蛋白-7（BMP-7）的基因修饰软骨细胞来测试增加软骨细胞基质合成是否可以增强软骨修复。虽然基因修饰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，它们无法整合到宿主软骨中，因此没有发现长期的益处。虽然该组织在深部区域具有透明样性质，但上部区域和关节面严重异常，纤维组织未与周围组织整合。以往的研究表明，软骨细胞从接近关节表面的软骨与那些在更深的区域有一个独特的表型。表浅（S）软骨细胞调节深层（D）软骨细胞的基质合成，并产生更高水平的基质降解酶。我们已经在初步研究中表明，S软骨细胞也有一个更大的能力比D软骨细胞迁移。本研究的目的是测试S软骨细胞是否可能比D软骨细胞更好地支持整体软骨修复。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用作重塑能力的替代指标。将使用我们小组先前建立的体外模型进行S与D软骨细胞的软骨修复。由于软骨修复在骨骼发育不成熟的个体中比在成年个体中更容易发生，因此将比较来自未成熟或老龄阉牛的S和D软骨细胞。在开发S软骨细胞的优化培养条件时，将测试未成熟和老化的S和D软骨细胞之间的基质附着和生长因子敏感性的差异。尽管大多数基于细胞的软骨修复策略，包括我们小组以前的研究，都集中在增加软骨细胞基质合成上，但这些研究将调查软骨细胞的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.