TGF-BETA AND IGF IN MESENCHYMAL STEM CELL CHONDROGENESIS

描述（由申请人提供）：骨折修复的骨再生依赖于骨折部位募集的软骨-骨祖细胞的数量。据报道，在美国每年发生的620万例骨折中，有10%的骨折愈合过程受损，导致显著的发病率和死亡率。干细胞数量的限制、合成代谢和分解代谢激素与生长因子之间的失衡是决定骨折修复失败的关键因素。软骨模板的形成在骨折修复过程中是必不可少的。成人骨髓（BM）含有大量间充质干细胞（MSC），具有体内和体外成为软骨的潜能。然而，将MSC从自我复制过程转化为软骨分化过程的分子信号和生长因子尚不清楚。我们的长期目标是了解决定MSC再生潜力的分子机制，以设计更有效的治疗方法来改善骨折愈合过程。我们的研究表明，转化生长因子β (tgf - β)和胰岛素样生长因子- 1 （IGF-I）通过诱导软骨祖细胞凝聚、生长和分化为软骨细胞来决定MSC的成软骨潜能。我们也证明了骨髓间充质干细胞在系统输注时被特异性地招募到骨折部位，并在那里分化成软骨细胞。我们假设tgf - β和IGF-I在间充质干细胞软骨形成过程中具有合成代谢诱导软骨作用。我们进一步假设tgf - β和IGF-I的诱导软骨作用可用于设计MSC以促进骨折愈合过程。本提案的两个具体目标是：1)发现tgf - β和igf - 1决定MSC软骨形成潜力的机制；2)确定tgf - β和IGF-I在MSC骨折修复能力中的作用。为了实现这些具体目标，建议将结构生物学，生物化学，小鼠模型和分子成像技术结合起来，在体内追踪MSC。我们期望这种多方面的实验方法的结果将为MSC的基本生物学和再生能力提供更好的理解。了解tgf - β和IGF-I在间充质干细胞成软骨潜能中的作用，将为开发基于间充质干细胞的体外tgf - β和IGF-I输送系统提供关键信息，该系统能够促进骨折愈合。

DESCRIPTION (provided by applicant): Regeneration of bone for fracture repair relies on the number of chondro-osteoprogenitors recruited to the fracture site. An impairment of the fracture healing process is reported in 10% of the 6.2 million fractures occurring annually in the United States, leading to significant morbidity and mortality. Limitation of stem cell number and imbalance between anabolic and catabolic hormones and growth factors are key elements in determining fracture repair failure. Formation of a cartilage template is essential during the fracture repair process. Adult bone marrow (BM) contains a reservoir of mesenchymal stem cells (MSC) with in vitro and in vivo potential of becoming cartilage. However, the molecular signals and growth factors that convert MSC from the process of self-replication to that of chondrogenic differentiation are unknown. Our long-term objective is to understand the molecular mechanisms that determine the regenerative potential of MSC to devise more effective therapies to ameliorate the fracture healing process. Our studies demonstrate that transforming growth factor beta (TGF-beta) and insulin-like growth factor-l (IGF-I) determine the chondrogenic potential of MSC by inducing chondroprogenitor condensation, growth and differentiation into chondrocytes. We have also demonstrated that MSC when systemically infused are specifically recruited to the fracture site where they differentiate into chondrocytes. We hypothesize that TGF-beta and IGF-I have anabolic chondroinductive effects in the cartilage formation process derived from MSC. We further hypothesize that the chondroinductive actions of TGF-beta and IGF-I can be used to engineer MSC to promote the fracture healing process. The two Specific Aims of this proposal are: 1) to discover the mechanisms by which TGF-beta and IGF-I determine the MSC chondrogenic potential; 2) to determine the role of TGF-beta and IGF-I in the fracture repair capacity of MSC. To accomplish these specific aims, proposal will combine structural biology, biochemistry, mouse models and molecular imaging techniques for tracing MSC in vivo. We expect that the results of this multi-faceted experimental approach will provide greater understanding of the basic biology and regenerative capacity of MSC. Understanding the role of TGF-beta and IGF-I in the chondrogenic potential of MSC will provide critical information for the development of an ex-vivo MSC-based TGF-beta and IGF-I delivery system capable of potentiating fracture healing.