Gene Delivery to Cartilage Defects via Marrow Coagulates

描述（由申请人提供）：人们普遍认为，软骨形成因子暴露于软骨损伤中的骨髓祖细胞可以增强修复组织的合成。该建议是基于这样的假设，即基因转移可以用作在软骨病变内实现持续合成特定蛋白质的手段，并且这可以用于增强间充质干细胞向体内软骨形成的分化。我们最近发现，从新鲜凝固的骨髓穿刺液中产生的天然凝块形成了一种简单但令人惊讶的有效基质，用于将基因转移载体和遗传修饰的细胞递送到骨软骨缺损处。形成的基质是供体完全天然的，是自然修复过程的一部分。从我们的初步结果中，我们已经发现，在培养凝固的骨髓抽吸物中的间充质干细胞将在适当的细胞因子刺激下分化为软骨组织。此外，作为载体或遗传修饰的MSC接种到凝块中的外源转基因将表达数周。拟议研究的实验方案旨在拓宽我们对蛋白质因子在软骨形成过程中的作用的认识，同时为开发基于基因和干细胞的方法以改善软骨病变的自然修复奠定基础。为此，我们将致力于以下具体目的：（1）确定用于将软骨形成转基因递送至MSC的合适载体;（2）评估候选转基因在沉淀培养系统中刺激MSC朝向软骨形成的能力;（3）优化软骨形成基因至骨髓凝块的体外递送;（4）评估候选转基因在细胞培养系统中刺激MSC朝向软骨形成的能力。（4）表征在骨软骨缺损中植入遗传修饰的骨髓凝块后体内转基因表达的模式;（5）评估遗传修饰的骨髓凝块在体内骨软骨缺损中诱导软骨形成的能力;和（6）阐明关节内软骨形成转基因长期表达的生物学效应。

DESCRIPTION (provided by applicant): It is widely thought that the exposure of chondrogenic factors to bone marrow progenitor cells in cartilage lesions can enhance the synthesis of a repair tissue. This proposal is based on the hypotheses that gene transfer can be used as a means to achieve sustained synthesis of specific proteins within a cartilaginous lesion, and that this can be used to augment the differentiation of mesenchymal stem cells toward chondrogenesis in vivo. We have recently found that a natural clot created from freshly coagulated bone marrow aspirate forms a simple, but surprisingly effective, matrix for delivery of gene transfer vectors and genetically modified cells to osteochondral defects. The matrix formed is completely native to the donor and part of the natural reparative process. From our preliminary results we have found that in culture mesenchymal stem cells within coagulated bone marrow aspirates will undergo differentiation into cartilaginous tissue under the proper cytokine stimulation. Furthermore exogenous transgenes seeded into the clot as vectors or genetically modified MSCs will be expressed for several weeks. The experimental scheme of the proposed study is designed to broaden our knowledge of the role of protein factors in the process of chondrogenesis while laying the foundation for development of gene- and stem cell-based approaches to improve the natural repair of cartilage lesions. For this we will address the following Specific Aims: (1) to determine the appropriate vector for delivery of chondrogenic transgenes to MSCs; (2) to evaluate the ability of candidate transgenes to stimulate MSCs toward chondrogenesis within a pellet culture system; (3) to optimize the delivery of chondrogenic genes to bone marrow clots in vitro; (4) to characterize patterns of transgene expression in vivo following implantation of genetically modified bone marrow clots in osteochondral defects; (5) to evaluate the capacity of genetically modified bone marrow clots to induce chondrogenesis in osteochondral defects in vivo; and (6) to elucidate the biological effects of long-term expression of chondrogenic transgenes within the joint.