Controlling IGF-I/Scaffold Binding to Enhance Gene Therapy for Cartilage Repair

描述（由申请人提供）：骨关节炎是一种导致约 2700 万 25 岁及以上美国人软骨退化的疾病，影响男性和女性。据估计，到 2030 年，将有 6700 万人患有医生诊断的关节炎。尽管患者在晚年出现症状，但这种疾病在生命早期就开始出现，病变最早可能在 20 岁出头就发生。然而，由于关节软骨不能自我修复，这些病变无法愈合。近二十年来，人们一直使用软骨细胞移植疗法来治疗局灶性软骨损伤。通过增加软骨细胞基质的合成可以增强这种治疗。软骨细胞代谢最有效的合成代谢调节剂之一是胰岛素样生长因子（IGF-I）。因此，许多努力都集中在通过基因治疗控制软骨细胞合成 IGF-I 上。然而，在这些系统中，增强的 IGF-I 产生仅持续一到两周。 增加细胞接触 IGF-I 时间的另一种策略是制造新材料来控制 IGF-I 运输。具体来说，通过将IGF-I结合蛋白（IGFBP）18,22的肽移植到藻酸盐上，通过碳二亚胺化学，可以延迟IGF-I的释放，并且这种释放取决于肽的结合亲和力和浓度。该提案的目标是将这两种技术结合起来，通过基因疗法控制软骨细胞产生 IGF-I，并通过使用经过修饰以含有与 IGF-I 结合的肽的藻酸盐凝胶来延迟 IGF-I 的释放，从而延长其暴露于 IGF-I 的时间。 当前的提案包含三个有助于实现这一目标的具体目标。具体目标 1 是在 3D 藻酸盐支架中创建基于腺相关病毒的质粒 (pAAV)/IGF-I，并测量培养物中 36 天的 IGF-I 释放、ECM 积累和凝胶机械特性。具体目标2是表征用pAAV/IGF-I转染的对照和KPLHALL修饰的含有藻酸盐的软骨细胞的IGF-I释放、基质合成和机械特性。最后，具体目标 3 是比较用来自 mini-IGFBP-5 的较长和较短序列（PRQDEEKPLHALL、KPLHALL 和 ALL）修饰的藻酸盐凝胶中接种 pAAV/IGF-I 转染软骨细胞的构建体的 IGF-I 释放、基质合成和机械特性。 我们相信，控制它们的细胞产生和 IGF-I 的细胞外结合将协同增强软骨细胞的生物合成并促进组织工程软骨的生成。

DESCRIPTION (provided by applicant): Osteoarthritis is a disease that causes cartilage degradation in approximately 27 million Americans age 25 and older, affecting both men and women. It is estimated that by 2030, 67 million people will have doctor-diagnosed arthritis. Although patients become symptomatic later in life, the disease initiates earlier in life with a lesion that could happened as early as in the early 20s. However, because articular cartilage does not self-repair, these lesions are unable to heal. For almost two decades focal cartilage lesions have been treated using chondrocyte transplantation therapy. Such therapy would be enhanced by increasing the chondrocyte matrix synthesis. One of the most potent anabolic regulators of chondrocyte metabolism is insulin-like growth factor (IGF-I). As such, much effort has been focused on controlling IGF-I synthesis by chondrocytes via gene therapy. However, in these systems enhanced IGF-I production persists only one to two weeks. An alternative strategy to increase the time of cell's exposure to IGF-I is based on fabricating new materials to control IGF-I transport. Specifically, by grafting peptides from IGF-I binding proteins (IGFBPs) 18,22 to alginate, through carbodiimide chemistry, can delay release of IGF-I, and that this release depends on the binding affinity and the concentration of the peptide. The goal of this proposal is to combine these two technologies to control production of IGF-I by chondrocytes via gene therapy and extend the time of their exposure to IGF-I by delaying its release using alginate gels modified to contain peptides that bind to IGF-I. The current proposal contains three specific aims that will contribute to the goal. Specific aim 1 is to create an adeno-associated virus based plasmid (pAAV)/IGF-I in 3D alginate scaffolds and to measure IGF-I release, ECM accumulation, and mechanical properties of gel over 36 days in culture. Specific aim 2 is to characterize IGF-I release, matrix synthesis, and mechanical properties of control and KPLHALL-modified alginate containing chondrocytes transfected with pAAV/IGF-I. Finally, Specific aim 3 is to compare IGF-I release, matrix synthesis, and mechanical properties of constructs seeded with pAAV/IGF-I transfected chondrocytes in alginate gels modified with longer and shorter the sequences (PRQDEEKPLHALL, KPLHALL, and ALL) from the mini-IGFBP-5. We believe that controlling both their cellular production and extracellular binding of IGF-I will synergistically enhance chondrocyte biosynthesis and facilitate generation of tissue engineered cartilage.