Clickable Microgel Scaffolds for MSC Expansion and Delivery

项目摘要 颅颌面骨缺损的修复是一个重要的临床问题，具有重大的社会经济影响。骨的 创伤性损伤或疾病通常需要手术修复，但5-10%的骨折无法愈合， 当患者的骨质受损时甚至更高（例如，（《反乌托邦》）。在这些病例中， 作为一种改善复杂颅面缺损愈合的方法受到越来越多的关注。拟议 研究集中在间充质干细胞（MSC）疗法，因为它们在临床试验中的广泛使用，以及 MSC在肌肉骨骼组织稳态和骨质疏松症的病理生理学中发挥的主要作用。但在 MSC体外扩增至治疗相关数量会降低其再生能力，之后，直接 单独注射MSC常常导致低存活率。拟议的研究解决了这一重要的临床问题 通过创新的基于材料的策略，即为MSC合成和组装可调微凝胶支架， 扩展和交付。利用有效的“点击”化学反应和开发光响应材料，我们假设 i）在体外扩增期间延长MSC的自我更新和再生能力 和ii）促进所递送的MSC的存活和再生功能，这将改善健康和 骨质疏松。具体而言，我们建议：目标1。开发用于MSC扩增的水凝胶培养系统并定量 机械刺激和传代史对MSC增殖、多能性、分泌特性的影响， 表观遗传景观;目的2.将水凝胶材料加工成用于MSC递送的模块化微凝胶单元，并定制它们的 促进MSC存活、保留和再生潜力的性质;和目的3.测试MSC扩展的影响 条件和模块化微凝胶递送系统对MSC存活和体内骨再生的影响。如果成功，这个项目 将通过提供一个强大的新平台来扩展和特定于站点， MSC的递送。考虑到该方法的多功能性，其可应用于许多细胞递送系统， 将有更广泛的意义，可以延伸到骨再生之外。

PROJECT SUMMARY Repair of craniofacial bone defects is an important clinical problem with significant socioeconomic impact. Bone that is traumatically injured or diseased often requires surgical repair, but 5-10% of bone fractures fail to heal and failure rates can be even higher when the patient's bone quality is compromised (e.g., osteoporotic). In these cases, stem cell-based therapies have received increasing attention as a method to improve the healing of complex craniofacial defects. The proposed research focuses on mesenchymal stem cell (MSC) therapies because of their extensive use in clinical trials, as well as the major role that MSCs play in musculoskeletal tissue homeostasis and the pathophysiology of osteoporosis. However, in vitro expansion of MSCs to therapeutically relevant numbers reduces their regenerative capacity, and afterwards, direct injection of MSCs alone often leads to low survival. The proposed research addresses this important clinical problem through an innovative materials-based strategy, namely the synthesis and assembly of tunable microgel scaffolds for MSC expansion and delivery. Using efficient “click” chemistries and by developing photoresponsive materials, we hypothesize that scaffolds can be tuned to: i) prolong the self-renewing and regenerative capacity of MSCs during in vitro expansion and ii) promote the survival and regenerative functions of delivered MSCs that will improve healing of both healthy and osteoporotic bone. Specifically, we propose to: Aim 1. Develop a hydrogel culture system for MSC expansion and quantify the effects of mechanical cues and passaging history on MSC proliferation, multipotency, secretory properties, and epigenetic landscape; Aim 2. Process the hydrogel materials into modular microgel units for MSC delivery and tailor their properties to promote MSC survival, retention and regenerative potential; and Aim 3. Test the influence of MSC expansion conditions and modular microgel delivery systems on MSC survival and bone regeneration in vivo. If successful, this project will have an important impact on public health by providing a powerful new platform for the expansion and site specific delivery of MSCs. Given the versatility of the approach, which can be applied to numerous cell delivery systems, the results will have broader implications that can extend beyond bone regeneration.