Injectable Cellular Composites for Cartilage Engineering

描述（由申请人提供）：本研究项目的最终目标是开发一种新型可注射、双层、可生物降解的水凝胶复合材料，用于共同递送软骨生长因子和间充质干细胞（MSC），以影响骨软骨缺损内软骨组织再生的程度和质量。我们假设，使用最佳释放动力学和剂量的转化生长因子-21（TGF-21）和胰岛素样生长因子-1（IGF-1）的受控双重递送将诱导受体内祖细胞的软骨形成分化，以影响骨软骨缺损中软骨组织的再生。此外，我们假设MSC在体外扩增过程中暴露于TGF-21和成骨培养基补充剂的持续时间将分别调节细胞的软骨形成和成骨分化阶段，这将反过来影响当细胞被封装在水凝胶构建体中并与水凝胶构建体一起移植时骨软骨组织再生的程度和质量。最后，我们假设来自水凝胶复合物的生长因子的共递送，加上包封在水凝胶内的祖细胞的移植，将协同作用以促进骨软骨缺损中的软骨组织的再生，其中初始细胞接种密度影响软骨再生的程度和质量。为了解决这些假设，提出了三个具体目标。首先，将TGF-21和IGF-1以不同的剂量加载到OPF水凝胶构建体中，并以不同的动力学释放，以确定这些参数对兔骨软骨缺损中组织再生的影响。其次，MSC将暴露于作为成软骨培养基补充剂或成骨培养基补充剂的TGF-21不同持续时间，以分别产生不同成软骨和成骨分化阶段的细胞，然后将它们封装在OPF水凝胶支架内并移植（无负载生长因子）移植入兔骨软骨缺损模型中，以评估移植细胞的分化阶段对骨软骨组织再生的影响。第三，将最佳分化阶段的细胞包封用于在对应于最佳生长因子递送制剂的OPF支架内移植，并将其植入兔骨软骨缺损中，以确定用于骨软骨组织再生的祖细胞的最佳接种密度，这将在植入后通过组织形态学分析和机械测试进行评估。这种新的战略，同时和空间定义的交付软骨生长因子和体外扩增的自体祖细胞骨软骨缺损的临床翻译和骨软骨组织再生的巨大潜力。 公共卫生相关性：由于软骨组织自身修复的天然能力有限，关节软骨和底层骨的损伤通常导致困扰全球数百万人的重大临床问题，包括疼痛、活动受限和骨关节炎。目前还没有持续成功治疗这种性质的软骨缺损的策略。本提案中描述的项目旨在开发新型可注射、双层、可降解材料，这些材料可作为同时递送生物活性分子和成人衍生干细胞的载体植入体内，以促进受损软骨组织的再生。

DESCRIPTION (provided by applicant): The ultimate goal of this research project is to develop a novel injectable, bilayered, biodegradable hydrogel composite for the co-delivery of chondrogenic growth factors and mesenchymal stem cells (MSCs) to influence the degree and quality of cartilage tissue regeneration within osteochondral defects. We hypothesize that controlled dual delivery of transforming growth factor-21 (TGF-21) and insulin-like growth factor-1 (IGF-1) using optimal release kinetics and doses will induce chondrogenic differentiation of progenitor cells within the recipient to influence the regeneration of cartilage tissue in an osteochondral defect. Additionally, we hypothesize that the duration of exposure of MSCs to TGF-21 and osteogenic medium supplements during in vitro expansion will modulate the chondrogenic and osteogenic differentiation stages of the cells, respectively, which will in turn influence the degree and quality of osteochondral tissue regeneration when the cells are encapsulated within and transplanted with a hydrogel construct. Finally, we hypothesize that the co-delivery of growth factor(s) from hydrogel composites, coupled with the transplantation of progenitor cells encapsulated within the hydrogels will act cooperatively to promote regeneration of cartilage tissue in an osteochondral defect, with the initial cell seeding density influencing the degree and quality of the cartilage regeneration. To address these hypotheses, three Specific Aims are proposed. First, TGF-21 and IGF-1 will be loaded into OPF hydrogel constructs at different doses and released with different kinetics to determine the effect of these parameters on tissue regeneration in a rabbit osteochondral defect. Second, MSCs will be exposed to TGF-21 as a chondrogenic culture medium supplement or osteogenic medium supplements for various durations to result in cells of different chondrogenic and osteogenic differentiation stages, respectively, then they will be encapsulated within and transplanted with OPF hydrogel scaffolds (without loaded growth factors) into a rabbit osteochondral defect model to assess the effect of the differentiation stages of the transplanted cells upon osteochondral tissue regeneration. Third, cells of the optimal differentiation stages will be encapsulated for transplantation within OPF scaffolds corresponding to the optimal growth factor delivery formulation and will be implanted into rabbit osteochondral defects to determine the optimal seeding density of the progenitor cells for osteochondral tissue regeneration, which will be assessed post-implantation through histomorphometric analysis and mechanical testing. This novel strategy for the concurrent and spatially defined delivery of chondrogenic growth factors and in vitro expanded autologous progenitor cells to osteochondral defects presents tremendous potential for clinical translation and osteochondral tissue regeneration. PUBLIC HEALTH RELEVANCE: Due to the limited natural ability of cartilage tissue to repair itself, damage to articular cartilage and underlying bone often leads to significant clinical problems that afflict millions of people worldwide, including pain, limited mobility and osteoarthritis. No strategies currently exist that are consistently successful in treating cartilage defects of this nature. The project described in this proposal aims to develop novel injectable, bilayered, degradable materials that can be implanted as a vehicle for the concurrent delivery of bioactive molecules and adult derived stem cells to promote regeneration of damaged cartilage tissue.