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的、双层的、可生物降解的水凝胶复合材料，用于软骨生长因子和间充质干细胞（MSCs）的共同递送，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控制转化生长因子-21 （TGF-21）和胰岛素样生长因子-1 （IGF-1）的双重递送将诱导受体内祖细胞的软骨分化，从而影响骨软骨缺损中软骨组织的再生。此外，我们假设MSCs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分化和成骨分化阶段，这将反过来影响细胞被包裹在水凝胶结构中并移植时骨软骨组织再生的程度和质量。最后，我们假设水凝胶复合材料中生长因子的共同递送，加上包裹在水凝胶中的祖细胞的移植，将协同作用，促进骨软骨缺损软骨组织的再生，而初始细胞播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以不同剂量加载到OPF水凝胶结构中，并以不同的动力学释放，以确定这些参数对兔骨软骨缺损组织再生的影响。其次，MSCs将在不同时间内暴露于TGF-21中，作为成软骨培养基补充剂或成骨培养基补充剂，分别产生不同的软骨和成骨分化阶段的细胞。然后将其包裹在OPF水凝胶支架内，并与OPF水凝胶支架（不加载生长因子）一起移植到兔骨软骨缺损模型中，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埋在符合最佳生长因子递送配方的OPF支架内进行移植，植入兔骨软骨缺损，确定骨软骨组织再生祖细胞的最佳播种密度，并在植入后通过组织形态学分析和力学测试进行评估。这种将软骨生长因子和体外扩增的自体祖细胞同时递送到骨软骨缺损的新策略在临床转化和骨软骨组织再生方面具有巨大的潜力。

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.