Bioinspired Mechanically Stiff Hydrogels for Osteochondral Tissue Regeneration

关节软骨和软骨下骨的病变最终导致骨关节炎， 无法治愈的疾病成功的治疗需要促进组织再生，支持整合修复， 保护周围组织不进一步退化该项目的总体目标是开发 一种机械能力，干细胞为基础的再生方法来治疗骨软骨（OC）缺陷。期间 在最初的资助期间，我们的团队开发了一种OC模拟水凝胶，其设计可以解耦负载， 轴承（即，结构）组分。这使我们能够创建一个 功能梯度，具有软骨匹配机械刚度的刚性结构，同时创建软细胞龛 支持间充质干细胞（MSC）分化。从关键的体外里程碑开始， 目的是在体内翻译OC模拟水凝胶。我们将检验OC模拟水凝胶 在体内诱导外源性MSC的快速和靶向分化，使其能够直接参与OC- 组织再生，同时保护和支持与周围组织的整合。一 我们的设计的一个新特点是水泥线模仿内的结构支持，类似于本地 骨水泥线将不渗透穿过软骨-骨界面的细胞迁移，但可渗透营养物质 运输这将保护软骨层中的MSC，使其能够快速分化并有助于软骨细胞的生长。 再生我们将在三个具体目标中检验总体假设。在目标1中，我们将确定 机械转导途径，差异控制MSC的命运在OC模拟水凝胶，这将 使我们能够建立一个机械的理解的理化线索，实现强大的MSC 在动态环境中的负载差异。在目标2中，我们将确定MSC在体内的命运。 通过追踪差异标记的分离的MSC在大鼠OC缺损模型中植入OC-模拟水凝胶后 来自DsRed+和GFP+大鼠。这一目标将证实MSC的命运及其对OC组织的直接和间接贡献 再生在目标3中，我们将创建一个结构支撑，该支撑经历表面降解以保持其 力学性能我们将评估这种完全可降解的机械 使用三种复杂性增加的模型：OC外植体缺损模型， 监测作为支撑结构的缺损附近的关节软骨的健康和与其的整合 降解;用于纵向研究的大鼠OC缺损模型，以监测结构的体内降解 伴随组织再生和整合修复;以及，在临床前动物（猪）模型中测试。 在这个项目结束时，我们希望（1）提高我们对 机械转导途径在MSC和他们的命运在体内和（2）建立了一个机械能力 和可降解的OC-模拟水凝胶，其实现OC-组织再生和一体化修复， 保持关节健康。

Lesions to articular cartilage and underlying subchondral bone eventually lead to osteoarthritis, a debilitating disease with no cure. A successful therapy will need to promote tissue regeneration, support integrative repair, and protect the surrounding tissue from further degeneration. The overarching goal for this project is to develop a mechanically competent, stem cell-based regenerative approach to treat osteochondral (OC) defects. During the initial funding period, our team developed an OC-mimetic hydrogel with a design that decoupled the load- bearing (i.e., structural) component from the soft cellular biomimetic component. This allowed us to create a functionally graded, stiff structure with cartilage-matched mechanical stiffness, while creating soft cellular niches that supported mesenchymal stem cell (MSC) differentiation. Building from key in vitro milestones, this renewal aims to translate the OC-mimetic hydrogel in vivo. We will test the hypothesis that the OC-mimetic hydrogel induces rapid and targeted differentiation of exogeneous MSCs in vivo, enabling their direct participation in OC- tissue regeneration while simultaneously protecting and supporting integration with the surrounding tissue. A new feature of our design is a cement line-mimetic within the structural support that similar to the native cement line will be impervious to cell migration across the cartilage-bone interface, but pervious to nutrient transport. This will protect the MSCs in the cartilage layer, enabling their rapid differentiation and contribution to regeneration. We will test the overarching hypothesis in three specific aims. In Aim1, we will identify mechanotransduction pathways that differentially control MSC fate in the OC-mimetic hydrogel, which will allow us to establish a mechanistic understanding of the physiochemical cues that achieve robust MSC differentiation in a dynamic environment with loading. In Aim 2, we will determine MSC fate in vivo within the OC-mimetic hydrogel after implantation in a rat OC defect model by tracking differentially labeled MSCs isolated from DsRed+ and GFP+ rats. This aim will confirm MSC fate and their direct and indirect contribution to OC-tissue regeneration. In Aim 3, we will create a structural support that undergoes surface degradation to maintain its mechanical properties. We will evaluate the effectiveness of this fully degradable and mechanically competent OC-mimetic hydrogel using three models of increasing complexity: an OC explant defect model to monitor the health of and integration with articular cartilage adjacent to the defect as the support structure degrades; a rat OC defect model for longitudinal studies to monitor in vivo degradation of the structure concomitant with tissue regeneration and integrative repair; and, testing in a pre-clinical animal (swine) model. At the conclusion of this project, we expect to have (1) advanced our fundamental understanding of the mechanotransduction pathways in MSCs and their fate in vivo and (2) established a mechanically competent and degradable OC-mimetic hydrogel that achieves OC-tissue regeneration and integrative repair, while maintaining joint health.