Hydrogels with Tunable Stress Relaxation and Mobility for Enhancing Articular Cartilage Regeneration

关节软骨的急性损伤很常见，可以显著增加个体发生发展的风险 骨性关节炎，但仍然缺乏有效的再生疗法。软骨具有有限的自我调节能力。 由于细胞密度低，缺乏维管组织而再生。软骨修复的一个很有希望的策略是使用 间充质干细胞(MSCs)。可注射水凝胶载体尤其适用于MSC输送，因为 它们可以应用于微创手术中的软骨缺损。水凝胶设计的灵感来自于 天然软骨组织特性，如僵硬和生化配体，已被广泛研究 在3D中的MSC软骨生成的背景下。软骨也是粘弹性的，表现出应力松弛。 对施加的压力作出反应的行为。使用藻酸盐水凝胶作为模型体系，最近已经 结果表明，更快的应力松弛增强了基于软骨细胞的软骨产生。然而，这种方式 粘弹性对骨髓间充质干细胞软骨再生的调节作用在很大程度上仍不清楚。 我们的实验室以前曾报道过带有可移动交联剂的滑动水凝胶(SG)，它可以沿着聚乙二醇键滑动 聚合物主干，与非移动式相比，显著加速了MSC在3D中的软骨形成， 共价交联水凝胶。与藻酸盐水凝胶不同，SG通过不可逆的共价键进行交联 并且没有表现出应力松弛。基于先前在SG和藻酸盐水凝胶体系中的发现， 我推测，将粘弹性引入SG将进一步加速基于MSC的软骨再生 通过增强体外和体内的机械转导，以剂量依赖的方式。为了检验这一假设， 我建议：(1)开发和表征具有可调节应力松弛的适应性滑动水凝胶(ASG)如下 通过加入动态交联物的3D干细胞生态位；(2)评估应力松弛的效果 ASG对骨髓间充质干细胞体外软骨形成的影响 机械转导信号；(3)优化应力松弛的ASG加速效应验证 利用大鼠骨软骨缺损模型进行体内MSC软骨再生。与海藻酸盐相比 水凝胶，建议的基于聚乙二醇基的ASG是一个更清洁的系统，呈现细胞具有高度受控的利基 暗示。这些结果将填补关于粘弹性影响MSC的方式的一个关键知识空白 三维软骨形成和率先将具有粘弹性的动态水凝胶体内转化为软骨 再生。我将得到一个基础和临床科学家团队的指导，他们在 生物材料和组织工程、聚合物化学、机械转导、成像和动物模型。这个 结果将填补关于粘弹性影响MSC软骨形成方式的一个关键知识空白 可适应滑动水凝胶作为一种新型生物材料促进间充质干细胞软骨的三维实验和验证 再生。

Acute injury to articular cartilage is common and can significantly increase an individual’s risk for developing osteoarthritis, yet effective regenerative therapies remain lacking. Cartilage has a limited capacity for self- regeneration due to low cellularity and lack of vasculature. One promising strategy for cartilage repair is the use of mesenchymal stem cells (MSCs). Injectable hydrogel carriers are particularly desirable for MSC delivery as they can be applied to cartilage defects in minimally invasive procedures. Hydrogel design can be inspired by native cartilage tissue properties such as stiffness and biochemical ligands, which have been extensively studied in the context of MSC chondrogenesis in 3D. Cartilage is also viscoelastic, demonstrating stress relaxation behavior in response to applied stresses. Using alginate hydrogels as a model system, it has been recently shown that faster stress-relaxation enhances chondrocyte-based cartilage production. However, the way viscoelasticity modulates MSC-based cartilage regeneration remains largely unknown. Our lab has previously reported sliding hydrogels (SG) with mobile crosslinks that can slide along the PEG polymer backbone, which significantly accelerated MSC chondrogenesis in 3D compared to non-mobile, covalently crosslinked hydrogels. Unlike alginate hydrogels, SG is crosslinked by irreversible covalent bonds and does not exhibit stress relaxation. Based on previous findings in both the SG and alginate hydrogel systems, I hypothesize that introducing viscoelasticity to SG would further accelerate MSC-based cartilage regeneration in a dose-dependent manner through enhanced mechanotransduction in vitro and in vivo. To test this hypothesis, I propose to: (1) Develop and characterize adaptable sliding hydrogels (ASG) with tunable stress relaxation as a 3D stem cell niche through the incorporation of dynamic crosslinks; (2) Evaluate the effect of stress relaxation in ASG on MSC chondrogenesis in vitro and elucidate the underlying mechanisms by characterizing mechanotransduction signaling; (3) Validate the efficacy of ASG with optimized stress relaxation in accelerating MSC-based cartilage regeneration in vivo using a rat osteochondral defect model. Compared to alginate hydrogels, the proposed PEG-based ASG is a cleaner system that presents cells with highly controlled niche cues. The outcomes will fill a critical gap in knowledge about the way viscoelasticity influences MSC chondrogenesis in 3D and pioneer the in vivo translation of dynamic hydrogels with viscoelasticity for cartilage regeneration. I will be mentored by a team of basic and clinical scientists with complementary expertise in biomaterials and tissue engineering, polymer chemistry, mechanotransduction, imaging and animal models. The outcomes will fill a critical gap in knowledge about the way that viscoelasticity influences MSC chondrogenesis in 3D and validate adaptable sliding hydrogels as a new biomaterial for accelerating MSC-based cartilage regeneration.