双重交联设计的凝胶应力松弛行为调控与干细胞诱导分化

The mechanical cues of substrate microenvironment play an essential role in stem cell fate. Besides the elastic modulus, the viscoelasticity of substrate, particularly the stress relaxation of gel matrix has been revealed to exert fundamental influence on cell behavior. On this basis, the design and exploration of gel matrix with regulatable stress relaxation is of great significance to study the mechanism of cell-matrix interaction, govern the specific functional expression of cell differentiation, and construct tissue-inducing biomaterials. To this end, this study intends to obtain the adhesive collagen hydrogel with fibrous structure and tunable stress relaxation. Specifically, the hydrogel model with cell adhesion activity, nanofiber structure and stress relaxation can be achieved by self-assembling of type I collagen under physiological conditions. Then, the introduction of reversible imide bonding and applied strain device are designed to enhance the stress relaxation of the hydrogel. Based on this, the constructed hydrogel model is further used to study the effect of stress relaxation on cell behavior in three-dimensional microenvironment, explore the transduction of mechanical signals mediated by cell-matrix adhesive traction and cell volume modulation, as well as its influence mechanism on inducing cell differentiation.relaxation of the hydrogel. Based on this, the constructed hydrogel model is further used to study the effect of stress relaxation on cell behavior in three-dimensional microenvironment, explore the transduction of mechanical signals mediated by cell-matrix adhesive traction and cell volume modulation, as well as its influence mechanism on inducing cell differentiation.

基质微环境力学信号对干细胞分化命运具有重要作用，除基质弹性模量外，基质粘弹性行为，特别是应力松弛效应被发现对细胞行为具有重要影响。基于此，设计和研究具有可调控应力松弛效应的凝胶基质对于研究细胞—基质作用规律，调控特定细胞分化功能表达，以及组织诱导性生物材料设计具有重要意义。为此，本研究拟通过生理条件下的I型胶原纤维自组装获得具有细胞粘附活性和纳米纤维结构的应力松弛水凝胶基础模型；通过可逆亚胺键的引入和外加应变装置设计增强凝胶应力松弛效应，获得具有可控应力松弛性质的粘附性纤维结构胶原水凝胶；在此基础上，研究三维微环境中应力松弛力学性能对细胞行为的影响，探索通过细胞-基质粘附牵拉和细胞体积感知介导的基质力学信号传导及其对细胞诱导分化的影响机制。

基质微环境力学信号对细胞命运的调控作用已被证实，但大多数研究主要关注基质的静态弹性模量对细胞功能的影响，而忽略了自然组织三维、动态的粘弹性力学特点。基于此，本项目重点围绕以应力松弛为核心的粘弹性基质力学微环境构建，探索基质动态力学信号对细胞分化诱导的调控作用，以及在此过程中动态力学信号的细胞内信号转导机制。基于仿生基质微环境的化学组成、物理结构、力学性能等特点，项目以胶原水凝胶作为兼具细胞粘附活性和纳米纤维网络结构的粘弹性基质模型基础，通过亚胺键、主客体作用、多重氢键等动态化学/物理键引入，建立仿生基质应力松弛力学特性的多种时空调控方式。基于仿生动态微环境中细胞行为响应，探明基质应力松弛动态力学信号调控细胞增殖、铺展与分化的分子机制以及重要细胞内信号转导路径，包括粘着斑介导的细胞骨架铺展与TRPV4信号通路，机械敏感电压门控通道介导的神经分化与YAP信号通路，以及miR-21迟滞性转录遗传信息介导的细胞力学记忆效应。在此基础上，探索基质粘弹性力学信号及其协同拓扑信号、电信号等，对神经功能表达以及脊髓损伤、颅脑创伤等神经损伤修复的调控规律，筛选获得具有神经诱导活性的粘弹性水凝胶材料，为神经诱导性基质材料设计奠定基础。项目将大多数研究关注的二维静态弹性基质表面细胞行为集中于更具有普适意义的三维粘弹性动态细胞微环境设计和机理研究，获得的材料构建策略以及动态力学信号调控细胞行为与组织再生的分子机制，对于构建基于微环境理化信号设计的组织诱导性生物材料具有普适性和很好的应用前景。

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