Injury to the central nervous system (CNS) usually leads to the activation of astrocytes, followed by glial scar formation. The formation of glial scars from active astrocytes in vivo has been found to be dependent on the cell microenvironment. However, how astrocytes respond to different microenvironmental cues during scar formation, such as changes in matrix stiffness, remains elusive. In this work, we established an in vitro model to assess the responses of astrocytes to matrix stiffness changes that may be related to pathophysiology. The investigated hydrogel backbones are composed of collagen type I and alginate. The stiffness of these hybrid hydrogels can be dynamically changed by association or dissociation of alginate chains through adding crosslinkers of calcium chloride or a decrosslinker of sodium citrate, respectively. We found that astrocytes obtain different phenotypes when cultured in hydrogels of different stiffnesses. The obtained phenotypes can be switched in situ when changing matrix stiffness in the presence of cells. Specifically, matrix stiffening reverts astrogliosis, whereas matrix softening initiates astrocytic activation in 3D. Moreover, the effect of matrix stiffness on astrocytic activation is mediated by Yes-associated protein (YAP), where YAP inhibition enhances the upregulation of GFAP and contributes to astrogliosis. To investigate the underlying mechanism of matrix stiffness-dependent GFAP expression, we also developed a mathematical model to describe the time-dependent dynamics of biomolecules involved in the matrix stiffness mechanotransduction process of astrocytes. The modeling results further indicate that the effect of matrix stiffness on cell fate and behavior may be related to changes in the cytoskeleton and subsequent activity of YAP. The results from this study will guide researchers to re-examine the role of matrix stiffness in reactive astrogliosis in vivo and inspire the development of a novel therapeutic approach for controlling glial scar formation following injury, enabling axonal regrowth and improving functional recovery by exploiting the benefits of mechanobiology studies.

中枢神经系统（CNS）损伤通常会导致星形胶质细胞活化，继而形成胶质瘢痕。已经发现体内活性星形胶质细胞形成神经胶质瘢痕取决于细胞微环境。然而，在瘢痕形成过程中星形胶质细胞如何响应不同的微环境提示，例如基质刚度的变化，仍然难以捉摸。在这项工作中，我们建立了一个体外模型，以评估星形胶质细胞对可能与病理生理有关的基质硬度变化的反应。研究的水凝胶骨架由I型胶原和藻酸盐组成。通过分别添加氯化钙的交联剂或柠檬酸钠的去交联剂，藻酸盐链的缔合或解离，可以动态改变这些杂化水凝胶的刚度。我们发现星形胶质细胞在不同硬度的水凝胶中培养时获得不同的表型。在存在细胞的情况下改变基质刚度时，可以原位转换获得的表型。具体而言，矩阵变硬可恢复星形胶质增生，而矩阵变软则可在3D模式下启动星形胶质细胞激活。此外，基质刚度对星形胶质细胞活化的影响是由Yes相关蛋白（YAP）介导的，其中YAP抑制会增强GFAP的上调并导致星形胶质细胞增生。为了研究基质刚度依赖性GFAP表达的潜在机制，我们还开发了一个数学模型来描述星形胶质细胞基质刚度机械转导过程中涉及的生物分子的时间依赖性动力学。建模结果进一步表明，基质刚度对细胞命运和行为的影响可能与细胞骨架的变化和YAP的后续活性有关。这项研究的结果将指导研究人员重新研究体内刚度在体内反应性星形胶质增生中的作用，并启发开发出一种新的治疗方法，以控制损伤后神经胶质瘢痕的形成，从而使轴突再生并通过利用其益处来改善功能恢复力学生物学研究。