Role of matrix shear stress in annulus fibrosus cell mechanobiology

描述（由申请人提供）：退行性椎间盘疾病（DDD）仍然是美国和全球普通人群和经济的负担。文献中有强有力的证据表明机械应力在DDD的进展中起作用。然而，椎间盘复杂的层状结构和细胞表型的带状变化使得难以将组织水平力学转化为支配椎间盘（IVD）细胞功能的细胞微力学环境。了解细胞如何对可以详细描述的刺激做出反应，对于开发修复策略非常重要，其中可以定制支架以提供适当的微机械提示。基于我们之前动物研究的观察结果以及最近报道的对正常和退行性纤维环（AF）中层间（IL）基质的描述，我们提出了一个关于机械应力调节IL空间的假设。该中心假设指出，径向和剪切应力通过AF细胞的机械调节来协调调节IL基质。为了在均匀的微机械环境中为细胞提供径向和剪切刺激，我们提出了一种新的胶原界面细胞培养模型。将在模拟IL基质的微纤维结构的纤维状胶原蛋白薄膜（CTF）和其类型匹配的胶原蛋白凝胶之间培养细胞并使其变形。使用这个界面培养模型，目标1将确定AF细胞如何响应宏观结构剪切。具体而言，它将表征内部和外部AF细胞的区域和基底依赖性变形，并研究内在或结构因素是否主导其反应。在目标2中，我们假设的AF细胞调节的径向和剪切应力的机械生物学模型将使用界面培养模型进行测试。将在健康IL隔室的背景下研究一系列拉伸-压缩应力和剪切应变。同时，一种新的有限元模型，明确纳入IL室将开发，使用光学相干断层扫描验证，并实施预测IL细胞的剪切环境。实验获得的机械生物学响应，然后可以在空间上“映射”到相应的剪切区域。 公共卫生相关性：有大量证据表明，基质剪切应力在椎间盘中产生，与损伤和退变有关。该项目的结果将提供详细的洞察力的机械剪切应力对细胞功能的影响。这些知识可以帮助开发针对退行性椎间盘疾病等疾病的再生策略。

DESCRIPTION (provided by applicant): Degenerative disc disease (DDD) continues to be a burden on the general population and economy both in the United States and worldwide. There is strong evidence from the literature that indicate that mechanical stress plays a role in the progression of DDD. However, the complex lamellar architecture of the disc and the zonal variation in cell phenotype have made it difficult to translate tissue level mechanics to the cellular micromechanical environment, which governs intervertebral disc (IVD) cell function. Understanding how cells respond to stimuli that can be characterized in detail is important for developing repair strategies where scaffolds can be tailored to provide the appropriate micromechanical cues. Based on observations from our previous animal studies and recently reported descriptions of the interlamellar (IL) matrix in normal and degenerate annulus fibrosus (AF), we have developed an hypothesis on the regulation of the IL space by mechanical stress. This central hypothesis states that radial and shear stress coordinately modulate the IL matrix through mechanoregulation of AF cells. In order to provide cells with both radial and shear stimuli in a uniform micromechanical environment, we propose to implement a novel collagen interface cell culture model. Cells will be cultured and deformed between a fibrillar collagen thin film (CTF) that mimics the microfibrillar structure of the IL matrix and its type-matched collagen gel. Using this interface culture model, Aim 1 will determine how AF cells respond to macrostructural shear. Specifically, it will characterize zonal- and substrate-dependent deformation of inner and outer AF cells, and investigate whether intrinsic or structural factors dominate their responses. In Aim 2, our hypothetical mechanobiologic model of AF cell regulation by radial and shear stress will be tested using the interface culture model. A range of tension-compression stress and shear strain will be studied in the context of the healthy IL compartment. In parallel, a novel finite element model that explicitly incorporates an IL compartment will be developed, validated using optical coherence tomography, and implemented to predict the shear environment for IL cells. The mechanobiologic response obtained experimentally can then be spatially "mapped" to corresponding shear regions. PUBLIC HEALTH RELEVANCE: There is substantial evidence that matrix shear stresses are generated in the intervertebral disc, related to injury and degeneration. Results of this project will provide detailed insight into the effects of mechanical shear stresses on cell function. Such knowledge can aid the development of regenerative strategies against disorders such as degenerative disc disease.