Microscale Mechanobiology for Musculoskeletal Tissue Engineering using Advanced Ultrasound Techniques

项目摘要 机械力是细胞微环境的一个关键组成部分，并且已经被公认具有 对细胞和组织的潜在影响。二维细胞基底的被动力学性能和 已经显示三维细胞外基质影响祖细胞表型， 用于指导细胞功能。此外，使用外部施加的力对细胞和组织进行主动刺激， 已经在细胞和组织水平上应用以诱导各种反应。机械生物学是 特别是与肌肉骨骼组织有关，但我们对身体组织的理解存在差距。 组织环境的性质在细胞感觉的长度尺度上。该项目建立在前期工作的基础上 项目组应用先进的超声技术研究微尺度物理特性 由细胞接种矿化水凝胶组成的工程化肌肉骨骼组织。它集成了光谱 超声成像（SUSI）、双模式超声弹性成像（DUE）和超声诱导压缩成像 刺激. SUSI是一种使用反向散射射频频谱来获取信息的技术 关于样本的成分。DUE应用声辐射力使水凝胶变形并测量 它们的机械性能。聚焦超声诱导的压缩还将声压施加到 机械地刺激组织。超声技术的一个关键特征是它们是非侵入性的， 因此可以用来研究随着时间的推移发育的组织。此外，成像和变形可以是 应用于亚毫米分辨率。该项目将联合收割机这些先进的超声技术， 一个系统，可以全面表征和刺激工程肌肉骨骼组织在 微尺度目标应用是利用间充质干细胞（MSC）增强骨形成 嵌入在3D水凝胶基质中。具体目的是：1）整合频谱超声成像（SUSI） 和双模式超声弹性成像（DUE），以组成和机械表征矿化 组织，2）使用SUSI-DUE探测被动基质机械性质对MSC表型的影响， 3)使用超声诱导的周期性刺激MSC在水凝胶基质中的成骨分化， 4）应用SUSI-DUE催化和监测体内骨再生。该项目将 研究肌肉骨骼机械生物学，使用创新的新工具，可能会产生重要影响， 再生医学长期目标是一种治疗性干预，以增强骨形成， 加速愈合可改善结局的适应症，例如治疗骨不连， 脊柱融合术。

Project Summary Mechanical forces are a key component of the cellular microenvironment, and are well established to have potent effects on cells and tissues. The passive mechanical properties of two-dimensional cell substrates and three-dimensional extracellular matrices have been shown to influence progenitor cell phenotype and can be used to direct cell function. In addition, active stimulation of cells and tissues using externally applied forces has been applied at both the cell and tissue level to induce a variety of responses. Mechanobiology is particularly relevant to musculoskeletal tissues, but there is a gap in our understanding of the physical properties of the tissue environment on length scales that cells sense. This project builds on preliminary work by the project team in applying advanced ultrasound techniques to studying the microscale physical properties of engineered musculoskeletal tissues composed of cell-seeded mineralizing hydrogels. It integrates spectral ultrasound imaging (SUSI), dual-mode ultrasound elastography (DUE), and ultrasound-induced compressive stimulation. SUSI is a technique that uses the backscattered radiofrequency spectrum to derive information about the composition of a sample. DUE applies acoustic radiation force to deform hydrogels and measure their mechanical properties. Focused ultrasound-induced compression also applies acoustic pressure to mechanically stimulate tissues. A key feature of ultrasound techniques is that they are noninvasive and therefore can be used to study developing tissues over time. In addition, imaging and deformation can be applied at sub-millimeter resolution. This project will combine these advanced ultrasound techniques to create a system that can comprehensively characterize and stimulate engineered musculoskeletal tissues at the microscale. The target application is to potentiate bone formation using mesenchymal stem cells (MSC) embedded in a 3D hydrogel matrix. The Specific Aims are 1) to integrate spectral ultrasound imaging (SUSI) and dual-mode ultrasound elastography (DUE) to compositionally and mechanically characterize mineralizing tissues, 2) to probe the effects of passive matrix mechanical properties on MSC phenotype using SUSI-DUE, 3) to actively stimulate osteogenic differentiation of MSC in hydrogel matrices using ultrasound-induced cyclic compression, and 4) to apply SUSI-DUE to catalyze and monitor bone regeneration in vivo. This project will investigate musculoskeletal mechanobiology using an innovative new tool that could have important impact on regenerative medicine. The long term goal is a therapeutic intervention to potentiate bone formation in indications where accelerated healing would lead to improved outcomes, such as treatment of non-unions and recalcitrant spinal fusions.