Regenerative Elastography: Monitoring Soft Tissue Reconstruction

描述(申请人提供)：组织工程学涉及依赖时间和顺序的过程，在修复的组织形成并发挥作用之前，最终结果是未知的。在组织发育、成熟、老化和发病过程中监测生物力学特性的变化，对于设计用于组织修复和再生的新的组织工程技术至关重要。对组织工程结构在组织生长过程中的硬度进行非侵入性定期监测，将使组织分化和发育的瞬时非破坏性手段成为可能。磁共振弹性成像(MRE)是一种以非侵入性方式测量生物软组织粘弹性性质的技术。磁共振成像生成描述剪切波运动的图像，从中我们可以计算组织硬度的局部值。由于目前的应用，磁共振成像不能用于研究微小的生物组织，也不能用于体内薄组织区域的成像，如厚度小于2 mm的关节软骨，以及亚毫米层次的明显结构。最近，我们将磁共振成像扩展到微观尺度，并将其称为显微磁共振弹性成像(&lt；MRE)。这类5MRE研究使用了低频声波剪切波激励(到目前为止高达1 kHz，高于常规MRE系统)、强磁场(11.74T)和高梯度强度(200G/cm)来评估具有高空间分辨率(34&lt；m x 34&lt；m x 500&lt；m)和改进的灵敏度的组织机械特性。我们首先使用琼脂糖凝胶复合模体验证了这项技术，然后在体外对不同的生物组织(青蛙卵母细胞和组织工程脂肪和骨)进行了研究。在每种情况下，使用各向同性和均质介质模型对低幅度剪切波模式进行分析，可以识别粘弹性特性。这项工作的目标是利用显微磁共振弹性成像技术在体外和体内监测和促进组织工程化脂肪的成脂作用。在最近与我们的组织工程合作者的工作中，使用间充质干细胞(HMSCs)和生物相容的支架结合在一起，形成了工程化成脂组织的基质。在组织刺激下，在特定成脂分化因子的作用下，组织工程构建物改变了其力学性能，因为脂肪基质是通过分化hMSCs而产生的。随着成脂细胞产生的成脂基质随着时间的推移逐渐增加，成脂组织变得更加柔软。该项目的最终目标是将组织工程与显微磁共振弹性成像技术相结合，通过提供一种实时、非侵入性的监测技术来评估组织发育和体内宿主组织的整合，从而加快组织工程技术在再生医学中的转化。具体目标是：1)优化工程成脂组织的MRE测试方案，促进体外成脂；2)开发和制造用于体内动物实验的高频机械致动器；3)应用&lt；MRE监测体内成脂组织工程构建。 公共卫生相关性：目前的癌症治疗通常包括手术、化疗或放射治疗。这些治疗在挽救患者生命方面发挥了至关重要的作用，但在乳腺癌和头颈癌中，这些治疗会使患者毁容和丧失正常功能。组织工程学将在康复和器官完全修复方面发挥重要作用。在这个项目中，我们建议监控组织工程过程，以加快组织工程在再生医学中的转化。

DESCRIPTION (provided by applicant): Tissue engineering involves time- and sequence-dependent procedures where the final outcome is unknown until the restored tissue is formed and functioning. Monitoring changes in the biomechanical properties during tissue development, maturation, ageing, and the onset of disease is critical to the design of new tissue engineering techniques for tissue repair and regeneration. Non-invasive periodic monitoring of the stiffness of a tissue-engineered construct during tissue growth would enable instantaneous non-destructive means for tissue differentiation and development. Magnetic resonance elastography (MRE) is such a technique that measures the viscoelastic properties of soft biological tissues in a non-invasive manner. MRE generates images that depict shear wave motion from which we can calculate local values of the tissue stiffness. MRE, as currently applied, cannot be used to study small biological tissues, or to image in vivo thin tissue regions, such as articular cartilage with thickness less than 2 mm and distinct structure in sub millimeter layers. Recently, we have extended MRE to the microscopic scale and have referred to it as microscopic MR elastography (<MRE). Such 5MRE studies have used a low frequency acoustic shear wave excitation (so far up to 1 kHz, which is higher than in conventional MRE systems), a strong magnetic field (11.74 T), and high gradient strengths (200 G/cm) to assess tissue mechanical properties with high spatial resolution (34 <m x 34 <m x 500 <m) and improved sensitivity. We validated this technique first using agarose gel composite phantoms, and second in studies of different biological tissues (frog oocyte and tissue engineered fat and bone) in vitro. In each case, analysis of the low amplitude shear wave pattern using isotropic and homogeneous models of the medium allowed the identification of the viscoelastic properties. The goal of this work is to monitor and enhance adipogenesis in tissue engineered fat using microscopic magnetic resonance elastography in vitro and in vivo. In recent work with our tissue engineering collaborators, using mesenchymal stem cells (hMSCs), and biocompatible scaffolds were combined to form substrates for engineered adipogenic tissues. Upon tissue stimulation, with specific adipogenic differentiation factors the tissue engineered constructs changed their mechanical properties as lipid matrix was produced by differentiating hMSCs. Adipogenic tissue became softer as adipogenic matrix production from the adipogenic cells gradually increases with respect to time. The ultimate goal of this project is to integrate tissue engineering with microscopic magnetic resonance elastography to speed the translation of tissue engineering technology in regenerative medicine by providing a real-time, non-invasive monitoring technique to assess tissue development and host tissue integration in vivo. The specific aims are: 1) Optimize <MRE testing protocols of engineered adipogenic tissues and enhance adipogenesis in vitro; 2) Develop and build high frequency mechanical actuators for in vivo animal testing; 3) Apply <MRE to monitor adipogenic tissue engineered constructs in vivo. PUBLIC HEALTH RELEVANCE: Current cancer treatments usually involve surgery, chemotherapy, or radiation. These treatments play a vital role in saving patient's lives but in breast cancer and head and neck cancer, for example, leave the patient with disfiguration and loss of normal function. Tissue engineering will play a vital role in rehabilitation and full organ restoration. In this project, we are proposing to monitor the tissue engineering process to speed the translation of tissue engineering in regenerative medicine.