Utilization of Engineered Skeletal Muscle Units to Repair Volumetric Muscle Loss

描述（由申请方提供）：多种病理状况，包括：肌肉创伤、手术损伤和肌病，可导致骨骼肌损失。容积性肌肉损失（VML）是肌肉的损失，导致不可恢复的肌肉功能。迄今为止，VML的治疗包括肌瓣或移植物，是无效的，并且受到有限的组织可用性和供体部位发病率的阻碍。构建具有功能性肌腱连接、腱-骨锚和神经支配的工程化肌肉骨骼组织，不仅可以恢复创伤性损伤或疾病后肌肉等复杂组织的功能，而且可以作为发育生物学和药理学研究的模型。为了满足这一需求，我们的实验室开发了一种可重复的方法来开发无支架工程化骨骼肌构建体。我们制造的工程肌肉由成纤维细胞产生的细胞外基质和肌管沿应变轴沿着的3D结构组成。这种体外结构可以自发地或响应于电场刺激产生力。工程化骨骼肌在体外是有限的，因为它在强度特性和组织组织结构方面不能发展超过新生儿表型。最近，我们已经表明，植入后短短一周，这些肌肉结构发展毛细血管系统，外肌样结缔组织外层，并增加肌纤维含量。移出后，该结构将最大等长力增加了245%，并开始发育将表型推向成人肌肉所需的必要界面。我们实验室的长期目标是设计一种组织工程化的功能性骨骼肌单元（SMU），该单元具有功能性界面，并且在植入时允许完全恢复天然肌肉力量。虽然我们的技术在修复和替换受损肌肉方面表现出了很大的潜力，但仍有大量工作要做，以确定如何利用这项技术来获得肌肉功能的最佳恢复。然而，关于在人类中使用这种新颖和创新技术的另一个问题是在患者中使用干细胞/前体细胞衍生组织的安全性。必须证明，主要或 用于产生这些构建体的基质细胞在移植后不构成长期威胁。该领域的主要关切是能否确定没有未分化的 细胞在移植的结构中持续存在，这可能导致细胞行为异常，如癌症。这是一个里程碑式的项目。该项目的交付成果将是一个组织工程化的功能性骨骼肌单位（SMU），具有适当的尺寸和功能，可用于临床小肌肉损伤的情况，例如手部和面部的肌肉损伤。此外，在授予期结束时，我们将更好地了解移植物结合的机制和移植物用于转化应用的安全性。SMU将能够治疗因创伤性损伤或疾病而遭受创伤性骨骼肌损失的患者，包括修复/更换面部和复合面部特征。

DESCRIPTION (provided by applicant): Multiple pathological conditions including: muscle trauma, surgical damage, and myopathies can lead to loss of skeletal muscle. Volumetric muscle loss (VML) is the loss of muscle resulting in unrecoverable muscle function. To date, the treatments for VML including, the muscle flap or graft, are not effective and are hindered by limited tissue availability and donor site morbidity. The creation of engineered musculoskeletal tissue with functional myotendinous junctions, tendon-bone anchor and innervation will not only restore the function of complex tissue such as muscle following traumatic injury or disease, but can also be used as a model for studying developmental biology and pharmacology. To address this need, our laboratory has developed a reproducible method for development of scaffold-less engineered skeletal muscle constructs. The engineered muscle we fabricate consists of a 3D construct with a fibroblast-produced extracellular matrix and myotubes aligned along the axis of strain. This in vitro construct can generate force either spontaneously or in response to electrica field stimulation. Engineered skeletal muscle is limited in vitro in that it does not develop beyon a neonatal phenotype in terms of strength characteristics and tissue organization. Recently, we have shown that following as little as one week of implantation, these muscle constructs develop a capillary system, an epimysium-like outer layer of connective tissue, and an increase in muscle fiber content. Upon explantation, the constructs increased maximum isometric force 245% and begins to develop the necessary interfaces needed to advance the phenotype toward adult muscle. The long term goal of our laboratory is to engineer a tissue-engineered functional skeletal muscle unit (SMU) which has functional interfaces and when implanted allows for the full recovery of native muscle forces. While our technology shows lots of promise for repair and replacement of damaged muscle, a lot of work remains to determine how to utilize this technology to obtain optimal recovery of muscle function. An additional concern regarding the use of this novel and innovative technology in humans, however, is the safety of use of stem/precursor cell-derived tissue in patients. It is imperative to demonstrate that the primary or stromal cells used for the generation of these constructs pose no long-term threat after transplantation. The main concern in the field is the ability to ascertain that no undifferentiated cells persist in the transplanted construct that might later lead to aberrant cellular behavior suc as cancer. This is a milestone driven project. The deliverable of this project will be a tissue-engineered functional skeletal muscle unit (SMU) of appropriate size and function for clinical use in situations of small muscle injuries, such as those found in the hand and face. In addition, at the end of the granting period, we will have a better understanding of the mechanism of graft incorporation and safety of the graft for translational applications. The SMU will enable the treatment of patients who have suffered traumatic skeletal muscle loss due to traumatic injuries or disease, including the repair/replacement of face and composite facial features.