Utilization of Engineered Skeletal Muscle Units to Repair Volumetric Muscle Loss

描述(申请人提供)：多种病理情况，包括：肌肉创伤、外科损伤和肌病可导致骨骼肌丧失。容积性肌肉丢失(VML)是指肌肉丧失，导致肌肉功能无法恢复。到目前为止，包括肌瓣或移植物在内的治疗VML的方法并不有效，而且由于组织可获得性有限和供区发病率的限制而受到阻碍。具有功能性肌腱连接、肌腱-骨锚和神经支配的工程化肌肉骨骼组织的建立，不仅可以恢复创伤或疾病后肌肉等复杂组织的功能，还可以作为研究发育生物学和药理学的模型。为了满足这一需求，我们的实验室开发了一种可重复使用的方法，用于开发无支架的工程化骨骼肌结构。我们制造的工程化肌肉由成纤维细胞产生的细胞外基质和沿应变轴排列的肌管组成的3D结构组成。这种体外构造可以自发地产生力，也可以响应电场刺激而产生力。工程化骨骼肌在体外是有限的，因为它在力量特征和组织结构方面不会形成新生儿的表型。最近，我们已经证明，在植入后短短一周，这些肌肉结构就形成了一个毛细血管系统，结缔组织的表肌样外层，以及肌肉纤维含量的增加。在移植后，构建物最大等长力增加了245%，并开始发展必要的界面，以推动表型向成年肌肉发展。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)，它具有功能接口，当被植入时，允许完全恢复自然肌力。虽然我们的技术在修复和替换受损肌肉方面显示出很大的前景，但如何利用这项技术获得肌肉功能的最佳恢复仍有很多工作要做。然而，对于在人类中使用这种新颖和创新的技术，另一个令人担忧的问题是在患者中使用干细胞/前体细胞来源的组织的安全性。必须证明主要的或 用于生成这些结构的基质细胞在移植后不会构成长期威胁。该领域的主要关注点是能否确定没有未分化的 细胞持续存在于移植的结构中，这可能会导致细胞行为异常，最终导致癌症。这是一个里程碑式的项目。该项目的成果将是一种组织工程功能骨骼肌单元(SMU)，其大小和功能适当，可用于临床上出现手部和面部等小型肌肉损伤的情况。此外，在授权期结束时，我们将对移植物合并的机制和移植物用于翻译应用的安全性有更好的了解。SMU将能够为因创伤或疾病而遭受创伤性骨骼肌丧失的患者提供治疗，包括修复/替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.