Utilization of Engineered Skeletal Muscle Units to Repair Volumetric Muscle Loss

描述（由申请人提供）：多种病理情况包括：肌肉创伤，手术损伤和肌病可导致骨骼肌丧失。体积性肌肉损失（VML）是肌肉的损失，导致肌肉功能无法恢复。迄今为止，包括肌肉瓣或移植物在内的VML治疗并不有效，并且受到组织可用性有限和供体部位发病率的阻碍。建立具有功能性肌腱连接、肌腱-骨锚和神经支配的工程肌肉骨骼组织，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的方法来开发无支架工程骨骼肌结构。我们制造的工程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。这种体外结构可以自发或响应电场刺激产生力。工程骨骼肌在体外是有限的，因为它在强度特征和组织组织方面没有发展超出新生儿表型。最近，我们的研究表明，在植入短短一周后，这些肌肉结构就形成了毛细血管系统，结缔组织的外膜样层，肌肉纤维含量增加。在外植后，构建体的最大等长力增加了245%，并开始发展必要的界面，将表型推进到成年肌肉。我们实验室的长期目标是设计一种组织工程功能骨骼肌单元（SMU），它具有功能接口，当植入时可以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显示出很大的希望，但如何利用这项技术来获得最佳的肌肉功能恢复还有很多工作要做。然而，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/前体细胞来源组织的安全性。必须证明，主要的或

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.