Engineering skeletal muscle using a humanoid bioreactor platform

骨骼肌是人体最大的器官系统，是产生运动和运动力量所必需的。与肌腱和韧带不同，肌肉组织在受到轻微伤害时可以很容易地自我再生。然而，仅在英国，每年就有成千上万的患者受到肌肉组织不可逆转的损失的影响，这种损失可能是由肌病、大创伤（例如爆炸伤害）和癌症组织切除等严重情况引起的。随着人口老龄化，肌肉损伤和疾病变得越来越频繁，这造成了越来越大的社会和经济负担。由于目前的维修策略不令人满意，学术界、工业界和最终用户越来越意识到需要新的维修方法。组织工程是一种很有前途的骨骼肌修复策略。这种方法包括使用生物材料、细胞和生物反应器系统，它们的组合允许控制细胞培养条件，为细胞-生物材料结构提供物理刺激，以在体外工程肌肉。机械和电刺激都与肌肉组织工程有关，并已被证明可以促进细胞的增殖和分化。我们的研究小组在生物材料开发和测试方面拥有丰富的经验，包括使用脱细胞生物组织，水凝胶和静电纺材料。我们最近还开发了一种独特的生物反应器系统，该系统使用肌肉骨骼类人机械臂来模拟在人类肩关节观察到的运动和力，并驱动细胞-生物材料结构（epsrc资助的类人生物反应器项目，EP/S003509/1）。肌肉骨骼类人机器人可以复制内部结构，如肌肉、肌腱或骨骼，以及使用由电动机驱动的弦来复制人体的生物力学。为了开发类人生物反应器平台，我们将这些机器人与柔软、灵活的生物反应器室结合起来，这些生物反应器室容纳细胞-生物材料结构，并使它们长时间存活。到目前为止，我们的努力主要集中在肌腱组织工程上，用于肩袖修复应用，同样的平台可以应用于工程骨骼肌。本博士项目将重点研究仿人生物反应器系统在骨骼肌组织工程中的应用。目的是确定与生理相关的机械刺激和电刺激对肌肉组织工程的重要性。这将有助于产生质量更好的肌肉移植物。如果这种方法是成功的，它将提供一个可靠和无限的自体肌肉移植来源，这将转化为更安全、更经济的患者护理。为了实现这一目标，需要通过肌肉脱细胞或水凝胶方法来开发能够支持骨骼肌组织生长的支架。现有的用于肌腱组织工程的类人生物反应器的软腔将适应于容纳新型肌肉支架，允许其机械和电刺激。这种刺激对骨骼肌细胞在支架上定植的影响将被研究。然后需要评估工程肌肉的功能。这个高度跨学科的项目涉及生物工程、生物学、生物电子学和生物力学的各个方面。虽然这里提出的最终应用是支持大肌肉缺陷的再生，但其他科学领域也可以从这个项目中受益。利用这种更生理的平台开发支架或生物材料将引起组织工程领域其他研究人员的极大兴趣，因为该策略可以应用于其他组织。此外，该项目将有助于生物致动器的发展，这将有利于生物机器人和软机器人的发展。

Skeletal muscle is the largest organ system in the body by mass and is necessary to generate forces for movement and locomotion. Unlike tendons and ligaments, muscle tissue can easily regenerate itself when subjected to minor injuries. However, irreversible loss of muscle tissue affects thousands of patients per year in the UK alone and can be caused by severe conditions such as myopathy, large trauma (e.g. blast injuries) and removal of cancer tissue. Muscle injuries and diseases are becoming more frequent as our population is aging, which causes an increasing societal and economic burden. As current repair strategies are not satisfactory, the awareness of the need for new repair approached is increasing in academia, in industry and also for end users. Tissue engineering is a promising repair strategy for skeletal muscle. This approach involves the use of biomaterials, cells and bioreactor systems, the combination of which allow control of cell culture conditions to provide physical stimulation to the cell-biomaterial constructs to engineer muscle in vitro. Both mechanical and electrical stimulation are relevant to muscle tissue engineering and have been shown to improve the improve cell proliferation and differentiation.Our research group has extensive experience of biomaterial development and testing, including use of decellularized biological tissues, hydrogels and electrospun materials. We have also recently developed a unique bioreactor system that uses a musculoskeletal humanoid robotic arm to mimic the motion and forces observed at the human shoulder joint and actuate cell-biomaterial constructs (EPSRC-funded Humanoid Bioreactor project, EP/S003509/1). Musculoskeletal humanoids can replicate the inner structures, such as muscles, tendons or bones, and the biomechanics of the human body using strings actuated by electric motors. To develop the humanoid bioreactor platform, we combined these robots with soft, flexible bioreactor chambers that host the cell-biomaterial constructs and maintain them alive for long periods of time. While our efforts have so far been focused on tendon tissue engineering for rotator cuff repair applications, the same platform can be applied to engineer skeletal muscle.This PhD project will focus on applying the humanoid bioreactor system to skeletal muscle tissue engineering. The aim is to determine the importance of physiologically-relevant mechanical stimulation and electrical stimulation for muscle tissue engineering. This will contribute to generating better quality muscle grafts. If such an approach is successful, it will provide a reliable and unlimited source of muscle autografts which would translate into safer and more cost-effective patient care.To achieve this goal, a scaffold able to support skeletal muscle tissue growth will need to be developed, either through muscle decellularization or hydrogel approaches. The existing soft chamber of the humanoid bioreactor, currently employed for tendon tissue engineering, will be adapted to host the novel muscle scaffold, allowing both its mechanical and electrical stimulation. The impact of such stimulations on the colonization of the scaffold by skeletal muscle cells will be investigated. The functionality of the engineered muscles will then need to be evaluated. This highly multidisciplinary project involves various aspects of bioengineering, biology, bioelectronics and biomechanics. Although the end application proposed here is to support the regeneration of large muscle defects, other areas in science could benefit from this project. The development of scaffold or biomaterials using this more physiological platform will be of significant interest to other researchers in the field of tissue engineering, as the strategy could be applied to other tissues. Additionally, this project will contribute to the development of bio-actuators, which would benefit developments in bio-robotics and soft robotics.