Bour Rachel K, Garner Gavin T, Peirce Shayn M, Christ George J
Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.
Department of Mechanical Engineering, University of Virginia, Charlottesville, Virginia, USA.
Tissue Eng Part A. 2025 May;31(9-10):373-386. doi: 10.1089/ten.TEA.2023.0315. Epub 2024 Jun 27.
Volumetric muscle loss (VML) injuries are defined by loss of sufficient skeletal muscle to produce persistent deficits in muscle form and function, with devastating lifelong consequences to both soldiers and civilians. There are currently no satisfactory treatments for VML injuries. The work described herein details the implementation of a fully enclosed bioreactor environment (FEBE) system that efficiently interfaces with our existing automated bioprinting and advanced biomanufacturing methods for cell deposition on sheet-based scaffolds for our previously described tissue-engineered muscle repair (TEMR) technology platform. Briefly, the TEMR technology consists of a porcine bladder acellular matrix seeded with skeletal muscle progenitor cells and preconditioned via 10% uniaxial cyclic stretch in a bioreactor. Overall, TEMR implantation in an established rat tibialis anterior (TA) VML injury model can result in 60 to ∼90% functional recovery. However, our original study documented >50% failure rate. That is, more than half of the implanted TEMR constructs produced no functional improvement beyond no treatment/repair. The high failure rate was attributed to the untoward mechanical disruption of TEMR during surgical implantation. In a follow-up study, adjustments were made to the geometry of both the VML injury and the TEMR construct, and the "nonresponder" group was reduced from over half the TEMR-treated animals to just 33%. Nonetheless, additional improvement is needed for clinical applicability. The main objectives of the current study were twofold: (1) explore the use of advanced biomanufacturing methods (i.e., FEBE bioreactor) to further improve TEMR reliability (i.e., increase functional response rate), (2) determine if previously established bioprinting methods, when coupled to the customized FEBE system would further improve the rate, magnitude or amplitude of functional outcomes following TEMR implantation in the same rat TA VML injury model. The current study demonstrates the unequivocal benefits of a customized bioreactor system that reduces manipulation of TEMR during cell seeding and maturation via bioprinting while simultaneously maximizing TEMR stability throughout the biofabrication process. This new biomanufacturing strategy not only accelerated the rate of functional recovery, but also eliminated all TEMR failures. In addition, implementation of bioprinting resulted in more physiomimetic skeletal muscle characteristics of repaired muscle tissue.
容积性肌肉损失（VML）损伤的定义是，骨骼肌损失过多，导致肌肉形态和功能持续出现缺陷，给士兵和平民都带来了灾难性的终身后果。目前对于VML损伤尚无令人满意的治疗方法。本文所述工作详细介绍了一种全封闭生物反应器环境（FEBE）系统的实施情况，该系统能与我们现有的自动化生物打印和先进生物制造方法有效对接，用于将细胞沉积在基于薄片的支架上，以应用于我们之前描述的组织工程化肌肉修复（TEMR）技术平台。简而言之，TEMR技术包括一个接种了骨骼肌祖细胞的猪膀胱脱细胞基质，并在生物反应器中通过10%的单轴循环拉伸进行预处理。总体而言，将TEMR植入已建立的大鼠胫前肌（TA）VML损伤模型中，可导致60%至约90%的功能恢复。然而，我们最初的研究记录显示失败率超过50%。也就是说，超过一半的植入TEMR构建体在未治疗/修复的基础上没有产生功能改善。高失败率归因于手术植入过程中TEMR受到的不良机械破坏。在一项后续研究中，对VML损伤和TEMR构建体的几何形状进行了调整，“无反应者”组在接受TEMR治疗的动物中从超过一半减少到仅33%。尽管如此，为了临床应用仍需要进一步改进。本研究的主要目标有两个：（1）探索使用先进的生物制造方法（即FEBE生物反应器）来进一步提高TEMR的可靠性（即提高功能反应率），（2）确定先前建立的生物打印方法与定制的FEBE系统相结合时，是否会进一步提高在同一大鼠TA VML损伤模型中植入TEMR后的功能结果的速率、幅度或程度。当前研究证明了定制生物反应器系统的明确益处，该系统通过生物打印减少了细胞接种和成熟过程中对TEMR的操作，同时在整个生物制造过程中最大限度地提高了TEMR的稳定性。这种新的生物制造策略不仅加快了功能恢复的速度，还消除了所有TEMR失败的情况。此外，生物打印的实施使修复后的肌肉组织具有更多模拟生理的骨骼肌特征。
