Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA; The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA; The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
Acta Biomater. 2019 Aug;94:243-252. doi: 10.1016/j.actbio.2019.06.025. Epub 2019 Jun 19.
Skeletal muscle possesses efficient ability to regenerate upon minor injuries, but its capacity to regenerate is severely compromised with traumatic injuries and muscle-associated diseases. Recent evidence suggests that skeletal muscle regeneration can be enhanced by transplantation of muscle satellite cells (MuSCs) or treatment with pro-myogenic factors, such as Wingless-type MMTV Integrated 7a (Wnt7a) protein. Although direct intramuscular injection is the simplest method to deliver MuSCs and Wnt7a for regenerative therapy, direct injections are not viable in many clinical cases where structural integrity is severely compromised. To address this challenge, we evaluated the feasibility of co-delivering pro-myogenic factors, such as Wnt7a, and MuSCs using a synthetic poly(ethylene glycol) (PEG)-based hydrogel to the affected skeletal muscles. The Wnt7a release rate can be controlled by modulating the polymer density of the hydrogel, and this release rate can be further accelerated through the proteolytic degradation of the hydrogel. Treating cryo-injured tibialis anterior (TA) muscles with Wnt7a-loaded hydrogels resulted in an improved regenerative response by day 14, measured by increased muscle fiber cross-sectional area, bulk TA mass, and the number of Pax7 MuSCs at the injury site, compared to the TA muscles treated with Wnt7a-free hydrogels. Co-delivery of Wnt7a and primary MuSCs using the synthetic hydrogel to the cryo-injured TA muscles significantly increased cellular migration during the engraftment process. This work provides a synthetic biomaterial platform for advancing treatment strategies of skeletal muscle conditions where direct intramuscular injection may be challenging. Finally, the current outcomes establish an important foundation for future applications in treating severe muscle trauma and diseases, where the endogenous repair capacity is critically impaired. STATEMENT OF SIGNIFICANCE: Skeletal muscle injuries and diseases cause debilitating health consequences, including disability and diminished quality of life. Treatment using protein and stem cell-based therapeutics may help regenerate the affected muscles, but direct intramuscular injection may not be feasible in severe muscle injuries due to the gravely damaged tissue structure. In chronic muscle diseases, such as Duchenne muscular dystrophy, local treatment of the diaphragm, a muscle critical for respiration, may be necessary but direct injection is difficult due to its thin dimensions. To address this challenge, this work presents a synthetic and bioactive muscle "patch" that enables concurrent administration of proteins and muscle stem cells for accelerated muscle healing.
骨骼肌在受到轻微损伤后具有很强的再生能力，但在受到创伤和肌肉相关疾病的影响后，其再生能力会严重受损。最近的证据表明，骨骼肌的再生能力可以通过移植肌肉卫星细胞（MuSCs）或使用促肌生成因子（如 Wingless-type MMTV Integrated 7a（Wnt7a）蛋白）来增强。虽然直接向肌肉内注射 MuSCs 和 Wnt7a 是进行再生治疗的最简单方法，但在结构完整性严重受损的许多临床情况下，直接注射是不可行的。为了解决这一挑战，我们评估了使用合成聚乙二醇（PEG）基水凝胶向受影响的骨骼肌同时递送促肌生成因子（如 Wnt7a）和 MuSCs 的可行性。通过调节水凝胶的聚合物密度可以控制 Wnt7a 的释放速率，并且通过水凝胶的蛋白水解降解可以进一步加速释放速率。用负载 Wnt7a 的水凝胶处理冷冻损伤的胫骨前肌（TA）可在第 14 天观察到更好的再生反应，表现在肌肉纤维横截面积增加、TA 总体积增加以及损伤部位的 Pax7 MuSCs 数量增加，与用不含 Wnt7a 的水凝胶处理的 TA 肌肉相比。将 Wnt7a 和原代 MuSCs 共同递送到冷冻损伤的 TA 肌肉中，使用合成水凝胶显著增加了植入过程中的细胞迁移。这项工作为推进骨骼肌疾病的治疗策略提供了一个合成生物材料平台，在这些疾病中，直接肌肉内注射可能具有挑战性。最后，目前的研究结果为未来在严重肌肉创伤和疾病的治疗中的应用奠定了重要基础，在这些疾病中，内源性修复能力受到严重损害。
骨骼肌损伤和疾病会导致身体虚弱，健康状况恶化，包括残疾和生活质量下降。使用蛋白质和干细胞治疗可能有助于再生受影响的肌肉，但由于组织结构严重受损，在严重的肌肉损伤中，直接肌肉内注射可能不可行。在慢性肌肉疾病（如杜氏肌营养不良症）中，需要对膈肌（一种对呼吸至关重要的肌肉）进行局部治疗，但由于其尺寸较薄，直接注射比较困难。为了解决这一挑战，这项工作提出了一种合成的、有生物活性的肌肉“补丁”，可以同时给药蛋白质和肌肉干细胞，以加速肌肉愈合。
