Electrophoretically decellularized xenogeneic extracellular matrix for large volume skeletal muscle regeneration
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Large volume skeletal muscle injuries, such as those that occur through traumatic or surgical means, are complex injuries that are unable to repair through the body’s native repair processes. These injuries, termed volumetric muscle loss (VML), result in fibrotic scar tissue formation and functional impairments. Within the last decade, there has been an immense push towards bioscaffold research and development to regenerate functional skeletal muscle tissue in VML injuries. The most promising bioscaffold is the use of a decellularized skeletal muscle-derived extracellular matrix (ECM). However, the use of skeletal muscle derived ECMs to replace lost tissues is limited by the inability to produce ECMs of clinically relevant sizes and shapes. Therefore, the purpose of this study was to develop an electrophoresis-based decellularization method that can render large volumes of porcine skeletal muscle ECM acellular time while also retaining the native ECM ultrastructure. Analysis of the resulting decellularized porcine skeletal muscle ECM determined most soluble proteins and DNA were removed, and the collagen framework of the ECM resembled that of native skeletal muscle. The decellularized ECM was implanted into a rodent lateral gastrocnemius (LGAS) VML injury model previously developed in our lab. Repair of the VML injury with the electrophoretically decellularized porcine ECM improved morphology of the LGAS and resulted in myofiber, blood vessel, and nerve growth throughout the ECM implant in vivo, and promoted an M2 macrophage profile. Addition of mesenchymal stem cells (MSCs) to the implanted ECM increased functional recovery, myofiber and blood vessel infiltration, and reduced fibrosis within the ECM implant region compared to saline treated implants 84 days after injury. The direct contribution of the injected MSCs tagged with green fluorescent protein (GFP) to myofiber development was not detected. These data demonstrate an electrophoresis-based decellularization protocol may be a better alternative to produce clinically relevant ECMs that can be used to repair VML injuries, and resulting porcine ECMs serve as a viable platform for muscle regeneration. Additionally, injection of MSCs into the ECM improves myofiber ingrowth, vascularization, and function most likely through modulation of the tissue microenvironment rather than differentiation and fusion into skeletal muscle.