Abstract
A bioengineered skeletal muscle tissue as an alternative for autologous tissue flaps, which mimics the structural and functional characteristics of the native tissue, is needed for reconstructive surgery. Rapid progress in the cell-based tissue engineering principle has enabled in vitro creation of cellularized muscle-like constructs; however, the current fabrication methods are still limited to build a three-dimensional (3D) muscle construct with a highly viable, organized cellular structure with the potential for a future human trial. Here, we applied 3D bioprinting strategy to fabricate an implantable, bioengineered skeletal muscle tissue composed of human primary muscle progenitor cells (hMPCs). The bioprinted skeletal muscle tissue showed a highly organized multi-layered muscle bundle made by viable, densely packed, and aligned myofiber-like structures. Our in vivo study presented that the bioprinted muscle constructs reached 82% of functional recovery in a rodent model of tibialis anterior (TA) muscle defect at 8 weeks of post-implantation. In addition, histological and immunohistological examinations indicated that the bioprinted muscle constructs were well integrated with host vascular and neural networks. We demonstrated the potential of the use of the 3D bioprinted skeletal muscle with a spatially organized structure that can reconstruct the extensive muscle defects.
Highlights
In recent decades, researchers have focused on mimicking the ultrastructure of native muscle tissue that is composed of highly oriented myofibers
A bioengineered skeletal muscle construct with the ultrastructural organization similar to the native muscle was designed and fabricated by the integrated tissue-organ printing (ITOP) technology (Fig. 1A,B)
This muscle construct consisted of three components: (i) a human muscle progenitor cell-laden hydrogel bioink, (ii) a sacrificing acellular gelatin hydrogel bioink, and (iii) a supporting poly(ε-caprolactone) (PCL) polymer (Fig. 1C)
Summary
Researchers have focused on mimicking the ultrastructure of native muscle tissue that is composed of highly oriented myofibers. The mechanical stimulation[25,26] and electrical fields[21,27] have been tested to align the muscle cells in biomaterial scaffolds These strategies could pre-align the muscle cells and improve their functionality in vitro; they only allowed micron-scale tissue or single-layered muscle bundle constructions that may be not suitable for treating extensive muscle defect[10,28,29,30,31,32]. The outcomes showed that the bioprinted organized muscle constructs could mature into functional muscle in vivo when implanted subcutaneously in rats Based on this initial success, we investigated the feasibility of using 3D bioprinted muscle constructs for treating extensive skeletal muscle defects. Muscle tissue regeneration and functional recovery were evaluated using a rodent muscle defect model of 30–40% of tibialis anterior (TA) muscle loss with ablation of extensor digitorum longus (EDL) and extensor hallucis longus (EHL) muscles[10] to determine the feasibility to treat critical-sized skeletal muscle injuries
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