Tissue engineering of injectable muscle: Three-dimensional myoblast-fibrin injection in the syngeneic rat animal model

Background: Surgical treatment of skeletal muscle loss resulting from trauma, tumor ablation, or inborn tissue defects is hampered by the scarcity of functional substitute tissue. By using techniques of tissue engineering, reconstitution of skeletal muscle defects might become a more viable option. However, it is necessary to develop an adequate, practical method for delivering myoblasts within a three-dimensional scaffold in vivo. The aim of this study was to create and evaluate a novel method for the transfer of myoblasts with clinically approved components within a three-dimensional matrix. Methods: The authors injected expanded primary male myoblasts, into muscle defects in female syngcneic rats using a two-way syringe (Duploject) within a three-dimensional fibrin matrix. Detection and evaluation were performed using Y chromosome in situ hybridization, antidesmin immunostaining, and hematoxylin and eosin staining. To identify possible differences by means of integration, the injected myoblasts were compared with 7 days of precultivated constructs. Results: Injected myoblasts showed increasing integration into host muscle fibers in a time-dependent manner, exclusively at the injection site. Antidesmin staining revealed a conserved myogenic phenotype of transplanted cells. The fibrin matrix resolved over a period of 12 weeks, with no indication of an inflammatory reaction. No significant difference in the number of detected Y chromosome-positive nuclei was found between the two transplantation groups. Conclusions: The presented technique of myoblast-fibrin injection indicates a clinical potential for reconstruction of skeletal muscle defects in vivo using a ready to-use device in combination with tissue-engineering methods.