Direct-writing Process and in vivo Evaluation of Prevascularized Composite Constructs for Muscle Tissue Engineering Application

Tissue engineered skeletal muscle is expected to treat muscle defects caused by trauma and disease. However, designing and manufacturing thick and complex tissue engineered skeletal muscle requires vascularization to ensure its internal cell viability and nutrient supply in vitro. In this article, we developed a set of Direct-Writing (DW) bio-printing procedure to manufacture a prevascularized composite construct with Human Umbilical Vein Endothelial Cell (HUVEC) and C2C12 cells for muscle tissue engineering application. We put the cells into the construct during the DW process to obtain the prevascularization and intend to promote its vascularization in vivo later. The constructs with cells or without cells were implanted respectively into nude mice back for 3 weeks, after which the mice healthily live for all the time and all the implants are tightly bonded to the host. From immunohistochemical analysis, CD31-positive blood vessels existed in the implanted samples with cells are more substantial than those without cells, but the implanted samples with HUVEC and C2C12 cells have much more number of small blood vessels distributing evenly. Moreover, the implants with cells, especially that with HUVEC and C2C12 cells, are able to get better fusion with the host skin and subcutaneous tissues. Histological analysis demonstrates that our DW-based constructs have the potential to be getting to vascularize the tissue engineered muscle.