Research of muscle tissue engineering for urethral sphincter

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To achieve the goals of engineering large complex tissues, and possibly internal organs, vascularization of the regenerating tissue is essential. To keep an initial volume after implantation of regenerated tissue, improved vascularization is considered to be important. Recent advances in understanding the process of blood vessel growth has offered significant tools for the neovascularization of bioengineered tissues and therapeutic angiogenesis. Several angiogenic growth factors including vascular endothelial cell growth factor (VEGF), basic fibroblast growth factor (bFGF) and hepatocyte growth factor (HGF), platelet derived growth factor (PDGF) were used for vascularization of ischemic tissues. Other approaches such as prevascularization of the matrix prior to cell seeding and incorporation of endothelial cells in the bioengineered tissues showed encouraging results. In this study, the engineered tissues were shown to form muscle, as evidenced by H&E staining and immunohistochemical probing. Neovascularization was detected in the engineered muscle tissues of VEGF-infected cells. EC were shown to participate in blood vessel formation by X-gal staining. In contrast, engineered muscle of non-infected cells had a significantly smaller mass of cells, less neovascularization and only a few HMEC-1 cells could be detected. The VEGF-expressing tissues maintained their initial volume for 8 weeks, whereas the non-infected tissues lost their volume significantly. Sustained expression of muscle specific genes, myosin and MyoD, was evident only in muscle tissues containing VEGF-infected myoblasts. These results show, for the first time, that a combination of VEGF and endothelial cells are useful for inducing muscle formation, neovascularization and volume preservation in engineered tissues, and this technique may be useful for urinary sphincter reconstruction.