Experimental study on tissue engineering of the small intestine by mesenchymal stem cell seeding

Background. We have succeeded in regenerating the small intestine by the use of tissue engineering techniques. However, the regenerated intestine proved to lack the muscle layer, which is essential for functional peristalsis. To induce regeneration of the muscle layer, we focused on autologous mesenchymal stem cells (MSC) as a source of muscle tissue. The aim of this study was to investigate the effect of MSC seeding onto the collagen scaffold on induction of the muscle layer. Materials and methods. We used six female beagle dogs. The small intestine was resected over a length of 5 cm and reconstructed by a collagen sponge graft in the same way as in our previous study. Autologous MSC derived from bone marrow (10⁷ cells) were seeded onto the collagen sponge just before implantation. Animals were sacrificed at 2, 4, and 16 weeks after surgery, and specimens were examined histologically. Results. All six dogs survived until the scheduled time of sacrifice. At 4 weeks, regeneration of the intestine was observed at the reconstructed site. Cells positive for α-smooth muscle actin appeared on the scaffold in the MSC-seeded group. However, they disappeared by 16 weeks and only a thin muscle layer regenerated beneath the mucosal layer, although the regenerated mucosal layer covered the luminal surface of the regenerated intestine. Conclusions. MSC seeding induced a transient distribution of cells positive for α-smooth muscle actin on the scaffold, but did not induce regeneration of the muscle layer. Further investigation is necessary to achieve this aim.