Percutaneous tissue-engineered pulmonary valved stent implantation: comparison of bone marrow-derived CD133+-cells and cells obtained from carotid artery.

OBJECTIVE

The aim of tissue engineering is, for instance, to create a new valve or organ that is similar to the native one. This new construct may have the capability of growth, repair, and remodeling. One instance where tissue engineering offers an enormous advantage is in the treatment of Tetralogy of Fallot. After repair of this defect, pulmonary valve regurgitation with late ventricular dysfunction is not uncommonly observed.

METHODS

In this study, we compared the use of endothelial cells (ECs) and smooth muscle cells (SMCs) derived from the carotid artery (group 1/n=5) with CD133+-cells derived from the bone-marrow (group 2/n=5) of juvenile sheep. Western blot analysis and histology were done before and after percutaneous pulmonary valved stent implantation. After seeding of the pulmonary valved stent with one of the cell groups, the construct was placed in a dynamic bioreactor for 16 days. After incubation, the valved stent was seeded again for 3 days. Finally, the valved stent was implanted percutaneously under angiographic control.

RESULTS

In group 1, α-actin and calponin were found in the EC and SMC population by using Western blot analysis. In contrast, CD31 was found in EC, but not in the SMC population. Cells from group 2 demonstrated a pure population. CD133+-cells were detected in the CD133+-cell population and no CD133+-cells were found in the negative fraction. Three months after implantation, the transvalvular gradient was significantly higher in group 1 compared to group 2. CD31-staining demonstrated a confluent monolayer in both groups. Immunohistochemistry revealed strong expression of α-smooth-muscle-actin and an in-growth into the leaflets of both groups (p=ns). CD3-, CD20-, CD45-, and CD68-staining confirmed no signs of inflammation in group 2, whereas in group 1 small amounts of inflammation were detected in all analyzed animals. Von Kossa staining revealed mild to moderate calcifications in the annular region of group 1. In contrast, less calcification was detected in group 2.

CONCLUSION

Autologous CD133+-cells derived from bone marrow had a better outcome with regard to calcification, inflammation, and transvalvular gradient compared to autologous cells derived from the carotid artery. Therefore, CD133+-cells are more advantageous for tissue engineering of heart valves.