For successful tissue engineering, neovascularization of the implanted tissue is critical. Factors generated by endothelial cells are also considered crucial for the process of osteogenesis. The direct effects of supplementing tissue engineered constructs with cultured endothelial progenitor cells (EPCs) for enhancing bone regeneration have not been reported. In this study, we investigated the potential of EPCs to facilitate neovascularization in implants and evaluated their influence on bone regeneration. The influence of EPC soluble factors on osteogenic differentiation of mesenchymal stem cells (MSCs) was tested by adding EPC culture supernatant to MSC culture medium. To evaluate the influence of EPCs on MSC osteogenesis, canine MSCs-derived osteogenic cells and EPCs were seeded independently onto collagen fiber mesh scaffolds and co-transplanted to nude mice subcutaneously. Results from coimplant experiments were compared to implanted cells absent of EPCs 12 weeks after implantation. Factors from the culture supernatant of EPCs did not influence MSC differentiation. Coimplanted EPCs increased neovascularization and the capillary score was 1.6-fold higher as compared to the MSC only group (p < 0.05). Bone area was also greater in the MSC + EPC group (p < 0.05) and the bone thickness was 1.3-fold greater in the MSC + EPC group than the MSC only group (p < 0.05). These results suggest that soluble factors generated by EPCs may not facilitate the osteogenic differentiation of MSCs; however, newly formed vasculature may enhance regeneration of tissue-engineered bone.

Recently, the possibility of tooth tissue engineering has been reported. Although there are a number of available materials, information about scaffolds for tooth tissue engineering is still limited. To improve the manageability of tooth tissue engineering, the effect of scaffolds on in vivo tooth regeneration was evaluated. Collagen and fibrin were selected for this study based on the biocompatibility to dental papilla-derived cells and the results were compared with those of polyglycolic acid (PGA) fiber and beta-tricalcium phosphate (beta-TCP) porous block, which are commonly used for tooth, dentin and bone tissue engineering. Isolated porcine tooth germ-derived cells were seeded onto one of those scaffolds and transplanted to the back of nude mice. Tooth bud-like structures were observed more frequently in collagen and fibrin gels than on PGA or beta-TCP, while the amount of hard tissue formation was less. The results showed that collagen and fibrin gel support the initial regeneration process of tooth buds possibly due to their ability to support the growth of epithelial and mesenchymal cells. On the other hand, maturation of tooth buds was difficult in fibrin and collagen gels, which may require other factors.

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This study demonstrated the feasibility of a CP membrane to regenerate bone at implant dehiscence defect.

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