Grellier Maritie, Granja Pedro L, Fricain Jean-Christophe, Bidarra Sílvia J, Renard Martine, Bareille Reine, Bourget Chantal, Amédée Joelle, Barbosa Mário A
INSERM, U577, Bordeaux and Université Victor Segalen Bordeaux 2, UMR-S577, F-33076 Bordeaux Cedex, France.
Biomaterials. 2009 Jul;30(19):3271-8. doi: 10.1016/j.biomaterials.2009.02.033. Epub 2009 Mar 18.
Bone regeneration seems to be dependant on cell communication between osteogenic and endothelial cells arising from surrounding blood vessels. This study aims to determine whether endothelial cells can regulate the osteogenic potential of osteoprogenitor cells in vitro and in vivo, in a long bone defect, when co-immobilized in alginate microspheres. Alginate is a natural polymer widely used as a biomaterial for cell encapsulation. Human osteoprogenitors (HOP) from bone marrow mesenchymal stem cells were immobilized alone or together with human umbilical vein endothelial cells (HUVEC) inside irradiated, oxidized and RGD-grafted alginate microspheres. Immobilized cells were cultured in dynamic conditions and cell metabolic activity increased during three weeks. The gene expression of alkaline phosphatase and osteocalcin, both specific markers of the osteoblastic phenotype, and mineralization deposits were upregulated in co-immobilized HOPs and HUVECs, comparing to the immobilization of monocultures. VEGF secretion was also increased when HOPs were co-immobilized with HUVECs. Microspheres containing co-cultures were further implanted in a bone defect and bone formation was analysed by muCT and histology at 3 and 6 weeks post-implantation. Mineralization was observed inside and around the implanted microspheres containing the immobilized cells. However, when HOPs were co-immobilized with HUVECs, mineralization significantly increased. These findings demonstrate that co-immobilization of osteogenic and endothelial cells within RGD-grafted alginate microspheres provides a promising strategy for bone tissue engineering.
骨再生似乎依赖于源自周围血管的成骨细胞和内皮细胞之间的细胞通讯。本研究旨在确定当共固定于藻酸盐微球中时，内皮细胞在体外和体内的长骨缺损中是否能够调节骨祖细胞的成骨潜能。藻酸盐是一种广泛用作细胞封装生物材料的天然聚合物。将来自骨髓间充质干细胞的人骨祖细胞（HOP）单独或与人脐静脉内皮细胞（HUVEC）一起固定在经辐照、氧化和接枝RGD的藻酸盐微球内。将固定化细胞在动态条件下培养，细胞代谢活性在三周内增加。与单培养固定化相比，共固定化的HOP和HUVEC中碱性磷酸酶和骨钙素的基因表达（两者均为成骨细胞表型的特异性标志物）以及矿化沉积物均上调。当HOP与HUVEC共固定化时，VEGF分泌也增加。将含有共培养物的微球进一步植入骨缺损处，并在植入后3周和6周通过微计算机断层扫描（muCT）和组织学分析骨形成情况。在含有固定化细胞的植入微球内部和周围观察到矿化。然而，当HOP与HUVEC共固定化时，矿化显著增加。这些发现表明，在接枝RGD的藻酸盐微球内共固定化成骨细胞和内皮细胞为骨组织工程提供了一种有前景的策略。
