Transplanted endothelial cells enhance orthotopic bone regeneration.

The aim of this study was to determine if endothelial cells could enhance bone marrow stromal-cell-mediated bone regeneration in an osseous defect. Using poly-lactide-co-glycolide scaffolds as cell carriers, we transplanted bone marrow stromal cells alone or with endothelial cells into 8.5-mm calvarial defects created in nude rats. Histological analyses of blood vessel and bone formation were performed, and microcomputed tomography (muCT) was used to assess mineralized bone matrix. Though the magnitude of the angiogenic response between groups was the same, muCT analysis revealed earlier mineralization of bone in the co-transplantation condition. Ultimately, there was a significant increase (40%) in bone formation in the co-transplantation group (33 +/- 2%), compared with the transplantation of bone marrow stromal cells alone (23 +/- 3%). Analysis of these data demonstrates that, in an orthotopic site, transplanted endothelial cells can influence the bone-regenerative capacity of bone marrow stromal cells.