Co-transplantation of endothelial progenitor cells and mesenchymal stem cells promote neovascularization and bone regeneration.

Background: Bone formation relies on sufficient blood supply and osteoprogenitor cells.

Objective: The study aims to evaluate the influence of endothelial progenitor cells (EPCs) in combination with mesenchymal stem cells (MSCs) on early vascularization and intramembranous bone regeneration.

Methods: Vertical bone regeneration was tested in rat calvarium guided bone regeneration model. Gold domes were filled with a mixture of 5 × 10(5) osteogenic transformed MSC and 5 × 10(5) EPC (EPC/MSC) that were mixed with β-tricalcium phosphate (βTCP) scaffold. Domes filled with βTCP alone served as control. Rats were sacrificed after 4 or 12 weeks. Histomorphometry was used to determine blood vessel (Bv) density, vertical bone height, and bone area in the regenerated tissue.

Results: At both time points, new augmented hard tissue filled the space under the dome, and Bv density was higher in the EPC/MSC transplanted group vs control. However, bone height and bone area were similar among the groups 4 weeks posttransplantation, but were doubled in the EPC/MSC transplanted group 12 weeks posttransplantation.

Conclusions: EPC/MSC transplantation increases Bv formation in the early stages of healing that precedes enhancement of extracortical bone regeneration in later stages.