It has been shown that mesenchymal stem cells (MSCs) and BMP are involved in bone formation. The aim of the study was to evaluate the osteogenic potential of human bone marrow (hBM), human expanded MSC (hexp-MSC), BMP-7, and hexp-MSC plus BMP-7, to treat a rat femoral segmental defect.

Sprague-Dawley (SD) and athymic rats (Nu) were used. SD rats where used in order to define surgical technique. Nu rats groups consisted of: G1-autoclaved bone and human bone marrow (hMNC); G2-bone and hexp-MSC; G3-bone with BMP-7 only; and G4-bone and hexp-MSC with BMP-7. A plate was attached to the femoral diaphysis with two cerclage wires. Then a 6-mm femoral gap was made and filled with a different graft. At regular intervals, the femoral defect was evaluated with radiographs, using a modified six-grade Cook classification.

At 8 weeks G1 showed non-visible new bone formation; G2 minimal new disorganised bone; G3 disorganised new bone bridging the graft to host at both ends; and G4 significant new bone and graft remodelling. Histological analysis confirmed these results.

Our results showed that although the osteogenic activity may be improved by hMSC (G2) as well as by BMP-7 (G3), the association hexp-MSC plus BMP-7(G4) produced graft osteointegration at 8 weeks after surgery. This may have a remarkable impact on future orthopaedics surgery strategies.