Osteoinductive properties of the bone marrow Myth or reality

The effect of fresh bone marrow cells on reconstruction of mouse calvarial defect combined with calvarial osteoprogenitor cells and collagen-apatite scaffold

Fresh bone marrow cells have already exhibited its advantages as osteogenic donor cells, but the combination between fresh bone marrow cells and other donor cells utilized for bone healing has not been fully explored. To highlight the impact of fresh bone marrow cells on scaffold-based bone regeneration, single or a combination of calvarial osteoprogenitor cells (OPCs) and bone marrow cells (BMCs) were used as donor cells combined with collagen-apatite scaffold for calvarial defect healing. The host and donor contributions to bone formation were assessed using histological and GFP imaging analysis. Although the amount of new bone formed by different cell sources did not show significant differences, the origin of the bone formation in the defects mainly depended on the types of donor cells employed: when only calvarial OPCs were used as donor cells, a donor-derived bone healing instead of host-derived bone ingrowth was observed; when only fresh BMCs were loaded, the host bone could grow into the defect along the lamellar structure of the scaffolds, but the amount of new bone formed was significantly lower than the defect loaded with calvarial OPCs only. The combination of calvarial OPCs and fresh BMCs had similar amount of new bone formation as the group loaded with calvarial osteoprogenitors alone, but did not induce any host-derived bone formation. These results provide compelling evidence of the importance of fresh BMCs to induce host-implant integration in bone tissue engineering.

Alveolar ridge augmentation in irradiated rabbit mandibles

Oral carcinomas are frequently treated with a nonsegmental mandibulectomy plus radiotherapy. Improving the quality of life of these patients depends on the possibilities for dental rehabilitation. The aim of this study was to increase the alveolar ridge height. Twelve white New Zealand rabbits underwent surgery to produce a 11 x 9 x 7 mm(3) horizontal bicortical full-thickness defect at the alveolar ridge of the left mandible. Six were implanted with a composite associating resorbable collagen membrane filled with micro-macroporous biphasic calcium phosphate granules. After a daily radiation delivery schedule for 4 weeks, a total autologous bone marrow graft was injected percutaneously into the center of the implant. All animals were sacrificed at 16 weeks. Successful osseous colonization was observed in all implants. Significant ridge augmentation was observed (p = 0.0349) in the implanted group compared with the control group. This study contributed to producing an experimental model for oncological mandible defects in rabbits.

Bone formation in a rat calvarial defect model after transplanting autogenous bone marrow with beta-tricalcium phosphate

In the present study, we evaluated the osteogenic potential of an autogenous bone marrow graft combined with beta-tricalcium phosphate (beta-TCP) in a rat calvarial bone defect model. The bone marrow harvested from the tibia of 7-week-old rats was grafted autogenously in a calvarial defect together with beta-TCP (=BTG group, n=16) or without beta-TCP (=BG group, n=16). Groups of animals were also treated with beta-TCP alone (=TG group, n=16) and control animals (n=8) received no graft implanted into the defect. We then observed the process of bone formation by histology, enzyme histochemistry and immunohistochemistry. Five days after grafting, in the BTG and BG groups, cell proliferation and osteogenic differentiation were observed. From 5 to 10 days after surgery, active Runx2, osteopontin (OPN), and TRAP- positive cells appeared in the BTG and BG groups. New bone formation started in the defect in both the BTG and BG groups. At 30 days after grafting, the BTG group showed new bone development and replacement of beta-TCP to fill the bone defect. New bone formation in the BTG group was significantly greater than in the BG group (P<0.01). The TG group showed no marked bone formation in the defect. The combination graft of bone marrow with beta-TCP showed marked bone formation in rat calvarial defects. Our results indicate that the combination grafts of bone marrow with beta-TCP may be an effective technique for repairing bone defects Beta-TCPgraft (TG) group.

Reconstruction of irradiated bone segmental defects with a biomaterial associating MBCP+(R), microstructured collagen membrane and total bone marrow grafting: an experimental study in rabbits

The bone tissue engineering models used today are still a long way from any oncologic application as immediate postimplantation irradiation would decrease their osteoinductive potential. The aim of this study was to reconstruct a segmental critical size defect in a weight-bearing bone irradiated after implantation. Six white New Zealand rabbits were immediately implanted with a biomaterial associating resorbable collagen membrane EZ(R) filled and micro-macroporous biphasic calcium phosphate granules (MBCP+(R)). After a daily schedule of radiation delivery, and within 4 weeks, a total autologous bone marrow (BM) graft was injected percutaneously into the center of the implant. All the animals were sacrificed at 16 weeks. Successful osseous colonization was found to have bridged the entire length of the defects. Identical distribution of bone ingrowth and residual ceramics at the different levels of the implant suggests that the BM graft plays an osteoinductive role in the center of the defect. Periosteum-like formation was observed at the periphery, with the collagen membrane most likely playing a role. This model succeeded in bridging a large segmental defect in weight-bearing bone with immediate postimplantation fractionated radiation delivery. This has significant implications for the bone tissue engineering approach to patients with cancer-related bone defects.