Leading Research Paper
Tissue Engineering
Bone formation in trabecular bone cell seeded scaffolds used for reconstruction of the rat mandible

https://doi.org/10.1016/j.ijom.2008.11.018Get rights and content

Abstract

This study tested whether different in vitro cultivation techniques for tissue-engineered scaffolds seeded with human trabecular bone cells affect in vivo bone formation when implanted into critical-size defects in rat mandibles. Human trabecular cells were isolated and seeded into three types of scaffolds (porous CaCO3, mineralized collagen, porous tricalcium phosphate). Four in vitro groups were produced: empty control scaffolds incubated with cell culture medium for 24 h; scaffolds seeded with trabecular bone cells, cultivated under static conditions for 24 h; scaffolds seeded with trabecular bone cells, cultivated for 14 days under static conditions; scaffolds seeded with trabecular bone cells, cultivated for 14 days in a continuous flow perfusion bioreactor. The scaffolds were implanted press fit into non-healing defects, 5 mm diameter, in rat mandibles. After 6 weeks the presence of human cells was assessed; none were detected. Histomorphometric evaluation showed that neither seeding human trabecular bone cells nor the culturing technique increased the amount of early bone formation compared with the level provided by osteoconductive bone ingrowth from the defect edges. It is concluded that human bone marrow stroma cells in tissue-engineered scaffolds and associated in vitro technology are difficult to test in the mandible in animal models.

Section snippets

Cells

Human trabecular bone cells were obtained from cancellous femur bone after ablative surgery for total knee arthroplasty. The cancellous bone was harvested from areas away from the joint pathology from the resected portions of the proximal femur bone. Ethical approval to use these specimens was obtained from the local regulatory board. The cancellous bone portions were minced and placed onto Petri dishes with ZKT-I medium15 (DIF 1000 w/o protein supplements, Biochrom, Berlin, Germany)

Human DNA analysis

RT-PCR revealed that only one of the probed scaffolds was positive for human DNA (Group VI: CaCO3 scaffold; dynamic culturing for 14 days) indicating that most of the grafted cells could no longer be detected at the end of the observation period (Fig. 1).

Histologic results

The calcium carbonate scaffolds seeded with trabecular bone cells and cultured for 24 h under static conditions (Group II) exhibited thin layers of immature bone tissue lined by high numbers of osteoblasts. The remaining pores were filled with

Discussion

Despite a decade of research in tissue engineering, there are few reports about the in vivo formation of bone by human BMSCs or mesenchymal stem cells grafted to skeletal sites24, 31. Positive results have been reported for ectopic bone formation after subcutaneous or intramuscular implantation into immuno-compromised rodents2, 17, 18, 19, 40, 41. The fact that the seeded cells have not been able to enhance bone formation in orthotopic sites in mandibular defects has to be considered carefully.

Acknowledgements

The authors wish to thank Dr. Johanna Napp for performing the PCR analyses. This study was supported by the Deutsche Forschungsgemeinschaft (DFG) (Schl 368/10-1 & 10-2 as well as MA 852/7-2 & 7/3).

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