IN VIVO OSTEOGENIC DURABILITY OF CULTURED BONE IN POROUS CERAMICS

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Abstract
Bone marrow cells differentiate into bone-forming osteoblasts when cultured in medium supplemented with 15% fetal bovine serum, ascorbic acid, β-glycerophosphate, and dexamethasone. To investigate in vivo osteoblastic activity and bone matrix formation by cultured bone marrow cells, Fischer rat marrow cells were cultured for 2 weeks in porous hydroxyapatite (HA) and then subcutaneously implanted into 7-week-old male syngeneic rats. The implants were harvested after 8 and 52 weeks for biochemical and histological analyses. At both times, formation of lamellar bone accompanied by regeneration of marrow were seen in many of the HA pores. When a fluorochrome (calcein) was administered at 50 weeks after implantation, it was detected in the pores of implants harvested at 52 weeks. Osteoclastic resorption followed by new bone formation was seen in some pores at 52 weeks, indicating that bone remodeling was continuing. The alkaline phosphatase activity of implants harvested at 52 weeks was comparable to that at 8 weeks, whereas the osteocalcin content of the implants harvested at 52 weeks was about twice that at 8 weeks. These results demonstrated that there was persistent in vivo osteogenic and hematopoietic activity in the prefabricated bone/HA constructs, and indicated that normal bone tissue was regenerated after grafting of the constructs, which were brittle before implantation. Tissue engineering using HA and cultured marrow cells culture may provide an alternative method of bone transplantation for patients with skeletal disorders, although further in vivo and in vitro experiments are needed.