[Preparation of xenogeneic bone graft and its osteoinductivity]

To develop a deantigenated porcine bone graft through enzyme treatment and to study the biomechanical properties and osteoinductivity of the xenogeneic bone graft.

Deantigenated xenogeneic bone was prepared from porcine bone by a series treatment including alpha-galactosidase (alpha-Gal) treatment, freeze drying and irradiation at a does of 25 kGy. Samples were divided into 4 groups according to the treatment methods: fresh bone (group A); deantigenated bone (group B); deantigenated and freeze dried bone (group C); deantigenated-freeze dried-irradiated bone (group D). SEM observation to group B samples was performed and the diameters of the caves of the porcine cancellous bone were measured. The a-Gal contents of samples of groups A, B, D were measured by ELISA. The effects of different treatments on porcine bone mechanic properties were evaluated through compressive test of 4 groups. The prepared porcine cortical bone were demineralized and ectopically implanted into muscle groups of hind limbs of Wistar rats as experimental group, and the demineralized cortical bone which were inactivated by high temperature and pressure were implanted as control group. Histological observation was performed and ALP activity was tested at different time postoperatively to investigate the osteoinductivity of the xenogeneic bone implants.

The porous structure of prepared porcine cancellous bone was similar to that of human cancellous bone. The diameters of the caves were between 150-600 microm. The A value of the groups A, B, D was 0.358 +/- 0.027, 0.191 +/- 0.011, 0.191 +/- 0.009, respectively, with statistically differences between groups (P < 0.05). While the biomechanical properties among 4 groups had no statistically difference (P > 0.05). Histological observation showed mesenchymal cells immigrated into cartilage and converted into chondrocytes at 3 weeks postoperatively. Cartilage was formed at 4 weeks and osteoid and more adult cartilage was formed at 6 weeks within the implants of experimental group, while there was no bone formation in control group. ALP activity of experimental group at different times were obviously higher than that of the control group (P < 0.05).

The main xenogeneic antigen of the porcine bone was removed while the mechanic properties and osteoinductivity remained, thus it may be a suitable bone substitute for clinical use.