| Artificial joint replacement is the most commonly used method treating joint disease in department of orthopaedics. The major complication is prosthesis loosening. Enhancement of the speed and extent of osteointegration into bone-prosthesis interface is very important for cementless arthroplasty after operation. Earlier and more extensive osteointegration enables the limb resumes its weight-bearing function earlier and may reduce the morbidity of prosthesis loosening.PurposeIn present study, conditions for in vitro expansion of rabbit bone mesenchymal stem cells (BMSCS) were established and the osteo- genie potential of the expanded cells was validated. BMSCs were adhered to metal prosthesis. Under osteogenic condition, the cells transformed into osteoblasts and formed tissue engineering bone which integrated firmly into the metal prothesis. We implantedthe metal prothesises into experimental amimals. After a certain period, we compared them with the metal prothesises with nothing and those which adhered recombinant human bone morphogenetic protein-2 (rhBMP-2) to observe whether the former are superior to the latter.MethodsDisposed group: we drew out marrow blood from 12 rabbits and cultured BMSCs in vitro. After transferred of culture, the cells were adhered to metal prothesises (PCA, PCA coated with HA). These metal prothesises had been induced by osteogenic agents for 12~14d. Control group: PCA, PCA coated with HA, PCA combined with rhBMP-2.We implanted the metal prothesises into femur internal condyle in rabbits. After 4 and 8 weeks, the animals were killed. Bone ingrowth and shear strength of the interface were studied and analysed by means of X-ray, fluorescence tag, nondecalcification ground section, computer-aided image analysis procedure and biomechanical test.Results1. Cell culture1.1 Primary cultured cells stuck to the bottom of cultured bottles after 3 to 4 days. The form of cells transformed from round or ellipse to short fusiform, and then become long fusiform soon.Cell plasm was abundant. The growth pattern of cells showed colony.1.2 12 hours after transfer of culture, the BMSCS completed adherence. The adhesive cells were spindle-shaped, just like the later stage of primary cultured cells. The cells were well-distributed and had strong capability of proliferation. Mineral nodules were not observed.1.3 After osteogenic induced, BMSCs became multi-corner shape. ALP activity of BMSCs increased significantly. The mineral nodules were observed 2 weeks later under osteogenic condition and tetracycline fluorescence tag was positive. MTT showed that the growth curves of BMSCS induced and uninduced were not obviously different.1.4 Enviroment scanning electron microscope showed that BMSCs adhered excellently after the cells had been implanted into metal prothesises for six days.2. Animal experiment1.1 Four weeks after implantation, non-decalcification ground section observation and computer aided image analysis showed: the new bone formation ratio of BMSCS groups were 46.05 5.74, and 47.94 5.66 which were much higher than other groups, and there were significant differences between the two BMSCs groups and each of the other group statistically.1.2 Eight weeks after implantation, non-decalcification ground section observation and computer aided image analysis showed:the new bone formation ratio of all groups increased and there was no significant difference between disposed groups and control groups statistically.1.3 Result of biomechanical study using push-out test showed that shear strength of each group appeared to rise with time. Shear strength of the two BMSCs groups reached a higher level at 4 weeks compared with the control groups. There was also statistical difference between BMP group and each of the other group. At eight weeks, all the groups had no significant difference statistically.Conclusion1. BMSCs grew excellently into metal prothesises (Co-Chrome-Mo alloy) and there were no toxic r... |
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