An Experimental Study On Compound Material Of Calcined Bone With BBMP Impregnated Bone Cement

In this study , we prepared tissue-engineered bone, which was manufactured by useing the compound materials of calcined bone (CB) particles impregnated with bovine bone morphogenetic protein (bBMP) and combined with polymethyl methacrylate (PMMA) bone cement(BC). After, we repaired the New Zealand rabbits' radius segmental bone defect using the tissue-engineered bone and observed possibility of the tissue-engineered bone as bone graft material. Firstly, The bBMP was extracted from cortical bone of one year old calfs . according to Urist's methods. Then, the bBMPs activity of osteogenesis were evalued by muscle pouch test. Secondly, we provided tree kinds of the support materials which repectively consisted of 40% ,50%,60% CB particles, then analysed the constructive and biomechanical properties of the different quantity ratio materials impregnated CB particles with bone cement by scanning electron microscope(SEM) and Instron mechanics testing-machine. At the same time, the data were compared with that of hydroxyapatite and adult female fresh femur. Finally, we observed the osteogenesis and way of new bone formatin in repairing bone defect model using the tissue-engineered bone consist of 50% CB particles with gross, X-ray, histomorphological and scanning electronicmicroscope at different periods after operation in contrast to using autologous bone. The results of the experiment prove the following facts: 1. The infiltration of inflamed cells was not seen hi the muscle pouch test , and also no obvious immune rejection was observed. Mesenchymal cells began to proliferate and differentiate into cartilage cells at one week post-implantation, afterward, the cartilage is resorbed and replaced by new bone and marrow at the end of a further two-week period, finally, the original implant is completely replaced by new bone tissue which has normal Haversian system at four-week after operation. The bBMPs have a propertiy of dosage-dependence, so it is better to use them by being compounded with delivery system. 2. The CB particles were connectd with BC by the multi-polar mode in the compounds; There were many irregular 100-400um gaps which were connected each other in the compounds. The BC acted as skeleton and connective intermediary. As the CB particles increased, the number of gaps increased. 3. There was no significant deferent in the rate of healing between the tissue-engineered bone and the autologous bone. Allogenic CB particles act as a good bBMP slow-releasing carriers, then the released BMPs which were contained in the CB particles and bBMP compounded with the tissue-engineered affected on the mesenchymal cells from host slowly, so the mesenchymal cells differentiated into cartilage cells and osteoblasts continually, finally, the new bone induced by the BMP were formed in the pores of the tissue-engineered bone, at the same time, no immune rejection were observe in the whole process of new bone growth. In conclusion, on one hand, the tissue-engineered bone have good biomechanical properties and good biocompatibility, on the other hand they were easy to be manufactured and remodeled. Moreover the tissue-engineered bone possess a superior boneinduction and conduction. As a result, the tissue-engineered bone provide a alternative to free autogenous bone grafts.