[Experimental studies on the porous calcium phosphate cement combined with recombinant human bone morphogenetic protein 2 for bone defects repair].

OBJECTIVE

To study in vitro sustained release behaviour of the recombinant human bone morphogenetic protein 2 (rhBMP-2) from the sample which porous calcium phosphate cement (PCPC) was combined with rhBMP-2, and to evaluate the effect of PCPC/rhBMP-2 composite on repairing bone defect in the animal study.

METHODS

rhBMP-2 was absorbed into PCPC by vacuum-adsorption and freeze-dried at -40 degrees C, the PCPC/rhBMP-2 enwrapped with chitosan as the experimental group, the pure PCPC/rhBMP-2 as the control group, then the sustained release of rhBMP-2 from PCPC was determined in simulated body fluid (SBF) by UV-VIS spectrophotometer. At same time, the PCPC/rhBMP-2 composites with chitosan were implanted into the (4.2 mm x 5.0 mm femora defects of rabbits, which were considered as the experimental group, whereas in the control group only PCPC was implanted. The effect of repairing bone defect was evaluated in the 4th and 8th week postoperatively by radiograph and histomorphology.

RESULTS

The PCPC have a high absorption efficiency to rhBMP-2, and the release of rhBMP-2 was sustained release system. The release of rhBMP-2 from PCPC in the experimental group (99% after 350 hours) was slower than that in the control group (100% after 150 hours). In the experimental group, the radiological and histomorphological evaluations showed that the interfaces between the materials and host bones became blurred both at 4th and 8th week. The implanted materials were partially absorbed, and the implanted areas exhibited the formation of new bone. In the control group, a little amount of new bones was observed.

CONCLUSION

The PCPC shows great clinical potential as a carrier for rhBMP-2. The PCPC/rhBMP-2 composite possesses much potentialities of osteoinductivity and the ability of repairing bone defect, so it can be used as a novel bone substitute clinically.