ObjectiveTo evaluate the ectopic osteogenesis of recombinant human bone morphogenetic protein 2 (rhBMP-2) loaded chitosan (CS)/dextran sulfate (DS) by micro-CT. MethodsrhBMP-2/CS/DS microspheres were prepared by the ionic crosslinking and its shape was observed under the scanning electron microscope. The release of rhBMP-2 was determined from resultant microspheres by ELISA assay. Forty-eight Sprague Dawley male rats were randomly divided into 4 groups (n=12), quadriceps muscle bag model was made, gelatin sponge (group A), CS/DS microspheres (group B), rhBMP-2 (group C), and CS/DS/rhBMP-2 microspheres (group D) were implanted into the bags respectively. The tissue samples with heterotopic ossification were harvested for micro-CT scanning at 4, 8, 12, and 16 weeks. The tissue mineral density (TMD), bone volume fraction (BVF), trabecular thickness (Tb.Th), trabecular number (Tb.N), bone mineral density (BMD), and tissue mineral content (TMC) were measured. ResultsThe prepared rhBMP-2/CS/DS microspheres with smooth surfaces were spherical and evenly disperses without obvious agglomeration. At 2 hours, microsphere started a sudden release period in vitro; the release reached a peak at 2 days; and the release cycle lasted about 20 days. The rats survived to the end of the experiment. At each time point after operation, no radiation developed and no osteogenesis was observed by three dimensional reconstruction in groups A and B. However, radioactive strength and reconstructed bone tissue gradually increased in groups C and D, and group D had more radioautography and more bone tissues than group C. At each time point, TMD, BVF, Tb.Th, Tb.N, BMD, and TMC of groups A and B were zero. Ectopic bone formed with time, the other parameters showed an increasing trend except Tb.N in groups C and D, showing significant difference when compared with groups A and B at each time point (P < 0.05). There was no significant difference between groups C and D at 4 weeks (P>0.05); the parameters of group D were significantly higher than those of group C at 8-16 weeks (P < 0.05). ConclusionrhBMP-2/CS/DS microspheres have stronger ability of ectopic bone formation than single rhBMP-2.
Objective To evaluate the osteogenic effect of dextran sulfate/recombinant human bone morphogenetic protein 2/chitosan (DS/rhBMP-2/CS) combined with coralline hydroxyapatite (CHA) in repairing large segmental bone defects by radiographic feature. Methods Fifty-seven 24-week-old male New Zealand rabbits were prepared for establishing right radius bone defect model of 20 mm in length. In which 54 rabbits were randomly divided into 3 groups (n=18), and the CHA, DS/rhBMP-2/CS/CHA, and rhBMP-2/CHA artificial bone grafts were implanted into the bone defect in groups A, B, and C respectively; the remaining 3 rabbits were implanted nothing as blank control group. After operation, the gross condition of the animals was observed; at 4, 8, and 12 weeks after operation, X-ray film observation, Micro-CT scanning, and three-dimensional reconstruction were performed to obtain the volume of the new bone. Results The experimental animals recovered well and were in normal condition. X-ray observation showed that the bone healing in group B was better than that in groups A and C at each time point. At each time point after operation, the X-ray scores of group B were significantly higher than that of group A and group C (P<0.05); the scores of group C at 8 and 12 weeks after operation were significantly higher than that of group B (P<0.05). Micro-CT scanning and three-dimensional reconstruction observation showed that at each time point after operation in group A, the bone defect area had less bone formation and poor osteogenesis; in group B, there were many new bone tissues in bone defect area, and the bone remodeling was well, and gradually closed to normal bone morphology at 12 weeks; in group C, there were many new bone tissues in bone defect area, but the bone formation was general. The new bone volume of group B was significantly higher than that of group A and group C (P<0.05) at each time point after operation, and the score of group C was higher than that of group A at 8 weeks after operation (P<0.05). Conclusion The osteogenic effect of DS/rhBMP-2/CS/CHA sustained-release artificial bone is much better than that of single CHA and rhBMP-2/CHA, which can provide a new idea for treating bone defect by using bone tissue engineering in the future.