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[Comparative study on repairing rabbit radius segmental defects with two different proportions of chitosan combined with allogeneic morselized bone].

OBJECTIVE
To give a preliminary experimental evidence and to prove chitosan and allogeneic morselized bone as potential bone substitutions in repairing rabbit radius segmental defect.


METHODS
Chitosan and allogeneic morselized bone were mixed with various ratios (1:5, 1:10, 1:25, 1:50, and 1:100). After preparation, the physical and chemical properties of the composites were preliminary detected; the composites at the ratios of 1:50 and 1:25 had good physical and chemical properties and were used for the animal experiment. The radius segmental defects of 15 mm in length were made in 50 adult New Zealand white rabbits (weighing 2.5-3.0 kg), then the animals were divided into 2 groups. In groups A and B, chitosan/allogeneic morselized bone composites were implanted at the ratio of 1:50 and 1:25, respectively. After 1, 2, 4, 8, and 12 weeks of operation, the gross, histological, immunohistochemical observations were performed. Before the rabbits were sacrificed, X-ray films were taken; the serum calcium and alkaline phosphatase (ALP) concentration were measured; and the biomechanical measurement was carried out at 12 weeks.


RESULTS
The results of gross observation were essentially consistent with those of the X-ray films. The histological observation showed that the bone formation was earlier in group A than in group B; the amount of new bone formation in group A was more than that in group B; and the bone forming area in group A was bigger than that in group B (P < 0.05) at 4 and 8 weeks after operation. The immunohistochemical staining showed that vascular endothelial growth factor and insulin-like growth factor receptor II proteins expressed in the cytoplasm of 2 groups after 4 and 8 weeks, and the expression in group A was higher than that in group B (P < 0.05). There was no significant difference in the serum calcium concentration between 2 groups at each time point (P > 0.05). After 4 and 8 weeks, the ALP concentration in group A was significantly higher than that in group B (P < 0.05). After 12 weeks, the radius maximum bending loads of groups A and B were (299.75 +/- 27.69) N and (278.54 +/- 17.09) N, respectively, showing significant difference (t=4.045, P=0.002).


CONCLUSION
The composite of chitosan and allogeneic morselized bone has good osteogenic activity and can be used as a bone tissue engineering scaffold, and the optimum ratio of chitosan to allogeneic morselized bone was 1:50.