| Objective:To study the rh BMP-2 chitosan nanosphere hydrogel sustained-release carrier that can be used to construct tissue engineered bone,and explore the polylactic acid glycolic acid/nano-hydroxyapatite(PLGA/n HA)scaffold composite rh BMP-2 chitosan nanosphere hydrogel sustained-release carrier induces osteogenic effects in animals,providing theoretical basis and experience for constructing practical tissue-engineered bone.Methods:An animal model of rabbit bilateral critical mandibular bone defects was made.Eighteen adult New Zealand rabbits were used and the experimental grouping was performed using autologous bilateral mandible controls.Experimental side: Chitosan nanosphere hydrogel loaded rh BMP-2 composite PLGA/n HA scaffold(PLGA/n HA/rh BMP-2/CS)was implanted in the mandibular defect;control side: blank PLGA was implanted in the mandibular defect /n HA bracket.At 4,8,and 12 weeks,the scaffold implantation site was taken.The specimens were observed by gross observation,Micro-CT,HE staining,Masson staining and immunohistochemistry to observe the osteogenic effect of the implanted scaffold.Results:(1)Gross observation: all the experimental animal wounds healed well,and the body was healthy during the feeding process.The outer bones of the experimental mandible were visible at all time points to surround the scaffold complex,and significantly more than the corresponding position on the control side;(2)Micro-CT results: At the 4th and 8th week,the experimental side showed more new bone production than the control side,and the osteogenic density was higher and the trabecular bone structure was more obvious.The BMD value and BV/TV ratio of the experimental side were higher than the control group and significantly different(p <0.05);(3)HE staining results: at 12 weeks,a large number of irregular bones were seen in the control side scaffold implantation area.Dispersed in the distribution,visible wavy red fibers around,sparsely divided vascular segments,no trabecular structure.At 12 weeks,a large number of new bone types and some trabecular bone mixed parts were found in the experimental side scaffold implantation area,and the matrix wascontinuously distributed.Some newly formed bone regions had regular trabecular bone arrangement and dense bone structure,showing a large number of bone lacunae.And the bone cells embedded therein,the blood vessels are widely distributed in the osteogenic region.(4)Masson staining results: Compared with the control side,the new bone tissue proliferated on the experimental side gradually replaced the implanted scaffold complex.The proportion of mature bone and immature bone gradually increased with time,and the mature bone mass gradually increased.Gradually close to normal bone tissue.Masson staining image analysis showed that at 12 weeks after implantation,the new bone on the control side accounted for19.2% of the area of the bone defect;the proportion of mature bone on the experimental side reached 45.5%,the difference was statistically significant(P<0.05);Histochemical staining results: osteocalcin-positive expression in the experimental side at the 4th,8th,and 12 th week,and more osteocalcin deposition in the newly formed bone region at the 8th and 12 th week,and osteocalcin in the new experimental period The content of bone was higher than that of the control side.The difference between the two groups was statistically significant(P<0.05).The positive results of type I collagen expression showed that the experimental side was significantly higher than the control side at the 4th week.Group differences were statistically significant(P < 0.05)and decreased at weeks 8 and 12.Conclusions:(1)Chitosan nanosphere hydrogel effectively control the early burst effect of rh BMP-2 in vivo.Chitosan nanosphere hydrogel is a good sustained release carrier of rh BMP-2.(2)Chitosan nanosphere hydrogel loaded rh BMP-2 complex PLGA/n HA has good osteogenic effect and can be used as a material for inducing tissue engineering bone in vivo. |
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