基因修饰的组织工程骨联合带血管蒂骨膜移植修复长段骨缺损的研究

目的评价骨形态发生蛋白2（bone morphogenetic protein2,BMP-2）基因修饰的组织工程骨联合带血管蒂骨膜移植修复长段骨缺损的效果。方法分离培养兔骨髓基质干细胞,经BMP-2基因转染后复合异种骨支架体外构建基因修饰的组织工程骨（gene modified tissue engineering bone,GMB）。建立兔双侧桡骨缺损（长2.5cm）模型,采用5种方法修复。A组：GMB＋带血管蒂骨膜移植;B组：GMB＋血管束植入;C组：GMB＋游离骨膜移植;D组：GMB;E组：单纯支架。于术后第4、8、12周行X线、组织学、生物力学测定和微血管墨汁灌注等观察血管形成及成骨情况。结果①A组血运建立快,第8周时即可修复骨缺损,其修复机制包括膜内成骨和软骨成骨两种机制;②B组血管束发出分支向移植骨内长入,但中心区成骨缓慢,第12周时骨缺损得到完全修复;③C组第4周时游离骨膜成活并发出微小血管,第8周时形成薄层外骨痂,第12周时骨缺损基本修复;④D组在BMP-2基因诱导下成骨速度和质量优于E组,可在第12周时使骨缺损部分修复,但中心区呈＂空心＂现象;而E组第12周时形成骨不连,缺损区内被纤维组织填充。结论带血管蒂骨膜与BMP-2基因修饰的组织工程骨联合移植,既提供了血运又提供了骨膜成骨细胞,同时具有良好的骨生成、骨诱导和骨引导作用,是治疗节段性骨缺损较为理想的方法。

Reconstruction of segmental bone defect by gene modified tissue engineering bone combined with vascularized periosteum

OBJECTIVE: To evaluate the therapeutic effect of bone morphogenetic protein 2 (BMP-2) gene modified tissue engineering bone (GMB) combined with vascularized periosteum in the reconstruction of segmental bone defect. METHODS: Adenovirus carrying BMP-2 gene (Ad-BMP-2) was transfected into the isolated and cultured rabbit bone marrow stromal cells (MSCs). The transfected MSCs were seeded on bovine cancellous bone scaffolds (BCB) to constmct gene modified tissue engineering bone (GMB). The bilateral rabbits radial defects (2.5 cm long) were created as animal model. The rabbits were divided into five groups to reconstruct the defects with CMB combined with vascularized periosteum (group A); or GMB combined with vascular bundle implantation (group B); or GMB combined with free periosteum (group C); or GMB only (group D); or BCB scaffolds only (group E). Angiogenesis and osteogenesis were observed by X-ray, histological examination, biomechanical analysis and capillary ink infusion. RESULTS: In group A, the grafted GMB was revascularized rapidly. The defect was completely reconstructed at 8 weeks. The mechanism included both intramemerbrane and endochondral ossification. In group B, the vascular bundle generated new blood vessels into the grafted GMB, but the osteogenesis process was slow in the central zone, which healed completely at 12 weeks. In group C, the free graft of periosteum took at 4 weeks with angiogenesis. The thin extemal callus was formed at 8 weeks and the reparing process almost finished at 12 weeks. Better osteogenesis was found in group D than in group E, due to the present of BMP2 gene-transfected MSCs. The defects in group D were partial repaired at 12 weeks with remaining central malunion zone. The defects in group E should nonunion at 12 weeks with only fibre tissue. CONCLUSIONS: BMP-2 gene modified tissue engineering bone combined with vascularized periosteum which provides periosteum osteoblasts as well as blood supply, has favorable ability of osteogenesis, osteoinduction and osteoconduction. It is an ideal method for the treatment of segmental bone defect.