新型仿生活性人工骨诱导兔腰椎横突间脊柱融合研究

Posterolateral spinal fusion in rabbits with a new bionic grafting material

目的采用先进快速成形技术(RP)结合骨组织工程方法研制新型仿生活性人工骨,并探讨其在兔腰椎横突间脊柱融合的应用情况.方法首先采用RP制备薄块型聚乳酸-聚羟乙酸/磷酸三钙(PLGA/TCP)人工骨载体,进而高效复合牛骨形态发生蛋白(bBMP)以制备仿生活性人工骨,扫描电镜观察载体材料及人工骨超微结构.将健康新西兰兔28只(平均体重4.1 kg)随机均分为A、B两组(每组14只).A组:于兔腰4～5右、左侧横突间分别植入仿生活性人工骨(A1组)、自体髂骨(A2组);B组:于兔腰4～5右、左侧横突间分别植入复合自体新鲜红骨髓的PLGA/TCP载体材料(B1组)、单纯PLGA/TCP载体材料(B2组).于术后6周和12周,定期大体观察、手法检测、组织学[苏木素-伊红(HE)、三色法及四环素-钙黄绿素荧光检测]和影像学方法(X、CT)系统评价脊柱融合情况.结果 RP制备的PLGA/TCP载体具有规则的空间支架结构、相互贯通的孔隙及材料表面微孔特征,这些均有利于bBMP的高效复合.动物实验结果显示,A1组仿生活性人工骨植入具有强的诱骨活性及骨性融合能力,不仅成骨早、新骨形成量大,而且在新骨形成及改塑的同时载体材料逐渐降解,术后12周可形成较为典型的骨小梁及骨髓结构,骨代谢活性亦接近正常.A2组自体髂骨移植能达到良好骨性融合,但术后12周所形成的新骨结构尚须进一步塑形及完善.B1组、B2组术后12周仍遗有较多的载体材料有待降解,基本无成骨能力.术后12周,A1、A2、B1、B2 4组横突间融合率分别为100.0%、58.3%、18.2%和0%,A1组融合率最高(P<0.01).结论先进RP制备的PLGA/TCP载体不仅具有良好的空间超微结构及孔隙特性,而且能高效复合bBMP以正确构建新型组织工程人工骨.该仿生活性人工骨诱导兔横突间脊柱融合获得成功,为生物制造脊柱外科所需的新型、高效人工骨移植材料奠定了重要基础.

Objective To investigate the effectiveness of rapid prototyping （RP） technique manufactured Poly （DL-lactic-co-glycolic acid）/Tricalcium phosphate （PLGA/TCP） loaded with bovine bone morphogenetic protein （bBMP） as a new graft material for posterolateral spinal fusion in an animal model.Methods Three-dimensional PLGA/TCP scaffolds were fabricated by RP and loaded with bBMP. Both the PLGA/TCP scaffolds and the PLGA/TCP-bBMP composites were observed under scanning electron microscopy. Twenty-eight New Zealand white rabbits were equally randomized into 2 groups （group A and group B） and bilaterally underwent posterolateral intertransverse process arthrodesis at the L4-L5 level using the following graft materials： In group A, PLGA/TCP-bBMP composite （on the right side, group A1） and autogenous iliac bone graft （on the left side, group A2） were used;In group B, PLGA/TCP scaffold plus fresh autogenous bone marrow （on the right side, group B1 ） and PLGA/TCP scaffold alone（on the left side, group B2） were utilized. The animals were killed at 6th and 12th week after surgery and the spine fusion were evaluated. Results RP manufactured PLGA/TCP scaffolds had controlled microstructure and porosity, bBMP was efficiently loaded into the porous scaffold to produce a new bionic grafting material. In group A1, histological analysis revealed that highly cellular bone marrow between the newly formed trabecular bone was present in the fusion mass. In group A2, the amount of newly formed bone was reduced. In both groups of B1 and 132, however, polymer remnants and fiber tissues were predominantly found. Twelve weeks after surgery, the fusion rates in groups of A1, A2, B1 and 132 were 100.0 %, 58.3 %, 18.2 % and 0, respectively. The rate of fusion was significantly higher in group A1 than in other 3 groups （P 〈 0.01）. Conclusion bBMP can be in vitro efficiently loaded into RPbased PLGA/TCP scaffolds to construct a new grafting material. This bionic artificial bone may be feasible and promising as an alternative to achieve bone formation for arthrodesis in spine surgery.