基因修饰的组织工程骨修复节段性骨缺损及相关免疫学研究

目的：观察骨形态发生蛋白-2（BMP-2）基因修饰的组织工程骨修复节段性骨缺损效果及异种骨支架体内应用的安全性。方法：①制备去抗原牛松质骨块（BCB），植入小鼠股四头肌袋内，术后行淋巴细胞转化试验和组织学观察。②在腺病毒载体介导下将BMP-2基因导入兔骨髓间质干细胞后，种植到BCB支架中，构建基因修饰的组织工程骨。于兔双侧桡骨中段造成15mm骨缺损，采用5种方法进行处理：BMP-2基因转染细胞＋B（B（A组）；未转染细胞＋重组BMP-2＋BCB（B组）；对照基因转染细胞＋BCB（C组）；未转染细胞＋B（B（D组）；单纯BCB（E组）。术后4、8、12周行X线、组织学和生物力学检测。结果：①BCB具有较低的抗原性和良好的组织相容性；②A组术后4周诱导生成软骨组织并向编织骨转化，12周骨缺损修复，髓腔再通，新骨强度明显优于其他各组（P〈0．01）。结论：BMP-2基因修饰的组织工程骨是修复节段性骨缺损的好方法。     

涂层双相陶瓷复合BMSC修复骨缺损的实验观察

目的比较双相陶瓷（Biphasie calcium phosphate，BCP）经低结晶羟基磷灰石（Low crystalline hydroxyapatite，LcHA）涂覆改性后构建的组织工程化骨（LcBCP）与单纯BCP复合骨髓基质干细胞（Bone marrow stromal cells，BMSCs）修复兔桡骨节段性缺损的成骨差异。方法BMSCs复合LcBCP（实验组）修复12只兔左侧桡骨15mm缺损；BMSCs复合BCP（对照组）植入右侧桡骨同样大小缺损，植入后第4、8和12周取材，通过大体形态、组织学、影像学和生物力学检测骨缺损修复效果。结果BMSCs—LcBCP复合物在体内骨缺损处生长良好。X线检测显示实验组连接处骨痂形成，对照组连接处在各个时间点愈合稍差。12周时，实验组骨修复良好，髓腔再通，组织学显示板层骨形成，连接处骨性愈合；对照组连接处尚有较多编织骨形成。实验组和对照组生物力学检测有统计学差异。结论BMSCs—LcBCP复合物可修复兔桡骨节段性缺损，低品态羟基磷灰石涂层有助于增强双相陶瓷的成骨能力。     

移植骨复合骨髓基质干细胞修复兔股骨缺损

目的观察同种异体骨复合骨髓基质干细胞对兔股骨大段缺损修复情况，探讨其修复骨缺损的可行性。方法将24只大耳兔随机分为2组，造成股骨大段缺损，对照组植入打孔同种异体骨，实验组植入打孔同种异体骨＋明胶海绵＋骨髓基质干细胞。术后2个月行X线片观察、病理组织学检查及骨密度测试。结果①放射学检查：对照组在异体骨结合部可见骨痂通过，实验组整个异体骨段均可见明显骨痂形成。②病理组织学检查：对照组可见少量内骨痂及外骨痂且被大量纤维结缔组织所分隔，实验组异体骨有坏死后弧形吸收窝，可见内外骨痂生长，髓腔内充满大量骨母细胞。③平均骨密度值测定：实验组高于对照组及正常股骨，差异有显著性（P〈0．05）。结论同种异体骨复合骨髓基质干细胞用于修复兔股骨大段缺损，较单纯异体骨成骨量大、迅速，能够对骨缺损进行有效的修复。     

骨形成蛋白-2转染兔骨髓基质细胞修复软骨缺损的研究

目的 观察骨形成蛋白-2(BMP-2)基因转染兔骨髓基质细胞(MSCs)复合藻酸钙修复兔膝关节软骨缺损的效果.方法 取4周龄的新西兰兔骨髓细胞,体外培养得到MSCs.选用24只成年新西兰兔,在两侧股骨髁非负重区造成全层软骨缺损模型,A组(实验组)植入BMP-2转染的MSCs+藻酸钙,B组(对照组Ⅰ)植入空质粒转染的MSCs+藻酸钙,C组(对照组Ⅱ)植入不含MSCs的藻酸钙,D组(对照组Ⅲ)旷置.12周后,观察软骨缺损修复情况及组织学评价.结果 实验组修复组织基本光滑,有大量Ⅱ型胶原蛋白表达,3个对照组修复组织Ⅱ型胶原蛋白表达量少,仍有明显缺损.实验组和3个对照组组织学评分差异有统计学意义(P＜0.05).结论 BMP-2转染兔MSCs修复软骨缺损效果优于其他对照组.     

组织工程骨修复山羊胫骨节段性缺损的实验研究

目的应用自体骨髓基质干细胞（BMSCs）复合β-磷酸三钙（β-TCP）构建组织工程化骨，修复山羊胫骨节段性缺损。方法体外扩增培养、成骨诱导山羊BMSCs。实验组将第2代细胞复合β-TCP后修复山羊自体右侧胫骨26mm的节段性缺损（n=8），对照组以单纯β-TCP材料植入骨缺损处（n=8），旷置组（n=2）。术后16、32周分别通过大体形态观察、影像学、组织学和生物力学的方法检测骨缺损的修复效果。结果旷置组术后32周骨缺损未修复，表明动物模型确实可靠。大体观察、X线片和MicroCT显示16周时实验组已有新骨形成，β-TCP材料降解吸收；对照组则只形成少量骨痂，材料无明显降解。组织学检测示实验组有大量幼稚编织骨生成，对照组为纤维结缔组织，并有大量材料残余。实验组骨密度和力学强度低于正常胫骨组（P〈0．05），但明显高于对照组（P〈0．01）。术后32周时大体观察X线片和MicroCT显示术后实验组骨愈合良好，对照组为骨不连；骨密度检测示实验组明显高于对照组（P〈0．05），且与正常胫骨组差异无统计学意义（P〉0．05）。组织学检测示实验组呈骨性愈合，有较多成熟骨组织，对照组为纤维连接。生物力学测试实验组与正常胫骨力学强度差异无统计学意义（P〉0．05）。结论成骨诱导的自体BMSCs复合β-TCP形成的组织工程骨可良好修复山羊胫骨节段性缺损。     

胶原/羟基磷灰石支架负载软骨细胞修复兔膝关节骨软骨缺损

目的 探讨胶原复合梯度羟基磷灰石(Col/HA)双相支架负载软骨细胞修复兔膝关节骨软骨缺损的可行性及疗效.方法 构建Col/HA双相支架,将软骨细胞种植于支架培养1周,再将软骨细胞-支架复合体移植修复兔膝关节股骨髁的骨软骨缺损,并对骨软骨缺损的修复进行检测.结果 光镜及扫描电镜观察显示软骨细胞在Col/HA支架中贴附良好,表型维持稳定,分泌胞外基质.大体观察和组织学检测显示,植入体内16周后实验组软骨层呈透明软骨样修复,软骨下骨缺损有新骨构建;对照组骨软骨缺损修复不良,组织学检测以纤维性组织或纤维软骨组织形成.Wakitani评分显示实验组修复组织优于对照组,差异有统计学意义(P＜0.05).结论 双相Col/HA复合支架可作为骨软骨组织工程支架,负载软骨细胞可修复兔膝关节骨软骨缺损,重建关节软骨的结构和功能.     

多孔磷酸钙人工骨与重组人骨形成蛋白2复合修复骨缺损的实验研究

目的研究多孔磷酸钙人工骨（porous calcium phosphate cement，PCPC）与重组人骨形成蛋白2（recombinant human bone morphogenetic protein2，rhBMP-2）复合后体外的缓释作用及其对兔骨缺损的修复作用。方法采用物理吸附法将rhBMP-2（0．4mg）溶液吸附至PCPC中，制备成PCPC／rhBMP-2复合材料。冻干后，扫描电镜观察复合材料内部形态。以包覆壳聚糖的PCPC／rhBMP-2为实验组，单纯PCPC／rhBMP-2为对照组，测试在模拟体液中的rhBMP-2缓释行为。取新西兰大白兔12只，股骨远端制成直径4．2mm，深5．0mm的骨缺损模型。将包覆壳聚糖的PCPC／rhBMP-2复合材料修复骨缺损作为实验组，以植入单纯PCPC作为对照组。术后观察动物一般情况，于4周和8周取材行X线片和组织学观察。结果扫描电镜显示PCPC／rhBMP-2复合材料孔隙中吸附了大量的rhBMP-2。rhBMP-2体外缓释：对照组rhBMP-2于150h基本全部释放；实验组rhBMP-2于350h缓释量约达99％，较对照组慢。动物实验：动物术后切口无感染，于4周行动自如。X线片示术后4周对照组骨缺损区材料清晰，实验组骨缺损区密度大部分接近宿主骨，材料模糊；8周对照组材料边缘较术后4周模糊，实验组骨缺损区密度已基本接近宿主骨。组织学观察，术后4周对照组可见少量成骨细胞和破骨细胞，实验组可见成熟骨组织和骨髓腔，新生骨逐渐取代材料；8周对照组可见大量成骨细胞和破骨细胞，少量新生骨并向材料内长入，实验组可见成熟骨小梁和骨髓组织。结论PCPC是rhBMP-2较理想的载体材料，复合后具有良好的诱导成骨作用，可作为一种新型复合人工骨修复骨缺损，具有良好的临床应用前景。     

骨形态发生蛋白-2基因活化纳米骨浆修复兔桡骨缺损的实验研究

目的观察骨形态发生蛋白-2（BMP-2）基因活化纳米骨浆在损伤部位的局部成骨基因表达和骨缺损重建修复效果。方法新西兰白兔54只，其中48只实验动物随机分成三组（每组16只32侧），制成双侧桡骨中段15mm骨缺损模型。A组：注入hBMP-2＋纳米骨浆；B组：注入空白质粒＋纳米骨浆；C组：注入纳米骨浆。另6只动物制作左桡骨中段骨缺损，不植入材料，作为空白对照。术后4、8和12周取材行影像学检查、组织学观察、分子生物学检测和生物力学检测。结果术后12周A、B和C组骨缺损均修复，A组骨缺损处有明显BMP-2的mRNA和蛋白质表达，在ALP水平、成骨速度、新生骨量及新生骨力学强度等方面均明显优于B、C两组（P〈0．05）。空白对照组骨缺损无愈合。结论纳米骨浆复合BMP-2质粒后，具有一定骨诱导作用，植入体内后成骨速度、质量及力学强度较单纯的纳米骨浆明显增强，能够有效修复骨缺损。     

骨形态发生蛋白2基因治疗与缓释载体修复骨缺损的比较研究

[目的]比较骨形态发生蛋白2（BMP-2）基因治疗与生长因子缓释方法修复节段性骨缺损效果。[方法]于兔双侧桡骨中段造成1．5cm骨缺损，采用4种方法修复：A组植入转基因骨髓间质干细胞（MSCs）与PLA／PCL（聚乳酸／聚己内酯）支架的复合物；B组植入单纯MSCs与含重组BMP-2的PLA／PCL缓释载体的复合物；C组植入单纯MSCs与PLA／PCL复合物；D组植入单纯PLA／PCL。术后4、8、12周行X线、组织学、生物力学和骨密度等检测，[结果]A组体内植入4周后，成骨细胞和间质细胞呈BMP-2强阳性表达；其成骨速度及成骨质量均明显优于B组，12周时骨缺损完全修复、C组成骨能力较弱，而D组则无新骨形成，残留骨缺损。[结论]BMP-2基因治疗是修复节段性骨缺损的好方法。     

仿生活性人工骨修复兔桡骨节段性骨缺损的研究

目的 研制在成分和结构上与天然骨基质高度仿生的新型材料，应用于节段性骨缺损的修复。方法 以Ⅰ型胶原蛋白分子为模板，引入钙磷盐生成体重，合成纳米相羟基磷灰石/胶原（NHAC）并以之为主体，以1：1的质量比加入聚乳酸（PLA）制备多孔框架，与重组人骨形态发生蛋白2（rh-BMP2)复合后植入兔桡骨15mm缺损，观察骨修复情况。结果 所合成的材料具有纳米级的层装排列结构。层间距为11.7nm，实验组中10只兔术后12周骨缺损均完全愈合。结论 NHAC可能成为修复骨缺损的较理想材料，具有较大的临床应用潜力。     

Implanting hydroxyapatite-coated porous titanium with bone morphogenetic protein-2 and hyaluronic acid into distal femoral metaphysis of rabbits

Objective： To assess the osseointegration capability of hydroxyapatite-coated porous titanium with bone morphogenetic protein-2 （BMP-2） and hyaluronic acid to repair defects in the distal femur metaphysis in rabbits.
Methods： Porous titanium implants were made by sintering titanium powder at high temperature, which were coated with hydroxyapatite by alkali and heat treatment and with BMP-2 combined with bone regeneration materials. And hyaluronic acid was further used as delivery system to prolong the effect of BMP-2. The implants were inserted into the metaphysis of the distal femur of rabbits. The animals were killed at 6, 12 and 24 weeks to accomplish histological and biomechanical analyses.
Results： According to the result of histological analysis, the osseointegration in BMP-2 group was better than that of the HA-coated porous titanium group. In push-out test, all the samples had bigger shear stress as time passed by. There was statistical difference between the two groups in 6 and 12 weeks but not in 24 weeks.
Conclusion： Hydroxyapatite-coated porous titanium with BMP-2 and hyaluronic acid has a good effect in repairing defects of distal fumur in rabbits, which is a fine biotechnology for future clinical application.     

Improved osseointegration of titanium implants after surface coating with polymers in a rabbit model

In this study we present the first results of the investigation of polymer-coated titanium implants implanted in the proximal tibia and distal femora of New Zealand white rabbits. The results of DEXA scans, micro-CT, and histological analysis showed an increase of osseointegration. We suggest that controlled release kinetics after coupling of these polymers with BMP-2 can additionally increase osseointegration.     

Verbesserte Osteointegration von Titanimplantaten nach Oberflächenbeschichtung mit Polymeren im Kaninchenmodell

In this study we present the first results of the investigation of polymer-coated titanium implants implanted in the proximal tibia and distal femora of New Zealand white rabbits. The results of DEXA scans, micro-CT, and histological analysis showed an increase of osseointegration. We suggest that controlled release kinetics after coupling of these polymers with BMP-2 can additionally increase osseointegration.     

An in vivo evaluation of bone response to three implant surfaces using a rabbit intramedullary rod model

Our study was designed to evaluate osseointegration among implants with three surface treatments: plasma-sprayed titanium (P), plasma-sprayed titanium with hydroxyapatite (PHA), and chemical-textured titanium with hydroxyapatite (CHA). Average surface roughness (Ra) was 27 microns for the P group, 17 microns for the PHA group, and 26 microns for the CHA group. Bilateral distal intramedullary implants were placed in the femora of thirty rabbits. Histomorphometry of scanning electron microscopy images was used to analyze the amount of bone around the implants at 6 and 12 weeks after implantation. Greater amounts of osseointegration were observed in the hydroxyapatite-coated groups than in the noncoated group. For all implant surfaces, osseointegration was greater at the diaphyseal level compared to the metaphyseal level. No significant differences were seen in osseointegration between the 6 and 12 week time points. Although the average surface roughness of the P and the CHA groups was similar, osseointegration of the CHA implants was significantly greater. The results of this in vivo lapine study suggest that the presence of an hydroxyapatite coating enhances osseointegration despite similarities in average surface roughness.     

Bioactive glass enhances bone ingrowth into the porous titanium coating on orthopaedic implants

Purpose

The aim of the study was to verify the ability of nanoparticulate bioactive glass (BAG) to infiltrate into the porous titanium (Ti) layer on Ti-based implants to promote osseointegration.

Methods

The porous titanium layer on Ti-based implants was impregnated with nanoparticulate BAG. The implants without or with BAG were implanted bilaterally in tibial holes of ten New Zealand white rabbits. The rabbits were sacrificed after ten weeks for examinations. Beside histological examination, EDXS analysis of polished cross-sections of explanted implants was also performed with the aim to quantitatively evaluate the bone-to-pore contact and bone-in-pore ratio.

Results

After ten weeks, EDXS analyses of cross-sections of the explanted implants confirmed that bioactive glass was fully resorbed and that the pores throughout the thickness of the porous titanium layer were to a large extent filled with a new bone. In the absence of bioactive glass, only the outer part of the porous layer was filled with bone. The implants without BAG in the porous Ti-layer exhibited similar bone-to-pore contact, while significant improvement of bone ingrowth into the pores was observed for the implants with BAG (38%), as opposed to those without it (22%).

Conclusion

This study confirmed that the nanoparticulate bioactive glass within the porous titanium surface layer on implants promotes osseointegration and stimulates the formation of bone within the pores.     

The bone-implant interface: a dynamic surface.

This study quantifies and compares bone formation on and around roughened titanium implants with roughened cobalt chromium, polished solid implants, and titanium fibermetal implants. Cylindrical rods were implanted into the medullary canal of the distal femur of rabbits. The bone-implant interface was studied 3, 6, and 12 weeks after surgery using histomorphometric methods. Roughened surface implants demonstrated significantly more bone directly apposed to the surfaces when compared to the polished or fiber/metal implants at 6 and 12 weeks after surgery. New bone formation and remodeling of bone occurred directly on roughened surfaces as late as 12 weeks after implantation, but not on the unroughened implants. These results suggest that roughening of the surfaces of both titanium and cobalt chromium implants can enhance osseointegration and may be useful clinically for the fixation of prosthetic components.     

Semiquantitative analysis of bone regeneration on porous metallic wire-mesh specimens with or without HA-coating in comparison to pure titanium in animal experiments

INTRODUCTION: The aim of this study was to analyse the bone regeneration on porous metallic wire-mesh specimens of pure titanium, uncoated CoCrMb and HA-coated CoCrMb in a comparative animal experiment. MATERIAL AND METHODS: Uncoated and hydroxyapatite-coated CoCrMb (one-sided) specimens were tested in an animal experiment. The statistical interpretation was done macroscopically as well as microscopically. RESULTS: With regard to the histological and quantitative evaluation, it has been shown that the proximal coated CrCoMb implants were superior to the other specimen. The bone regeneration with the most distinctive extent of osseointegration has been seen by the HA-coated CrCoMb specimen. The uncoated distal CoCrMb specimen demonstrated the worst results. DISCUSSION: This study shows that specimens of titanium and uncoated CrCoMb implanted at the proximal metaphysis deliver comparable effects on the bone regeneration and osseointegration. The best results with regard to the bone regeneration and osseointegration were seen with the implanted hydroxyadaptite-coated CrCoMb specimen. In addition, it has been observed that the bone regeneration and osseointegration of the specimen depends on the place of implantation.     

The bisphosphonate ibandronate accelerates osseointegration of hydroxyapatite-coated cementless implants in an animal model

Background There is evidence that bisphosphonates can improve fixation of cementless metal implants by enhancing the extent of osseointegration. The current preclinical study examined whether the nitrogen-containing bisphosphonate ibandronate can accelerate this process, resulting in early achievement of secondary stability and sealing of the bone–implant interface to prevent wear debris migration. Methods The study was conducted on 88 female Sprague-Dawley rats in which uncoated titanium and hydroxyapatite-coated titanium implants were surgically inserted into the medullary canal of each femur. The animals were randomly assigned to receive subcutaneous treatment with 1.0, 2.5, or 5.0 μg/kg per day ibandronate or saline solution as a control. The extent of osseointegration expressed by the osseointegrated implant surface was quantified by histomorphometry at eleven time points during the study period. To determine the time course of osseointegration, the data were expressed using third-order polynomial regression analysis. Results For hydroxyapatite-coated implants, the highest dose of ibandronate (5 μg) reduced the time for a sufficient implant fixation of 60% osseointegrated implant surface to 18 days compared to 38 days in the control group. This reduction of 20 days (52.6%) represents a halving in the time required for sufficient osseointegration of the implant. For hydroxyapatite-coated implants and low-dose ibandronate application (1 μg, 2.5 μg) and for uncoated titanium implants, acceleration of osseointegration was not observed in any of the study arms. Conclusion Continuous treatment with 5 μg/kg per day ibandronate is potent in accelerating osseointegration of hydroxyapatite-coated implants. As a result, improved early secondary stability and prevention of wear debris migration by the sealing of the implant–bone interface can be expected, therefore prolonging the long-term survival of the implant.     

Relative contributions of chemistry and topography to the osseointegration of hydroxyapatite coatings

The purpose of the current study was to ascertain the relative contributions of surface chemistry and topography to the osseointegration of hydroxyapatite-coated implants. A canine femoral intramedullary implant model was used to compare the osseous response to commercially pure titanium implants that were either polished, grit-blasted, plasma-sprayed with hydroxyapatite, or plasma-sprayed with hydroxyapatite and masked with a very thin layer of titanium using physical vapor deposition (titanium mask). The titanium mask isolated the chemistry of the underlying hydroxyapatite layer without functionally changing its surface topography and morphologic features. At 12 weeks, the bone-implant specimens were prepared for undecalcified thin section histologic evaluation and serial transverse sections were quantified with backscattered scanning electron microscopy for the percentage of bone apposition to the implant surface. Bone apposition averaged 3% for the polished implants and 23% for the grit-blasted implants. Bone apposition to the hydroxyapatite-coated implants averaged 74% whereas bone apposition to the titanium mask implants averaged 59%. Although there was significantly greater osseointegration with the hydroxyapatite-coated implants, 80% of the maximum bone forming response to the implant surfaces developed with the titanium mask implants. This simple, controlled experiment revealed that topography is the dominant factor governing bone apposition to hydroxyapatite-coated implants.     

Osteogene Aktivität BMP-3-beschichteter Titanprüfkörper unterschiedlicher Oberflächenbeschaffenheit im orthotopen Lager des Riesenkaninchens

INTRODUCTION: The successful combination of osteoinductive factors with current materials used in both endoprosthetics and implantology improves bony ingrowth and long-term stability of the chosen implants. The aim of the present experimental animal study was to clarify in what way faster bony integration can be achieved through additional BMP-3-coating of titanium test implants of different surface textures (hydroxy-apatite-coated or corundum-blasted). METHODS: Thirty of 60 cylindrical titanium test implants with a hydroxy-apatite or corundum-blasted surface were coated with 230 microg porcine, high-purified BMP-3-precipitate per implant to check their osteoinductive potential in a bioassay. In each case a BMP-3-coated and an uncoated control-device were implanted with a gap formation of 1 mm into the femoral part of the patellofemoral joint of the right and left leg of 30 adult giant rabbits. Serial saw slices of all explanted specimens were prepared, and the osseous integration of the implant and time-dependent bone neoformation were analyzed microscopically and histomorphometrically 14, 35, and 56 days after implantation. RESULTS: Coating of TiAl4V6-test devices with BMP-3 led in both groups after gap implantation to an improved osseointegration, that was histomorphological and histomorphometrical verifiable. Statistical evaluation using the t-test for matched samples showed 5 weeks after surgery a significant higher volume of new formed bone of the BMP-3-coated corundum-blasted or hydroxy-apatite-coated TiAl4V6 test devices compared to the non-coated controls of the same type (P < 0.01). Light microscopy demonstrated osseointegration without connective tissue membrane around the surface of the implants after 2, 5, and 8 weeks. Better osseointegration was achieved in the hydroxy-apatite-coated implants than in the corundum-blasted implants. CONCLUSIONS: Our results indicate that composite metal implants, as used in endoprosthetics and implantology, are suitable carriers for BMP-3 and improved fixation of the implants can be achieved.