预分化脂肪干细胞与纤维蛋白胶和磷酸钙骨水泥自体异位构建血管化移植物

背景：预构骨皮瓣研究启发人们构建预构血管化骨进行游离移植来替代带血管蒂游离自体骨移植修复大段骨缺损的想法。 目的：设计一种基于预分化脂肪干细胞、纤维蛋白胶和多孔磷酸钙骨水泥支架复合体的血管化移植物。 方法：将体外分离培养的大鼠脂肪干细胞在条件培养基中进行血管内皮细胞定向分化,经鉴定活性后,复合至纤维蛋白胶和多孔磷酸钙骨水泥构建血管化组织工程支架。将血管化组织工程支架、纤维蛋白胶/多孔磷酸钙骨水泥支架及多孔磷酸钙骨水泥支架分别植入SD大鼠股四头肌肌袋内,植入后2,4周进行组织学检测、血管定量分析和Western blot检测。 结果与结论：向血管内皮细胞分化的脂肪干细胞与纤维蛋白胶和多孔磷酸钙骨水泥共培养7 d,可见细胞密度适中,与支架组织结合较好。植入实验中,各组支架孔隙中充填有纤维血管组织和脂肪组织,血管化组织工程组支架孔隙中均长入大量血管,并有小动脉长入,不同时间点的血管直径和数量及血管内皮生长因子C的表达量均优于纤维蛋白胶/多孔磷酸钙骨水泥组和多孔磷酸钙骨水泥组(P < 0.01)。表明构建的血管化组织工程支架能够实现可靠迅速血管化。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

骨水泥间隔器表面微观形貌改变对诱导膜内成骨因子表达的影响

文题释义： 聚甲基丙烯酸甲酯骨水泥：为临床上常用的骨科植入材料,具有很大的抗压能力,抗压缩能力为97 MPa,也具有良好的生物相容性。1987年Galibert等首次报道用聚甲基丙烯酸甲酯骨水泥来治疗椎体血管瘤,并将此技术称之为经皮椎体成形。1970年Buchholz首次应用载抗生素骨水泥控制关节感染,目前以聚甲基丙烯酸甲酯骨水泥作为抗生素的缓释载体被广泛应用于人工全髋关节置换及骨髓炎的治疗。 转化生长因子β1：是具有多种功能的蛋白多肽,是“转化生长因子β超家族”成员之一,大量存在于骨组织与血小板中,可以刺激间充质干细胞的增殖、分化,并抑制间充质干细胞向脂肪细胞分化,也促进成骨细胞、成软骨细胞的增殖及细胞外基质的合成,诱导膜内成骨和软骨内成骨。 背景：目前国内外学者试图通过改变植入材料的种类和形貌、改良诱导膜厚度、光滑程度等机械化学性能来促进植骨生长。 目的：比较大鼠股骨骨缺损处不同表面粗糙程度聚甲基丙烯酸甲酯骨水泥形成的诱导膜在膜内血管化程度和部分成骨因子表达的差异。 方法：取48只雄性SD大鼠(购自广州中医药大学实验动物中心)建立大鼠临界尺寸股骨缺损模型,按随机数字表法分为A、B、C、D组,分别在股骨骨缺损处植入表面粗糙度<1.5 µm、1.5-2.0 µm、5.0-7.0 µm、14.0-20.0 µm的聚甲基丙烯酸甲酯骨水泥占位器。植入6周大鼠体内诱导膜形成后取出骨水泥周围的诱导膜,苏木精-伊红染色观察诱导膜病理组织形态结构变化,采用Western Blot印迹方法和免疫组织化学染色法对诱导膜中骨形态发生蛋白2、转化生长因子β1、血管内皮生长因子蛋白进行定量和定性分析。实验获得广州中医药大学动物实验伦理委员会批准,批准号：20181101006。 结果与结论：①苏木精-伊红染色显示,4种表面粗糙程度不同的骨水泥均可以形成较为规则的诱导膜,4组诱导膜之间血管化程度和细胞的数量大体相似;②Western Blot印迹检测显示,各组诱导膜内骨形态发生蛋2、转化生长因子β1、血管内皮生长因子蛋白平均含量基本相似(P > 0.05);③免疫组织化学染色显示,各组诱导膜内骨形态发生蛋2、转化生长因子β1、血管内皮生长因子蛋白阳性表达基本相似(P > 0.05);④结果表明,骨水泥表面粗糙程度改变对诱导膜的组织形态结构和骨形态发生蛋2、转化生长因子β1、血管内皮生长因子表达在6周时无明显影响。 ORCID: 0000-0003-1405-0765(李树源) 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

纳米级羟基磷灰石/骨形态发生蛋白复合物修复兔桡骨大段缺损及局部血管内皮细胞生长因子的表达

背景：研究发现,在小段骨缺损中植入骨或仿生骨组织,坏死组织逐渐被替换,移植骨中会长入有活性的血管肉芽组织,移植骨被吸收,新骨主动形成。但在大段骨缺损,这一过程发生较慢且不完全。 目的：观察纳米级羟基磷灰石材料复合骨形态发生蛋白后大段骨缺损修复能力及诱导生成血管能力。 方法：制作兔桡骨大段骨缺损模型,抽签随机分2组,选择一侧分别植入纳米级羟基磷灰石/骨形态发生蛋白、纳米级羟基磷灰石修复,均以另一侧为空白对照。植入后6个月行大体观察、X射线、组织形态学检查、组织切片碱性磷酸酶染色、成骨量分析、血管内皮细胞生长因子阳性细胞率及阳性血管数检测。 结果与结论：空白对照组基本无骨组织生成。纳米级羟基磷灰石植入后被新生骨组织分割成小块,材料原有结构破坏。纳米级羟基磷灰石/骨形态发生蛋白组较纳米级羟基磷灰石组残存材料更少,材料降解更为彻底。纳米级羟基磷灰石/骨形态发生蛋白组成骨量、血管内皮细胞生长因子表达及血管内皮细胞生长因子阳性血管数目均明显高于纳米级羟基磷灰石组(P < 0.001),且血管内皮细胞生长因子表达与血管内皮细胞生长因子阳性血管数目成正比关系。说明纳米级羟基磷灰石与骨形态发生蛋白复合后,骨修复能力进一步增强,诱导血管生成能力明显提高。     

重组人骨形态发生蛋白2复合骨在腰椎融合中的效果

背景：诸多研究已证实重组人骨形态发生蛋白2在骨形成及骨折愈合中发挥十分重要的作用,但单纯予以重组人骨形态发生蛋白2植入容易出现扩散和降解,无法对新骨形成予以持续性的影响。 目的：观察重组人骨形态发生蛋白2复合骨在兔腰椎中的融合效果。 方法：取30只新西兰大白兔,构建后路腰椎横突间植骨融合模型,随机均分为3组,分别在L5-6横突间植入自体髂骨、同种异体骨及重组人骨形态发生蛋白2复合骨(重组人骨形态发生蛋白2与同种异体骨复合物),植入后6周,进行大体观察、X射线检查及组织学观察。 结果与结论：重组人骨形态发生蛋白2复合骨组融合率、新生骨组织在总面积中所占百分比高于自体髂骨组、同种异体骨组(P < 0.05);重组人骨形态发生蛋白2复合骨组、自体髂骨组拉伸强度大于同种异体骨组(P < 0.05),前两组拉伸强度无差异。X射线显示3组植骨区均可见骨痂形成;组织学显示,自体髂骨组移植物已消失,形成大量软骨,有少量骨小梁,并有一定编织骨形成;同种异体骨组有较多的纤维组织包裹材料,有骨岛形成,有数量较少的骨小梁及软骨形成;重组人骨形态发生蛋白2复合骨组存在大量骨小梁和少量软骨,形成编织骨且有皮质骨形成。表明重组人骨形态发生蛋白2复合骨在兔腰椎中可以获得良好的融合效果。 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

负载骨形态发生蛋白新型骨填充材料应用于椎体成形

背景：磷酸钙骨水泥克服了聚甲基丙烯酸甲酯的诸多缺点并具有良好的生物相容性。而负载复合重组人类骨形态发生蛋白2的磷酸钙骨水泥经固化后可具有微孔结构,可提高经皮椎体成形充填材料的临床价值。 目的：探讨以可注射型磷酸钙骨水泥和纤维蛋白胶作为共同载体,复合重组人类骨形态发生蛋白2,替代聚甲基丙烯酸甲酯应用于新西兰大白兔椎体成形的可行性。 方法：制备磷酸钙骨水泥/纤维蛋白胶/复合重组人类骨形态发生蛋白2新型复合材料。采用小鼠肌袋异位诱导成骨模型对不同植入材料进行骨诱导活性评价;模仿椎体成形观察新型复合材料和聚甲基丙烯酸甲酯植入兔椎体后的生物力学改变。 结果与结论：新型复合材料植入后2,4周碱性磷酸酶水平最高,植入后4周软骨细胞逐渐成熟,新骨形成,抗压强度和抗扭转强度明显低于正常椎体和聚甲基丙烯酸甲酯植入后(P < 0.05),8周后材料被进一步降解,抗压强度和抗扭转强度均有所上升,扛扭转强度与正常椎体相比无显著差别,但仍明显低于聚甲基丙烯酸甲酯(P < 0.05)。microCT提示其新生骨形成多而早,但聚甲基丙烯酸甲酯未见材料吸收及周围骨质长入。说明新型复合材料植入椎体后能够获得良好的骨诱导和骨传导功能,材料降解和新骨替代同步,接近于正常椎体的骨愈合,可望替代聚甲基丙烯酸甲酯应用于椎体成形。     

磷酸钙人工骨联合雷洛昔芬修复兔下颌骨缺损

背景：雷洛昔芬是第3代选择性雌激素受体调节剂,可减少骨量的丢失,增加骨组织中的矿物质含量,降低骨折风险。 目的：观察雷洛昔芬结合自固化磷酸钙人工骨修复兔下颌骨缺损的效果。 方法：在36只新西兰大白兔左侧下颌骨制作8 mm×4 mm×3 mm的缺损模型,随机分组,实验组12只植入自固化磷酸钙人工骨,并给予雷洛昔芬7.5 mg/(kg•d);药物组12只给予雷洛昔芬7.5 mg/(kg•d);人工骨组12只植入自固化磷酸钙人工骨。分别于治疗4,8,12周取下颌骨标本,免疫组织化学法观察骨形态发生蛋白2的表达,激光共聚焦显微镜观察转化生长因子β的表达。 结果与结论：实验组治疗后4,8周时的骨形态发生蛋白2免疫组织化学染色阳性细胞数明显高于药物组与人工骨组,治疗后12周时实验组骨改建基本完成,骨形态发生蛋白2免疫组织化学染色阳性细胞数目低于其他两组。实验组转化生长因子β免疫荧光染色表达为逐步升高,到第8周时达到峰值,而药物组和人工骨组的转化生长因子β免疫荧光表达从4-12周一直呈上升状态,趋近于最高峰。说明雷洛昔芬能够促进自固化磷酸钙人工骨在骨缺损过程中骨形态发生蛋白的早期表达及早期骨痂的形成,加快骨缺损修复。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

不同组织部位诱导膜血管化及成骨因子表达的比较

文题释义 诱导膜技术：又称膜诱导技术、Masquelet技术,1986年由Masquelet等最先提出并使用,是一种重建超临界尺寸骨缺损的有效方法。该技术在清创后所形成的骨缺损处植入骨水泥占位器,以形成一层生物膜,并在所形成的膜内进行植骨对骨缺损进行二次重建。该技术修复大段骨缺损具有重建时间短、骨愈合率高、并发症发生率较低等优势,其疗效已经被广泛证实。 血管内皮生长因子：是一种生长因子,在血管生成中发挥重要作用。血管内皮生长因子与血管内皮表面的特异性受体结合,可以促进内皮细胞的增殖、迁移,并可增加局部毛细血管的通透性,促使纤维蛋白原渗出,为血管内皮细胞的迁移和血管形成提供基质。在促进骨愈合方面,血管内皮生长因子通过促进血管增生,协调软骨细胞的消长、细胞外基质的改建,加快软骨内成骨。血管内皮生长因子还可以趋化并促进成骨细胞的分化,使碱性磷酸酶活性增强,局部钙盐沉积增加,促进骨愈合。 背景：研究发现在皮下、肌肉等部位植入聚甲基丙烯酸甲酯骨水泥也可形成诱导膜,膜内同样具有微血管的形成并分泌多种成骨因子。 目的：比较皮下、肌肉、股骨骨缺损处诱导膜内血管化程度和成骨因子表达的差异。 方法：将36只雄性SD大鼠(购自广州中医药大学实验动物中心)随机分为3组,分别在后肢皮下、肌肉内、股骨骨缺损处植入聚甲基丙烯酸甲酯抗生素骨水泥占位器,每组12只。植入6周后,取出骨水泥周围的诱导膜,苏木精-伊红染色观察诱导膜组织形态结构变化,Western Blot印迹方法、RT-qPCR法、免疫组织化学染色法检测诱导膜中骨形态发生蛋白2、转化生长因子β1、血管内皮生长因子的表达情况。实验获得广州中医药大学动物实验伦理委员会批准,批准号：20181101006。 结果与结论：①苏木精-伊红染色显示3组均可形成诱导膜,但骨缺损组诱导膜组织切片外层血管数量较肌肉组、皮下组多,靠近骨水泥侧的内层成纤维细胞和肌纤维细胞数量较肌肉组、皮下组多;②免疫组织化学染色显示,骨缺损组骨形态发生蛋白2、转化生长因子β1、血管内皮生长因子阳性表达最多,皮下组最少;③Western Blot与RT-qPCR检测显示,骨缺损组骨形态发生蛋白2、转化生长因子β1、血管内皮生长因子表达均多于肌肉组、皮下组(P < 0.001);④结果表明,不同的周围组织条件对诱导膜的组织结构和成骨因子表达有重要影响,在骨缺损处植入聚甲基丙烯酸甲酯骨水泥可提高诱导膜的形成质量,膜内新生血管更丰富,骨生长因子的表达量更多。ORCID: 0000-0003-1405-0765(李树源) 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

自固化磷酸钙人工骨Ⅱ型诱导成骨及修复腱骨界面损伤的生物力学分析

背景：自固化磷酸钙人工骨Ⅱ型与重组人骨形态发生蛋白均有一定的成骨诱导作用,存在修复腱骨界面损伤的可能。 目的：探讨自固化磷酸钙人工骨Ⅱ型的成骨诱导作用及修复腱骨界面损伤生物力学情况。 方法：35只成年健康的新西兰白兔,随机选取5只,处死后取双侧肩关节腱骨界面标本作为正常对照。剩余30只构建腱骨界面损伤模型后,随机等分为实验组和模型组,模型组不填塞任何药物,实验组填塞自固化磷酸钙人工骨Ⅱ型进行修复。 结果与结论：填塞自固化磷酸钙人工骨Ⅱ型后,兔损伤腱骨界面明显恢复,且随时间的延长,修复效果更佳,骨形态发生蛋白2表达水平也随之增加,损伤腱骨界面最大抗拉强度以及最大刚度明显增加。表明利用自固化磷酸钙人工骨Ⅱ型复合重组人骨形态发生蛋白对腱骨界面损伤进行修复具有良好的成骨诱导作用,可以促进损伤的修复。 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

注射型纳米壳聚糖骨形态发生蛋白2复合体诱导牙周组织的再生

背景：壳聚糖水凝胶具有良好的生物兼容性、生物可降解性及抗菌性等特点,具有促进组织愈合和成骨诱导的作用,作为支架材料载负生长因子可保证外源生长因子的缓慢高效释放。目的：观察可注射性纳米壳聚糖骨形态发生蛋白2复合体促进大鼠牙周组织再生的效果。方法：将54只Wistar大鼠随机均分为3组,建立第二磨牙慢性牙周炎模型,建模成功后,实验组于第二磨牙牙周内植入可注射性纳米壳聚糖骨形态发生蛋白2复合体,对照组于第二磨牙牙周内植入可注射性纳米壳聚糖凝胶,空白组牙周内不植入任何药物。术后3,6,9周,进行牙龈出血指数、探诊深度、松动度、X射线片及组织病理学切片观察。结果与结论：实验组术后9周的探诊深度、松动度均低于对照组及空白组(P < 0.05)。术后9周,实验组牙槽骨高度修复再生至根分叉处,骨小梁致密,分布均匀,可见大量牙骨质样结构、牙周韧带生成,新生牙槽骨致密且均匀分布在骨缺损区域,修复效果明显优于对照组及空白组。表明可注射性纳米壳聚糖骨形态发生蛋白2复合体具有抗炎和引导牙周组织再生的作用。 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程      

川续断复合磷酸钙骨修复骨缺损

背景：复合磷酸钙骨植入材料的物理结构和无机成分与人体骨相似,具有良好的生物可吸收性和生物相容性。研究证实续断细粉能明显提高骨缺损修复速度。 目的：观察川续断复合磷酸钙骨复合植入材料修复骨缺损的效果。 方法：在新西兰大白兔双侧下颌骨体部制备长约1.0 cm、宽约0.5 cm、深约0.3 cm的骨缺损,右侧植入川续断复合磷酸钙材料作为实验组,左侧植入磷酸钙骨材料作为对照组。植入后4,8,12周取材,进行大体观察、CBCT检测、扫描电镜、组织学观察。 结果与结论：①大体观察：实验组成骨速度、材料降解率及硬度高于对照组。②CBCT检测：实验组材料与周围组织结合紧密度强于对照组,且材料降解速度快于对照组。③扫描电镜：两组材料与周围正常骨组织间大多由纤维结缔组织充盈,实验组比对照组更为紧密,空隙更加微小,随着时间的增加,材料与周围正常骨组织的结合更为紧密。④组织学观察：实验组成骨速度及成骨活性优于对照组。表明川续断复合磷酸钙骨植入材料具有明显加速成骨的作用。     

多孔磷酸钙骨水泥与转染骨形态发生蛋白2基因的骨髓间充质干细胞复合修复股骨髁骨缺损

BACKGROUND: Bone morphogenetic protein (BMP) can improve the osteogenesis capacity of tissue-engineered bone. However, how to prolong BMP release is a key for constructing tissue-engineered bone. OBJECTIVE: To study the repair effect of porous calcium phosphate cement (CPC) with bone marrow mesenchymal stem cells transfected with BMP-2 gene on bone defects. METHODS: After modeling of bilateral femoral condyle bone defects, 12 model rabbits were given implantation of porous CPC with bone marrow mesenchymal stem cells transfected with BMP-2 on the left (experimental group) and given implantation of porous CPC with bone marrow mesenchymal stem cells on the right (control group). Bilateral femoral condyles were taken and analyzed histologically at 4 and 12 weeks after implantation. RESULTS AND CONCLUSION: Better osteogenesis including more newly formed bone tissues and faster scaffold absorption was observed in the experimental group compared with the control group at 4 and 12 weeks after implantation. The area of newly formed bone tissues at different time and rate of bone formation at 12 weeks were significantly higher in the experimental group than in the control group (P < 0.001, P < 0.05). These findings indicate that transfer of BMP-2 into bone marrow mesenchymal stem cells combined with porous CPC could increase repair of bone defects.     

A differential effect of bone morphogenetic protein-2 and vascular endothelial growth factor release timing on osteogenesis at ectopic and orthotopic sites in a large-animal model

In bone tissue engineering, growth factors are widely used. Bone morphogenetic proteins (BMPs) and vascular endothelial growth factor (VEGF) are the most well-known regulators of osteogenesis and angiogenesis. We investigated whether the timing of dual release of VEGF and BMP-2 influences the amount of bone formation in a large-animal model. Poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) were loaded with BMP-2 or VEGF to create sustained-release profiles, and rapidly degrading gelatin was loaded with either growth factor for fast-release profiles. To study in vivo osteogenicity, the two delivery vehicles were combined with biphasic calcium phosphate (BCP) scaffolds and implanted in 10 Beagle dogs for 9 weeks, at both ectopic (paraspinal muscles) and orthotopic sites (critical-size ulnar defect). The 9 ectopic groups contained combined or single BMP/VEGF dosage, in sustained- or fast-release profiles. In the ulnae of 8 dogs, fast VEGF and sustained BMP-2 were applied to one leg, and the other received the opposite release profiles. The two remaining dogs received bilateral control scaffolds. Bone growth dynamics was analyzed by fluorochrome injection at weeks 3, 5, and 7. Postoperative and posteuthanization X-rays of the ulnar implants were taken. After 9 weeks of implantation, bone quantity and bone growth dynamics were studied by histology, histomorphometry, and fluorescence microscopy. The release of the growth factors resulted in both enhanced orthotopic and ectopic bone formation. Bone formation started before 3 weeks and continued beyond 7 weeks. The ectopic BMP-2 fast groups showed significantly more bone compared to sustained release, independent of the VEGF profile. The ulna implants revealed no significant differences in the amount of bone formed. This study shows that timing of BMP-2 release largely determines speed and amount of ectopic bone formation independent of VEGF release. Furthermore, at the orthotopic site, no significant effect on bone formation was found from a timed release of growth factors, implicating that timed-release effects are location dependent.     

In vivo bone response to porous calcium phosphate cement

We conducted an in vivo experiment to evaluate the resorption rate of a calcium phosphate cement (CPC) with macropores larger than 100 microm, using the CPC called Biocement D (Merck Biomaterial, Darmstadt, Germany), which after setting only shows pores smaller than 1 microm. The gas bubble method used during the setting process created macroporosity. Preset nonporous and porous cement implants were inserted into the trabecular bone of the tibial metaphysis of goats. The size of the preset implants was 6 mm and the diameter of the drill hole was 6.3 mm, leaving a gap of 0.3 mm between implant surface and drill wall. After 2 and 10 weeks, the animals were euthanized and cement implants with surrounding bone were retrieved for histologic evaluation. Light microscopy at 2 weeks revealed that the nonporous implants were surrounded by connective tissue. On the cement surface, we observed a monolayer of multinucleated cells. Ten weeks after implantation, the nonporous implants were still surrounded by connective tissue. However, a thin layer of bone now covered the implant surface. No sign of cement resorption was observed. In contrast, the porous cement evoked a completely different bone response. At 2 weeks, bone formation had already occurred inside the implant porosity. Bone formation even appeared to occur as a result of osteoinduction. Also, at their outer surface, the porous implants were completely surrounded by bone. At 2 weeks, about 31% of the initial cement was resorbed. After 10 weeks, 81% of the initial phosphate cement was resorbed and new bone was deposited. On the basis of these observations, we conclude that the creation of macropores can significantly improve the resorption rate of CPC. This increased degradation is associated with almost complete bone replacement.     

Injectable calcium phosphate cement with PLGA, gelatin and PTMC microspheres in a rabbit femoral defect

In this study, we investigated the in vivo degradation properties and tissue response towards injectable calcium phosphate cement (CPC) with no further addition, or calcium phosphate composite cement containing approximately 50 vol.% of microspheres. Three types of spheres were assessed, i.e. poly(lactic-co-glycolic acid) (PLGA), gelatin (GEL) and poly(trimethylene carbonate) (PTMC). The cements were injected into 4.6 mm diameter and 6mm deep cylindrical defects in the femoral condyle of New Zealand white rabbits, hardened in situ and, after wound closure, left to heal for 4, 8 and 12 weeks (n=6 for each composition and time period). After retrieval, specimens were analyzed using histological and histomorphometrical methods. Results showed that non-modified CPCs showed excellent bone contact but only very limited erosion at the surface. The CPC/PLGA implant degraded almost completely, while tissue response significantly improved at each time period. CPC/PTMC showed slower degradation characteristics compared to CPC/PLGA. Finally, at all time periods, there was an evident inflammatory response to the CPC/GEL composite cement. In conclusion, the degradation properties of the CPC/PLGA microspheres composite and its bone response when implanted into the femoral condyles of rabbits were significantly better than those of CPC/gelatin and CPC/PTMC microspheres composites.     

In vivo evaluation of a porous hydroxyapatite/poly-DL-lactide composite for bone tissue engineering

As reported previously, a porous composite of uncalcined hydroxyapatite (u-HA) and poly-DL-lactide (PDLLA) showed excellent osteoconductivity and biodegradability as a bone substitute in rabbit model. In this study, to investigate the usefulness of this composite as a scaffold loaded with cells, we estimated whether this material showed osteogenesis on implantation to extraosseous site. On loading with syngeneic bone marrow cells and implantation into rat dorsal subcutaneous tissue, osteogenesis with enchondral ossification was seen both on and in the material at 3 weeks after implantation. The osteogenesis in the u-HA/PDLLA had progressed, and newly formed bone tissue was found in the material by 6 weeks. To investigate the osteoinductive properties of the material, we implanted this porous composite material into extraosseous canine dorsal muscle. At 8 weeks, osteogenesis was seen in the pores of the material. Newly formed bone could be observed adjacent to the material. In addition, cuboidal osteoblasts adjacent to the newly formed bone were evident. Neither cartilage nor chondrocytes were found. These results might indicate that the material induced osteogenesis by intramembranous ossification. Conversely, similar porous PDLLA did not induce osteogenesis during the observation period. Therefore, porous HA/PDLLA, which has osteoconductive and osteoinductive properties, might be a useful material for use as a bone substitute and cellular scaffold.     

VEGF and BMP-6 enhance bone formation mediated by cloned mouse osteoprogenitor cells

New strategies such as combined utilization of growth factors may provide a better treatment for difficult fractures. We have demonstrated enhanced angiogenesis and osteogenesis through the actions of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-6 (BMP-6) on the osteogenic differentiation of a cloned mouse osteoprogenitor cell in vitro and ectopic bone formation in vivo. Human VEGF and BMP-6 genes expressed together produced a significant increase in alkaline phosphatase activity, expression of the RunX2 and osteocalcin genes and mineralization. Microcomputed tomographic analysis of subcutaneous implants consisting of cells transfected with VEGF and BMP-6 cDNA and delivered on a 3D poly (lactic-co-glycolic acid) scaffold confirmed the additive effects between VEGF and BMP-6. Ectopic bone formation in the VEGF plus BMP-6 group was greatest compared to that in either VEGF or BMP-6 alone. This is the first study that demonstrates osteogenesis in vitro and in vivo through the additive effects of VEGF and BMP-6.     

Incorporation of bioactive glass in calcium phosphate cement: An evaluation

Bioactive glasses (BGs) are known for their unique ability to bond to living bone. Consequently, the incorporation of BGs into calcium phosphate cement (CPC) was hypothesized to be a feasible approach to improve the biological performance of CPC. Previously, it has been demonstrated that BGs can successfully be introduced into CPC, with or without poly(d,l-lactic-co-glycolic) acid (PLGA) microparticles. Although an in vitro physicochemical study on the introduction of BG into CPC was encouraging, the biocompatibility and in vivo bone response to these formulations are still unknown. Therefore, the present study aimed to evaluate the in vivo performance of BG supplemented CPC, either pure or supplemented with PLGA microparticles, via both ectopic and orthotopic implantation models in rats. Pre-set scaffolds in four different formulations (1: CPC; 2: CPC/BG; 3: CPC/PLGA; and 4: CPC/PLGA/BG) were implanted subcutaneously and into femoral condyle defects of rats for 2 and 6 weeks. Upon ectopic implantation, incorporation of BG into CPC improved the soft tissue response by improving capsule and interface quality. Additionally, the incorporation of BG into CPC and CPC/PLGA showed 1.8- and 4.7-fold higher degradation and 2.2- and 1.3-fold higher bone formation in a femoral condyle defect in rats compared to pure CPC and CPC/PLGA, respectively. Consequently, these results highlight the potential of BG to be used as an additive to CPC to improve the biological performance for bone regeneration applications. Nevertheless, further confirmation is necessary regarding long-term in vivo studies, which also have to be performed under compromised wound-healing conditions.     

Quantitative analysis of the resorption and osteoconduction process of a calcium phosphate cement and its mechanical effect for screw fixation

The clinical application of calcium phosphate cements (CPCs) composed of tetracalcium phosphate and dicalcium phosphate anhydrous has been limited because of its longer setting time, so that we developed the CPC in which the setting time was shortened to approximately 10 min. Aiming at clinical application, we evaluated the histological response in the bone quantitatively and the biomechanical effectiveness of this substance. The CPC was implanted in the rabbit femoral condyle up to 52 weeks for histological evaluation. In mechanical testing, small cancellous screws were inserted into the condyle, both with and without augmentation with the CPC, and the pull-out strength was measured. The micro-computed tomography finding demonstrated that the cross-sectional area of the implanted CPC at 24 weeks was approximately two-thirds of the initial area. The amount of newly calcified bone around the CPC was significantly greater than that of the sintered hydroxyapatite. Histologically, the new bone was formed on the surface of the implanted CPC 1 week after the implantation and resorption of the CPC was evident at 3 weeks. The pull-out strength was enhanced significantly by augmentation with the CPC and the initial strength was maintained for a 6 week period. This CPC showed good osteoconductivity and was resorbed without adverse inflammation. Using the CPC as augmentation may be capable of useful treatment options in fractures with poor bone quality.     

Effect of local sequential VEGF and BMP-2 delivery on ectopic and orthotopic bone regeneration

Bone regeneration is a coordinated cascade of events regulated by several cytokines and growth factors. Angiogenic growth factors are predominantly expressed during the early phases for re-establishment of the vascularity, whereas osteogenic growth factors are continuously expressed during bone formation and remodeling. Since vascular endothelial growth factor (VEGF) and bone morphogenetic proteins (BMPs) are key regulators of angiogenesis and osteogenesis during bone regeneration, the aim of this study was to investigate if their sequential release could enhance BMP-2-induced bone formation. A composite consisting of poly(lactic-co-glycolic acid) microspheres loaded with BMP-2 embedded in a poly(propylene) scaffold surrounded by a gelatin hydrogel loaded with VEGF was used for the sequential release of the growth factors. Empty composites or composites loaded with VEGF and/or BMP-2 were implanted ectopically and orthotopically in Sprague–Dawley rats (n = 9). Following implantation, the local release profiles were determined by measuring the activity of ¹²⁵I-labeled growth factors using scintillation probes. After 8 weeks blood vessel and bone formation were analyzed using microangiography, μCT and histology. The scaffolds exhibited a large initial burst release of VEGF within the first 3 days and a sustained release of BMP-2 over the full 56-day implantation period. Although VEGF did not induce bone formation, it did increase the formation of the supportive vascular network (p = 0.03) in ectopic implants. In combination with local sustained BMP-2 release, VEGF significantly enhanced ectopic bone formation compared to BMP-2 alone (p = 0.008). In the orthotopic defects, no effect of VEGF on vascularisation was found, nor was bone formation higher by the combination of growth factors, compared to BMP-2 alone. This study demonstrates that a sequential angiogenic and osteogenic growth factor release may be beneficial for the enhancement of bone regeneration.