富血小板纤维蛋白对兔下颌骨牵引成骨区骨形态发生蛋白-4表达的影响

目的:探讨富血小板纤维蛋白(PRF)对牵引成骨区骨形态发生蛋白-4(BMP-4)表达的影响。方法:25只大耳白兔随机分2组,分别行双侧下颌骨皮质骨切开术,一侧下颌骨牵引间隙放置PRF膜作为实验组,对侧作为对照组,分别于稳定期第3、7、14、21、28天处死一组动物,切取牵引间隙处骨痂行H-E染色和BMP-4免疫组织化学显色,细胞图像分析仪测量牵引间隙处骨痂BMP-4表达情况。结果:下颌牵引延长后牵引间隙均有新骨形成,免疫组织化学显色显示BMP-4主要定位于成骨细胞的细胞质中。实验组在稳定期3、7、14、21 d BMP-4表达的阳性细胞率和阳性面积百分比均显著高于对照组,稳定期28 d BMP-4表达的阳性细胞率和阳性面积百分比与对照组比较差异均无统计学意义。结论:PRF能促进兔下颌骨牵引成骨区新骨的生成,BMP-4可能在牵引成骨过程中调控组织细胞应力信号传递,发挥成骨作用。     

磷酸钙骨水泥复合骨形态发生蛋白6和血管内皮生长因子修复骨缺损

背景：单独将骨形态发生蛋白或血管内皮生长因子植入体内易被血液冲刷掉而不能最大限度发挥诱导成骨和血管生成作用,同时缺少载体的支撑作用。 目的：观察骨形态发生蛋白6、血管内皮生长因子及磷酸钙骨水泥联合应用在骨缺损修复过程中的作用。 方法：制作新西兰兔双侧股骨内侧髁骨缺损模型,左侧分别植入磷酸钙骨水泥/骨形态发生蛋白6/血管内皮生长因子、磷酸钙骨水泥/骨形态发生蛋白6及磷酸钙骨水泥,右侧不植入任何物质作为空白对照。植入8,16周通过硬组织切片组织学观察、电镜扫描等手段观察新骨形成情况。 结果与结论：各组材料的组织相容性良好,未见明显炎症组织反应。植入8周时,磷酸钙骨水泥/骨形态发生蛋白6/血管内皮生长因子组骨水泥-骨组织交界处基本上被新生骨小梁包绕,材料进一步降解,新生骨小梁表面可见大量活跃的成骨细胞;16周时,新生骨小梁继续长入,进一步增长、增粗、增多,有大量新生编织骨成网格状长入材料中,骨水泥材料降解明显,与周围组织结合紧密,降解与骨长入同步,此组不同时间点成骨速度及成骨效果均明显优于其他两组材料(P < 0.05)。表明3种材料联合应用可协同促进骨缺损修复。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：     

骨不连断端及周围组织骨形态发生蛋白2与核心蛋白多糖的表达

背景：骨形态发生蛋白2和核心蛋白多糖两种因子均具有促进成骨的活性,并有相关报道两者在促进成骨方面相互促进。 目的：了解骨不连骨折区不同部位组织骨形态发生蛋白2、核心蛋白多糖的表达情况。 方法：11例骨不连患者,骨折持续时间平均11个月。在手术中分类获取骨折端及其周围的组织,包括骨断端、髓腔内容物和贴骨瘢痕,采用免疫组化染色、Real-time PCR检测不同部位组织中骨形态发生蛋白2、核心蛋白多糖的表达。 结果与结论：贴骨瘢痕组织骨形态发生蛋白2的表达最高,与骨断端和髓腔内容物组织比较,差异有显著性意义(P < 0.05);骨断端组织核心蛋白多糖的表达最高,与髓腔内容物和贴骨瘢痕组织比较,差异有显著性意义(P < 0.05)。结果可见骨不连接区组织的抗纤维化和成骨能力的低下,与骨形态发生蛋白2和核心蛋白多糖不能同时高表达有关,因此骨不连区联合注射促成骨因子骨形态发生蛋白2和核心蛋白多糖不但可以促进骨诱导能力的提高,还有可能增强陈旧瘢痕的转化,从而使骨不连的治疗效果更好。     

转染血管内皮细胞生长因子骨髓间充质干细胞与牛松质骨支架复合组织工程骨的血管形成

背景：小块组织工程骨植入动物体内后,早期依靠组织液的渗透可获得营养,但大块组织工程骨的营养仅靠组织液的渗透是远远不够的,必须通过血管再生来获得。 目的：观察转染血管内皮细胞生长因子表达载体骨髓间充质干细胞复合组织工程骨植入动物体内后的血管形成能力。 方法：制作日本大耳白兔双侧尺骨中段骨缺损模型,左侧尺骨缺损植入转染血管内皮细胞生长因子表达载体的自体骨髓间充质干细胞复合脱钙脱脂去蛋白的牛松质骨支架组织工程骨为实验组,右侧尺骨缺损植入自体骨髓间充质干细胞复合脱钙脱脂去蛋白的牛松质骨支架组织工程骨为对照组。术后12周行X射线摄片观察、大体标本观察、苏木精-伊红染色和Masson染色组织切片观察、MiFas图像分析系统定量分析。 结果与结论：实验组与对照组尺骨缺损处均有连续骨痂形成;组织切片经苏木精-伊红染色、Masson三色法染色及MiFas图像分析系统定量分析可见实验组和对照组均有大量的新生骨,但实验组新生血管明显多于对照组(P < 0.01),且血管较粗大,而且与新生骨接近。说明将转染血管内皮细胞生长因子表达载体的骨髓间充质干细胞复合在组织工程骨上植入动物体内可明显促进新生血管的形成。     

骨碎补总黄酮调控H型血管影响大鼠股骨Masquelet诱导膜模型的骨重建

背景:多项研究发现,骨碎补总黄酮可促进诱导膜中血管新生、改善诱导膜生物性能、加速诱导膜技术骨重建,但相关分子机制仍需进一步探究。目的:观察骨碎补总黄酮通过调控H型血管对大鼠股骨Masquelet诱导膜模型骨重建的影响。方法:将36只雄性SD大鼠按体质量分层后随机分为空白组、模型组、中药组,每组12只,3组均建立4 mm右后肢股骨骨缺损模型,模型组与中药组骨缺损处充填聚甲基丙烯酸甲酯骨水泥;造模后6周,空白组骨缺损处填充大鼠自体尾骨,模型组与中药组取出诱导膜内的骨水泥后植入大鼠自体尾骨。植骨第3天开始,中药组灌胃给予骨碎补总黄酮157.5 mg/(kg·d),其余两组灌胃给予生理盐水,连续给药至植骨后8周。植骨后8周取材进行相关检测。结果与结论:①X射线片显示,空白组缺损区骨折线清晰,仅有少量骨痂形成;模型组缺损区可见不连续皮质骨,骨缺损区仍存在;中药组缺损区充满新生骨组织,骨髓腔与部分皮质骨形成,骨折线消失。②Micro-CT扫描显示,空白组缺损区新生骨量较少,模型组缺损区骨小梁数量明显增多,中药组大量新生骨组织填充于骨缺损区。③苏木精-伊红染色显示,空白组缺损区仅见少量新骨形成,成骨质量较差;模型组缺损区有较多的新骨形成,但骨组织内夹杂有部分纤维结缔组织;中药组缺损区可见大量新骨形成,成骨质量最佳。④CD31/Emcn免疫荧光双标染色显示,空白组骨缺损区新生骨组织内H型血管数量稀少、分布稀疏;相比空白组,模型组骨缺损区骨组织内含更多H型血管,血管呈相对规则的条状分布;中药组骨缺损区H型血管数量最多,并且血管分布密集。⑤结果表明,骨碎补总黄酮可通过上调H型血管表达增强成血管-成骨作用,提高大鼠股骨Masquelet诱导膜模型成骨效能、促进骨重建。     

过表达BMP-4基因的BMSCs复合生物陶瓷骨在同种异体骨缺损模型中的研究

目的 研究骨形态发生蛋白BMP-4转染骨髓间充质干细胞后与生物陶瓷骨形成复合材料对兔桡骨缺损的修复作用和机制。方法 离体分离培养鉴定兔BMSCs,构建过表达BMP-4基因的慢病毒载体并转染BMSCs细胞,并通过流式细胞术和Western blot鉴定;制备复合生物陶瓷骨,ALP试剂盒检测桡骨组织ALP活性;HE染色观察桡骨组织形态变化;依据Lane-Sandhu法评价受体兔挠骨改善情况;采用免疫荧光检测桡骨组织Col I、OC和OPN表达;Western blot检测桡骨骨膜VEGF和EGF水平。结果 成功分离兔BMSCs细胞,并获得BMP-4基因过表达的BMSCs细胞。BMP-4过表达的BMSCs复合生物陶瓷骨能够显著修复缺损的兔桡骨组织形态,提高组织的Lane-Sandhu评分,并上调挠骨的I型胶原、骨钙素和骨桥素的表达水平和骨膜中血管内皮生长因子（VEGF）和表皮生长因子（EGF）的表达。结论 BMP-4转染BMSCs与生物陶瓷骨复合材料能显著修复兔骨缺损,并增加骨膜组织中VEGF和EGF的表达。     

2型糖尿病大鼠骨痂内Osx、Dlx5表达变化与骨折愈合

背景：研究表明Osx、Dlx5等基因的表达水平与骨折愈合障碍可能存在一定关系。目的：分析2型糖尿病大鼠牵引骨痂中Osx、Dlx5表达变化与骨折愈合障碍的关系。方法：选择8周龄SD大鼠32只,随机分为2组,实验组(18只)高糖高脂饲料喂养8周,链脲佐菌素腹腔注射制作2型糖尿病大鼠模型;对照组喂普通大鼠饲料予以同样剂量柠檬酸腹腔注射。2组大鼠同时建立骨折牵引模型,定期延长外固定架,牵引模型建立后15 d处死大鼠并收集血液标本检测生化指标,X射线观察骨痂生长情况,取左胫骨骨痂组织进行组织学观察,检测骨痂组织中Dlx5、Osx蛋白及相关基因的表达。结果与结论：X射线摄片结果：实验组牵引骨痂较对照组明显减少,骨痂组织苏木精-伊红染色显示：实验组较对照组的微骨柱明显减少;初始基质前沿浅染。而骨痂的组织学定量分析则显示：实验组新生骨痂的形成面积较对照组减少而骨折近端脂肪细胞数量增多(P < 0.01)。QPCR检测则显示：实验组较对照组骨痂组织中Osx表达降低(P < 0.05),Dlx5表达降低(P < 0.05)。结果提示,2型糖尿病大鼠骨折愈合较正常大鼠明显减慢,可能与2型糖尿病Osx、Dlx5表达降低具有相关性。 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;组织工程全文链接：     

骨形态发生蛋白2和血管内皮生长因子mRNA在股骨骨不连大鼠损伤区域的动态表达

背景:骨形态发生蛋白2和血管内皮生长因子可以促进新骨的形成,提高骨不连的治愈率。目的:观察大鼠股骨骨不连修复过程中骨缺损区骨形态发生蛋白2与血管内皮生长因子mRNA的表达情况。方法:SD大鼠股骨左建立骨不连模型后,随机分为7组,分别于造模后1,3,7,14,21,28,35d,处死取材。大鼠右股骨不做缺损直接缝合伤口,作为对照。RT-PCR技术检测大鼠股骨骨形态发生蛋白2和血管内皮生长因子mRNA的表达。结果与结论:大鼠股骨骨不连损伤后,损伤周围区骨形态发生蛋白2与血管内皮生长因子mRNA表达上升,至7d时达到顶峰,而后随时间的延长而下降;而在损伤中心区骨形态发生蛋白2与血管内皮生长因子mRNA表达延迟,且表达量低于损伤周围区。提示大鼠股骨骨不连缺损中心区域在修复早期骨形态发生蛋白2与血管内皮生长因子mRNA的低表达及时间滞后可能是其骨不连发生的重要原因,在相应的时期补充外源性骨形态发生蛋白2与血管内皮生长因子可能助于骨不连的修复愈合。     

亲骨荧光素间接标记软骨内成骨的早期血管新生北大核心

背景:虽然当前有多种方法可以观察和检测软骨内成骨早期血管新生,但是均存在一定的不足。目的:探讨四环素和茜素络合酮间接标记软骨内成骨过程中新生血管的可能性。方法:制备新西兰兔双侧桡骨骨缺损模型并植入β-磷酸三钙材料,分别于术后第1天和第15天注射四环素和茜素络合酮,第28天取材。部分标本在墨汁灌注后行硬组织切片荧光/光学显微镜观察,部分标本经脱钙后行免疫组化染色观察,比较软骨内成骨过程中亲骨荧光素标记管腔结构与免疫组化、墨汁灌注标记血管结构的一致性。结果与结论:(1)亲骨荧光素标记的管腔结构经免疫组化染色证实为CD34阳性的血管结构;(2)在荧光显微镜下,亲骨荧光素标记的血管形态与墨汁灌注的血管形态一致;荧光素标记后经墨汁灌注的血管在荧光显微镜下可见荧光管腔中有黑色墨汁走行;(3)此外,亲骨荧光素标记的管腔结构颜色绚丽、三维结构更加生动,可通过不同颜色的荧光显示不同时期的血管新生和演变过程,具有独特的优势,可用于软骨内成骨早期血管发生的形态学检测。     

骨形成蛋白信号分子在小鼠椎间盘发育中的表达

目的:探索促进成骨相关的骨形成蛋白(BMP)-2、-4、-6、-7、-9以及抑制成骨作用的BMP-3在小鼠不同年龄段椎间盘中表达情况,为椎间盘发育过程中BMP信号途径的研究奠定重要基础.方法:解剖获取出生后1d、3d、1周、1个月、3个月、6个月龄小鼠的椎间盘及胸腰椎脊柱.RT-PCR检测BMP-2、-3、-4、-6、-7、-9在生后不同年龄段小鼠椎间盘的表达情况,免疫印迹及免疫组织化学验证在RT-PCR中有明显表达差异的BMP-3、-6.结果:RT-PCR结果显示BMP-2、-7、-9的表达在小鼠椎间盘组织中有一定的基础表达,但随着年龄增大没有明显的变化趋势,而BMP-3和BMP-6的表达整体呈现出下降的趋势,BMP-4在椎间盘中无表达,免疫印迹及免疫组织化学结果也证实BMP-3和BMP-6随着小鼠椎间盘的发育表达降低.结论:正常小鼠脊柱,随着年龄的增加,椎间盘中BMP-2、-7、-9的表达无明显变化趋势,各年龄段都维持着一定量的表达,BMP-3和BMP-6的表达整体呈现出下降的趋势,具有明显成骨作用的BMP-4则没有表达.     

Papillary thyroid carcinoma with bone formation

Bone formation is a rarely encountered finding during histological examination of papillary thyroid carcinoma (PTC). This study aimed to analyze clinicopathological parameters in patients with PTC showing bone formation, to document histological features of bone formation in PTC, and to investigate osteogenic proteins. Bone morphogenic protein (BMP)-9 is known as the most potent osteoinductive protein of the BMP subtypes. Recent research suggests that the activin receptor-like kinase (ALK) 1 is an essential cellular receptor that mediates BMP-9-induced osteogenic signaling. A retrospective review of tumor sections from 567 patients with a diagnosis of PTC was performed. Using immunohistochemistry and quantitative real-time polymerase chain reaction, we investigated the expression of ALK1 and BMP-9 in normal thyroid tissue and PTC samples with and without bone formation. Bone formation was found in 13% of patients with PTC. A significant association was seen between bone formation and old age. BMP-9 expression in tumors was increased compared to that in normal thyroid tissues. BMP-9 expression in tumors with bone formation was not significantly different from that in tumors without bone formation. ALK1 expression in tumors with bone formation was increased compared to that in normal thyroid tissue and tumors without bone formation. Our study suggests that upregulation of ALK1 might be an underlying molecular mechanism that explains osteogenesis in PTC.     

Human endothelial colony forming cells undergo vasculogenesis within biphasic calcium phosphate bone tissue engineering constructs

An important consideration in bone regeneration is the need for expedited neovascularization within the defect site. Formation of a vascular network is critical for cell viability and normal function leading to tissue regeneration, but spontaneous angiogenesis is too slow to yield sufficient vessel formation. In this pilot study, human umbilical cord blood (hUCB)-derived endothelial colony forming cells (ECFCs) were evaluated for in vivo vasculogenesis in the macropores of biphasic calcium phosphate (BCP)/bone morphogenetic protein-2 (BMP-2) bone tissue engineering constructs. Constructs were implanted on the abdominal wall of NOD/SCID mice for 4 weeks. This study demonstrated in vivo vasculogenesis by human ECFCs within the macropore space of BCP/BMP-2 constructs. The human ECFC-derived vessels anastomosed with the host vasculature and perfused vessels were visible in the very center of the 5mm diameter, 2.5mm tall scaffolds. Additionally, the vessels were evenly distributed throughout the construct. This study suggests that scaffolds containing ECFCs have significant potential for expedited neovascularization in bony defects.     

鼠神经生长因子治疗胫骨骨不连效果的实验研究

目的　研究鼠神经生长因子（NGF）对白兔胫骨骨不连的治疗效果,为NGF在骨不连的临床运用提供实验基础。 方法　选择健康成年雄性新西兰大白兔40只,随机各选20只分为实验组和对照组,分别于右胫骨粗隆下3~5 cm处造成横行骨折骨不连模型,实验组在骨折处每周注射NGF一次,连续12周;对照组在骨折处每周注射生理盐水一次,连续12周。试验期间两组均同时接受X线和组织学检查以观察骨痂生长和骨折愈合情况。 结果　实验组动物骨痂出现时间为（2.0±0.5）周,骨折线模糊时间为（8.2±1.2）周,骨折愈合时间为（12±1.7）周;对照组骨痂出现时间为8周以上,未出现骨折线模糊和骨折愈合。实验组骨折愈合情况远好于对照组,差异具有统计学意义（P<0.05）。 结论　NGF有较强的促进骨不连骨痂生长和愈合作用,NGF在骨不连的临床治疗中有良好的运用前景。     

Bone morphogenetic protein receptors and activin receptors are highly expressed in ossified ligament tissues of patients with ossification of the posterior longitudinal ligament.

Ossification of the posterior longitudinal ligament (OPLL) is a pathological ossification in the spinal ligament, with formation of ectopic bone mainly through endochondral ossification. Bone morphogenetic proteins (BMPs) and activins are multifunctional proteins that belong to the transforming growth factor-beta superfamily and that have been implicated in the formation of new bone and cartilage. BMPs and activins signal via type I and type II receptors for BMPs (BMPRs) and activins (ActRs), respectively. OP-1/BMP-7 binds to BMPR-II and ActR-II and forms complexes with BMPR-IA and -IB and ActR-I. We studied the expression of BMPR-IA, -IB, and -II, ActR-I, ActR-II, and OP-1/BMP-7 by immunohistochemistry in ossified ligament tissues of patients with OPLL and control ligament tissues from patients with cervical disc herniation. The expression of BMPRs and ActRs was elevated in OPLL compared with controls. Expressions of BMPR-IA, -IB, and -II were observed not only in chondrocytes at the fibrocartilage tissue around the calcified zone but also in fibroblast-like spindle cells at the nonossified ligament. ActR-I and -II were found co-localized in the hypertrophic chondrocytes near the calcified zone and in the ossified tissue. OP-1/BMP-7 was expressed in chondrocytes near the calcified zone. In the control cases, the BMPRs and ActRs were only weakly expressed in the fibrocartilage tissue at the site of ligament attachments to bone and OP-1/BMP-7 was not detected. Enhanced expression of BMPRs at the nonossified ligament in OPLL patients suggests that these cells have a greater potential to differentiate into osteogenic cells than ligament cells from non-OPLL patients. The high expression of BMPRs and ActRs in the ectopic ossified ligament suggests that BMPs and activin may be tightly involved in the pathological ossification process of OPLL.     

The effect on bone regeneration of a liposomal vector to deliver BMP-2 gene to bone grafts in peri-implant bone defects

Successful bone-implant osseointegration in large peri-implant bone defects is often difficult, even through autologous bone grafting. Recently, cell-mediated regional gene therapy was introduced to deliver potent morphogens or growth factors in regenerative medicine. We applied liposomal vectors carrying bone morphogenetic protein (BMP)-2 cDNA directly into freshly created peri-implant bone defects on pig calvariae, with or without autologous bone graft. The BMP-2 gene was efficiently introduced into immigrating cells and trabecular cells lining the marginal bone surrounding the bony defect. After 1 week, abundant BMP-2 protein was detected throughout the peri-implant bone defect by immunohistochemistry. At 4 weeks, BMP-producing cells were still present in the defect and peri-implant area, which significantly enhanced new bone formation, compared with the control groups. Interestingly within a week of BMP-2 gene delivery with bone grafts, most osteoblastic cells lining the grafted bone chips also produced BMP-2. Particulated bone was immediately reorganized into newly formed trabecular bone. Grafted bone without BMP-2 gene delivery was still scattered and new bone matrix formation was not detected until 4 weeks after bone grafting. In conclusion, direct application of the BMP-2 gene using a liposomal vector enhanced bone regeneration in a bony defect and gene delivery combined with bone graft could induce a rapid osseointegration of the bone-implant interface at earlier stage.     

The use of injectable sonication-induced silk hydrogel for VEGF(165) and BMP-2 delivery for elevation of the maxillary sinus floor

Sonication-induced silk hydrogels were previously prepared as an injectable bone replacement biomaterial, with a need to improve osteogenic features. Vascular endothelial growth factor (VEGF(165)) and bone morphogenic protein-2 (BMP-2) are key regulators of angiogenesis and osteogenesis, respectively, during bone regeneration. Therefore, the present study aimed at evaluating in situ forming silk hydrogels as a vehicle to encapsulate dual factors for rabbit maxillary sinus floor augmentation. Sonication-induced silk hydrogels were prepared in?vitro and the slow release of VEGF(165) and BMP-2 from these silk gels was evaluated by ELISA. For in?vivo studies for each time point (4 and 12 weeks), 24 sinus floors elevation surgeries were made bilaterally in 12 rabbits for the following four treatment groups: silk gel (group Silk gel), silk gel/VEGF(165) (group VEGF), silk gel/BMP-2 (group BMP-2), silk gel/VEGF(165)/BMP-2 (group V?+?B) (n?=?6 per group). Sequential florescent labeling and radiographic observations were used to record new bone formation and mineralization, along with histological and histomorphometric analysis. At week 4, VEGF(165) promoted more tissue infiltration into the gel and accelerated the degradation of the gel material. At this time point, the bone area in group V?+?B was significantly larger than those in the other three groups. At week 12, elevated sinus floor heights of groups BMP-2 and V?+?B were larger than those of the Silk gel and VEGF groups, and the V?+?B group had the largest new bone area among all groups. In addition, a larger blood vessel area formed in the remaining gel areas in groups VEGF and V?+?B. In conclusion, VEGF(165) and BMP-2 released from injectable and biodegradable silk gels promoted angiogenesis and new bone formation, with the two factors demonstrating an additive effect on bone regeneration. These results indicate that silk hydrogels can be used as an injectable vehicle to deliver multiple growth factors in a minimally invasive approach to regenerate irregular bony cavities.     

The role of recombinant human bone morphogenetic protein-2 in PLGA capsules at an extraskeletal site of the rat.

Bone morphogenetic protein-2 (BMP-2) is a member of the transforming growth factor-beta (TGF-beta) superfamily and has strong bone-inductive activity in vivo. To examine the role of BMP-2 in an extraskeletal site of rat using a controlled release system of peptides, we encapsulated the recombinant human BMP-2 (rhBMP-2) with poly(DL-lactide-co-glycolide) (PLGA) and implanted the rhBMP-2/PLGA capsules in the subcutaneous area of rats. Upon histochemical examination, it was found that bone-inducing cells having alkaline phosphatase (ALP) activity appeared around the capsules by the suitably released rhBMP-2. In addition, the temporal histological examination showed that direct bone formation without cartilage occurred in the process of this ectopic bone induction. These data indicate that the role of rhBMP-2 in the extraskeletal site of rats is to induce the differentiation of mesenchymal cells into the osteoblasts.Copyright 1999 John Wiley & Sons, Inc.     

Dual growth factor delivery from bilayered,biodegradable hydrogel composites for spatially-guided osteochondral tissue repair

The present work investigated the use of biodegradable hydrogel composite scaffolds, based on the macromer oligo(poly(ethylene glycol) fumarate) (OPF), to deliver growth factors for the repair of osteochondral tissue in a rabbit model. In particular, bilayered OPF composites were used to mimic the structural layers of the osteochondral unit, and insulin-like growth factor-1 (IGF-1) and bone morphogenetic protein-2 (BMP-2) were loaded into gelatin microparticles and embedded within the OPF hydrogel matrix in a spatially controlled manner. Three different scaffold formulations were implanted in a medial femoral condyle osteochondral defect: 1) IGF-1 in the chondral layer, 2) BMP-2 in the subchondral layer, and 3) IGF-1 and BMP-2 in their respective separate layers. The quantity and quality of osteochondral repair was evaluated at 6 and 12 weeks with histological scoring and micro-computed tomography (micro-CT). While histological scoring results at 6 weeks showed no differences between experimental groups, micro-CT analysis revealed that the delivery of BMP-2 alone increased the number of bony trabecular islets formed, an indication of early bone formation, over that of IGF-1 delivery alone. At 12 weeks post-implantation, minimal differences were detected between the three groups for cartilage repair. However, the dual delivery of IGF-1 and BMP-2 had a higher proportion of subchondral bone repair, greater bone growth at the defect margins, and lower bone specific surface than the single delivery of IGF-1. These results suggest that the delivery of BMP-2 enhances subchondral bone formation and that, while the dual delivery of IGF-1 and BMP-2 in separate layers does not improve cartilage repair under the conditions studied, they may synergistically enhance the degree of subchondral bone formation. Overall, bilayered OPF hydrogel composites demonstrate potential as spatially-guided, multiple growth factor release vehicles for osteochondral tissue repair.     

Enhanced healing of rat calvarial defects with sulfated chitosan-coated calcium-deficient hydroxyapatite/bone morphogenetic protein 2 scaffolds

Calcium phosphate cements (CPCs), which are widely used in bone regeneration, possess good biocompatibility and osteoconductivity and have been demonstrated to be candidate carriers for bone growth factors. However, limited release of growth factors from CPCs and slow degradation of the materials are not desirable for certain clinical applications. Previous studies have shown that calcium-deficient hydroxyapatite (CDHA) from CPCs presents more rapid degradation rate than CPCs. In this study, a hybrid growth factor delivery system was prepared by using bone morphogenetic protein 2 (BMP-2) loaded CDHA porous scaffold with sulfated chitosan (SCS) coating for improved release profile. We tested the BMP-2 release characteristic of CDHA/BMP-2/SCS composite in vitro and its ability to repair rat calvarial bone defects. A higher percentage of BMP-2 was released when sulfated chitosan coating was present compared with CDHA/BMP-2 group. Eight weeks postoperation, the repaired crania were evaluated by microcomputed tomography, sequential fluorescent labeling, histological analysis, and immunohistochemistry. CDHA/BMP-2/SCS group promoted the most extensive new bone formation than CDHA/BMP-2 and CDHA groups. Our observations suggest that sulfated chitosan coating could enhance the release profile of CDHA/BMP-2 composite in vitro and promote new bone formation in vivo. The hybrid CDHA/BMP-2/SCS system is a promising growth factor delivery strategy for bone regeneration.     

Controlled release by biodegradable hydrogels enhances the ectopic bone formation of bone morphogenetic protein

The objective of this study is to develop a carrier for the controlled release of bone morphogenetic protein-2 (BMP-2) suitable for enhancement of the bone regeneration activity. Hydrogels with different water contents were prepared through glutaraldehyde crosslinking of gelatin with an isoelectric point of 9.0 under varied reaction conditions. Following subcutaneous implantation of the gelatin hydrogels incorporating 125I-labeled BMP-2 into the back of mice, the in vivo retention period of BMP-2 prolonged with a decrease in the water content of hydrogels used, although every time period was much longer than that of BMP-2 solution injection. Ectopic bone formation studies demonstrated that the alkaline phosphatase (ALP) activity and osteocalcin content around the implanted site of BMP-2-incorporated gelatin hydrogels were significantly high compared with those around the injected site of BMP-2 solution. The values became maximum for the gelatin hydrogel incorporating BMP-2 with a middle period of BMP-2 retention, while bone formation was histologically observed around the hydrogel incorporating BMP-2. The ALP activity was significantly higher than that of the collagen sponge incorporating BMP-2. We concluded that the controlled release technology of BMP-2 for a certain time period was essential to induce the potential activity for bone formation.