组织工程化肌腱修复鸡趾屈肌腱缺损的生物力学特性研究

组织工程化肌腱植入体内修复的肌腱其抗拉强度达不到正常肌腱的数值。为探讨这一问题的原因，我们选择罗曼雏鸡足趾屈肌腱细胞与可降解聚羟基乙酸筛网体外复合培养构建组织工程化肌腱。用此工程化肌腱修复20只罗曼鸡第二趾深屈肌腱0．5～0．8cm缺损。术后第2、4、6、8周取材，测定样品中材料的重量、羟脯氨酸含量及抗拉强度等力学特性指标。结果显示，植入2、4、6、8周，支架材料重量下降很快，至第8周基本降解；修复的肌腱中代表胶原合成总量的羟脯氨酸含量随时间增加，但变化不明显；修复的肌腱断裂能量和抗拉强度均随时间呈一先降低后逐渐增大的变化，抗拉强度在第8周才达到正常肌腱的23％。结果提示，植入的组织工程化肌腱在其材料迅速降解的同时，胶原生成量并不多，二者出现明显的不匹配，导致修复的肌腱抗拉强度低。     

组织工程软骨植入缺损后修复区力学特性分析

目的利用组织工程技术建立体外软骨缺损实验模型,研究修复区人工软骨和宿主软骨的力学特性。方法采用一种琼脂糖凝胶作为人工软骨,制作猪软骨深层缺损,在缺损处仿临床植入人工软骨,用生物胶黏接,建立组织工程修复膝关节软骨缺损的体外模型;在压缩载荷作用下,通过数字图像相关技术研究组织工程软骨植入缺损后修复区即刻力学行为。结果压缩过程中界面处没有出现开裂现象,压缩分别为软骨层厚度的3.5%、5.6%、7.04%和9.0%时获得了修复区中间层应变分布图和应变变化曲线。压缩量从3.5%增加到9%时,在垂直软骨面方向上宿主软骨最大压应变增加75.9%,人工软骨最大拉应变增加226.99%;在平行软骨表面方向,交界面处最大拉应变增加116.9%,增加量远高于宿主软骨区和人工软骨区;对于修复区剪应变,随着压缩量增加交界处剪应变方向发生相反的改变。结论软骨组织工程修复缺损效果有很大的不确定性,这与修复区的力学环境有关。组织工程软骨植入缺损后,修复区受到复杂应变状态,随着压缩量增加,界面处、宿主软骨、人工软骨都发生较大的应变变化,界面处垂直软骨面方向的应变由压应变可转化为拉应变,平行软骨表面方向的拉应变有显著增加,交界处剪应变方向甚至发生了相反的改变,而且剪应力数值迅速增加。这种复杂应变状态造成修复区细胞力学环境的较大变化,还可能引起界面的开裂,影响缺损修复过程,这些力学环境变化应受到临床治疗的重视。     

蚕丝组织工程化肌腱的生物力学研究

目的探讨用蚕丝与同种异体肌腱细胞联合培养植入体内,构建组织工程化肌腱的生物力学指标。方法实验分2组,一组是植入附着了肌腱细胞的蚕丝材料组,另一组是单纯植入蚕丝材料组。分别在术后的第2,4,6,8周进行随机取材,在每次取材时每组分别取20只,对材料进行生物力学测定。所得数据均采用SPSS13．0统计软件进行处理和分析。结果在第2,4,6,8周进行取材,生物力学的测定结果显示在同时间点内,细胞组的结果明显优于非细胞组（P≮0．05）,细胞组自身在不同时间点的比较中,发现除第8周以外（P〉O．05）,时间越长,力学的结果越优秀（P〈O．05）;而在非细胞组则只有第8周的结果与前3次测定结果的差异有统计学意义（P〈0．05）。结论本实验的结果说明蚕丝材料对肌腱细胞的黏附性好,生物力学性能优越,附着肌腱细胞后可以构成组织工程化肌腱。经更深入的实验和研究,蚕丝材料可能会在肌腱缺损的治疗方面具有良好的应用前景。     

组织工程化肌腱种子细胞的研究

组织工程化肌腱有望成为临床肌腱缺损修复最为理想的替代物。随着种子细胞功能研究的逐步深入、新型种子细胞的不断发掘以及相关科学技术的进步,制约组织工程化肌腱发展的瓶颈之一“种子细胞”问题逐渐得到解决,组织工程化肌腱的体外构建及体内应用亦随之日趋成熟。着重就肌腱种子细胞的研究进展作一综述。     

玻璃化冷冻保存组织工程肌腱植入大鼠体内的组织学变化

背景：应用玻璃化冷冻方法保存组织工程肌腱具有可行性和应用前景,有待进一步研究。 目的：探讨应用玻璃化冷冻保存组织工程肌腱体内植入对大鼠跟腱缺损修复的影响。 方法：选用成年SD大鼠64只,于大鼠跟腱中段制备5 mm肌腱缺损模型,随机摸球法均分为2组,分别植入玻璃化冷冻保存组织工程肌腱和新鲜非冷冻保存组织工程肌腱。植入后2,4,6,8周,观察植入肌腱材料及周围组织的大体形态和组织学变化。 结果与结论：两组肌腱材料体内植入后的大体形态和组织学反应无明显差异。植入后2,4周,植入的肌腱材料发生降解,材料中间及周围有大量炎性细胞浸润和纤维结缔组织增生。植入后6,8周,大量新生胶原纤维组织长入并替代降解的植入材料,形态和排列方式趋近于正常肌腱组织,大鼠跟腱缺损基本修复。结果表明玻璃化冷冻保存组织工程肌腱体内植入可修复大鼠跟腱缺损。     

修复运动性肌腱损伤组织工程化肌腱及种子细胞和支架材料

背景：获得大规模、具有再生活力的种子细胞以及具有与正常人体肌腱组织相接近的力学性能的理想支架材料是当前组织工程化肌腱研究面临的最为关键的限制性因素。 目的：总结和分析组织工程肌腱研究中的种子细胞和支架材料的研究进展。 方法：查阅近年来肌腱组织工程研究的相关文献,综合国内外最新研究成果,就肌腱组织工程中合适的种子细胞来源、研究更为理想的支架材料及组织相容性等方面的进展进行概述。 结果与结论：肌腱组织工程中常用的种子细胞有间充质干细胞、肌腱干细胞及胚胎干细胞等,可以向骨、软骨和脂肪分化,修复肌腱损伤的理想细胞。肌腱组织工程支架材料有天然材料及人工合成材料等,肌腱组织工程支架材料应有良好的生物相容性和适度的机械性能,复合材料将是肌腱组织工程支架材料研究的重点。 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      

组织工程化肌腱

文章对组织工程肌腱的研究进行系统阐述。对细胞外基质材料如聚乳酸（PEA）、聚羟基乙酸（PGA）及二者共聚物（PLGA）、胶原蛋白、葡胺聚糖、几丁质等和种子细胞如间充质干细胞（MSC）、成纤维细胞、人胚腱细胞等研究进展做了评述，提出体外构建的人工肌腱也必须完成细胞与材料的相互作用才能形成具有活力的肌腱组织。同时综述现在的研究热点是基质材料的智能化、细胞材料复合体的冻存等。     

组织工程化肌腱在肌腱修复过程中的作用

目的：综述肌腱组织工程在肌腱修复过程中的应用进展。 方法：应用计算机检索1993-01/2009-10 PubMed数据库及维普数据库有关肌腱组织工程研究进展、肌腱支架材料生物力学分析、生物材料在肌腱组织工程中应用及组织工程技术在修复肌腱缺损临床应用方面的相关文献,英文检索词为“tendon transplantation,tissue engineering,biologicalmaterial,cell stent”,中文检索词为“肌腱移植,组织工程,生物材料,细胞支架”。检索文献量总计132篇。 结果：目前组织工程化肌腱的研究已经取得了显著的成果,但要真正应用于临床,大批量生产,仍存在一些问题。诸如最适的种子细胞来源、理想的支架材料、最佳的培养条件以及植入体内的检测方法等,在组织工程真正成为一种治疗肌腱缺损和功能重建的选择之前,这些问题都是有待进一步研究和解决的。 结论：要真正实现体外预制有生命的种植体完全替代人体组织、器官功能,尚面临着许多挑战。     

人工肌腱材料与运动性肌腱损伤的修复

背景：运动或疾病导致肌腱损伤,若未予以及时修复常会导致肢体功能障碍,植入人工肌腱后,可形成类似生物腱的组织。 目的：分析运动导致肌腱损伤的原理,以及人工肌腱在运动导致的肌腱损伤的应用价值。 方法：作者检索1990/2010 PubMed数据库及中国知网数据库检索与人工肌腱在运动导致的肌腱损伤的应用的相关研究。 结果与结论：过度运动可导致肌腱断裂损伤,人工肌腱由细胞、生长因子及可降解生物材料构成,在植入人体后,能恢复患者肌腱原有的生物学特性,部分人工肌腱甚至可以增殖和合成胶原。随人工肌腱支架材料的降解,患者体内将逐渐形成在功能和形态上与正常肌腱相似的新生肌腱组织。且随组织工程学的发展,将出现更多应用于运动导致的肌腱损伤、断裂等疾病治疗的新型人工肌腱。     

Mechanical property characterization of electrospun recombinant human tropoelastin for vascular graft biomaterials

The development of vascular grafts has focused on finding a biomaterial that is non-thrombogenic, minimizes intimal hyperplasia, matches the mechanical properties of native vessels and allows for regeneration of arterial tissue. In this study, the structural and mechanical properties and the vascular cell compatibility of electrospun recombinant human tropoelastin (rTE) were evaluated as a potential vascular graft support matrix. Disuccinimidyl suberate (DSS) was used to cross-link electrospun rTE fibers to produce a polymeric recombinant tropoelastin (prTE) matrix that is stable in aqueous environments. Tubular 1 cm diameter prTE samples were constructed for uniaxial tensile testing and 4 mm small-diameter prTE tubular scaffolds were produced for burst pressure and cell compatibility evaluations from 15 wt.% rTE solutions. Uniaxial tensile tests demonstrated an average ultimate tensile strength (UTS) of 0.36 ± 0.05 MPa and elastic moduli of 0.15 ± 0.04 and 0.91 ± 0.16 MPa, which were comparable to extracted native elastin. Burst pressures of 485 ± 25 mm Hg were obtained from 4 mm internal diameter scaffolds with 453 ± 74 μm average wall thickness. prTE supported endothelial cell growth with typical endothelial cell cobblestone morphology after 48 h in culture. Cross-linked electrospun rTE has promising properties for utilization as a vascular graft biomaterial with customizable dimensions, a compliant matrix and vascular cell compatibility.     

人工关节植入物涂层力学性能

目的 对多孔型人工关节植入物的涂层性能(包括涂层形貌和涂层力学性能)进行分析,总结目前主流产品的涂层性能范围,为新产品的设计研发提供参考,同时为远期植入物取出分析提供依据。 方法 试验中所用的涂层表面形貌、剪切强度和拉伸强度样品,分别按照 ASTM F1854、ASTM F1044 和 ASTM F1147 标准制备,涂层采用等离子喷涂技术加工。 共对 17 套件产品(编号 1~ 17 号)的涂层表面形貌(涂层厚度、孔隙率和孔隙截距)进行试验;对编号为 1~ 7 号和 15、16 号产品,首先按照 ASTM F1044 的试验方法,进行涂层与基体之间的剪切强度试验;然后按照 ASTM F1147 的试验方法,进行涂层与基体之间的拉伸强度试验。 对编号为 17 的产品,按照 ASTM F1044 和ASTM F1147 的试验方法,分别测试复合涂层和单纯钛涂层的剪切和拉伸强度。 结果 全部产品中,共 15 套产品(占比 88. 2% )涂层厚度 300~ 500 μm;金属涂层的产品共 16 套(编号 1 ~ 16),其中 11 套(占比 68. 75% )涂层孔隙率 30% ~ 50% ,14 套(占比 87. 5% )涂层孔隙截距 50 ~ 150 μm;涂层的力学性能与基体材质无关;添加羟基磷灰石(HA)后的复合涂层的剪切强度和拉伸强度与纯金属涂层相比,均明显降低。 结论 针对多孔涂层人工关节的设计制造,其涂层的性能可以参考以下指标:涂层厚度 300 ~ 500 μm,涂层孔隙率 30% ~ 50% ,涂层孔隙截距 50 ~150 μm;可以根据产品的用途选择基体材质;在设计含有 HA 的复合涂层的植入物时,应考虑结合力较低对产品性能的影响。 该性能指标范围能够为远期临床取出物分析提供对照。     

膝关节制动对髌韧带力学特性影响的实验研究

探讨膝关节制动对髌韧带力学特性和影响。我们将兔膝关节伸直位制动６周。然后对制动前后髌韧带的本构方程、极限强度、弹性模量、极限载荷等力学性进行研究．结果显示：正常组与制动组间髌韧带的应力－应变关系理论曲线有明显不同,其材料常数亦有显著差异;制动组髌韧带的极限强度张弹性模校正常组均有明显下降,其极限载荷下降不明显。上述结果表明膝关节制动使得髌韧带所受应力下降,为适应这种改变,组织将进行重塑,从而导致其     

Dynamic Mechanical Conditioning of Collagen-Gel Blood Vessel Constructs Induces Remodeling In Vitro

Dynamic mechanical conditioning is investigated as a means of improving the mechanical properties of tissue-engineered blood vessel constructs composed of living cells embedded in a collagen-gel scaffold. This approach attempts to elicit a unique response from the embedded cells so as to reorganize their surrounding matrix, thus improving the overall mechanical stability of the constructs. Mechanical conditioning, in the form of cyclic strain, was applied to the tubular constructs at a frequency of 1 Hz for 4 and 8 days. The response to conditioning thus evinced involved increased contraction and mechanical strength, as compared to statically cultured controls. Significant increases in ultimate stress and material modulus were seen over an 8 day culture period. Accompanying morphological changes showed increased circumferential orientation in response to the cyclic stimulus. We conclude that dynamic mechanical conditioning during tissue culture leads to an improvement in the properties of tissue-engineered blood vessel constructs in terms of mechanical strength and histological organization. This concept, in conjunction with a proper biochemical environment, could present a better model for engineering vascular constructs. © 2000 Biomedical Engineering Society. PAC00: 8719Rr, 8714Ee, 8718-h, 8768+z     

Effect of Strain Magnitude on the Tissue Properties of Engineered Cardiovascular Constructs

Mechanical loading is a powerful regulator of tissue properties in engineered cardiovascular tissues. To ultimately regulate the biochemical processes, it is essential to quantify the effect of mechanical loading on the properties of engineered cardiovascular constructs. In this study the Flexercell FX-4000T (Flexcell Int. Corp., USA) straining system was modified to simultaneously apply various strain magnitudes to individual samples during one experiment. In addition, porous polyglycolic acid (PGA) scaffolds, coated with poly-4-hydroxybutyrate (P4HB), were partially embedded in a silicone layer to allow long-term uniaxial cyclic mechanical straining of cardiovascular engineered constructs. The constructs were subjected to two different strain magnitudes and showed differences in biochemical properties, mechanical properties and organization of the microstructure compared to the unstrained constructs. The results suggest that when the tissues are exposed to prolonged mechanical stimulation, the production of collagen with a higher fraction of crosslinks is induced. However, straining with a large strain magnitude resulted in a negative effect on the mechanical properties of the tissue. In addition, dynamic straining induced a different alignment of cells and collagen in the superficial layers compared to the deeper layers of the construct. The presented model system can be used to systematically optimize culture protocols for engineered cardiovascular tissues.     

Mechanical Analysis of Extra-Articular Knee Ligaments. Part two: Tendon grafts used for knee ligament reconstruction

Objectives

The aim of this study was to provide information about the mechanical properties of grafts used for knee ligament reconstructions and to compare those results with the mechanical properties of native knee ligaments.

Long-Term Cyclic Distention Enhances the Mechanical Properties of Collagen-Based Media-Equivalents

In this study, we sought to identify the key parameters involved in long-term cyclic distension (CD) as they pertain to the development of collagen-based media-equivalents (MEs). By using only highly compacted, cross-linked constructs, we avoided the complicating issues of irrecoverable creep and transient alignment, and isolated the effects of cyclic mechanical loading on ME development. Our system allowed us to study this development over a wide range of parameters including strain amplitude, pulse frequency, pulse shape, and culture time. We found that in most cases involving cyclic distension, MEs were both stronger and stiffer than constructs that were grown under static conditions. The mechanical properties were not significantly different from static controls after two weeks of CD, however, five weeks of CD was sufficient to note significant increases in both stiffness and strength. The strain, stretch time, and relaxation time were all important variables in determining ME mechanical properties. While we were unable to detect a significant net change in the amount of total collagen, we observed significant deposition of insoluble elastin in our CDMEs, something that has never been previously reported using adult smooth muscle cells. Finally, these changes in ME development did not depend on the age of the MEs prior to the initiation of CD. © 2003 Biomedical Engineering Society. PAC2003: 8719Rr, 8768+z, 8719Ff, 8780Rb