关节软骨缺损修复区应力状态分析

本文基于横观各向同性理论建立关节软骨固液耦合双相三维缺损及修复的有限元模型。本文通过研究邻近修复界面的宿主软骨的应力状态判别其变形类型,探讨致软骨修复界面开裂的原因。研究表明,表层缺损修复时,邻近修复界面的宿主软骨表面节点发生压缩变形;中间层、深层或全层缺损修复时,节点发生拉伸变形,此时软骨径向尺寸增加,修复界面易开裂。若采用全层缺损修复,组织工程化软骨(TEC)的弹性模量较低(0.1 MPa、0.3 MPa)时,邻近修复界面的宿主软骨表层和中间层主要发生拉伸变形;TEC的弹性模量较高(0.6 MPa、0.9 MPa)时,宿主软骨各层均发生压缩变形。因此,全层缺损修复时,可适当增大TEC的弹性模量。本文为评估软骨组织工程修复效果提供了新的思路,或对临床有一定的指导意义。     

组织工程修复关节软骨缺损的力学状态研究

背景：力学状态对软骨的正常生理有重要影响,若应力集中过大将造成人工软骨退变和原宿主软骨退化,影响治疗效果。目前的各种力学手段很难实现活体软骨力学状态测量,而有限元动态分析能有效地模拟修补后软骨的受力情况。 目的：通过有限元仿真研究组织工程修复膝关节软骨缺损后人工软骨和宿主软骨的力学状态。 方法：以人体膝关节软骨受滚压部分为研究对象,建立滚动运动下关节软骨的有限元模型。根据行走过程中股骨与胫骨间的滚压边界条件,对软骨在取不同弹性模量、不同压缩量、不同载荷速度及不同缺损大小的情况进行了滚压受力分析。 结果与结论：在滚压载荷下,植入人工软骨弹性模量和软骨压缩量的不同都使人工软骨和宿主软骨受到的Mises应力值变化,二者对修复缺损处软骨Mises应力分布的影响比较明显,是临床治疗软骨缺损和术后康复阶段值得注意的因素。模拟中使用的载荷速度和缺损大小对软骨应力值的影响不明显。当人工软骨弹性模量取某个值时,人工软骨和宿主软骨的Mises应力差别可以达到很小值,二者趋于吻合。应力差别还和个体宿主软骨的力学性能有关,据此,应针对不同病例选择最佳弹性模量的人工软骨植入。     

软骨缺损形状对组织工程修复区的力学影响

目的通过有限元仿真探究组织工程修复软骨缺损后缺损形状对修复区力学状态的影响。方法运用Abaous6.10软件建立软骨纤维增强的多孔黏弹性模型,包括软骨的两相结构、不同层区胶原纤维的作用、方向及渗透率的特征。在压缩载荷下分析缺损截面形状(矩形、梯形、圆弧形)和缺损深度(浅表层、中间层、深层、全层)对软骨修复区应力的影响。结果对于中间层缺损,矩形截面修复界面处的Mises应力最小,梯形次之,圆弧形最大。对于不同缺损深度,当弹性模量0.3 MPa时浅表层修复界面处应力最大,其他缺损深度的应力相差不大;当0.4 MPa时,应力由小到大依次为浅表层、中间层、全层、深层缺损;而在此之间时应力与泊松比大小有关。结论软骨缺损截面形状和深度对修复区应力都有影响,临床上可制作矩形缺损截面和不同的缺损深度,并选择合适的弹性模量和泊松比的软骨植入达到较好的修复效果。     

不同弹性模量人工软骨对缺损软骨修复区细胞力学环境影响的研究

应用有限元软件COMSOL建立关节软骨固液双相模型和细胞微观模型,跨尺度研究在生理载荷作用下不同弹性模量的人工软骨修复缺损时,宿主软骨各层细胞的力学环境和液相流场。模拟结果表明,均一弹性模量的人工软骨对不同层区细胞微环境的影响规律不同。随着人工软骨弹性模量增大,浅表层、中间层细胞应力增大,深层细胞应力减小。人工软骨植入改变了中间层、底层软骨的流场方向和营养供给方式,可能会造成软骨细胞营养供应障碍。上述影响可造成修复结果不确定。通过对跨尺度软骨细胞有限元模型进行仿真分析,可定量地评价宿主软骨各层细胞的力学环境,有助于更准确地评估软骨缺损修复的临床效果。     

早期体内力学刺激促进藻酸钙复合自体软骨细胞修复羊关节负重区软骨缺损的实验研究

目的观察膝关节持续被动活动仪(CPM)体内力学刺激对组织工程软骨修复大动物关节负重区软骨缺损效果的影响。方法研究、设计和制造能够适用于体内力学刺激羊膝关节软骨缺损修复的膝关节连续被动活动仪(CPM);将实验动物(山羊膝关节双髁负重区制造直径6 mm软骨缺损)分为三组:空白组:单纯缺损未植入修复组织;藻酸钙+骨膜+细胞组:藻酸钙复合自体软骨细胞凝胶植入软骨缺损区,自体骨膜覆盖缺损区;藻酸钙+骨膜+细胞+CPM组:藻酸钙复合自体软骨细胞凝胶植入软骨缺损区,自体骨膜覆盖缺损区,术后早期接受CPM锻炼。分别于术后3个月、6个月、12个月(12个月组仅包括CPM力学刺激组)取材,通过修复组织的大体、组织学观察及其评分比较3组软骨修复效果。结果藻酸钙复合软骨细胞能够较好地修复羊负重区关节面软骨缺损,将缺损修复的大体观察、组织学等结果进行单因素统计学分析,发现接受体内CPM力学刺激组效果最好,其修复组织中透明软骨比例最多,其次为藻酸钙+骨膜+细胞组。结论膝关节持续被动活动仪(CPM)体内力学刺激能够促进组织工程软骨修复大动物关节负重区软骨缺损的效果。     

滑动载荷作用下关节软骨不同层区的法向位移

目的 获得滑动载荷作用下关节软骨不同层区的法向位移分布,探讨压缩应变、滑动速率和滑动次数对不同软骨深度法向位移的影响。方法 以新鲜猪关节软骨为研究对象,采用非接触式数字图像相关技术,对滑动载荷作用下软骨不同层区的法向位移分布进行研究。 结果 滑动载荷作用下,关节软骨表层的法向位移最大,深层的法向位移最小,中间层的位移介于二者之间;随着压缩应变的增大,沿软骨厚度方向的法向位移都增大,并且表层的法向位移增加幅度最大。滑动速率越大,软骨沿厚度方向的法向位移越小。在不同的滑动次数下,法向位移随滑动时间的进行都呈上升趋势;随着滑动次数的增加,不同滑动时间时的法向位移都增大,并且发现从第1次到第2次滑动时法向位移增大最明显。结论 滑动载荷作用下,软骨不同层区的法向变形有差异,不同层区的法向位移随着压缩应变、滑动速率和滑动次数的变化而变化。本研究可以为临床软骨疾病治疗和软骨缺损修复等方面提供依据,同时对人工软骨结构组成、人工构建、力学功能评价有重要意义。     

脱钙骨基质与骨髓间充质干细胞共培养关节腔内的成软骨活性

背景：将骨髓间充质干细胞附着到支架材料上再植入关节软骨缺损处,细胞不但不消失,而且可形成新的软骨。 目的：观察同种异体脱钙骨基质与骨髓间充质干细胞共培养在关节内的成软骨活性。 方法：在54只青紫蓝兔单侧膝关节制作关节软骨全层缺损模型,随机分组：实验组在缺损处植入自体骨髓间充质干细胞与同种异体脱钙骨基质复合物,对照组缺损处仅植入同种异体脱钙骨基质,空白对照组未植入任何物质。 结果与结论：植入后12周,实验组缺损处修复组织呈软骨样,表面光滑平坦,与周围软骨整合的软骨细胞更为成熟,修复组织与软骨下骨结合牢固;修复组织的细胞为透明软骨样细胞,柱状排列,Ⅱ型胶原染色阳性,与周围软骨及软骨下骨整合良好,且实验组组织学评分优于对照组和空白对照组 (P < 0.01)。对照组缺损处修复组织呈纤维样,与周围软骨未结合,空白对照组缺损区无修复组织,两组均无Ⅱ型胶原染色阳性表达。表明同种异体脱钙骨基质与骨髓间充质干细胞共培养后植入膝关节可形成软骨样组织,有效修复关节软骨缺损。     

不同来源蚕丝蛋白修复骨软骨组织缺损的效果比较

背景：目前还没有研究比较不同种属来源蚕丝蛋白修复骨软骨的效果。 目的：观察桑蚕和柞蚕来源蚕丝蛋白支架材料修复骨软骨缺损的效果差异。 方法：取新西兰兔20只,制备单侧膝关节骨软骨缺损模型,随机分为5组：其中1组不植入任何材料,作为空白对照;实验1组将3层桑蚕丝蛋白支架粘在一起,充填于缺损处;实验2组将1个包被转化生长因子β3的桑蚕丝蛋白支架与2个包被骨形态发生蛋白2的桑蚕丝蛋白支架粘在一起,充填于缺损处;实验3组将3层柞蚕丝蛋白支架粘在一起,充填于缺损处;实验4组将1个包被转化生长因子β3的柞蚕丝蛋白支架与2个包被骨形态发生蛋白2的柞蚕丝蛋白支架粘在一起,充填于缺损处。术后8周,取关节骨软骨修复区行组织病理学观察,检测Ⅰ型和Ⅱ型胶原蛋白表达。 结果与结论：实验1组胶原蛋白广泛分布于缺损区全层;实验2组胶原纤维在修复区表面呈平行分布,在中间和底部呈垂直顶部的方向分布;实验3组在修复区表面可见胶原;实验4组在支架表面和底部可见软骨样细胞有成团分布。4个实验组修复区Ⅰ型胶原蛋白呈强阳性表达;实验1组、实验2组修复区Ⅱ型胶原蛋白呈微弱表达,实验3组、实验4组修复区Ⅱ型胶原蛋白呈强阳性表达。表明两种蚕丝蛋白均能修复骨软骨缺损,桑蚕丝蛋白倾向于形成骨组织,柞蚕丝蛋白倾向于形成软骨组织。 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      

缺损关节软骨在循环压缩载荷下棘轮行为的实验研究

目的研究缺损软骨在循环压缩载荷下的棘轮应变行为,探索缺损关节软骨的损伤演化规律。方法取新鲜的成年猪股骨远端关节软骨,对不同缺损深度软骨试样进行不同参数的三角波循环加载。结合非接触式数字图像技术,获得软骨不同层区的棘轮应变。结果随循环加载圈数的增加,软骨各层棘轮应变均表现为先急剧增大,然后缓慢增加并趋于平稳,由浅层到深层棘轮应变逐渐减小。各层区对循环圈数响应不同,浅层在50圈内应变增加较快,中层在100圈内应变增加较快,深层在75圈内应变增加较快。除了中层区域响应有滞后性,浅层、深层的棘轮应变与应力幅值、缺损深度呈正相关,与加载速率呈负相关。结论软骨的棘轮行为受软骨的特殊结构的影响,缺损使软骨各层区的应变增大,易造成损伤加剧。实验结果为组织工程软骨的构建提供参考依据。     

聚羟基烷酸酯聚合物负载软骨细胞修复同种异体喉软骨缺损

背景：软骨组织工程基础研究相当深入,但在耳鼻咽喉科实际应用研究颇少,探索组织工程技术简便实用的喉软骨修复方法是值得研究的课题。 目的：比较多孔海绵状聚羟基丁酸酯与聚羟基己酸酯共聚物生物材料负载软骨细胞体外培养形成的初期组织工程软骨组织与体内植入一定时期形成的较成熟组织工程软骨组织修复同种异体甲状软骨缺损的效果。 方法：收集体外培养第3代乳兔(3 d龄)软骨细胞,以多孔海绵状聚羟基丁酸酯与聚羟基己酸酯共聚物生物材料为细胞外基质,采用组织工程技术制备细胞-材料复合物,共同体外培养形成初级组织工程软骨组织后直接应用于成兔甲状软骨缺损的修复(实验组A,n=5)或将初级组织工程软骨组织体内植入一定时期形成较成熟组织工程软骨再应用于甲状软骨缺损的修复(实验组B,n=5)。设单纯聚羟基丁酸酯与聚羟基己酸酯共聚物材料修复组(对照A组,n=4)和单纯软骨细胞修复组(对照B组,n=4)作为对照。分别于术后4周(实验B组)和8周(实验A组、对照A组、对照B组)取材,对甲状软骨缺损修复效果进行大体和组织学评价。 结果与结论：两者大体支架形态基本一致,修复区与原有软骨均相续平坦,无凹陷及缺损。但实验A组存在界面无细胞区,修复区基质分泌不丰富;实验B组界面区有细胞生长,基质分泌良好。两者炎细胞浸润均不明显。对照组修复区凹陷,呈暗红色软组织充填,组织学及特殊染色检查未发现软骨样结构及其分泌的基质成分。结果表明在有免疫力的动物体内,初级组织工程软骨组织直接应用与体内植入后再应用均能有效修复同种异体甲状软骨缺损,无明显免疫反应;相同时期内,应用较成熟组织工程软骨组织修复效果优于应用初级组织工程软骨组织。然而,直接应用初级组织工程软骨组织可节省时间、成本、工作量及操作环节,避免二次皮下手术的痛苦,是比较实用的方法之一。     

含裂纹缺损关节软骨的单轴准静态拉伸性能

背景:关节软骨一旦出现裂纹缺损其力学性能会发生改变,而先前研究中针对受损关节软骨的探究多集中在压缩,对于拉伸性能的研究较少。目的:预先在软骨层试样上制造裂纹缺损,测试其单轴准静态拉伸性能。方法:选取新鲜成年猪膝关节的关节软骨,制备含裂纹缺损的软骨试样,在不同应力率下(0.001,0.01,和0.1 MPa/s)测试其拉伸性能,在不同恒定应力下(1,2,3 MPa)测试其蠕变性能。结果与结论:①不同应力速率下的拉伸实验中,随着应力速率的增加,达到相同应变所需的应力逐渐增大,且试件的杨氏模量随应力率的增加而增加;②不同应力速率下含裂纹缺损关节软骨的拉伸应力-应变曲线不重合,说明含裂纹缺损关节软骨的拉伸性能具有率相关性;③不同恒定拉应力水平下的蠕变实验中,蠕变应变随着拉应力水平的提高而增大,蠕变柔量随拉应力水平的提高而降低,并且随着蠕变时间的推移蠕变应变先快速增加后缓慢增加;④结果表明,不同应力率和不同恒定应力对含裂纹缺损关节软骨的拉伸力学性能影响较大,该实验结果可为缺损关节软骨的修复提供力学参考。     

The Effect of Intermittent Static Biaxial Tensile Strains on Tissue Engineered Cartilage

Mechanical stimulation of engineered cartilage constructs is a commonly applied method used to accelerate tissue formation and improve the mechanical properties of the developed tissue. While the effects of compression and shear have been widely studied, the effect of tension has received relatively little attention. As articular cartilage in vivo is subjected to a degree of static tension (pre-tension) even in the absence of externally applied loads, the purpose of this study was to investigate the effect of intermittent static biaxial tensile strains (BTS) on chondrocyte metabolism and resultant tissue formation. Using a custom-design loading fixture to apply BTS, the optimal conditions for stimulating extracellular matrix synthesis were under average magnitudes of 3.8% radial and 2.1% circumferential tensile strains for 30 min. Tissue constructs subjected to tensile strain stimulation 3 times/week for a period of 4 weeks displayed increased thickness (35 ± 18%) and proteoglycan content (22 ± 7%) without an associated change in mechanical properties. In contrast, constructs stimulated daily over the same time period exhibited negligible effects in terms of ECM accumulation suggesting that the frequency of stimulation needs to be precisely controlled. The results of this study demonstrate that while tension can be used as potential biomechanical stimulus to improve tissue formation, further optimization of this process needs to be conducted to improve ECM accumulation and tissue mechanical properties after long-term exposure to tensile stimuli.     

An instrumented scaffold can monitor loading in the knee joint

No technique has been consistently successful in the repair of large focal defects in cartilage, particularly in older patients. Tissue-engineered cartilage grown on synthetic scaffolds with appropriate mechanical properties will provide an implant, which could be used to treat this problem. A means of monitoring loads and pressures acting on cartilage, at the defect site, will provide information needed to understand integration and survival of engineered tissues. It will also provide a means of evaluating rehabilitation protocols. A "sensate" scaffold with calibrated strain sensors attached to its surface, combined with a subminiature radio transmitter, was developed and utilized to measure loads and pressures during gait. In an animal study utilizing six dogs, peak loads of 120N and peak pressures of 11 MPa were measured during relaxed gait. Ingrowth into the scaffold characterized after 6 months in vivo indicated that it was well anchored and bone formation was continuing. Cartilage tissue formation was noted at the edges of the defect at the joint-scaffold interfaces. This suggested that native cartilage integration in future formulations of this scaffold configured with engineered cartilage will be a possibility.     

Induction of cartilage integration by a chondrocyte/collagen-scaffold implant

The integration of implanted cartilage is a major challenge for the success of tissue engineering protocols. We hypothesize that in order for effective cartilage integration to take place, matrix-free chondrocytes must be induced to migrate between the two tissue surfaces. A chondrocyte/collagen-scaffold implant system was developed as a method of delivering dividing cells at the interface between two cartilage surfaces. Chondrocytes were isolated from bovine nasal septum and seeded onto both surfaces of a collagen membrane to create the chondrocyte/collagen-scaffold implant. A model of two cartilage discs and the chondrocyte/collagen-scaffold sandwiched in between was used to effect integration in vitro. The resulting tissue was analysed histologically and biomechanically. The cartilage–implant–cartilage sandwich appeared macroscopically as one continuous piece of tissue at the end of 40 day cultures. Histological analysis showed tissue continuum across the cartilage–scaffold interface. The integration was dependent on both cells and scaffold. Fluorescent labeling of implanted chondrocytes demonstrated that these cells invade the surrounding mature tissue and drive a remodelling of the extracellular matrix. Using cell-free scaffolds we also demonstrated that some chondrocytes migrated from the natural cartilage into the collagen scaffold. Quantification of integration levels using a histomorphometric repair index showed that the chondrocyte/collagen-scaffold implant achieved the highest repair index compared to controls, reflected functionally through increased tensile strength. In conclusion, cartilage integration can be achieved using a chondrocyte/collagen-scaffold implant that permits controlled delivery of chondrocytes to both host and graft mature cartilage tissues. This approach has the potential to be used therapeutically for implantation of engineered tissue.     

Photocrosslinked tyramine-substituted hyaluronate hydrogels with tunable mechanical properties improve immediate tissue-hydrogel interfacial strength in articular cartilage

Articular cartilage lacks the ability to self-repair and a permanent solution for cartilage repair remains elusive. Hydrogel implantation is a promising technique for cartilage repair; however for the technique to be successful hydrogels must interface with the surrounding tissue. The objective of this study was to investigate the tunability of mechanical properties in a hydrogel system using a phenol-substituted polymer, tyramine-substituted hyaluronate (TA-HA), and to determine if the hydrogels could form an interface with cartilage. We hypothesized that tyramine moieties on hyaluronate could crosslink to aromatic amino acids in the cartilage extracellular matrix. Ultraviolet (UV) light and a riboflavin photosensitizer were used to create a hydrogel by tyramine self-crosslinking. The gel mechanical properties were tuned by varying riboflavin concentration, TA-HA concentration, and UV exposure time. Hydrogels formed with a minimum of 2.5 min of UV exposure. The compressive modulus varied from 5 to 16 kPa. Fluorescence spectroscopy analysis found differences in dityramine content. Cyanine-3 labelled tyramide reactivity at the surface of cartilage was dependent on the presence of riboflavin and UV exposure time. Hydrogels fabricated within articular cartilage defects had increasing peak interfacial shear stress at the cartilage-hydrogel interface with increasing UV exposure time, reaching a maximum shear stress 3.5× greater than a press-fit control. Our results found that phenol-substituted polymer/riboflavin systems can be used to fabricate hydrogels with tunable mechanical properties and can interface with the surface tissue, such as articular cartilage.     

Hydrodynamic parameters modulate biochemical, histological, and mechanical properties of engineered cartilage

Functional engineered cartilage constructs represent a promising therapeutic approach for the replacement of damaged articular cartilage. The in vitro generation of cartilage tissue suitable for repair requires an understanding of the complex interrelationships between environmental cues, such as hydrodynamic forces, and tissue growth and development. In the present study, engineered cartilage constructs were cultivated in four well-defined hydrodynamic environments within a bioreactor, and correlations were established between construct ultrastructural and mechanical properties and key hydrodynamic parameters. Results suggest that even for similar composition, constructs may exhibit different mechanical properties due to differences in their ultrastructure that can be modulated by hydrodynamic parameters. For example, improved mechanical properties were observed in constructs that exhibited a thick fibrous outer capsule as a result of cultivation under increased hydrodynamic shear. In particular, uniformity in the contribution of the fluid velocity vectors (axial, radial, and tangential) to the total fluid velocity and shear stress were the hydrodynamic parameters that most affected the construct properties under investigation. The correlations identified here may be useful in the development of engineered tissue growth models that inform the design of bioreactor cultivation systems toward the production of clinically relevant engineered cartilage.     

Osteochondral defect repair with autologous bone marrow-derived mesenchymal stem cells in an injectable, in situ, cross-linked synthetic extracellular matrix

A co-cross-linked synthetic extracellular matrix (sECM) composed of chemically modified hyaluronic acid and gelatin was used as a cell delivery vehicle for osteochondral defect repair in a rabbit model. A full-thickness defect was created in the patellar groove of the femoral articular cartilage in each of 2 rabbit joints, and 4 experimental groups were assigned (12 rabbits/group): untreated control, autologous mesenchymal stem cells (MSCs) only, sECM only, and MSCs + sECM. The sECM hydrogels were allowed to cross-link in the defect in situ. Rabbits were sacrificed at 4, 8, and 12 weeks post-surgery, and cartilage repair was evaluated and scored. In the controls, defects were filled with fibrous tissue. In the MSC-only group, hyaline-like cartilage filled the peripheral area of the defect, but the center was filled with fibrous tissue. In the sECM-only group, hyaline cartilage with zonal architecture filled the defect at 12 weeks, but an interface between repaired and adjacent host cartilage was evident. In the MSCs + sECM group, defects were completely filled with elastic, firm, translucent cartilage at 12 weeks and showed superior integration of the repair tissue with the normal cartilage. The sECM delivers and retains MSCs, and the injectable cell-seeded sECM could be delivered arthroscopically in the clinic.     

The maturity of tissue-engineered cartilage in vitro affects the repairability for osteochondral defect

Cartilage tissue engineering using cells and biocompatible scaffolds has emerged as a promising approach to repair of cartilage damage. To date, however, no engineered cartilage has proven to be equivalent to native cartilage in terms of biochemical and compression properties, as well as histological features. An alternative strategy for cartilage engineering is to focus on the in vivo regeneration potential of immature engineered cartilage. Here, we used a rabbit model to evaluate the extent to which the maturity of engineered cartilage influenced the remodeling and integration of implanted extracellular matrix scaffolds containing allogenous chondrocytes. Full-thickness osteochondral defects were created in the trochlear groove of New Zealand white rabbits. Left knee defects were left untreated as a control (group 1), and right knee defects were implanted with tissue-engineered cartilage cultured in vitro for 2 days (group 2), 2 weeks (group 3), or 4 weeks (group 4). Histological, chemical, and compression assays of engineered cartilage in vitro showed that biochemical composition became more cartilagenous, and biomechanical property for compression gradually increased with culture time. In an in vivo study, gross imaging and histological observation at 1 and 3 months after implanting in vitro-cultured engineered cartilage showed that defects in groups 3 and 4 were repaired with hyaline cartilage-like tissue, whereas defects were only partially filled with fibrocartilage after 1 month in groups 1 and 2. At 3 months, group 4 showed striking features of hyaline cartilage tissue, with a mature matrix and a columnar arrangement of chondrocytes. Zonal distribution of type II collagen was most prominent, and the International Cartilage Repair Society score was also highest at this time. In addition, the subchondral bone was well ossified. In conclusion, in vivo engineered cartilage was remodeled when implanted; however, its extent to maturity varied with cultivation period. Our results showed that the more matured the engineered cartilage was, the better repaired the osteochondral defect was, highlighting the importance of the in vitro cultivation period.     

Dynamic mechanical stimulations induce anisotropy and improve the tensile properties of engineered tissues produced without exogenous scaffolding

Mechanical strength and the production of extracellular matrix (ECM) are essential characteristics for engineered tissues designed to repair and replace connective tissues that are subject to stress and strain. In this study, dynamic mechanical stimulation (DMS) was investigated as a method to improve the mechanical properties of engineered tissues produced without the use of an exogenous scaffold, referred to as the self-assembly approach. This method, based exclusively on the use of human cells without any exogenous scaffolding, allows for the production of a tissue sheet comprised of cells and ECM components synthesized by dermal fibroblasts in vitro. A bioreactor chamber was designed to apply cyclic strain to engineered tissues in order to determine if dynamic culture had an impact on their mechanical properties and ECM organization. Fibroblasts were cultured in the presence of ascorbic acid for 35 days to promote ECM production and allow the formation of a tissue sheet. This sheet was grown on a custom-built anchoring system allowing for easy manipulation and fixation of the tissue in the bioreactor. Following the 35 day period, tissues were maintained for 3 days in static culture (SC), or subjected either to a static mechanical stimulation of 10% strain, or a dynamic DMS with a duty cycle of 10% uniaxial cyclic strain at 1Hz. ECM was characterized by histology, immunofluorescence labeling and Western blotting. Both static and dynamic mechanical stimulation induced the alignment of assessed cytoskeletal proteins and ECM components parallel to the axis of applied strain and increased the ECM content of the tissues compared to SC. Measurement of the tensile mechanical properties revealed that mechanical stimulation significantly increases both the ultimate tensile strength and tensile modulus of the engineered tissues when compared to the non-stimulated control. Moreover, we demonstrated that cyclic strain significantly increases these parameters when compared to a static-loading stimulation and that mechanical stimulation contributes to the establishment of anisotropy in the structural and mechanical properties of self-assembled tissue sheets.