关节软骨力学特性间接预测方法的研究进展

关节软骨具有非常优异的力学特性,是影响人体运动、载荷传递的关键因素之一.随着人们参与体育运动的增多以及老龄化程度的加剧,出现关节软骨损伤及其相关病症的人数显著增多.实现关节软骨力学特性的有效表征,是对关节软骨进行损伤评估和功能评价的核心环节.总结当前国内外关于关节软骨力学特性间接测量方法的研究进展,并对关节软骨力学特性...     

关节软骨生物力学与力学生物学 2022 年研究进展

关节软骨是动关节内骨表面具有弹性的负重结缔组织,能提供低磨损润滑、缓冲震荡、传递载荷等支撑作用,具有层级纤维复合结构和优异的力学性能。软骨内没有血管、神经和淋巴,代谢缓慢,损伤后难以实现自我修复。目前,高发的关节炎疾病仍是基础与临床研究的一大热点。关节软骨是力学敏感组织,力学环境影响着组织不同方向的发展。2022年,学者们继续对关节软骨的生物力学与力学生物学开展大量研究;对软骨形态、功能与力学状态,以及不同条件下软骨力学状态的研究报道较多;研究设计了一些软骨相关的动物、组织及细胞水平的加载装置,也开展了体外及在体力学载荷下软骨退变、损伤的修复研究,获得了重要的修复方法及手段。关节软骨的生物力学与力学生物学研究是关节炎、软骨缺损及修复的基础,关节软骨损伤修复定量力学条件的影响还需体内和体外深入研究。     

关节软骨体外构建力学环境的研究进展

很多物理因素都影响软骨组织的生长和发育,其中力学因素起主要作用。软骨的生长、发育是力学调控的适应过程。当前采用多种力学条件应用于软骨生物反应器,如流体剪应力、液体压力、直接压缩等,或其中部分组合,但这些条件还没有构建出与活体软骨结构-功能相匹配的人工软骨。如果一种载荷能适合构建软骨,那么这种载荷首先能保证培养物内部信号分子、营养和废物的有效运输;其次,能对支架内种子细胞特定的力学刺激;第三,能促进培养物结构-功能的发展。本文回顾、分析当前多种力学条件的作用效果,其中流体剪应力、液体压力、拉伸、直接压缩或变形剪应力都是软骨受力状态的部分体现。作者认为滚压载荷是软骨培养的合适力学环境,它是当前多种力学条件的一个综合指标,对软骨培养物可以形成纵向的动态压缩和横向的动态变形剪应力,并且有利于细胞新陈代谢物质的运输,因此,滚压环境可能是人工软骨结构-功能构建的发展方向。     

关节软骨胶原纤维增强特性

目的在COMSOL关节软骨计算中引入胶原纤维增强特性,并分析引入前后模型结果的差异。方法以软骨中胶原纤维的走向为基础,对胶原纤维的应力单独建模,将胶原纤维的应力写入到原来软骨多孔弹性模型中。为避免应变2次项的出现采用了函数调用方式,同时提高求解器的迭代次数以更好收敛。结果胶原纤维增强模型表面的Y方向初始位移仅为15μm,是非增强模型的17.6%。增强模型的X方向正应变仅为非增强模型的10%,而近表面的X方向正应力超过非增强模型的10倍。结论在COMSOL关节软骨计算中实现了胶原纤维增强特性的引入,为软骨胶原纤维损伤提供了计算模型和理论分析。胶原纤维通过横向增强约束了竖直方向的应变,提高了软骨承载能力,改善了软骨的力学性能。     

关节软骨缺损修复策略的研究进展

关节软骨包含有高度发达的细胞外基质，主要含有Ⅱ型胶原和蛋白多糖（包括软骨素和硫酸素糖胺多糖）以及相对稀疏、特化的细胞群（关节软骨细胞）；细胞占总软骨体积小于5％。软骨与胶原纤维关系上可分为三个区：紧贴关节腔的外层是表浅的正切区，该区约占软骨的10％；中区占40～60％；接近骨化区的深部区，占软骨的30～40％。表浅区含少量糖胺多糖，在此区的细胞呈长扁形，走形与表面平行，胶原纤维也正切走向。     

关节软骨损伤修复研究进展

各种原因导致的关节软骨损伤在临床十分常见,关节软骨缺乏血供,一旦受损,其自愈能力十分有限,甚至遗留永久性病变.所以关节软骨损伤的修复一直是国内外研究的热点问题.近年来随着生物学、力学、材料学等多学科的交叉发展,在关节软骨损伤修复方面又有了诸多发现.本文就目前各种关节软骨损伤修复方法,包括新兴的组织工程软骨与基因治疗技术的研究进展作一综述.     

关节软骨组织工程的研究进展

介绍了关节软骨组织工程中种子细胞、支架材料的研究现状以及生长因子在关节软骨组织工程中的应用进展，阐明了随着对细胞行为、支架材料特性、细胞与材料的组合构建研究的深入，组织工程在关节软骨修复方面应用前景十分广阔。     

T_2 mapping评价关节软骨损伤及修复的研究进展

T2mapping是近年来发展的MRI新技术,能间接反应关节软骨结构及组织学成分的变化,发现关节软骨形态学变化之前的组织学改变。笔者就T2mapping成像原理、软骨损伤的组织学表现,以及成像影响因素等方面作一综述,重点介绍了T2mapping在软骨损伤、退变、修复等方面的研究进展,并展望了T2mapping未来发展前景。     

关节软骨的微摩擦接触力学特性

目的使用修饰后的原子力显微镜(atomic force microscopy,AFM)探针研究关节软骨的微摩擦接触力学性能。方法使用微操作器对AFM氮化硅探针进行修饰处理,具体操作为在探针上粘贴玻璃微球作为针尖,然后使用修饰后的探针研究人体和牛关节软骨的微摩擦接触力学性能。结果人体和牛软骨的粗糙度分别为(68.63±6.22)、(50.16±6.47)nm,随着载荷的增大,人体和牛软骨的摩擦力逐渐增大。当探针滑动速度从0增加到100μm/s时,试样与探针之间的摩擦力增速很快;当速度从100μm/s增加到300μm/s时,摩擦力上升缓慢。结论软骨表面具有明显的纤维状结构,软骨的粗糙度与测量范围直接相关。随着速度或载荷的增大,人体和牛软骨的摩擦力增大,变化范围相同。探讨关节软骨在微摩擦试验中的力学和摩擦学性能表现,对于认识软骨损伤机制和医用人工关节抗磨材料的开发具有重要意义。     

模拟微重力对大鼠关节软骨力学特性的影响

目的基于大鼠尾吊实验,研究模拟微重力对关节软骨组织力学特性的影响。方法通过14 d的尾吊实验建立模拟微重力作用的大鼠模型,获得12块后肢大腿骨关节处软骨样本,运用高频超声测量技术获取大鼠关节软骨特定位置因自由膨胀引起的组织应变,基于三相模型估计软骨组织的轴向弹性模量,并比较尾吊组和对照组大鼠关节软骨的力学特性。结果尾吊组大鼠后肢特定测量位置处软骨厚度的平均值略小于对照组,但差异不显著;尾吊组大鼠特定位置关节软骨组织的平均轴向弹性模量为(5.05±2.98)MPa,小于对照组((6.31±3.37)MPa),两者存在着显著差异(P<0.05)。结论微重力环境会影响关节软骨组织的力学特性,本研究结果为人类长期的太空活动提供参考信息。     

Quantification of Stiffness Change in Degenerated Articular Cartilage Using Optical Coherence Tomography-Based Air-Jet Indentation

Articular cartilage is a thin complex tissue that covers the bony ends of joints. Changes in the composition and structure of articular cartilage will cause degeneration, which may further lead to osteoarthritis. Decreased stiffness is one of the earliest symptoms of cartilage degeneration and also represents the imperfect quality of repaired cartilage. An optical coherence tomography (OCT)-based air-jet indentation system was recently developed in our group to measure the mechanical properties of soft tissues. In this study, this system was applied to quantify the change of mechanical properties of articular cartilage after degeneration induced by enzymatic digestions. Forty osteochondral disks (n = 20 × 2) were prepared from bovine patellae and treated with collagenase and trypsin digestions, respectively. The apparent stiffness of the cartilage was measured by the OCT-based air-jet indentation system before and after the degeneration. The results were also compared with those from a rigid contact mechanical indentation and an ultrasound water-jet indentation. Through the air-jet indentation, it was found that the articular cartilage stiffness dropped significantly by 84% (p < 0.001) and 63% (p < 0.001) on average after collagenase and trypsin digestions, respectively. The stiffness measured by the air-jet indentation system was highly correlated (R > 0.8, p < 0.001) with that from the other two indentation methods. This study demonstrated that the OCT-based air-jet indentation can be a useful tool to quantitatively assess the mechanical properties of articular cartilage, and this encourages us to further develop a miniaturized probe suitable for arthroscopic applications.     

胶原纤维束对软骨力学性能的影响

目的 研究胶原纤维束对软骨力学性能的影响,为临床医生指导早期软骨损伤患者的康复运动提供参考。方法 建立一种纤维增强的多孔黏弹性二维数值模型,考虑纤维分布、弹性模量、孔隙率和渗透率随软骨深度的变化关系。研究纤维束局部断裂和从表面渐进断裂以及纤维束尺寸对软骨力学性能的影响,获得软骨基质的最大主应变。结果 基质的最大主应变出现在软骨中层靠上某个位置,此位置不受纤维断裂模式和纤维束尺寸的影响。含较粗纤维束软骨的应变降低。结论 软骨中层易发生力学损伤,纤维束增粗可以降低基质的最大主应变,一旦纤维束发生断裂,较粗纤维束的软骨的基质最大主应变更大,使软骨更易发生损伤演化情况。     

Minor Influence of Lifelong Voluntary Exercise on Composition,Structure, and Incidence of Osteoarthritis in Tibial Articular Cartilage of Mice Compared with Major Effects Caused by Growth,Maturation, and Aging

We investigated the effects of lifelong voluntary exercise on articular cartilage of mice. At the age of 4 weeks C57BL mice (n = 152) were divided into two groups, with one group serving as a sedentary control whereas the other was allowed free access to a running wheel from the age of 1 month onward. Mice were euthanized at four different time points (1, 2, 6, and 18 months of age). Articular cartilage samples were gathered from the load-bearing area of the tibial medial plateaus, and osteoarthritis was graded. Additionally, the proteoglycan content distribution was assessed using digital densitometry, collagen fibril orientation, and parallelism with polarized light microscopy, and collagen content using Fourier transform infrared imaging spectroscopy. The incidence of osteoarthritis increased with aging, but exercise had no effect on this trend. Furthermore, the structure and composition revealed significant growth, maturation, and age-dependent properties. Exercise exerted a minor effect on collagen fibril orientation in the superficial zone. Fibril orientation at 2 months of age was more perpendicular to surface (p < 0.05) in controls compared with runners, whereas the situation was reversed at the age of 18 months (p < 0.05). The collagen content of the superficial zone was higher (p < 0.01) at the age of 18 months in controls compared with runners but the proteoglycan content did not display any exercise-dependent changes. In conclusion, growth, maturation, and aging exerted a clear effect on integrity, structure, and composition of medial tibial plateau articular cartilage in mice, whereas lifelong voluntary exercise had only a minor effect on collagen architecture and content.     

老龄关节软骨和软骨下骨的变化及相互作用机制研究进展

衰老是骨关节炎(osteoarthritis,OA)和骨质疏松等疾病的主要影响因素。然而,它们并不是衰老的必然结果,而且与衰老有关的骨和软骨的变化与疾病发展之间的关系尚不清楚。研究表明,骨关节炎的发生和发展并不是简单的软骨磨损过程,它的发生包括整个关节各组织复杂的生物、化学和力学变化,特别是软骨和软骨下骨之间生化和力学的相互作用。衰老促成OA的发生和发展,但并不是直接导致OA的原因。与衰老相关的变化为OA的发生提供了一个基础,使关节更容易受到其他因素(如异常的生物力学和生物化学)影响,从而促进OA发展。因此,了解衰老影响关节组织的基本机制可能会为减缓或预防OA发展提供新的靶点。从衰老过程中软骨和软骨下骨的年龄相关性变化、力学传导作用和血管新生机制3个方面对相关研究进展进行综述。     

SOX Trio Decrease in the Articular Cartilage with the Advancement of Osteoarthritis

SOX trio (SOX-5, SOX-6, and SOX-9) maintain the chondrocytic phenotypes and are vital for chondrogenesis in embryonic development. The purpose of this study is to investigate the change in the expression of SOX trio with the advancement of osteoarthritis (OA) in human articular cartilage (AC). Human OA samples from eight patients were obtained from the distal femoral condyles during total knee arthroplasty. Minimally OA cartilage taken from areas with no obvious surface defects on lateral condyles was compared with advanced OA cartilage obtained from areas within 1 cm of overt lesion located on medial condyle surface. SOX-5, SOX-6, and SOX-9 gene expressions significantly decreased by 41% (p = 0.047), 46% (p = 0.047), and 56% (p = 0.029) in advanced OA area compared with the minimally OA area. There was a significant decrease in aggrecan and type II collagen (COL2A1) gene expressions by 73% (p = 0.029) and 65% (p = 0.029), respectively, in advanced OA area compared with the minimally OA area. From Western blotting and immunohistochemistry, SOX-5, SOX-6, SOX-9, type II collagen, and aggrecan protein expressions also significantly decreased in advanced OA cartilage compared with minimally OA cartilage. DNA methylation study of SOX-9 promoter regions revealed no difference in the epigenetic status between the two areas. It is concluded that SOX trio gene and protein decreased with advancement of OA in human articular cartilage.     

Age-Related Changes in the Synthesis of Matrix Macromolecules by Bovine Articular Cartilage

Calf and mature cow articular cartilage was labeled in vitro with [³⁵S]SO₄ and [³H]glycine and kinetics of incorporation of both isotopes by cartilage fragments was determined by scintillation spectroscopy. The cartilage fragments were then extracted in sequence with 4M GuHCl (Guanidium chloride) and pepsin. The pepsin digest was adjusted to 1.3 M NaCl and pepsin-solubilized collagen salted out. The 4M GuHCl extract, collagen and pepsin-resistent residue were then freeze-dried. The 4M GuHCl extract was further fractionated by DEAE (Diethylaminoethyl) 52 ion exchange chromatography to obtain protein and PG (Proteoglycan) fractions. The protein fraction was also characterised by SDS-PAGE and PG fraction by Sepharose C1–2B chromatography under associative conditions in the presence and absence of an exogenous HA (Hyaluronic acid). The GAG (Glycosaminoglycan) side chains of the PG samples were analysed by Sephadex G-200 column chromatography and their composition determined by paper chromatography after chondroitinase ABC digestion.

Linear incorporation of both isotopes was observed from 1 to 18 hours of incubation and roughly equal amounts of f³⁵S]SO₄ counts were found on per cell bases in both cartilages although less [³H]glycine was incorporated by cow chondrocytes. It was also found that calf chondrocytes synthesize much greater proportion of the collagen whereas the cow cells synthesize PGs of smaller hydrodynamic sizes, bearing shorter GAG side chains that are enriched in KS (Keratan sulfate) and Ch-6S (Chondroitin-6 sulfate isomer). A failure of cow ³⁵S-PGs monomers to interact with an exogenous HA in the presence of other extracted components was also demonstrated.

The relevance of these findings for the mechanism of cartilage damage in aging and osteoarthritis is discussed.     

高频超声对关节软骨消肿与肿胀行为的定量分析

关节软骨可减轻关节滑动中所产生的关节面间的摩擦,具有负重传导、润滑及耐磨损的特性。关节软骨肿胀属性的改变可作为检测早期关节炎的指标之一。本研究的目的在于利用高频超声技术和信号处理技术建立一个实时超声监测系统,以一种非接触、无损的方法研究软骨的瞬时渗透性消肿(收缩)及肿胀(膨胀)行为。样本取自新鲜成年牛膝盖骨,通过改变外溶液的浓度引入渗透压,促使软骨发生收缩膨胀反应,利用实时超声监测系统进行无损测量。实验表明关节软骨的肿胀消肿过程出现“过激松弛”现象,最大收缩膨胀应变的绝对值分别为0.75%±0.57%和0.28%±0.28%,膨胀应变与收缩应变具有显著性差异(p<0.05)。同时发现软骨内超声速度随时间的指数性变化可以表征离子的渗透过程。实验证明该超声系统具有良好的可重复性(组内相关系数ICC>0.98)和可靠性(相对误差<5%)。应用高频超声技术不仅可无损量化地研究软骨的渗透性消肿膨胀行为,而且为今后研究软骨病变及早期发现关节炎提供一个有效可行的方法。     

低温保护剂载入关节软骨过程的传质建模

掌握加载过程中软骨组织内部低温保护剂浓度的时空分布特性,这对合理设计加载程序进而成功保存关节软骨至关重要,为此构建描述低温保护剂载入关节软骨过程的扩散传质模型。根据二元扩散热力学模型,将有效扩散系数与无限稀释扩散系数进行关联,活度系数采用UNIFAC模型估算,扩散系数的浓度依赖性采用Vignes公式表示,无限稀释扩散系数采用Siddiqi-Lucas公式计算。对于二甲亚砜(Me₂SO)、甘油(GLY)、乙二醇(EG)和丙二醇(PG)这4种典型的低温保护剂(CPA),由模型计算得到的软骨组织内CPA的平均浓度与文献报道的实验值之间的平均相对偏差(MRE)和决定系数(R²)分别为1.90%～36.29%和0.959～0.998(Me₂SO),13.56%～19.19%和0.990～0.995(GLY),8.89%～22.09%和0.969～0.988(EG),5.35%～23.76%和0.971～0.992(PG)。结果表明,该模型能较好地适用于这4种CPA,可用于直接预测加载过程中软骨组织内部CPA浓度的时空分布,从而指导加载程序的设计与优化。     

Effect of Temperature on the Metabolism of Proteoglycans in Explants of Bovine Articular Cartilage

The turnover of proteoglycans in bovine articular cartilage was determined in explant cultures, maintained at 32°C or 37°C. Both the rate of proteoglycan synthesis and the release of newly synthesized proteoglycans were decreased in cultures incubated at 32°C compared to 37°C.

At both temperatures the newly synthesized proteoglycans were similar in hydrodynamic size and chain length of the glycosaminoglycans. However, the ratio of 6-sulfated disaccharides over 4-sulfated disaccharides of the newly synthesized glycosaminoglycans, differed less from the endogenous ratio at 32°C than at 37°C.

At both temperatures, the incorporated ³⁵S-sulfate is released from explants in two pools. Twenty-three percent of the ³⁵S-radiolabel was released into the culture medium during an initial short phase (t_1/2 = 1.1 day at 32°C, 1.3 day at 37°C), 77% had a much longer half-life. The lowered temperature markedly decreased the release of ³⁵S-sulfate with a slow turnover (t_1/2 = 60 days at 32°C, 38 days at 37°C).