关节软骨光透明的拉曼光谱研究

为探讨原位条件下关节软骨及下骨组织成分含量变化等深层次微观信息,采用拉曼光谱技术结合组织光透明技术来研究软骨组织的光透明效果。选用甘油、碘海醇作为光透明剂,对在不同光透明剂浓度和浸渍时间下的犬膝关节股骨端软骨样本进行拉曼光谱采集。通过计算磷酸基团(920~960 cm-1 ) 和酰胺Ⅰ带(1 595~1 700 cm-1)的积分强度,获得拉曼强度比(磷酸基团/酰胺Ⅰ),探索在不同浸渍时间(10~60 min)、不同浓度下(甘油40%,60%,80%和100%,碘海醇50,150,250和350 mg·mL-1)组织光透明的规律,即寻找合适的透明浓度和透明时间。结果显示：相比于无透明剂情形,两种透明剂均使该强度比信号增强。在同一时间范围内,甘油和碘海醇分别在60%和150 mg·mL-1 浓度下能获得较好的透明效果;而在不同浓度下,甘油的透明效果均在20 min最强,而碘海醇的透明效果一般是在50 min后开始增强。在光透明剂的作用下激发光透过软骨可以直接探测到软骨下骨的拉曼光谱信息,这为研究骨关节炎深层次病因提供了方法和思路。     

A comparative study at 3 T of sequence dependence of T2 quantitation in the knee

Objective

T₂ mapping has been used widely in detecting cartilage degeneration in osteoarthritis. Several scanning sequences have been developed in the determination of T₂ relaxation times of tissues. However, the derivation of these times may vary from sequence to sequence. This study seeks to evaluate the sequence-dependent differences in T₂ quantitation of cartilage, muscle, fat and bone marrow in the knee joint at 3 T.

Methods

Three commercial phantoms and 10 healthy volunteers were studied using 3 T MR. T₂ relaxation times of the phantoms, cartilage, muscle, subcutaneous fat and marrow were derived using spin echo (SE), multiecho SE (MESE), fast SE (FSE) with varying echo train length (ETL), spiral and spoiler gradient (SPGR) sequences. The differences between these times were then evaluated using Student's t test. In addition, the signal-to-noise ratio (SNR) efficiency and coefficient of variation of T₂ from each sequence were calculated.

Results

The average T₂ relaxation time was 36.38±5.76 ms in cartilage and 34.08±6.55 ms in muscle, ranging from 27 to 45 ms in both tissues. The times for subcutaneous fat and marrow were longer and more varying, ranging from 41 to 143 ms and from 42 to 160 ms, respectively. In FSE acquisition, relaxation time significantly increases as ETL increases (P<.05). In cartilage, the SE acquisition yields the lowest T₂ values (27.52±3.10 ms), which is significantly lower than those obtained from other sequences (P<.002). T₂ values obtained from spiral acquisition (38.27±6.45 ms) were higher than those obtained from MESE (34.35±5.62 ms) and SPGR acquisition (31.64±4.53 ms). These differences, however, were not significant (P>.05).

Conclusion

T₂ quantification can be a valuable tool for the diagnosis of degenerative disease. Several different sequences exist to quantify the relaxation times of tissues. Sequences range in scan time, SNR efficiency, reproducibility and two- or three-dimensional mapping. However, when choosing a sequence for quantitation, it is important to realize that several factors affect the measured T₂ relaxation time.     

毛细管整体柱在线二维分离系统应用于人体软骨的蛋白质组分析

将已建立的 7 cm 柱长的磷酸基团强阳离子交换富集整体柱与85 cm柱长的C12烷基反相整体柱结合的在线二维分离平台应用于软骨提取蛋白的蛋白质组分析。对20 μg软骨提取蛋白的酶解产物进行14个盐梯度的分级,然后对14个馏分进行反相色谱梯度分离及串联质谱鉴定,成功地鉴定得到了7434个独立肽段对应的1901个非冗余蛋白质。对所鉴定到的蛋白质进行定位分类,结果表明鉴定到的大部分蛋白质是来自于软骨细胞内部的低丰度蛋白质,这对于许多关节类疾病的研究有重要意义。     

Transverse relaxation mechanisms in articular cartilage

Relaxation rates in the rotating frame (R1rho) and spin-spin relaxation rates (R2) were measured in articular cartilage at various orientations of cartilage layer to the static magnetic field (B0), at various spin locking field strengths and at two different static magnetic field strengths. It was found that R1rho in the deep radial zone depended on the orientation of specimens in the magnet and decreased with increasing the spin locking field strength. In contrast, R1rho values in the transitional zone were nearly independent of the specimen orientation and the spin locking field strength. Measurements of the same specimens at 2.95 and 7.05 T showed an increase of R1rho and most R2 values with increasing B0. The inverse B0 dependence of some R2 values was probably due to a multicomponent character of the transverse magnetization decay. The experiments revealed that the dominant T1rho and T2 relaxation mechanism at B0 < or = 3 T is a dipolar interaction due to slow anisotropic motion of water molecules in the collagen matrix. On average, the contribution of scalar relaxation due to rapid proton exchange in femoral head cartilage at 2.95 T is about 6% or less of the total R1rho at the spin locking field of 1000 Hz.     

牛膝关节软骨的摩擦行为研究

采用UMT．2型微观多功能测试系统，在试验环境为牛血清，法向加载应力0．8MPa，加载时间从5s到60min变化条件下分别测定了牛膝关节软骨在静态加载和滑行时的法向位移以及滑行时的摩擦系数．结果表明：上、下软骨间的法向位移与加载时间呈非线性增加；滑行时法向位移影响软骨间摩擦系数，启动摩擦系数高于平坦滑行过程中的摩擦系数；滑行速率对软骨摩擦系数的影响较小，加载时间越长，法向位移越大，所对应的启动摩擦系数越大；加载时法向位移和滑行时启动摩擦系数具有类似的变化趋势．     

人工关节滑液的摩擦学性能及摩擦化学研究

采用小牛血清和0.9%NaCl生理盐水配制了关节滑液,在四球摩擦磨损试验机上考察了其摩擦学性能,并用X射线光电子能谱仪分析了磨斑表面膜的元素组成和化学状态.结果表明:生理盐水的减摩抗磨性能较差,而小牛血清具有优异的减摩抗磨性能;滑液的减摩抗磨性能随小牛血清体积分数增加而逐步提高;滑液具有优良减摩抗磨性能的原因在于,血清在摩擦过程中发生摩擦化学反应,生成由蛋白质吸附膜、CaCO3沉积膜以及FePO4化学反应膜等组成的边界润滑膜.     

Tough,Semisynthetic Hydrogels for Adipose Derived Stem Cell Delivery for Chondral Defect Repair

Cell‐based therapies have great potential to regenerate and repair injured articular cartilage, and a range of synthetic and natural polymer‐based hydrogels have been used in combination with stem cells and growth factors for this purpose. Although the hydrogel scaffolds developed to date possess many favorable characteristics, achieving the required mechanical properties has remained a challenge. A hydrogel system with tunable mechanical properties, composed of a mixture of natural and synthetic polymers, and its use for the encapsulation of adipose derived stem/stromal cells (ASCs) is described. Solutions of methacrylated chondroitin sulfate (MCS) are mixed with solutions of acrylate‐poly(trimethylene carbonate)‐b‐poly(ethylene glycol)‐b‐poly(trimethylene carbonate)‐acrylate (PEG‐(PTMC‐A)₂) in phosphate buffered saline and crosslinked via thermally initiated free radical polymerization. The hydrogel compressive equilibrium moduli and toughness are readily tailored by varying the concentration of the pre‐polymers, as well as the molecular weight of the PEG used to prepare the PEG‐(PTMC‐A)₂. Two peptide sequences, GVOGEA and GGGGRGDS, are individually conjugated to the MCS to facilitate cell binding. The presence of the peptide ligands yields high ASC viability and long term metabolic activity following encapsulation in hydrogels prepared using the thermal initiator system. Overall, these hydrogels show promise as a minimally invasive ASC delivery strategy for chondral defect repair.

     

Automatic knee cartilage segmentation from multi-contrast MR images using support vector machine classification with spatial dependencies

Accurate segmentation of knee cartilage is required to obtain quantitative cartilage measurements, which is crucial for the assessment of knee pathology caused by musculoskeletal diseases or sudden injuries. This paper presents an automatic knee cartilage segmentation technique which exploits a rich set of image features from multi-contrast magnetic resonance (MR) images and the spatial dependencies between neighbouring voxels. The image features and the spatial dependencies are modelled into a support vector machine (SVM)-based association potential and a discriminative random field (DRF)-based interaction potential. Subsequently, both potentials are incorporated into an inference graphical model such that the knee cartilage segmentation is cast into an optimal labelling problem which can be efficiently solved by loopy belief propagation. The effectiveness of the proposed technique is validated on a database of multi-contrast MR images. The experimental results show that using diverse forms of image and anatomical structure information as the features are helpful in improving the segmentation, and the joint SVM-DRF model is superior to the classification models based solely on DRF or SVM in terms of accuracy when the same features are used. The developed segmentation technique achieves good performance compared with gold standard segmentations and obtained higher average DSC values than the state-of-the-art automatic cartilage segmentation studies.     

关节软骨模拟运动摩擦磨损行为研究

采用牛关节软骨与不锈钢摩擦副在人工膝关节模拟运动试验机上进行模拟膝关节运动的摩擦学试验研究,探讨载荷和时间对摩擦磨损行为的影响并分析其作用机理,同时对软骨表面进行分析。结果表明：随着载荷从640增至1000 N,牛软骨表面磨痕的宽度的深度均增大;在同样载荷下,随着模拟运动时间从20增至60 min,牛软骨表面磨痕的宽度和深度增大。软骨磨损表面的磨痕和破损表面检测有铁元素的存在,表明不锈钢材料在摩擦过程中发生转移。试验后得到的磨粒包括长条形的金属磨粒和圆形的软骨成分磨粒。