State Key Laboratory of Software Development Environment, Key Laboratory of Ministry of Education for Biomechanics and Mechanobiology, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China.
Sci China Life Sci. 2011 Nov;54(11):1029-35. doi: 10.1007/s11427-011-4235-1. Epub 2011 Dec 16.
Subtle changes of articular cartilage (AC) can lead to tissue degeneration and even osteoarthritis (OA). The early degeneration of AC is closely related to a change in proteoglycans (PG) content. The observation of PG is therefore an appropriate way of studying OA and evaluating the degree of AC degeneration. In this study, 20 cartilage-bone samples were prepared from normal porcine femoral condyle cartilage and 10 samples were digested over 2 h using 0.25% trypsin solution. The dynamic process of PG-digestion was explored using a conventional A-mode ultrasound (US) experimental system with a 10 MHz center frequency. Quantitative acoustic parameters were calculated from ultrasonic radio-frequency echo signals and included US speed (USS), US amplitude attenuation coefficient (UAA) and broadband US attenuation coefficient (BUA). The experimental results showed that the conventional A-mode ultrasound is valuable for tracking the degree of PG-digestion. Histology also confirmed the validity of the ultrasound observations. For every AC sample, the degree of PG-digestion within a given time was different and was affected by individual differences. After two hours of degeneration, USS showed a mean decrease of 0.4% (P<0.05). UAA was significantly lower after a two-hour PG depletion period (from (2.45±0.23) to (2.28±0.41) dB mm⁻¹). BUA showed no significant differences during this process. In conclusion, conventional ultrasound can provide useful information about trypsin-induced progressive PG depletion in AC and can reflect variations of PG content via the quantitative acoustic parameters USS and UAA. The results of this study may be used to identify an indirect indicator of cartilage matrix integrity and OA disease progression.
关节软骨（AC）的细微变化可导致组织退化甚至骨关节炎（OA）。AC 的早期退变与糖胺聚糖（PG）含量的变化密切相关。因此，观察 PG 是研究 OA 和评估 AC 退变程度的一种合适方法。在这项研究中，从正常猪股骨髁软骨中制备了 20 个软骨-骨样本，并用 0.25%的胰蛋白酶溶液消化了 10 个样本 2 小时。使用具有 10MHz 中心频率的传统 A 型超声（US）实验系统探索 PG 消化的动态过程。从超声射频回波信号中计算出定量声参数，包括 US 速度（USS）、US 幅度衰减系数（UAA）和宽带 US 衰减系数（BUA）。实验结果表明，传统 A 型超声可用于跟踪 PG 消化程度。组织学也证实了超声观察的有效性。对于每个 AC 样本，在给定时间内的 PG 消化程度不同，并且受到个体差异的影响。经过两小时的退变，USS 平均下降 0.4%（P<0.05）。经过两小时的 PG 耗竭期后，UAA 明显降低（从（2.45±0.23）降至（2.28±0.41）dB mm⁻¹）。在此过程中，BUA 没有明显差异。总之，传统超声可以提供有关 AC 中胰蛋白酶诱导的渐进性 PG 耗竭的有用信息，并可以通过定量声参数 USS 和 UAA 反映 PG 含量的变化。本研究的结果可用于识别软骨基质完整性和 OA 疾病进展的间接指标。
