Wu Yi-Ting, Wu Yen-Ting, Huang Tzu-Chieh, Su Fong-Chin, Jou I-Ming, Wu Chia-Ching
Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Taiwan.
Department of Nursing, Tzu Hui Institute of Technology, Taiwan.
J Orthop Translat. 2020 Apr 2;23:113-121. doi: 10.1016/j.jot.2020.03.004. eCollection 2020 Jul.
BACKGROUND & OBJECTIVE: Tendinopathy is a tendon disease with abnormal mechanical loading to induce chronic repetitive injury. However, lack of a comparable animal model to demonstrate clinical progressions has hindered the understanding of anatomical and pathological changes. The major extracellular matrix (ECM) in the tendon consists of abundant type I collagen (COL) and minimal amount of elastin (ELN).
To study the ECM breakdown and inflammation, rat Achilles tendon was harvested and ex vivo incubated with specific enzymes of elastase (ELNase) or collagenase (COLase).
The ELNase broke down ELN, loosened the tendon structure, and increased the COL composition. Increases in cyclooxygenase-2 expression levels in tenocytes were revealed to induce inflammation with either ELNase or COLase. However, incubation of COLase for 12 hours severely digested the tendon. To create a proper ELN degradation in rats, the present study used high-frequency ultrasound to guide the injection of ELNase at the paratendon tissue of the Achilles tendon. The effect of mechanically triggered inflammatory responses was investigated by applying treadmill exercise (15 m/min for 20 min per day). After ELNase injection for 14 and 28 days, a significant loss of ELN was observed, and exercise further facilitated the pathological transition of COL. The dynamics of inflammatory cell recruitments was revealed by specific staining of CD-11b (neutrophils) and CD-68 (macrophage) after in vivo injection of ELNase or COLase for 1, 3, 7, 14, and 28 days. The combination of ELNase and exercise caused early recruitment of neutrophil on day 1 and sequential expression of macrophage on day 7 in peritendinous tissue.
These results suggested that ELN degradation with repetitive mechanical loading may present a suitable model for the pathogenesis of tendinopathy.
This discover the role of elastin degradation in tendinopathy and the interaction of exercise in the histological changes. The established the pathological model mimicking the pathogenesis to the human disease by injecting the elastase using ultrasound guidance and then applying treadmill exercise. The loss of elastin and change of collagen composition in clinical tendinopathy samples were observed in the rats. In addition, the sequential inflammation cascades were observed in the histological outcomes with combination of elastase injection and treadmill exercise. Thus, this model may be used to test the clinical treatment of tendinopathy in different stages.
肌腱病是一种因异常机械负荷导致慢性重复性损伤的肌腱疾病。然而，缺乏可用于展示临床进展的可比动物模型阻碍了对解剖学和病理学变化的理解。肌腱中的主要细胞外基质（ECM）由大量的I型胶原蛋白（COL）和少量的弹性蛋白（ELN）组成。
为研究ECM分解和炎症反应，采集大鼠跟腱并在体外与弹性蛋白酶（ELNase）或胶原酶（COLase）等特定酶一起孵育。
ELNase分解了ELN，使肌腱结构松弛，并增加了COL的组成。研究发现，无论是ELNase还是COLase处理，肌腱细胞中环氧合酶-2表达水平的增加都会引发炎症。然而，COLase孵育12小时会严重消化肌腱。为在大鼠中实现适当的ELN降解，本研究使用高频超声引导将ELNase注射到跟腱的腱旁组织。通过进行跑步机运动（每天15米/分钟，持续20分钟）来研究机械触发的炎症反应的影响。在注射ELNase 14天和28天后，观察到ELN显著减少，运动进一步促进了COL的病理转变。在体内注射ELNase或COLase 1、3、7、14和28天后，通过对CD-11b（中性粒细胞）和CD-68（巨噬细胞）进行特异性染色揭示了炎症细胞募集的动态变化。ELNase与运动相结合导致腱周组织在第1天早期募集中性粒细胞，并在第7天依次出现巨噬细胞表达。
这些结果表明，重复性机械负荷导致的ELN降解可能为肌腱病的发病机制提供一个合适的模型。
本研究发现了弹性蛋白降解在肌腱病中的作用以及运动在组织学变化中的相互作用。通过超声引导注射弹性蛋白酶然后进行跑步机运动，建立了模拟人类疾病发病机制的病理模型。在大鼠中观察到了临床肌腱病样本中弹性蛋白的丧失和胶原蛋白组成的变化。此外，在弹性蛋白酶注射和跑步机运动相结合的组织学结果中观察到了连续的炎症级联反应。因此，该模型可用于测试不同阶段肌腱病的临床治疗。
