Elastic fibers containing elastin play an important role in tendon functionality, but the knowledge on presence and function of elastin during tendon healing is limited. The aim of this study was to investigate elastin content and distribution in intact and healing Achilles tendons and to understand how elastin influence the viscoelastic properties of tendons. The right Achilles tendon was completely transected in 81 Sprague-Dawley rats. Elastin content was quantified in intact and healing tendons (7, 14, and 28 days post-surgery) and elastin distribution was visualized by immunohistochemistry. Degradation of elastin by elastase incubation was used to study the role of elastin on viscoelastic properties. Mechanical testing was either performed as a cyclic test (20x 10 N) or as a creep test. We found significantly higher levels of elastin in healing tendons at all time-points compared to intact tendons (4% in healing tendons 28 days post-surgery vs 2% in intact tendons). The elastin was more widely distributed throughout the extracellular matrix in the healing tendons in contrast to the intact tendon where the distribution was not so pronounced. Elastase incubation reduced the elastin levels by approximately 30% and led to a 40-50% reduction in creep. This reduction was seen in both intact and healing tendons. Our results show that healing tendons contain more elastin and is more compliable than intact tendons. The role of elastin in tendon healing and tissue compliance indicate a protective role of elastic fibers to prevent re-injuries during early tendon healing.

中文翻译：

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愈合肌腱中的弹性蛋白水平高于完整肌腱，并影响组织顺应性

含有弹性蛋白的弹性纤维在肌腱功能中起着重要作用，但是关于弹性蛋白在肌腱愈合过程中的存在和功能的知识是有限的。这项研究的目的是调查完整和愈合的跟腱中的弹性蛋白含量和分布，并了解弹性蛋白如何影响肌腱的粘弹性。右跟腱完全切除了81只Sprague-Dawley大鼠。弹性蛋白的含量在完整和愈合的肌腱（手术后7、14和28天）中进行定量，弹性蛋白的分布通过免疫组织化学观察。通过弹性蛋白酶孵育降解弹性蛋白用于研究弹性蛋白在粘弹性性质上的作用。机械测试以循环测试（20x 10 N）或蠕变测试进行。与完整的肌腱相比，我们发现在所有时间点的愈合肌腱中的弹性蛋白水平均显着较高（手术后28天的愈合肌腱为4％，完整肌腱为2％）。与完整肌腱分布不那么明显的情况相反，弹性蛋白在愈合肌腱中分布在整个细胞外基质中。弹性蛋白酶孵育可将弹性蛋白水平降低约30％，并使蠕变降低40-50％。在完整和愈合肌腱中均可见到这种减少。我们的结果表明，与完整的肌腱相比，愈合的肌腱包含更多的弹性蛋白，并且更顺应。弹性蛋白在肌腱愈合和组织顺应性中的作用表明弹性纤维在肌腱早期愈合过程中具有防止再次损伤的保护作用。