Since the majority of a tendon's dry weight is collagen fibers, tendon healing consists mainly of collagen repair and observing three-dimensional networks of collagen fibers with scanning electron microscopy (SEM) is optimal for investigating this process. In this report, a cell-maceration/SEM method was used to investigate extrasynovial- tendon (unwrapped tendon in synovial tissue such as the tendon sheath) healing of an injured Achilles tendon in a rat model. In addition, since mechanical stimulation is important for tendon healing, a novel, tensionless, rat lower leg tendon injury model was established and verified by visualizing the structural change of collagen fibers under tensionless conditions by SEM. This new model was created by transplanting the leg of a rat with a tendon laceration to the back, removing mechanical stimulation. We then compared the process of tendon healing with and without tension using SEM. Under tension, collagen at the tendon stump shows axial alignment and repair that subsequently demarcates the paratenon (connective tissue on the surface of an extrasynovial tendon) border. In contrast, under tensionless conditions, the collagen remains randomly arranged. Our findings demonstrate that mechanical stimulation contributes to axial arrangement and reinforces the importance of tendon tension in wound healing.

中文翻译：

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使用新型无张力模型可视化受机械刺激影响的肌腱愈合的微观结构变化

由于肌腱的大部分干重是胶原纤维，因此肌腱愈合主要由胶原修复组成，用扫描电子显微镜 (SEM) 观察胶原纤维的三维网络是研究这一过程的最佳选择。在本报告中，使用细胞浸渍/SEM 方法研究了大鼠模型中受伤的跟腱的滑膜外肌腱（滑膜组织中未包裹的肌腱，例如腱鞘）愈合情况。此外，由于机械刺激对肌腱愈合很重要，因此通过 SEM 可视化无张力条件下胶原纤维的结构变化，建立并验证了一种新型、无张力的大鼠小腿肌腱损伤模型。这种新模型是通过将肌腱撕裂的大鼠腿移植到背部，去除机械刺激而创建的。然后，我们使用 SEM 比较了有张力和无张力的肌腱愈合过程。在张力下，肌腱残端处的胶原蛋白显示出轴向排列和修复，随后划定了腱旁（滑膜外肌腱表面的结缔组织）边界。相反，在无张力条件下，胶原蛋白保持随机排列。我们的研究结果表明，机械刺激有助于轴向排列并加强肌腱张力在伤口愈合中的重要性。