Department of Physical Therapy, University of Florida, Gainesville, FL 32610, USA.
J Neurotrauma. 2013 Feb 1;30(3):227-35. doi: 10.1089/neu.2012.2504. Epub 2013 Jan 22.
Contusion spinal cord injury (SCI) animal models are used to study loss of muscle function and mass. However, parallels to the human condition typically have been confounded by spontaneous recovery observed within the first few post-injury weeks, partly because of free cage activity. We implemented a new rat model combining SCI with cast immobilization (IMM) to more closely reproduce the unloading conditions experienced by SCI patients. Magnetic resonance imaging was used to monitor hindlimb muscles' cross-sectional area (CSA) after SCI, IMM alone, SCI combined with IMM (SCI+IMM), and in controls (CTR) over a period of 21 days. Soleus muscle tetanic force was measured in situ on day 21, and hindlimb muscles were harvested for histology. IMM alone produced a decrease in triceps surae CSA to 63.9±4.9% of baseline values within 14 days. In SCI, CSA decreased to 75.0±10.5% after 7 days, and recovered to 77.9±10.7% by day 21. SCI+IMM showed the greatest amount of atrophy (56.9±9.9% on day 21). In all groups, muscle mass and soleus tetanic force decreased in parallel, such that specific force was maintained. Extensor digitorum longus (EDL) and soleus fiber size decreased in all groups, particularly in SCI+IMM. We observed a significant degree of asymmetry in muscle CSA in SCI but not IMM. This effect increased between day 7 and 21 in SCI, but also in SCI+IMM, suggesting a minor dependence on muscle activity. SCI+IMM offers a clinically relevant model of SCI to investigate the mechanistic basis for skeletal muscle adaptations after SCI and develop therapeutic approaches.
脊髓挫裂伤（SCI）动物模型用于研究肌肉功能和质量的丧失。然而，由于在损伤后最初几周内观察到自发恢复，与人类状况的平行关系通常存在混淆，部分原因是自由笼内活动。我们建立了一种新的大鼠模型，将 SCI 与石膏固定（IMM）相结合，以更接近地模拟 SCI 患者经历的卸载条件。磁共振成像（MRI）用于监测 SCI、单独 IMM、SCI 与 IMM 相结合（SCI+IMM）以及对照组（CTRL）大鼠后肢肌肉横截面积（CSA）21 天。在第 21 天进行比目鱼肌强直力的原位测量，并收获后肢肌肉进行组织学检查。单独的 IMM 在 14 天内使比目鱼肌 CSA 减少至基线值的 63.9±4.9%。在 SCI 中，CSA 在第 7 天减少到 75.0±10.5%，并在第 21 天恢复到 77.9±10.7%。SCI+IMM 显示出最大的萎缩程度（第 21 天为 56.9±9.9%）。在所有组中，肌肉质量和比目鱼肌强直力呈平行下降，因此比力得以维持。所有组的伸趾长肌（EDL）和比目鱼肌纤维大小均减小，尤其是在 SCI+IMM 中。我们观察到 SCI 中肌肉 CSA 存在显著的不对称性，但在 IMM 中则没有。这种影响在 SCI 中从第 7 天到第 21 天增加，但在 SCI+IMM 中也增加，表明对肌肉活动的依赖较小。SCI+IMM 提供了一种具有临床相关性的 SCI 模型，可用于研究 SCI 后骨骼肌适应的机制基础，并开发治疗方法。
