Spinal cord injury (SCI) usually results in permanent functional impairment and is considered a worldwide medical problem. However, both motor and sensory functions can spontaneously recover to varying extents in humans and animals with incomplete SCI. This study observed a significant spontaneous hindlimb locomotor recovery in Sprague-Dawley rats at four weeks after post-right-side spinal cord hemisection at thoracic 8 (T8). To verify whether the above spontaneous recovery derives from the ipsilateral axonal or neuronal regeneration to reconnect the lesion site, we resected either the scar tissue or right side T7 spinal cord at five weeks post-T8 hemisected injury. The results showed that the spontaneously achieved right hindlimb locomotor function had little change after resection. Furthermore, when T7 left hemisection was performed five weeks after the initial injury, the spontaneously achieved right hindlimb locomotor function was dramatically abolished. A similar result could also be observed when T7 transection was performed after the initial hemisection. The results indicated that it might be the contralateral axonal remolding rather than the ipsilateral axonal or neuronal regeneration beyond the lesion site responsible for the spontaneous hindlimb locomotor recovery. The immunostaining analyses and corticospinal tracts (CSTs) tracing results confirmed this hypothesis. We detected no substantial neuronal and CST regeneration throughout the lesion site; however, significantly more CST fibers were observed to sprout from the contralateral side at the lumbar 4 (L4) spinal cord in the hemisection model rats than in intact ones. In conclusion, this study verified that contralateral CST sprouting, but not ipsilateral CST or neuronal regeneration, is primarily responsible for the spontaneous locomotor recovery in hemisection SCI rats.

中文翻译：

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对侧轴突发芽但不是同侧再生负责脊髓半切除后的自发运动恢复。

脊髓损伤 (SCI) 通常会导致永久性功能障碍，被认为是一个世界性的医学问题。然而，在不完全 SCI 的人类和动物中，运动和感觉功能都可以在不同程度上自发恢复。本研究观察到 Sprague-Dawley 大鼠在胸椎 8 (T8) 右侧脊髓半切术后 4 周后显着的自发性后肢运动恢复。为了验证上述自发恢复是否来自同侧轴突或神经元再生以重新连接病变部位，我们在 T8 半切伤后五周切除了疤痕组织或右侧 T7 脊髓。结果表明，自发实现的右后肢运动功能在切除后几乎没有变化。此外，在初始损伤后 5 周进行 T7 左半部切除时，自发实现的右后肢运动功能显着消失。在初始半切后进行 T7 横切时，也可以观察到类似的结果。结果表明，负责自发性后肢运动恢复的可能是对侧轴突重塑，而不是病变部位以外的同侧轴突或神经元再生。免疫染色分析和皮质脊髓束 (CST) 追踪结果证实了这一假设。我们在整个病变部位没有检测到大量的神经元和 CST 再生；然而，与完整模型大鼠相比，在半切模型大鼠的腰椎 4 (L4) 脊髓的对侧发芽的 CST 纤维明显更多。