Bareyre Florence M, Kerschensteiner Martin, Raineteau Olivier, Mettenleiter Thomas C, Weinmann Oliver, Schwab Martin E
Department of Neuromorphology, Brain Research Institute, University of Zürich, Switzerland.
Nat Neurosci. 2004 Mar;7(3):269-77. doi: 10.1038/nn1195. Epub 2004 Feb 15.
In contrast to peripheral nerves, central axons do not regenerate. Partial injuries to the spinal cord, however, are followed by functional recovery. We investigated the anatomical basis of this recovery and found that after incomplete spinal cord injury in rats, transected hindlimb corticospinal tract (CST) axons sprouted into the cervical gray matter to contact short and long propriospinal neurons (PSNs). Over 12 weeks, contacts with long PSNs that bridged the lesion were maintained, whereas contacts with short PSNs that did not bridge the lesion were lost. In turn, long PSNs arborize on lumbar motor neurons, creating a new intraspinal circuit relaying cortical input to its original spinal targets. We confirmed the functionality of this circuit by electrophysiological and behavioral testing before and after CST re-lesion. Retrograde transynaptic tracing confirmed its integrity, and revealed changes of cortical representation. Hence, after incomplete spinal cord injury, spontaneous extensive remodeling occurs, based on axonal sprout formation and removal. Such remodeling may be crucial for rehabilitation in humans.
与周围神经不同，中枢轴突不会再生。然而，脊髓的部分损伤之后会出现功能恢复。我们研究了这种恢复的解剖学基础，发现大鼠脊髓不完全损伤后，横断的后肢皮质脊髓束（CST）轴突会向颈灰质中生长，与短和长的脊髓固有神经元（PSN）接触。在12周的时间里，与跨越损伤部位的长PSN的接触得以维持，而与未跨越损伤部位的短PSN的接触则消失了。反过来，长PSN在腰段运动神经元上形成分支，建立了一个新的脊髓内回路，将皮质输入传递到其原来的脊髓靶点。我们通过在CST再次损伤前后进行电生理和行为测试，证实了这个回路的功能。逆行跨突触示踪证实了其完整性，并揭示了皮质代表区的变化。因此，脊髓不完全损伤后，基于轴突发芽形成和消除会发生自发的广泛重塑。这种重塑可能对人类康复至关重要。
