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Contrasting neuropathology and functional recovery after spinal cord injury in developing and adult rats

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Abstract

Conflicting findings exist regarding the link between functional recovery and the regrowth of spinal tracts across the lesion leading to the restoration of functional contacts. In the present study, we investigated whether functional locomotor recovery was attributable to anatomical regeneration at postnatal day 1 (PN1), PN7, PN14 and in adult rats two months after transection injury at the tenth thoracic segment of the spinal cord. The Basso, Beattie, and Bresnahan scores showed that transection led to a failure of hindlimb locomotor function in PN14 and adult rats. However, PN1 and PN7 rats showed a significant level of stepping function after complete spinal cord transection. Unexpectedly, unlike the transected PN14 and adult rats in which the spinal cord underwent limited secondary degeneration and showed a scar at the lesion site, the rats transected at PN1 and PN7 showed massive secondary degeneration both anterograde and retrograde, leaving a >5-mm gap between the two stumps. Furthermore, retrograde tracing with fluorogold (FG) also showed that FG did not cross the transection site in PN1 and PN7 rats as in PN14 and adult rats, and re-transection of the cord caused no apparent loss in locomotor performance in the rats transected at PN1. Thus, these three lines of evidence strongly indicated that the functional recovery after transection in neonatal rats is independent of regrowth of spinal tracts across the lesion site. Our results support the notion that the recovery of locomotor function in developing rats may be due to intrinsic adaptations in the spinal circuitry below the lesion that control hindlimb locomotor activity rather than the regrowth of spinal tracts across the lesion. The difference in secondary degeneration between neonatal and adult rats remains to be explored.

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Authors and Affiliations

  1. Department of Anatomy, The University of Hong Kong, Pokfulam, Hong Kong SAR, China

    Qiuju Yuan, Kin Chiu & Wutian Wu

  2. School of Chinese Medicine, Faculty of Science, The Chinese University of Hong Kong, Shatin, N.T. Hong Kong SAR, China

    Qiuju Yuan & Zhi-Xiu Lin

  3. State Key Laboratory of Quality Research in Chinese Medicine and Institute of Chinese Medical Sciences, University of Macau, Macao SAR, China

    Huanxing Su

  4. State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China

    Wutian Wu

  5. Research Center of Reproduction, Development and Growth, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China

    Wutian Wu

  6. GHM Institute of CNS Regeneration, Jinan University, Guangzhou, China

    Wutian Wu

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  1. Qiuju Yuan
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  2. Huanxing Su
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  3. Kin Chiu
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  5. Zhi-Xiu Lin
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Correspondence to Wutian Wu or Zhi-Xiu Lin.

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Yuan, Q., Su, H., Chiu, K. et al. Contrasting neuropathology and functional recovery after spinal cord injury in developing and adult rats. Neurosci. Bull. 29, 509–516 (2013). https://doi.org/10.1007/s12264-013-1356-5

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  • DOI: https://doi.org/10.1007/s12264-013-1356-5

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