The injured spinal cord spontaneously forms a new intraspinal circuit in adult rats

Abstract

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.

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Figure 1: Innervation of the cervical spinal cord (cervical segment C5 presented here) by collaterals of the corticospinal tract originating from the hindlimb motor cortex.
Figure 2: Anatomical localization of retrogradely labeled propriospinal neurons in the cervical cord (cervical segment C4 presented here) of intact rats.
Figure 3: Quantification of close appositions formed by hindlimb CST collaterals on short (a,c,e,g) or long (b,d,f,h) propriospinal neurons in the cervical gray matter.
Figure 4: Contacts between long PSN axons and lumbar motor neurons.
Figure 5: Localization of the trans-synaptic retrograde tracer PRV in the spinal cord and motor cortex after hindlimb injection.
Figure 6: Spontaneous partial recovery of the hindlimb placing response to light touch of the foot in mid-thoracic dorsal hemisected rats includes a CST contribution.
Figure 7: Electrophysiological assessment of the CST reorganization.
Figure 8: Cortical localization of the CST neurons labeled retrogradely trans-synaptically by PRV from the hindlimb.

References

  1. 1

    Schwab, M.E. & Bartholdi, D. Degeneration and regeneration of axons in the lesioned spinal cord. Physiol. Rev. 76, 319–370 (1996).

  2. 2

    Rossignol, S., Drew, T., Brustein, E. & Jiang, W. Locomotor performance and adaptation after partial or complete spinal cord lesions in the cat. Prog. Brain Res. 123, 349–365 (1999).

  3. 3

    Wernig, A. & Muller, S. Laufband locomotion with body weight support improved walking in persons with severe spinal cord injuries. Paraplegia 30, 229–238 (1992).

  4. 4

    Dietz, V., Wirz, M., Curt, A. & Colombo, G. Locomotor pattern in paraplegic patients: training effects and recovery of spinal cord function. Spinal Cord 36, 380–390 (1998).

  5. 5

    Hiersemenzel, L.P., Curt, A. & Dietz, V. From spinal shock to spasticity: neuronal adaptations to a spinal cord injury. Neurology 54, 1574–1582 (2000).

  6. 6

    Holaday, J.W. & Faden, A.I. Spinal shock and injury: experimental therapeutic approaches. Adv. Shock Res. 10, 95–98 (1983).

  7. 7

    Gensert, J.M. & Goldman, J.E. Endogenous progenitors remyelinate demyelinated axons in the adult CNS. Neuron 19, 197–203 (1997).

  8. 8

    Lawrence, D.G. & Kuypers, H.G. The functional organization of the motor system in the monkey. I. The effects of bilateral pyramidal lesions. Brain 91, 1–14 (1968).

  9. 9

    Pettersson, L.G., Lundberg, A., Alstermark, B., Isa, T. & Tantisira, B. Effect of spinal cord lesions on forelimb target-reaching and on visually guided switching of target-reaching in the cat. Neurosci. Res. 29, 241–256 (1997).

  10. 10

    Weidner, N., Ner, A., Salimi, N. & Tuszynski, M.H. Spontaneous corticospinal axonal plasticity and functional recovery after adult central nervous system injury. Proc. Natl. Acad. Sci. USA 98, 3513–3518 (2001).

  11. 11

    Fouad, K., Pedersen, V., Schwab, M.E. & Brosamle, C. Cervical sprouting of corticospinal fibers after thoracic spinal cord injury accompanies shifts in evoked motor responses. Curr. Biol. 11, 1766–1770 (2001).

  12. 12

    Raineteau, O. & Schwab, M.E. Plasticity of motor systems after incomplete spinal cord injury. Nat. Rev. Neurosci. 2, 263–273 (2001).

  13. 13

    Murray, M. & Goldberger, M.E. Restitution of function and collateral sprouting in the cat spinal cord: the partially hemisected animal. J. Comp. Neurol. 158, 19–36 (1974).

  14. 14

    Jankowska, E., Lundberg, A., Roberts, W.J. & Stuart, D. A long propriospinal system with direct effect on motoneurones and on interneurones in the cat lumbosacral cord. Exp. Brain Res. 21, 169–194 (1974).

  15. 15

    Miller, S., van Berkum, R., van der Burg, J. & van der Meche, F.G. Interlimb co-ordination in stepping in the cat. J. Physiol. 230, 30P–31P (1973).

  16. 16

    Giovanelli Barilari, M. & Kuypers, H.G. Propriospinal fibers interconnecting the spinal enlargements in the cat. Brain Res. 14, 321–330 (1969).

  17. 17

    Alstermark, B., Lundberg, A., Pinter, M. & Sasaki, S. Subpopulations and functions of long C3–C5 propriospinal neurones. Brain Res. 404, 395–400 (1987).

  18. 18

    Alstermark, B., Lundberg, A., Pinter, M. & Sasaki, S. Long C3–C5 propriospinal neurones in the cat. Brain Res. 404, 382–388 (1987).

  19. 19

    Alstermark, B., Kummel, H., Pinter, M.J. & Tantisira, B. Branching and termination of C3–C4 propriospinal neurones in the cervical spinal cord of the cat. Neurosci. Lett. 74, 291–296 (1987).

  20. 20

    Alstermark, B., Isa, T., Kummel, H. & Tantisira, B. Projection from excitatory C3–C4 propriospinal neurones to lamina VII and VIII neurones in the C6-Th1 segments of the cat. Neurosci. Res. 8, 131–137 (1990).

  21. 21

    Neafsey, E.J. et al. The organization of the rat motor cortex: a microstimulation mapping study. Brain Res. 396, 77–96 (1986).

  22. 22

    De Ryck, M., Van Reempts, J., Duytschaever, H., Van Deuren, B. & Clincke, G. Neocortical localization of tactile/proprioceptive limb placing reactions in the rat. Brain Res. 573, 44–60 (1992).

  23. 23

    Z'Graggen, W.J. et al. Compensatory sprouting and impulse rerouting after unilateral pyramidal tract lesion in neonatal rats. J. Neurosci. 20, 6561–6569 (2000).

  24. 24

    Li, W.W., Yew, D.T., Chuah, M.I., Leung, P.C. & Tsang, D.S. Axonal sprouting in the hemisected adult rat spinal cord. Neuroscience 61, 133–139 (1994).

  25. 25

    Aoki, M., Fujito, Y., Satomi, H., Kurosawa, Y. & Kasaba, T. The possible role of collateral sprouting in the functional restitution of corticospinal connections after spinal hemisection. Neurosci. Res. 3, 617–627 (1986).

  26. 26

    Jankowska, E. & Hammar, I. Spinal interneurones; how can studies in animals contribute to the understanding of spinal interneuronal systems in man? Brain Res. Brain Res. Rev. 40, 19–28 (2002).

  27. 27

    Mariani, J. Elimination of synapses during the development of the central nervous system. Prog. Brain Res. 58, 383–392 (1983).

  28. 28

    Chen, C. & Regehr, W.G. Developmental remodeling of the retinogeniculate synapse. Neuron 28, 955–966 (2000).

  29. 29

    Hubel, D.H., Wiesel, T.N. & LeVay, S. Plasticity of ocular dominance columns in monkey striate cortex. Philos. Trans. R. Soc. Lond. B Biol. Sci. 278, 377–409 (1977).

  30. 30

    Colman, H., Nabekura, J. & Lichtman, J.W. Alterations in synaptic strength preceding axon withdrawal. Science 275, 356–361 (1997).

  31. 31

    Masson, R.L., Jr., Sparkes, M.L. & Ritz, L.A. Descending projections to the rat sacrocaudal spinal cord. J. Comp. Neurol. 307, 120–130 (1991).

  32. 32

    Jankowska, E., Lundberg, A. & Stuart, D. Propriospinal control of last order interneurones of spinal reflex pathways in the cat. Brain Res. 53, 227–231 (1973).

  33. 33

    Raineteau, O., Fouad, K., Noth, P., Thallmair, M. & Schwab, M.E. Functional switch between motor tracts in the presence of the mAb IN-1 in the adult rat. Proc. Natl. Acad. Sci. USA 98, 6929–6934 (2001).

  34. 34

    Bareyre, F.M., Haudenschild, B. & Schwab, M.E. Long-lasting sprouting and gene expression changes induced by the monoclonal antibody IN-1 in the adult spinal cord. J. Neurosci. 22, 7097–7110 (2002).

  35. 35

    Gordon, T., Yang, J.F., Ayer, K., Stein, R.B. & Tyreman, N. Recovery potential of muscle after partial denervation: a comparison between rats and humans. Brain Res. Bull. 30, 477–482 (1993).

  36. 36

    Card, J.P. et al. Neurotropic properties of pseudorabies virus: uptake and transneuronal passage in the rat central nervous system. J. Neurosci. 10, 1974–1994 (1990).

  37. 37

    Strack, A.M., Sawyer, W.B., Platt, K.B. & Loewy, A.D. CNS cell groups regulating the sympathetic outflow to adrenal gland as revealed by transneuronal cell body labeling with pseudorabies virus. Brain Res. 491, 274–296 (1989).

  38. 38

    Steward, O., Zheng, B. & Tessier-Lavigne, M. False resurrections: Distinguishing regenerated from spared axons in the injured central nervous system. J. Comp. Neurol. 459, 1–8 (2003).

  39. 39

    Sloan, T.B. Anesthetic effects on electrophysiologic recordings. J. Clin. Neurophysiol. 15, 217–226 (1998).

  40. 40

    Sanes, J.N., Suner, S. & Donoghue, J.P. Dynamic organization of primary motor cortex output to target muscles in adult rats. I. Long-term patterns of reorganization following motor or mixed peripheral nerve lesions. Exp. Brain Res. 79, 479–491 (1990).

  41. 41

    Donoghue, J.P. Plasticity of adult sensorimotor representations. Curr. Opin. Neurobiol. 5, 749–754 (1995).

  42. 42

    Kaas, J.H., Florence, S.L. & Jain, N. Subcortical contributions to massive cortical reorganizations. Neuron 22, 657–660 (1999).

  43. 43

    Bruehlmeier, M. et al. How does the human brain deal with a spinal cord injury? Eur. J. Neurosci. 10, 3918–3922 (1998).

  44. 44

    Chen, R., Corwell, B., Yaseen, Z., Hallett, M. & Cohen, L.G. Mechanisms of cortical reorganization in lower-limb amputees. J. Neurosci. 18, 3443–3450 (1998).

  45. 45

    Nguyen, Q.T., Sanes, J.R. & Lichtman, J.W. Pre-existing pathways promote precise projection patterns. Nat. Neurosci. 5, 861–867 (2002).

  46. 46

    Schnell, L. & Schwab, M.E. Sprouting and regeneration of lesioned corticospinal tract fibres in the adult rat spinal cord. Eur. J. Neurosci. 5, 1156–1171 (1993).

  47. 47

    Merkler, D. et al. Locomotor recovery in spinal cord-injured rats treated with an antibody neutralizing the myelin-associated neurite growth inhibitor Nogo-A. J. Neurosci. 21, 3665–3673 (2001).

  48. 48

    Jons, A. & Mettenleiter, T.C. Green fluorescent protein expressed by recombinant pseudorabies virus as an in vivo marker for viral replication. J. Virol. Methods 66, 283–292 (1997).

  49. 49

    Herzog, A. & Brosamle, C. 'Semifree-floating' treatment: a simple and fast method to process consecutive sections for immunohistochemistry and neuronal tracing. J. Neurosci. Methods 72, 57–63 (1997).

  50. 50

    Roof, R.L., Schielke, G.P., Ren, X. & Hall, E.D. A comparison of long-term functional outcome after 2 middle cerebral artery occlusion models in rats. Stroke 32, 2648–2657 (2001).

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Acknowledgements

The authors would like to thank T. Misgeld for discussion, B. Klupp (TCM laboratory) for providing the PRV and the RK13 cells, K. Fouad, B. Haudenschild and J. Scholl for technical help and R. Schoeb for help with the photographs. The Swiss National Science Foundation (SNF, grant 31-63633.00), the SNF NCCR "neural plasticity and repair" and the Christopher Reeve Paralysis Foundation (Spinal Cord Consortium, Springfield, NJ) supported this work.

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Correspondence to Florence M Bareyre.

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Supplementary information

Supplementary Fig. 1

Original photomicrographs of Fig. 1a-c without highlighting of CST collaterals. Legend equal to Fig. 1. (JPG 38 kb)

Supplementary Fig. 2

Quantification of sprouting of the intact ventral CST component in response to mid-thoracic dorsal hemisection in rats. (a): Sprouting of ventral CST collaterals into the cervical grey matter at 3 and 12 weeks after the lesion. (b): Sprouting of ventral CST collaterals into the lumbar grey matter at 3 and 12 weeks after the lesion. The quantification of "ventral collaterals/ main ventral CST" was performed in the cervical and lumbar enlargements of the spinal cord, in the segments C3 to C5 and L2 to L4 respectively. The absolute number of collaterals emanating from the main ventral CST tract and entering the gray matter was counted in 20 consecutive transverse sections. In order to correct for inter animal variation in the tracing efficiency, we divided the absolute number of ventral collaterals by the number of traced fibers in the main ventral CST. No significant differences were found between rats sustaining a mid-thoracic dorsal hemisection 3 or 12 weeks prior to the evaluation and their respective controls in the cervical cord. It is therefore unlikely that additional contacts between ventral CST collaterals and long propriospinal cell bodies are created in injured animals compared to control animals and contribute to the functional recovery described in our manuscript. However, the number of ventral collaterals per main ventral CST doubled in the lumbar cord in rats sustaining a mid-thoracic dorsal hemisection 3 or 12 weeks prior to the evaluation compared to their respective controls. Even if the difference did not reach statistical significance, it remains possible that ventral collaterals in the lumbar cord may also contribute to some of the functional recovery seen in our study e.g. by directly contacting lumbar motoneurons. This additional level of reorganization would be in line with a previous study10 in which the authors demonstrated that after bilateral section of the dorsal CST at cervical level C3, substantial sprouting from the spared ventral corticospinal tract occurred onto medial motoneuron pools in the cervical spinal cord caudal to the lesion. (JPG 38 kb)

Supplementary Fig. 3

Quantification of the close appositions formed by hindlimb CST collaterals on long propriospinal neurons in the cervical grey matter after treatment with the mIN-1 antibody, a control anti-HRP antibody or without treatment. No significant differences were found between the injured groups. (JPG 22 kb)

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Bareyre, F., Kerschensteiner, M., Raineteau, O. et al. The injured spinal cord spontaneously forms a new intraspinal circuit in adult rats. Nat Neurosci 7, 269–277 (2004). https://doi.org/10.1038/nn1195

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