Original Research ARTICLE

Front. Neurol., 25 October 2010 | http://dx.doi.org/10.3389/fneur.2010.00136

Observations at the CNS–PNS border of ventral roots connected to a neuroma

  • 1 Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
  • 2 Department of Clinical Neuroscience, Division of Neurology, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden
  • 3 Department of Clinical Science and Education, Hand Surgery, Södersjukhuset, Stockholm, Sweden

Previous studies have shown that numerous sprouts originating from a neuroma, after nerve injury in neonatal animals, can invade spinal nerve roots. However, no study with a focus on how such sprouts behave when they reach the border between the central and peripheral nervous system (CNS–PNS border) has been published. In this study we have in detail examined the CNS–PNS border of ventral roots in kittens with light and electron microscopy after early postnatal sciatic nerve resection. A transient ingrowth of substance P positive axons was observed into the CNS, but no spouts remained 6 weeks after the injury. Using serial sections and electron microscopy it was possible to identify small bundles of unmyelinated axons that penetrated from the root fascicles for a short distance into the CNS. These axons ended blindly, sometimes with a growth cone-like terminal swelling filled with vesicles. The axon bundles were accompanied by p75 positive cells in both the root fascicles and the pia mater, but not in the CNS. It may thus be suggested that neurotrophin presenting p75 positive cells could facilitate axonal growth into the pia mater and that the lack of such cells in the CNS compartment might contribute to the failure of growth into the CNS. A maldevelopment of myelin sheaths at the CNS–PNS border of motor axons was observed and it seems possible that this could have consequences for the propagation of action potential across this region after neonatal nerve injury. Thus, in this first detailed study on the behavior of recurrent sprouts at the CNS–PNS border.

Keywords: cat, nerve lesion, sprouting, electron microscopy, immunohistochemistry, regeneration, PNS–CNS transition

Citation: Remahl S, Angeria M, Nilsson Remahl I, Carlstedt T and Risling M (2010) Observations at the CNS–PNS border of ventral roots connected to a neuroma. Front. Neur. 1:136. doi: 10.3389/fneur.2010.00136

Received: 22 April 2010; Accepted: 28 September 2010;
Published online: 25 October 2010

Edited by:

Peter Shortland, Barts and The London School of Medicine and Dentistry, UK

Reviewed by:

Peter Shortland, Barts and The London School of Medicine and Dentistry, UK
Leif A. Havton, University of California at Los Angeles Neurorehabilitation and Research Center, USA

Copyright: © 2010 Remahl, Angeria, Nilsson Remahl, Carlstedt and Risling. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.

*Correspondence: Mårten Risling, Department of Neuroscience, Experimental Traumatology Unit, Retzius väg 8, Karolinska Institutet, S-171 77 Stockholm, Sweden. e-mail: marten.risling@ki.se