Low intensity repetitive transcranial magnetic stimulation does not induce cell survival or regeneration in a mouse optic nerve crush model

PLoS One. 2015 May 20;10(5):e0126949. doi: 10.1371/journal.pone.0126949. eCollection 2015.

Abstract

Low intensity repetitive Transcranial Magnetic Stimulation (LI-rTMS), a non-invasive form of brain stimulation, has been shown to induce structural and functional brain plasticity, including short distance axonal sprouting. However, the potential for LI-rTMS to promote axonal regeneration following neurotrauma has not been investigated. This study examined the effect of LI-rTMS on retinal ganglion cell (RGC) survival, axon regeneration and levels of BDNF in an optic nerve crush neurotrauma model. Adult C57Bl/6J mice received a unilateral intraorbital optic nerve crush. Mice received 10 minutes of sham (handling control without stimulation) (n=6) or LI-rTMS (n = 8) daily stimulation for 14 days to the operated eye. Immunohistochemistry was used to assess RGC survival (β-3 Tubulin) and axon regeneration across the injury (GAP43). Additionally, BDNF expression was quantified in a separate cohort by ELISA in the retina and optic nerve of injured (optic nerve crush) (sham n = 5, LI-rTMS n = 5) and non-injured mice (sham n = 5, LI-rTMS n = 5) that received daily stimulation as above for 7 days. Following 14 days of LI-rTMS there was no significant difference in mean RGC survival between sham and treated animals (p>0.05). Also, neither sham nor LI-rTMS animals showed GAP43 positive labelling in the optic nerve, indicating that regeneration did not occur. At 1 week, there was no significant difference in BDNF levels in the retina or optic nerves between sham and LI-rTMS in injured or non-injured mice (p>0.05). Although LI-rTMS has been shown to induce structural and molecular plasticity in the visual system and cerebellum, our results suggest LI-rTMS does not induce neuroprotection or regeneration following a complete optic nerve crush. These results help define the therapeutic capacity and limitations of LI-rTMS in the treatment of neurotrauma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axons / pathology
  • Brain-Derived Neurotrophic Factor / metabolism
  • Cell Survival
  • Disease Models, Animal
  • Enzyme-Linked Immunosorbent Assay
  • Mice, Inbred C57BL
  • Nerve Crush*
  • Nerve Regeneration*
  • Optic Nerve Injuries / pathology*
  • Optic Nerve Injuries / physiopathology*
  • Retina / pathology
  • Retinal Ganglion Cells / pathology
  • Transcranial Magnetic Stimulation*

Substances

  • Brain-Derived Neurotrophic Factor

Grants and funding

This work was supported by the National Health and Medical Research Council (634386, APP1002258; http://www.nhmrc.gov.au/) Neurotrauma Research Program, State Government of Western Australia (no grant number available, http://www.nrp.org.au/), and the Australian Research Council (LP110100201; http://www.arc.gov.au/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.