The potential of electric field for promoting neurite guidance in spinal cord injury regeneration strategies

Anna Varone, University of Aberdeen

Authors*A. VARONE, Z. N. MUHAMAT, A. M. RAJNICEK, W. HUANG;
Lab Abstract:

Introduction Spinal cord injury, for which there is no cure, can lead to permanent loss of neurological function. Reasons for failed axon regrowth include poor intrinsic growth capacity of adult CNS neurons, inhibitory chemicals and physical barriers formed post injury. Electric field (EF) stimulation is a promising strategy for spinal repair because it promotes directional neurite growth in cultured non-mammalian or embryonic neurons. Here, we investigated the effects of EF exposure on postnatal rat cortical neurons and organotypic spinal cord slices to further explore its potential for spinal repair.

Methods Cortices and spinal cords of Sprague Dawley rats at postnatal days 0-3 were used to culture cortical neurons and organotypic spinal cord slices. Neurons were cultured directly in the EF migration chamber for 48h before applying EFs ranging from 50 to 350mV/mm for 3-6h. To examine if an EF could overcome the effects of inhibitory molecules present post-spinal injury, 10µg/ml Chondroitin Sulphate Proteoglycan-6 (CSPG6) was added to the culture medium during EF exposure. Spinal cord slices were prepared at 350µm thickness and lesioned with surgical blades to produce a 700µm lesion gap. Four days after lesion, slices were transferred to the migration chamber and 50mV/mm EF was applied for 24h.

Results Cortical neurons showed an increase in the proportion of neurites facing the anode and facing perpendicular to the EF vector compared to the random growth of controls without an EF. This bias increased as the EF strength increased, with 220mV/mm being optimal. However, EF stimulation did not increase neurite length compared to no-EF conditions at any field strength. Moreover, the EF stimulation overcame the inhibitory effects of CSPG6 on growth of anode facing cortical cell neurites. In spinal cord slice cultures, there was a substantial increase in the alignment of re-growing axons when an EF was applied at 50mV/mm for 24h compared to the non-EF condition. Alignment was abolished when an Epac antagonist or Rho agonist were present in the culture medium.

Summary This is the first demonstration that EF stimulation promotes directional growth of cultured postnatal rat cortical neurons and that an EF aligns growth of re-growing axons in an ex vivo model of spinal injury. Future studies will investigate its in vivo efficacy alone and in combinational with other spinal repair strategies.

Authors*A. VARONE, Z. N. MUHAMAT, A. M. RAJNICEK, W. HUANG;
Univ. of Aberdeen, Aberdeen, United KingdomDisclosures A. Varone: None. Z.N. Muhamat: None. A.M. Rajnicek: None. W. Huang: None.

Grant Support University of Aberdeen, Tenovus Scotland, Scottish Rugby Union

Program No. 213.23. 2018 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience, 2018. Online.