An oscillating extracellular voltage gradient reduces the density and influences the orientation of astrocytes in injured mammalian spinal cord

We have studied the cellular basis for recovery from acute spinal cord injury induced by applied electric fields. We have emphasized this recovery is due to the regeneration of spinal axons around and through the lesion, and have begun to evaluate the contribution of other cells to the recovery process. We have imposed a voltage gradient of about 320 muV/mm across puncture wounds to the adult rat spinal cord in order to study the accumulation and orientation of GFAP(+) astrocytes within and adjacent to the lesion. This electric field was imposed by a miniaturized electronic implant designed to alternate the polarity of the field every 15 minutes. Astrocytes are known to undergo hyperplastic transformation within injured mammalian cords forming a major component of the scar that forms in response to injury. We have made three observations using a new computer based morphometry technique: First, we note a slight shift in the orientation of astrocytes parallel to the long axis of the spinal cord towards an imaginary reference perpendicular to this axis by approximately 10 degrees -but only in undamaged white matter near the lesion. Second, the relative number of astrocytes was markedly, and statistically significantly, reduced within electrically-treated spinal cords, particularly in the lesion. Third, the imposed voltage gradient statistically reduced the numbers of astrocytes possessing oriented cell processes within the injury site compared to adjacent undamaged regions of spinal cord.