J Korean Soc Spine Surg.  2019 Mar;26(1):1-10. 10.4184/jkss.2019.26.1.1.

Microelectric Treatment by Transcutaneous Electrical Nerve Stimulation in a Rat Model of Acute Spinal Cord Injury

• Sohn HM
• Lim W
• Kim YW
• Ko Y
• Park M
• Kim B

• KMID: 2442342
• DOI: http://doi.org/10.4184/jkss.2019.26.1.1

Abstract

STUDY DESIGN: Animal study.
OBJECTIVES
To investigate the effects of microelectric treatment by transcutaneous electrical nerve stimulation (TENS) on functional recovery and histological changes in a rat model of spinal cord injury (SCI). SUMMARY OF LITERATURE REVIEW: The effects of TENS on spasticity and its underlying mechanisms remain unclear.
MATERIALS AND METHODS
SCI was induced by a 1.5-mm impactor with 200,000-260,000 dyne after laminectomy. Rats were divided into the following groups: group I (normal control), group II (microelectric treatment of 0 A), group III (microelectric treatment of 100 µA for 1 hr/day), group IV (microelectric treatment of 400 µA for 1 hr/day), and group V (microelectric treatment of 400 µA for 24 hr/day). After inducing SCI, rats were assessed by a sensory test with von Frey filaments and the locomotor recovery test (BBB rating scale) at 1, 4, 7, 14, 21, and 28 days. To evaluate spinal cord damage, histopathological studies were performed with hematoxylin and eosin. Brain-derived neurotrophic factor (BDNF) and TrkB immunohistochemistry studies were performed at 28 days.
RESULTS
In groups IV and V, the BBB score had significantly improved on days 21 and 28 after SCI, and the TENS-treated groups showed significant neuronal recovery. After SCI, groups IV and V showed a significant recovery of locomotor function and the motor sensory response of the withdrawal threshold to 3.5 g. In addition, necrotic tissue and cystic spaces in the spinal cord were significantly reduced and BDNF/TrkB-positive cells were highly expressed in groups III, IV, and V.
CONCLUSIONS
Microelectric treatment can play a role in facilitating the recovery of locomotion following SCI.

Keyword

Spinal cord injury; Microelectric treatment; Transcutaneous electric nerve stimulation; Histologic finding; Functional recovery

MeSH Terms

Animals
Brain-Derived Neurotrophic Factor
Eosine Yellowish-(YS)
Hematoxylin
Immunohistochemistry
Laminectomy
Locomotion
Models, Animal*
Muscle Spasticity
Neurons
Rats*
Spinal Cord Injuries*
Spinal Cord*
Transcutaneous Electric Nerve Stimulation*
Brain-Derived Neurotrophic Factor
Eosine Yellowish-(YS)
Hematoxylin

Figure

• 

  Fig. 1. Establishment of the spinal cord injury (SCI) model in the rats and confirmation of T9-10 laminectomy. (A) Establishment of the SCI model in the rats using the Modified Ohio Impactor. (B) Confirmation of T9-10 lesions using micro-computed tomography.

• 

  Fig. 2. Transcutaneous electrical nerve stimulation (TENS) treatment in the rat model of spinal cord injury (SCI). (A) Schematic representation of the rat model system for TENS treatment through 2 coated electrodes located below the instrument. (B) Constant current stimuli were applied to the dorsal surface of the SCI rats.

• 

  Fig. 3. Locomotor recovery test using BBB scoring. (A) Transcutaneous electrical nerve stimulation (TENS)-treated animals (400 μA) showed better BBB locomotor scores than the animals treated with 0 A (∗p<0.05). (B) TENS treatment for 1 hr/day and 24 hr/day improved BBB locomotor scores more than 0 hr/day of treatment (∗p<0.05).

• 

  Fig. 4. Motor sensory response test by the 50% withdrawal threshold through von Frey filament application. (A) Transcutaneous electrical nerve stimulation (TENS)-treated animals (400 μA) had a lower 50% withdrawal threshold than the animals treated with 0 A (∗p<0.05). (B) TENS treatment for 1 hr/day and 24 hr/day led to a lower 50% withdrawal threshold than 0 hr/day of treatment (∗p<0.05).

• 

  Fig. 5. Photographs taken from the site of a spinal cord injury, excised 28 days after the injury. The spinal cord segments were cut into 8-μm axial sections. Lesion swelling is seen on low-power magnification (×40) with hematoxylin and eosin staining. (A) Transcutaneous electrical nerve stimulation (TENS)-treated animals (400 μA) showed better spinal cord recovery than the animals treated with 0 A. (B) TENS treatment for 1 hr/day and 24 hrs/day favored spinal cord recovery in comparison with 0 hr/day of treatment.

• 

  Fig. 6. Immunohistochemical study of brain-derived neurotrophic factor (BDNF) expression at the site of a spinal cord injury, excised 28 days after the injury. Each field was examined at ×100 (10 objective × 10 ocular) magnification. (A) Transcutaneous electrical nerve stimulation (TENS)-treated animals (400 μA) showed higher BDNF expression than the animals treated with 0 A. (B) TENS treatment for 1 hr/day and 24 hr/day led to higher BDNF expression than 0 hr/day of treatment.

• 

  Fig. 7. Immunohistochemical study of TrkB expression at the site of a spinal cord injury, excised 28 days after the injury. Each field was examined at ×100 (10 objective × 10 ocular) magnification. (A) Transcutaneous electrical nerve stimulation (TENS)-treated animals (400 μA) showed higher TrkB expression than the animals treated with 0 A. (B) TENS treatment for 1 hr/day and 24 hr/day led to higher TrkB expression than 0 hr/day of treatment.

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