Abstract
Background: Transcutaneous electrical nerve stimulation (TENS) is commonly used for pain control. However, the effects of TENS on osteoarthritis (OA) pain and potential underlying mechanisms remain unclear. Objective: The objective of this study was to investigate the effect of TENS on OA pain treatment and underlying mechanisms related to glial cell inhibition. Design: This was an experimental study. Methods: OA was induced by injection of monosodium iodoacetate into the synovial space of the right knee joint of rats. High-frequency (HF) TENS (100 Hz), low-frequency (LF) TENS (4 Hz), or sham TENS was applied to the ipsilateral knee joint for 20 minutes. Paw withdrawal threshold (PWT), weight bearing, and knee bend score (KBS) were measured. Immunohistochemistry for microglia and astrocytes was performed with L3 to L5 spinal segment samples. To investigate the effects of glial inhibition on OA pain, minocycline, l-α-aminoadipate, or artificial cerebrospinal fluid was injected intrathecally, and PWT and KBS were measured. Results: Compared with sham TENS, both HF TENS and LF TENS significantly increased PWT, decreased KBS, and inhibited activated microglia in the L3 to L5 segments but did not decrease the total number of microglia, except in the L4 segment (HF TENS). Astrocyte expression was significantly decreased in the L3 to L5 segments following LF TENS and in the L3 segment following HF TENS. Compared with artificial cerebrospinal fluid, both minocycline and l-α-aminoadipate increased PWT and decreased KBS. Limitations: These results cannot be generalized to humans. Conclusions: TENS alleviates OA pain in rats by inhibiting activated microglia and reducing astrocyte expression in the spinal cord. Although these results may not be generalizable to chronic pain in patients with OA, within the limitation of the experimental animal model used in the present study, they suggest a possible mechanism and preclinical evidence supporting further experimentation or clinical use of TENS in humans.
| Original language | English |
|---|---|
| Pages (from-to) | 1211-1223 |
| Number of pages | 13 |
| Journal | Physical Therapy |
| Volume | 99 |
| Issue number | 9 |
| DOIs | |
| Publication status | Published - 2019 Sept 1 |
Bibliographical note
Funding Information:This work was supported by the Convergence Technology Development Program for Bionic Arm and by the Basic Science Research Program through the National Research Foundation of Korea, which is funded by the Ministry of Science, Information and Communications Technologies and Future Planning (ref. no. 2014M3C1B2048632), and by the Ministry of Education (ref. no. 2016R1D1A1B03933986). It was also partially supported by a grant from the Korea University College of Health Science (ref. no. K1508371). The funders played no role in the design, conduct, analyses, interpretation, and reporting of this study.
Funding Information:
This work was supported by the Convergence Technology Development Program for Bionic Arm and by the Basic Science Research Program through the National Research Foundation of Korea, which is funded by the Ministry of Science, Information and Communications Technologies and Future Planning (ref. no. 2014M3C1B2048632), and by the Ministry of Education (ref. no. 2016R1D1A1B03933986 and 2017M3C1B2085303). It was also partially supported by a grant from the Korea University College of Health Science (ref. no. K1508371).
Publisher Copyright:
© 2019 American Physical Therapy Association.
ASJC Scopus subject areas
- Physical Therapy, Sports Therapy and Rehabilitation