Silver Needle Thermotherapy Regulates TRPV1 to Alleviate Endoplasmic Reticulum Stress and Relieve Myofascial Pain

Silver needle thermotherapy (SNT) has a remarkable therapeutic effect on myofascial pain syndrome (MPS), but its mechanism of action remains to be clarified. This study aims to explore the effect of SNT on endoplasmic reticulum stress (ERS) in myofascial trigger points (MTrPs) of MPS rats and reveal its potential molecular mechanism.

The MPS rat model was established. SNT treatment and TRPV1 adeno-associated virus injection were respectively performed on MTrPs of rats in different groups. After successful virus transfection, Hematoxylin-eosin staining, Transmission electron microscope, Western Blotting, Immunofluorescence analysis were performed. Experiments were conducted to observe the ERS of MTrPs and pain changes in each group of rats.

(1) The mechanical withdrawal threshold (MWT) of MPS rats decreased significantly, while SNT treatment could reverse the changes in MWT; (2) In MPS rats, MTrPs muscle fibers showed atrophy, degeneration and disordered arrangement. However, SNT treatment or interference with TRPV1 expression could improve the changes in muscle fibers; (3) SNT treatment or interference with TRPV1 expression can alleviate endoplasmic reticulum (ER) dilation and cystic space widening in MTrPs of MPS rats; (4) SNT treatment or interference with the expression of TRPV1 can inhibit the expressions of TRPV1, p-TRPV1, CaMKII, CHOP and BIP in the MTrPs muscle tissue of MPS rats.

SNT can increase the pain threshold, repair the damaged myofascia, alleviate ERS and pain of MPS rats.