RhoA Interacts With TPM4 to Promote Myofascial Trigger Point Pain in Rats via the ERK Signaling Pathway.

Myofascial pain syndrome (MPS) is characterized by myofascial trigger points (MTrPs), which are defined by contracted sarcomeres and inflammation. Human-derived MTrPs have elevated expression of Ras homolog gene family member A (RhoA); however, whether RhoA participates in sarcomere contraction and inflammatory pain in MTrPs remains unclear. We investigated the role of RhoA in MTrP development and the underlying mechanisms. A rat model of MTrPs was established using blunt striking combined with eccentric exercise (8 weeks), followed by resting recovery (4 weeks). Lower limb withdrawal thresholds and histomorphologies were evaluated to confirm the model's success. Immunohistochemical staining and western blotting (WB) were used to assess the RhoA and ERK pathway expression in MTrPs. The MTrP ultrastructure and Z-line distances were evaluated using transmission electron microscopy. Lentiviral overexpression and knockdown of RhoA revealed its functional roles. Co-immunoprecipitation (Co-IP) and mass spectrometry identified tropomyosin 4 (TPM4) as a RhoA-interacting protein. Lentivirus-mediated TPM4 knockdown revealed its biological functions. The animal model showed reduced mechanical withdrawal thresholds; microscopy revealed enlarged, rounded muscle fibers in the MTrPs. Rat model MTrPs had significantly increased RhoA expression. RhoA overexpression in normal rats promoted inflammatory pain-like behaviors and sarcomere contraction via ERK signaling pathway activation. RhoA knockdown in MTrPs alleviated these changes. TPM4 knockdown in MTrPs attenuated inflammatory pain-like behaviors and sarcomere contraction and suppressed ERK signaling pathway activation in MTrP rats. RhoA induces inflammatory pain-like behaviors and sarcomere contraction in MTrP rats, potentially via the ERK signaling pathway. Thus, RhoA is a potential therapeutic target for MTrP treatment.