Exploring the mechanism of myofascial trigger points deactivation by Tuina via the TGF-β1/Smad3 signaling pathway

To investigate whether Tuina alleviates fibrotic symptoms in myofascial trigger points (MTrPs) by regulating transforming growth factor (TGF)-β1/Smad3 signaling pathway, thereby deactivating these points. This study comprised two experimental phases. In phase 1, 27 specific pathogen-free (SPF) grade female Sprague-Dawley (SD) rats were randomized into three groups: control 1, model 1, and Tuina 1 groups. Model 1 and Tuina 1 groups underwent an 8-week MTrPs modeling protocol involving blunt impact and eccentric exercise. After successful modeling, rats in Tuina 1 group received manual pressing on nodules or cord-like taut bands on the medial aspect of the left hindlimb. Pain sensitivity and tissue stiffness were evaluated via pressure pain threshold (PPT) and soft tissue tension (STT). Muscle histopathology and fibrosis were observed using hematoxylin and eosin (HE) and Masson staining. Inflammatory factors in muscle were measured by enzyme-linked immunosorbent assay (ELISA), while immunofluorescence (IF) and Western blot (WB) were used to detect the expression levels of α-smooth muscle actin (α-SMA), collagen Ⅲ, and TGF-β1. In phase 2, 45 SPF female SD rats were randomized into five groups: control 2, model 2, Tuina 2, TGF-β1 inhibitor (TI), and Tuina + TGF-β1 agonist (Tuina + TA) groups. All groups except control 2 underwent standardized MTrPs modeling. Rats in Tuina 2 group received consistent pressing manipulation. TI group received intraperitoneal injections of oxymatrine, while Tuina + TA group received intraperitoneal injections of SRI-011381 hydrochloride followed by the same pressing protocol as Tuina 2 group. WB was used to detect the expression of collagen I, collagen III, TGF-β1, and phosphorylated-Smad3 (p-Smad3)/Smad3. In phase 1, Tuina significantly improved PPT and STT in MTrPs of rats ( P < 0.01), reversed pathological damages including disorganized muscle fiber arrangement, abnormal myocyte morphology, and exacerbated fibrosis. In addition, in MTrPs of rats in model 1 group, expression levels of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and fibrosis markers (α-SMA, collagen I, and collagen III) were upregulated, and all exhibited a significant downward trend after Tuina intervention ( P < 0.05 or P < 0.01). This indicates that the therapeutic effects of Tuina are directly associated with reduced local inflammation and fibrosis in MTrPs. In phase 2, compared with model 2 group, rats in TI and Tuina 2 groups had decreased expression levels of TGF-β1 and p-Smad3/Smad3 in MTrPs, alongside reduced levels of inflammatory factors (IL-1β, IL-6, NF-κB, and TNF-α) and fibrosis markers (α-SMA, collagen I, and collagen III) ( P < 0.05 or P < 0.01). When co-administered with TGF-β1 agonist, the therapeutic effects of Tuina were significantly attenuated, with rebounded TGF-β1 expression and p-Smad3/Smad3 in local MTrPs, and fibrosis and inflammatory responses were re-exacerbated ( P < 0.05 or P < 0.01). Tuina can effectively reduce inflammatory responses and fibrosis in MTrPs tissue, and its mechanism is closely related to the inhibition of the TGF-β1/Smad3 signaling pathway, which plays a critical role in Tuina-mediated regulation of MTrPs fibrosis.