Acupotomy Alleviates Capsular Fibrosis in Frozen Shoulder Rats by Modulating CCL2 to Inhibit Macrophage Recruitment and Suppress the Inflammatory Response.

Background: Frozen shoulder (FS) is a debilitating condition characterized by chronic inflammation and fibrosis of the glenohumeral capsule. Macrophage recruitment, facilitated by C-C motif chemokine ligand 2 (CCL2), plays a crucial role in tissue fibrosis progression. Acupotomy has proven effective in alleviating FS symptoms; however, the mechanism by which it influences CCL2-mediated macrophage chemotaxis in FS requires further exploration. Methods: Forty male Sprague-Dawley rats were randomly assigned to four groups (n = 10 per group): Control (no modeling/intervention), Untreated (FS modeling only), Acupotomy (FS model + acupotomy therapy), and Sham Apo (FS model + superficial acupotomy stimulation). FS was induced by unilateral shoulder plaster immobilization. The Acupotomy and Sham Apo groups then underwent their respective procedures (once weekly; two sessions in total). Shoulder function was evaluated using arthritis scoring, gait analysis, and maximum passive abduction angle measurement. Pathological changes were examined using hematoxylin and eosin and Masson's trichrome staining. Inflammation- and fibrosis-related molecules in serum and tissue samples were detected using biochemical and molecular biology analyses. Macrophage-related biomarkers, CCL2, and α-SMA were evaluated by immunostaining, with protein-protein docking for further analysis. Results: Acupotomy significantly enhanced shoulder function and mobility in FS rats. Histopathological analysis revealed that the capsular structure improved after acupotomy with notably decreased inflammatory infiltration and collagen deposition. Furthermore, acupotomy markedly reduced inflammation- and fibrosis-related factors in both serum and lesion tissues. Mechanistic studies demonstrated that acupotomy diminished macrophage recruitment, adjusted the M1/M2 polarization ratio, and reduced α-SMA expression, all of which were linked to CCL2 inhibition. Further analysis confirmed a positive correlation between CCL2 and α-SMA expression, and protein-protein docking suggested potential interactions between CCL2 and macrophage polarization markers and α-SMA. Conclusion: Acupotomy demonstrated significant efficacy in enhancing shoulder function and reducing fibrosis in FS rats, primarily by suppressing inflammatory responses and inhibiting CCL2-mediated macrophage recruitment.