From inflammatory activation to fibrotic remodeling: the central role of macrophage heterogeneity in frozen shoulder.

Researchers have published a comprehensive review examining how immune cells called macrophages contribute to frozen shoulder, a painful condition that causes stiffness and limited movement in the shoulder joint. Frozen shoulder affects many people and can significantly impact daily activities and quality of life. The study focused on understanding how macrophages change their behavior during different stages of the condition, shifting from promoting inflammation in early stages to driving the buildup of scar tissue (fibrosis) that causes stiffness later on. The researchers found that macrophages don't act alone—they communicate with other cells called fibroblasts through specific chemical signals, particularly through a pathway called CCL2/CCR2. They also discovered that mechanical forces in the tissue can keep macrophages in a harmful, activated state, potentially creating a cycle that makes fibrosis worse. Understanding these mechanisms is important because it may help identify new treatment targets. For patients considering acupuncture, this research suggests that therapies addressing inflammation and tissue mechanics early in the condition may be beneficial. While this review doesn't directly study acupuncture, the mechanisms identified—particularly related to immune regulation and mechanical tissue stress—align with theoretical frameworks for how acupuncture may work in musculoskeletal conditions. Breaking the inflammation-fibrosis cycle early could potentially improve outcomes. Patients interested in acupuncture for frozen shoulder should consult with a licensed acupuncturist experienced in treating musculoskeletal conditions.

This systematic review examines macrophage heterogeneity in frozen shoulder pathogenesis, highlighting the dynamic polarization states that govern disease progression from inflammatory activation to fibrotic remodeling. The authors identify the CCL2/CCR2 chemotactic axis as a critical regulator of macrophage recruitment and differentiation. Key findings emphasize the bidirectional signaling between macrophages and fibroblasts, with mechanical tissue forces maintaining pathogenic macrophage activation in a positive feedback loop that perpetuates fibrosis. The review is mechanistic rather than clinical, presenting no original data, sample sizes, or effect sizes. Clinical relevance lies in identifying upstream regulatory targets for intervention, particularly disrupting the inflammation-fibrosis link through modulation of macrophage polarization and mechanotransduction pathways. For acupuncture practitioners, this underscores the potential value of early intervention targeting inflammatory processes and tissue mechanics in frozen shoulder, supporting treatment strategies that address both immune dysregulation and biomechanical factors contributing to capsular fibrosis.