Translational targeting of inflammation and fibrosis in frozen shoulder: Molecular dissection of the T cell/IL-17A axis

Significance Frozen shoulder (FS) is a classic example of a prevalent debilitating pathological inflammatory fibrosis. Using approaches to dissect the molecular pathways subserving FS, we demonstrate the immune cell landscape in FS shifts from primarily macrophages to T cells in disease. We find T cells from FS tissue are able to secrete the inflammatory cytokine IL-17A, and fibroblasts from FS have greater expression of the receptor IL-17RA. Thus, FS fibroblasts produce greater fibrotic and inflammatory responses following IL-17A stimulation, which can be abrogated following NF-κB pathway inhibition or cytokine blockade using an anti–IL-17A antibody. This single-cell dissection of FS highlights a T cell–driven disease with both small molecule and anti-cytokine attenuation of disease-like features.