Cellular mechanical phenotyping and therapeutic drug screening in frozen shoulder based on micropillar arrays

Frozen shoulder (FS) is a common musculoskeletal disorder characterized by fibrosis-induced restriction of shoulder movement. Nevertheless, the mechanisms underlying disrupted cellular mechanical homeostasis and the development of effective antifibrotic treatments for FS remain unclear. Cellular traction force (CTF) reflects the mechanical state of cells and is maintained through dynamic interactions between cells and the extracellular matrix. Evaluating CTF is essential for clarifying the mechanisms that contribute to FS fibrosis. In this study, we fabricated force-sensing polydimethylsiloxane micropillar arrays (PDMS-MA) to quantify CTF in synovial cells. Our findings demonstrate that elevated CTF during FS fibrosis is associated with activation of the TGF-β1/SMAD3 pathway, resulting in elevated α-smooth muscle actin (α-SMA) expression and the assembly of focal adhesions (FAs). Using PDMS-MA for mechanopharmacological screening, we identified Pirfenidone and Ketotifen as the most effective compounds at suppressing α-SMA expression, FA assembly, and CTF in fibrotic synovial cells. In vivo experiments further confirmed that Pirfenidone and Ketotifen effectively alleviate shoulder movement restrictions and joint capsule fibrosis. These results suggest that PDMS-MA is a promising tool for mechanopharmacological evaluation and antifibrotic drug screening for FS.