Single-cell RNA sequencing identifies PD-L1+ mesenchymal stem cells with enhanced immunomodulatory capacity and alleviated the degree of ectopic new bone formation in ankylosing spondylitis

• PD-L1+ MSCs identified via scRNA-seq exhibit superior immunomodulatory capacity, suppressing T-cell proliferation and reducing TNF-α levels in vitro. • In a curdlan-induced SKG mouse model of ankylosing spondylitis, PD-L1+ MSCs significantly alleviated joint inflammation and reduced pathological ectopic bone formation. • PD-L1+ MSCs modulate immune responses by decreasing Th17 cells and increasing Th2 and Treg populations, along with lowering pro-inflammatory cytokines. • These findings highlight PD-L1+ MSCs as a promising cell-based therapy for AS, potentially surpassing conventional MSC treatments.