CD248 Deletion Promotes Destructive Synovial Fibroblasts and Bone Damage in Mice

CD248/endosialin is upregulated on synovial fibroblasts during inflammation and has been proposed as a therapeutic target in inflammatory arthritis. In a study published in Arthritis & Rheumatology, researchers compared wildtype and Cd248-knockout mice using K/BxN serum transfer–induced arthritis. They profiled stromal cells with single-cell RNA sequencing and assessed arthritis severity and structural damage using clinical scoring, microcomputed tomography, histology, and synovial flow cytometry. Separate cohorts were aged to 20 months. Sample sizes were not reported in the supplied abstract.

Fibroblasts with high Cd248 expression also expressed the Pi16 progenitor gene signature. Cd248 deletion altered progenitor differentiation, favoring destructive lining-layer fibroblasts. Arthritic knockout mice developed rapid, extensive bone damage. Aged knockout mice also showed bone erosion and resulting deformity without an inflammatory stimulus. The abstract did not provide quantitative effect estimates.

The findings suggest that CD248 may restrain bone damage by limiting fibroblast differentiation toward a destructive phenotype, rather than simply marking inflammation. They raise a potential safety concern for therapies targeting CD248. However, these results derive from genetic deletion in mice, not therapeutic inhibition in humans; their clinical relevance remains unestablished.