In addition to immune-regulatory tissue resident macrophages, sub-lining fibroblasts expressing markers such as dickkopf WNT signaling pathway inhibitor 3 (DKK3), osteoglycin (OGN), cell adhesion molecule 1 (CADM1) & microfibrillar-associated protein 2 (MFAP2) are present in inflamed murine and RA synovium (39, 42). Here, CADM1 is linked to rheumatoid arthritis.