THY1 and arthritic joint disease: Conversely, the S4b SF subset actively contributes to arthritis inflammation by expressing the proliferation marker ki-67 (Mki67), platelet-derived growth factor subunit a (Pdgfa), baculoviral IAP repeat containing 5 (Birc5), aquaporin 1 (Aqp1), actin alpha 2 (Acta2), C1q, and TNF-related 3 (C1qtnf3) adipokines, alongside high THY1 and PRG4 expression [12].