PDPN and arthritic joint disease: This is the first study showing that SF-FLSs isolated from the joint of JIA patients with active arthritis exhibit a CD45−CD34−THY+PDPN+ phenotype and present higher expression of genes coding for several pro-inflammatory cytokines than for MMPs in response to stimuli present in the synovial environment, as well as the capacity to differentiate into chondrocytes.