PTGS2 and rheumatoid arthritis: In addition, osteoblast-synthesized VEGF enhances EPC angiogenesis during RA progression [7], while we have previously demonstrated that S1P stimulates IL-1β production through the JAK and STAT3 signaling pathways in osteoblasts [20], and the S1P/S1P receptor axis reportedly promotes cyclooxygenase-2 and prostaglandin E2 in RA [21].