Synovial chondromatosis: the possible role of FGF 9 and FGF receptor 3 in its pathology

Primary synovial chondromatosis (PSC) is a rare disorder of the synovium ty pified by cartilaginous nodule formation within the synovial membrane. Fibr oblast growth factor receptor 3 (FGFR3) is a recently described specific ma rker of mesenchymal precartilaginous stem cells. Expression patterns of FGF R3 and its specific ligand, fibroblast growth factor 9 (FGF 9), were evalua ted both in situ and in cell cultures. Histologically, cells at the periphe ry of the cartilage nodules express FGFR3 and PCNA (proliferating cell nucl ear antigen). Elevated levels of FGF 9, its specific ligand, have been foun d in synovial fluids of patients with synovial chondromatosis. Synoviocytes but not chondrocytes from affected patients express FGF9 in culture. This pattern is absent in normal synovium and cartilage. Downregulation of FGF9 may provide a possible nonoperative therapy for PSC.