Macrophage-like synoviocytes display phenotypic polymorphisms in a serum-free tissue-culture medium

Synovial macrophages play an outstanding role in many rheumatic diseases. However, traditional serum-containing tissue-culture techniques hamper in vitro studies due to fibroblast activation not found in vivo. The objective of this study was to examine dissociated synovial cells in a macrophage-selective, serum-free tissue-culture medium. Osteoarthritis synovial tissue (n=11) was cultured in Iscove's Modified Dulbecco's Medium (IMDM) with 10% fetal bovine serum (FBS) and compared to a serum-free, insulin-supplemented medium. After 9-11 and 19-21 days in vitro, immunohistochemistry was performed for macrophage/lymphocyte markers and cell division. Cytokine profiles were determined by RT-PCR. In serum, cells with a bipolar morphology rapidly proliferated. Respectively, 14.34+/-12.94% and 13.25+/-12.66% expressed CD68 and HLA-DR. These markers further decreased after one passage. In serum-free medium, proliferation was infrequent, and cells with diverse morphologies expressed 83.10+/-6.80% and 55.03+/-6.88% CD68 and HLA-DR respectively. CD14 was rare, and lymphocytes were missing. Both cultures expressed interleukin-6 and interleukin-8. This novel serum-free method permits the culture of distinct CD68/HLA-DR associated phenotypes.