CYTOKINE MESSENGER-RNA REPERTOIRE OF ARTICULAR CHONDROCYTES FROM ARTHRITIC PATIENTS, INFANTS, AND NEONATAL MICE

Articular chondrocytes from nine arthritic patients, five infants, and Balb/c neonatal mice were analyzed for the presence of various cytoki ne mRNAs by a reverse transcriptase polymerase chain reaction (RT-PCR) . Four cytokine mRNAs, interleukin (IL)-6, IL-8, IL-11, and macrophage colony stimulating factor (M-CSF), were detected in all human chondro cytes, regardless of source. IL-10, IL-12p35, and tumor necrosis facto r alpha (TNF-alpha) transcripts were found in at least 12 of the 14 hu man samples. IL-13, granulocyte colony stimulating factor (G-CSF), gra nulocyte macrophage colony stimulating factor (CM CSF),and TNF-beta mR NAs were found more predominantly in infant samples and in samples fro m patients with rheumatoid arthritis (RA) compared with samples from p atients with osteoarthritis (OA). Another group of cytokine mRNAs, IL- 1 (alpha, beta), IL-4, IL-5, and IL-7, were only weakly expressed in s ome human samples. The cytokine transcripts that were not found were I L-2, IL-3, and interferon gamma (IFN-gamma). Because of the large arra y of cytokine transcripts detected, human chondrocyte preparations wer e further purified by reacting them with a monoclonal antibody specifi c to chondrocyte differentiation antigen and subjecting them to fluore scent-activate cell sorting, A similar array of cytokines was found be tween the sorted and unsorted chondrocytes, although TNF-alpha, G-CSF and GM-CSF transcripts appeared to be upregulated during the sorting p rocess. Human chondrocytes that dedifferentiated into fibroblasts (a 4 0-day and a 77-day culture) no longer expressed mRNAs for IL-1, G-CSF, CM-CSF and TNF-alpha, but all other cytokine mRNAs remained detectabl e. Although certain phenotypic characteristics were lost, including re activity to chondrocyte-specific monoclonal antibodies and morphologic al features, chondrocytes in long-term culture still expressed cytokin e mRNAs. As expected, more consistent results were obtained when seven preparations of chondrocytes from neonatal Balb/c mice were examined using available cytokine primers. They contained IL-1,IL-5, IL-6, IL-7 , IL-12, GM-CSF M-CSF transforming growth factor beta (TGF-beta), TNF- alpha and TNF-beta mRNAs but lacked IL-2, IL-3, IL-4, IL-10, and IFN-g amma mRNAs. Future experiments to define conditions by which these cyt okine protein products are expressed are needed to help assess their r oles in chondrocyte biology and in disease states.