INTERCELLULAR CALCIUM SIGNALING BETWEEN CHONDROCYTES AND SYNOVIAL-CELLS IN COCULTURE

Intercellular communication allows the co-ordination of cell metabolis m between tissues as well as sensitivity to extracellular stimuli. Par acrine stimulation and cell-to-cell coupling through gap junctions ind uce the formation of complex cellular networks that favour the interce llular exchange of nutrients and second messengers. Heterologous inter cellular communication was studied in co-cultures of articular chondro cytes and HIG-82 synovial cells by measuring mechanically induced cyto solic changes in Ca2+ ion levels by digital fluorescence video imaging . In confluent co-cultures, mechanical stimulation induced intercellul ar Ca2+ waves that propagated to both cell types with similar kinetics . Intercellular wave spreading was inhibited by 18 alpha-glycyrrhetini c acid and by treatments inhibiting the activation of purinoreceptors, suggesting that intercellular sig nailing between these two cell type s occurs both through gap junctions and ATP-mediated paracrine stimula tion. In rheumatoid arthritis the formation of the synovial pannus ind uces structural changes at the chondrosynovial junction, where chondro cyte and synovial cells come into close apposition: these results prov ide the first evidence for direct intercellular communication between these two cell types.