The Chloride Channel Regulator, Calcium-Activated-1 Is Expressed in Synoviocytes and Articular Chondrocytes in Health and Disease.

The chloride channel regulator, calcium-activated-1, CLCA1, acts as a multifunctional secreted glycoprotein in anion channel modulation, mucus homeostasis, immune regulation, and other functions. So far, it has been described in goblet and other mucus-producing cells in mucous membranes, primarily of the respiratory, alimentary, and urogenital tracts. Here, we identify the expression of CLCA1 in fibroblast-like synoviocytes and superficial as well as, to a lesser extent, intermediate zone chondrocytes of diarthrodial articular joints. The expression pattern was found to be conserved in major joints in mice, pigs, and humans. First analyses of degenerate or infectious inflammatory joint conditions in mice or pigs, respectively, suggest rather continuous expression levels in articular disease. We speculate that CLCA1 may be involved in articular anion conductance, proteoglycan homeostasis, and inflammation of articular joints, possibly similar to analogous functions of this molecule as established in mucous membranes of the lungs and intestine.