Interleukin-1 stimulation of equine articular cells

Prostaglandin E2 (PGE2) and stromelysin are produced by equine chondrocytes and synovial cells in vitro in response to recombinant human (rh) interleukin-1 (IL-1) alpha and beta, and equine mononuclear cell supernatants (MCS) containing IL-1. However, culture conditions are important. PGE2 concentrations increase in proportion to the concentration of fetal calf serum (FCS) in the culture medium, whereas stromelysin concentrations are inversely proportional to the concentration of FCS. Equine MCS, containing a lower concentration of IL-1 than the concentration of rhIL-1 used in these experiments, stimulated production of much higher levels of PGE2 than rhIL-1. In addition, equine MCS induced the production of broadly similar levels of PGE2 by both chondrocytes and synovial cells, whereas rhIL-1 was more active on equine synovial cells than equine chondrocytes. Although equine MCS induced both stromelysin and PGE2 production by equine articular cells, on the whole rhIL-1 failed to induce stromelysin production. This supports previous observations of species restrictions in the activity of human IL-1 on equine cells. Therefore, experiments using mammalian cells and heterologous IL-1 should be interpreted with caution.