RARRES2 and osteoarthritis: Other evidence supporting a role for extravascular proteolytic factors in the production of active chemerin comes from a recent human chemerin study by Zhao et al. Using selective human prochemerin and chemerin ELISAs, they detected an increased fraction of active chemerin157+158 in the synovial fluid of rheumatoid arthritis and osteoarthritis patients compared to healthy human plasma [71].