Results: Local administration of ASCs at various time-points (days 7 or 14) after DMM induction had no effect on OA pathology. At day 7 of CIOA, already 6 h after ASC injection mRNA expression of proinflammatory mediators S100A8/A9, interleukin-1beta (IL-1b) and KC was down-regulated in the synovium. IL-1b protein, although low, was down-regulated by ASC-treatment of CIOA. S100A8/A9
protein levels were very high at 6 and 48 h and were decreased by ASC-treatment. The protective action of ASC treatment in CIOA was only found when high synovial inflammation was present at the time of deposition which was reflected by high serum S100A8/A9 levels. Finally, successful treatment resulted in significantly lower levels of serum S100A8/A9