AdhIL13 injected in naïve knee joints results in 1000 pg/ml hIL-13 after 1 day, and increased to 3000 pg/ml detected at days 2, 3 and 7. Surprisingly, IL-13 did not diminish joint inflammation, because the influx of inflammatory cells was similar in the Addel70 and AdhIL13 group. MMP-mediated VDIPEN expression was not found 1 day after ICA onset because of the early time point. At day 3, IL-13 overexpression resulted in a twofold reduction in VDIPEN expression and a threefold reduction at day 7, compared with the control group. This decrease might be the result of a declined production of MMPs. However, the mRNA level of MMP-3 was comparable between the two groups, whereas MMP-12 and MMP-13 mRNA levels were three times higher in the IL-13 group.