A simple novel ex vivo bioassay technique was used to analyze matrix metalloproteinases (MMPs) in skin wash samples taken from 23 atopic dermatitis (AD) patients and 24 controls. Skin wash samples from AD lesions contained 10-24-fold the MMP activity from normal skin (P < 0.02) and fivefold that from unaffected AD skin (P < 0.05). A broad-spectrum MMP inhibitor, Ro 31-9790 (50 umol/L) inhibited this activity by 5-11-fold. AD skin wash samples contained substantial amounts of MMP-8 and MMP-9 and lower levels of MMP-1 and MMP-3. Tissue inhibitors of MMPs (TIMP-1, TIMP-2 and TIMP-4) were also detected. This novel assay may be useful for future research into AD pathogenesis and treatment (Harper, ...