Topical synthetic inhibitor of matrix metalloproteinases delays epidermal regeneration of human wounds

Matrix metalloproteinases (MMPs) degrade extracellular proteins during epit helialization of wounds. To evaluate the biological significance of MMPs in epidermal healing, the synthetic broad-spectrum MMP inhibitor GM 6001 (als o called Galardin and Ilomastat) was applied topically to standardized huma n wounds. GM 6001 (10 mug/mul) or vehicle alone was applied every second da y onto 4 de-roofed 6 mm. suction blister wounds on the volar forearm of hea lthy male volunteers for 12 days. GM 6001 delayed healing by 2-4 days as as sessed macroscopically and microscopically. In situ hybridization or immuno histochemistry showed that MMP-1 (interstitial collagenase) was present in and MMP-2 (gelatinase A) close to laterally migrating keratinocytes whereas MMP-9 (gelatinase B) was seen during maturation of new epidermis. MMP-1 wa s undetectable in blister roofs (normal epidermis) and found in low levels in normal skin. Total MMP-1 activities increased about 100-fold in wounds, independent of treatment, compared to normal skin as analyzed by specific E LISA-based activity assay. By gelatin zymography, MMP-2, but not MMP-9, was detected in blister roofs and wound healing was associated with increased active MMP-2 and latent MMP-9 levels. GM 6001 prevented activation of MMP-2 and increased latent MMP-9 levels. GM 6001 delayed re-appearance of lamini n-5, the synthesis of which correlated with epidermal regeneration. Restora tion of stratum corneum, measured indirectly by transepidermal water loss, was also impaired (P<0.05) in the GM 6001 group. In conclusion, pharmacolog ical MMP inhibition delayed epidermal regeneration in vivo, suggesting that MMPs are required to restore epidermis after epidermal ablation in humans.