Several matrix metalloproteinases and serine proteinases are upregulated in migrating keratinocytes during cutaneous wound repair. Single cell culture studies indicate the necessity for matrix metalloproteinases but not for serine proteinases in keratinocyte locomotion. To account for epithelial-mesenchymal interactions, an ex vivo human skin wound model was used to investigate the contribution of matrix metalloproteinases and serine proteinases to wound healing by treatment with broad-spectrum inhibitors of matrix metalloproteinases (BB-3103) or serine proteinases (aprotinin). Human skin explants with circular 3 mm superficial defects were incubated in culture medium without (controls) or with the proteinase inhibitors for 7 d. BB-3103 abrogated epithelialization (p \u003c 0.001), whereas aprotinin-treated wounds and controls were covered with new epithelium. Lack of epithelialization was unlikely due to cytotoxicity because the matrix metalloproteinase inhibitor did neither influence viability of cultured epidermal keratinocytes nor apoptosis in wounds. Involvement of specific matrix metalloproteinases in epithelialization was analyzed by gelatin zymography, western blotting, immunohistochemistry, and in situ hybridization. Wound healing was accompanied by active matrix metalloproteinase-1 and increased active matrix metalloproteinase-2 but irrespectively of active matrix metalloproteinase-9. BB-3103 blocked activation of matrix metalloproteinase-2 and matrix metalloproteinase-9 but not of matrix metalloproteinase-1. Active matrix metalloproteinase-2 localized solely to the dermis, whereas matrix metalloproteinase-9 was consistently found in new epithelium. Membrane-type 1 matrix metalloproteinase was undetectable in wound keratinocytes. BB-3103 and aprotinin reduced tumor necrosis factor-alpha in media but did not appreciably alter amounts of other soluble regulators of matrix metalloproteinases and epithelialization. Our findings demonstrate that keratinocyte migration is associated with active matrix metalloproteinase-2 but occurs independently of serine proteinases and active matrix metalloproteinase-9 in fibrin-deficient skin wound healing.
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