Keratinocyte collagenase-1 expression requires an epidermal growth factor receptor autocrine mechanism

In response to cutaneous injury, expression of collagenase-1 is induced in keratinocytes via alpha(2)beta(1) contact with native type I collagen, and enzyme activity is essential for cell migration over this substratum. Howev er, the cellular mechanism(s) mediating integrin signaling remain poorly un derstood. We demonstrate here that treatment of keratinocytes cultured on t ype I collagen with epidermal growth factor receptor (EGFR) blocking antibo dies or a specific receptor antagonist inhibited cell migration across type I collagen and the matrix-directed stimulation of collagenase-1 production . Additionally, stimulation of collagenase-1 expression by hepatocyte growt h factor, transforming growth factor-beta 1, and interferon-gamma was block ed by EGFR inhibitors, suggesting a required EGFR autocrine signaling step for enzyme expression. Collagenase-1 mRNA was not detectable in keratinocyt es isolated immediately from normal skin, but increased progressively follo wing 2 h of contact with collagen, In contrast, EGFR mRNA was expressed at high steady-state levels in keratinocytes isolated immediately from intact skin but was absent following 2 h cell contact with collagen, suggesting do wn-regulation following receptor activation. Indeed, tyrosine phosphorylati on of the EGFR was evident as early as 10 min following cell contact with c ollagen, Treatment of keratinocytes cultured on collagen with EGFR antagoni st or heparin-binding (HB)-EGF neutralizing antibodies dramatically inhibit ed the sustained expression (6-24 h) of collagenase-1 mRNA, whereas initial induction by collagen alone (2 h) was unaffected. Finally, expression of c ollagenase-1 in ex vivo wounded skin and re-epithelialization of partial th ickness porcine burn wounds was blocked following treatment with EGFR inhib itors. These results demonstrate that keratinocyte contact with type I coll agen is sufficient to induce collagenase-1 expression, whereas sustained en zyme production requires autocrine EGFR activation by HB-EGF as an obligato ry intermediate step, thereby maintaining collagenase-l-dependent migration during the re-epithelialization of epidermal wounds.