Matrix metalloproteinase-9 delays wound healing in a murine wound model
Accepted 5 October 2009. published online 11 December 2009.
Background
Metalloproteinase-9 (MMP-9) is a type IV collagenase found at elevated levels in chronic wounds. As wounds heal, MMP-9 diminishes. In this study, we investigated whether MMP-9 directly contributes to chronic wound pathogenesis.
Methods
Recombinant proMMP-9 was prepared using immortalized keratinocytes transduced by a lentivirus. ProMMP-9 was purified from cell culture media and activated using 4-aminophenylmercuric acetate. Active MMP-9 was then suspended in xanthan gum to a concentration paralleling that found in human chronic wounds. Two parallel 6-mm punch biopsies were made on the backs of C57BL mice. Wounds were treated daily with MMP-9 or vehicle. Wound areas were measured and tissues examined by densitometry, real-time RT-PCR, histology, and immunohistochemistry at days 7, 10, and 12.
Results
Exogenous MMP-9, at the level found within chronic wounds, delayed wound healing in this animal model. By 7 days, wounds in the MMP-9–injected group were 12% larger than control wounds (P = .008). By day 12, wounds in the MMP-9–injected group were 25% larger than those of the control group (P = .03). Histologic examination shows that high levels of active MMP-9–impaired epithelial migrating tongues (P = .0008). Moreover, consistent with elevated MMP-9, the collagen IV in the leading edge of the epithelial tongue was diminished.
Conclusion
MMP-9 appears to directly delay wound healing. Our data suggests that this may occur through interference with re-epithelialization. We propose that MMP-9 interferes with the basement membrane protein structure, which in turn impedes keratinocyte migration, attachment, and the reestablishment of the epidermis.
Division of Plastic Surgery, University of Southern California, Los Angeles, CA
Reprint requests: Warren L. Garner, MD, Division of Plastic Surgery, University of Southern California, 1200 N. State Street, Suite 12-700, Los Angeles, CA 90033.
ABSTRACT