Matrix metalloproteinase-9 delays wound healing in a murine wound model.
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.


CONCLUSIONS
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.
Reiss
Matthew J
MJ
Division of Plastic Surgery, University of Southern California, Los Angeles, CA, USA.
Han
Yan-Ping
YP
Garcia
Edwin
E
Goldberg
Mytien
M
Yu
Hong
H
Garner
Warren L
WL
D000818:Animals; D001485:Basement Membrane / Q000187:drug effects / Q000473:pathology; D015153:Blotting, Western; D002465:Cell Movement / Q000187:drug effects; D004591:Electrophoresis, Polyacrylamide Gel; D004792:Enzyme Precursors / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects / Q000473:pathology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism* / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D011994:Recombinant Proteins / Q000494:pharmacology; D012867:Skin / Q000293:injuries*; D014945:Wound Healing / Q000187:drug effects / Q000502:physiology*
D004792:Enzyme Precursors; D011994:Recombinant Proteins; C120487:pro-matrix metalloproteinase 9; D020780:Matrix Metalloproteinase 9