Expression of matrix metalloproteinases 2 and 9 and tissue inhibitors of metalloproteinase 1 and 2 in inflammation-induced corneal neovascularization.
OBJECTIVE
Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase (TIMPs) have been linked to the angiogenic process in general. In order to understand the potential roles of MMP-2, MMP-9 and TIMPs in the corneal neovascularization process, we examined the expression and activities of MMP-2, MMP-9 and TIMPs during the course of cauterization-induced corneal neovascularization in a rat model.


METHODS
Neovascularization of rat corneas was induced by silver nitrate cauterization. The expression of MMP-2, MMP-9, TIMP-1 and TIMP-2 was examined by immunohistochemistry and RT-PCR. The protein activities of MMPs and TIMPs were compared in pre- and postcauterization corneas by gelatin zymography and reverse zymography, respectively.


RESULTS
MMP-2, TIMP-1 and TIMP-2 immunoreactivities were expressed in normal corneas, predominantly in the corneal epithelium. After injury, immunoreactivities of both MMPs and TIMPs were increased, notably in the healing corneal epithelium, infiltrating inflammatory cells, stromal fibroblasts and ingrowing vascular endothelial cells. The increase in gross MMP-2 enzymatic activity paralleled the maximal vascular ingrowth on day 4, while the gross MMP-9 enzymatic activity rose immediately on day 1, then decreased steadily, which paralleled the magnitude of inflammatory cell infiltration. The immunoreactivity of MMPs/TIMPs decreased significantly 2 weeks after cauterization. On day 35, MMP-2, TIMP-1 and TIMP-2 staining was seen only in corneal epithelium and vascular endothelial cells. Both the RT-PCR and reverse zymography results revealed a more constant expression of TIMP-2, while the TIMP-1 expression appeared to be more inducible.


CONCLUSIONS
MMPs as well as TIMPs were upregulated in cauterization-induced corneal neovascularization, suggesting that both may participate in extracellular matrix remodeling in the corneal wound healing, inflammation and neovascularization processes.
Ma
D H
DH
Ocular Cell and Gene Therapy Laboratory, Department of Ophthalmology, University of California, San Francisco, Calif., 94143-0730, USA.
Chen
J K
JK
Kim
W S
WS
Hao
Y X
YX
Wu
H C
HC
Tsai
R J
RJ
Hwang
D G
DG
Zhang
F
F
D000818:Animals; D016510:Corneal Neovascularization / Q000139:chemically induced / Q000201:enzymology* / Q000473:pathology; D005260:Female; D007124:Immunoenzyme Techniques; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis* / Q000235:genetics; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis* / Q000235:genetics; D023421:Models, Animal; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012835:Silver Nitrate; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000096:biosynthesis* / Q000235:genetics; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000096:biosynthesis* / Q000235:genetics
D012333:RNA, Messenger; D019715:Tissue Inhibitor of Metalloproteinase-1; D019716:Tissue Inhibitor of Metalloproteinase-2; D012835:Silver Nitrate; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9