Purpose: Findings in studies have suggested a role for matrix metalloproteinase (MMP)-2 in angiogenesis, including choroidal neovascularization (CNV). To investigate further, the current study was conducted to observe the formation of experimental CNV in MMP-2-deficient mice.
Methods: CNV was induced in wild-type and MMP-2-deficient mice by krypton laser photocoagulation of the fundus. The time-course of expression of MMP-2 mRNA after laser treatment was determined by in situ hybridization with anti-sense and sense cRNA probes. MMP-2 protein distribution was determined by immunohistochemistry. Ten days after treatment, the extent of CNV was evaluated on hematoxylin-eosin stained serial sections. The maximum height of the CNV lesions was calculated by image analysis of digitized histologic images.
Results: Expression of MMP-2 mRNA was detected in the CNV lesions at day 3 after laser treatment and peaked at day 5, after which it slowly declined. MMP-2 mRNA expression appeared to be highest at the margins of the membrane. Immunostaining for MMP-2 confirmed the presence of MMP-2 protein in the CNV lesions. The CNV lesions of MMP-2-deficient mice showed that relative thickness was reduced by 31% compared with wild-type mice (P = 0.006).
Conclusions: The present study demonstrated that MMP-2 mRNA and protein are upregulated during experimental CNV in the mouse. The marked difference in thickness of the CNV membrane between wild-type and MMP-2-deficient mice shows that MMP-2 is involved in the formation of experimental CNV in the mouse. These results suggest that pharmacologic targeting of MMPs, including MMP-2, may reduce formation of CNV in conditions such as age-related macular degeneration.