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Shimin Li, Tracy Thuy Nguyen, Joseph A Bonanno; CD147 Expression Required for Corneal Lactate Efflux. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2030.
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CD147 acts as a chaperone protein to facilitate the expression and membrane trafficking of monocarboxylate (e.g., lactate) transporters, MCT1 and MCT4. Lactate:H+ efflux is a significant component of the endothelial pump. Therefore we expect corneal edema and diminished pump capacity in corneas with reduced CD147 expression. Previously, we found that CD147 is required for corneal lactate efflux and maintenance of endothelial cell pH in ex vivo rabbit corneas. In this study, we conducted animal experiments to confirm these findings.
CD147 expression was knocked down via Lentiviral vector facilitated shRNA transfection. Pseudoviral particles of Lenti-shRNA-CD147 were injected into the anterior chamber of NZW rabbit eyes (OD) and Lenti-shRNA-luciferase was injected into left eyes (OS), n=5. Corneal thickness was measured by SD-OCT for up to 4 weeks post-injection. An Azopt stress test (two drops of 1% Brinzolamide suspension, a carbonic anhydrase inhibitor) was performed at two weeks post-injection. Animals were euthanized and endothelium dissected for western blot of CD147 and MCTs. Cornea stroma-epithelium was analyzed for [lactate].
A preliminary dose trial indicated that 5x106 IFU titer of lenti-shRNA particles was most effective in knocking down the expression of CD147, MCT1 and MCT4 in corneal endothelium. Significant differences in central corneal thickness were observed between control and KD eyes at 6 days post-injection and Lenti-shRNA-CD147 eyes were 24µm thicker than paired control corneas by 3 weeks (p<0.05). Peak corneal swelling following Brinzolamide application (3 hours) was 12.0µm (3.3% swelling) in control and 24.4µm (6.5% swelling) in Lenti-shRNA-CD147 transfected corneas. Lactate concentration was 47.95 ± 2.1 nmol/mg dry cornea tissue in the KD and 17.75 ± 1.09 nmol/mg in the control corneas (p<0.05). Western blot showed that CD147 was reduced by 67% ± 0.03, MCT1 by 60% ± 0.06 and MCT4 by 55% ± 0.11 in KD corneas. MCT2 was not changed.
CD147 is required for MCT1 and MCT4 expression in corneal endothelium in vivo. Knockdown slows lactate efflux leading to corneal edema, reduced endothelial pump capacity, and increased corneal lactate concentrations, consistent with lactate efflux being a significant contributor to the corneal endothelial pump.
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