Corneal lymphangiogenesis ameliorates corneal inflammation and edema in late stage of bacterial keratitis.

Lymphatic vessels play a crucial role in systemic immune response and regulation of tissue fluid homeostasis. Corneal lymphangiogenesis in bacterial keratitis has not been studied. In this study, we investigated the mechanism and the role of corneal lymphangiogenesis in a murine bacterial keratitis model using Pseudomonas aeruginosa. We first demonstrated that corneal lymphangiogenesis was enhanced mainly in the late stage of bacterial keratitis, contrary to corneal angiogenesis that started earlier. Corresponding to the delayed lymphangiogenesis, expression of the pro-lymphangiogenic factors VEGF-C and VEGFR-3 increased in the late stage of bacterial keratitis. We further found that F4/80 and CD11b positive macrophages played an essential role in corneal lymphangiogenesis. Notably, macrophages were specifically involved in corneal lymphangiogenesis in the late stage of bacterial keratitis. Finally, we demonstrated the beneficial role of corneal lymphangiogenesis in ameliorating the clinical course of bacterial keratitis. Our study showed that bacterial activity was not directly involved in the late stage of keratitis, while corneal lymphangiogenesis reduced corneal edema and clinical manifestation in the late stage of bacterial keratitis. These findings suggest that the process of lymphangiogenesis in bacterial keratitis ameliorates corneal inflammation and edema in the late stage of bacterial keratitis.

Investigation of the Role of Bacteria in the Development of Acanthamoeba Keratitis.

PURPOSE: Recently, much interest has been shown in bacteria extracted from Acanthamoeba strains isolated from patients with Acanthamoeba keratitis (AK). We hypothesized that the bacteria in Acanthamoeba strains may be a contributing factor in the development of AK. To prove this hypothesis, we investigated the involvement of bacteria harbored by Acanthamoeba in causing progressive ocular infection in rabbit corneas. METHODS: One Acanthamoeba strain (T4 genotype) that harbored bacteria was isolated from a patient with AK. The Acanthamoeba strain pretreated or not pretreated with levofloxacin (LVFX) was inoculated into rabbit corneas. We also tested the effect of LVFX eye drops on keratitis induced by the Acanthamoeba strain. The infected rabbit eyes were evaluated for clinical scores, Acanthamoeba 18S rDNA and bacterial 16S rDNA numbers were analyzed by the real-time polymerase chain reaction, and the presence of Acanthamoeba was analyzed by histological examination. RESULTS: Inoculation of nonpretreated Acanthamoeba resulted in severe keratitis. In contrast, inoculation of LVFX-pretreated Acanthamoeba did not induce keratitis (mean clinical score, 17.3 vs. 2.3; P < 0.05). Rabbit corneas inoculated with nonpretreated Acanthamoeba followed by topical LVFX therapy developed severe keratitis. In corneas inoculated with nonpretreated Acanthamoeba followed by LVFX therapy, the number of Acanthamoeba 18S rDNA copies was significantly higher than in other groups (P < 0.05), whereas the bacterial 16S rDNA gene was undetectable. Acanthamoeba cysts were detected by Fungiflora Y staining only in corneas inoculated with nonpretreated Acanthamoeba followed by LVFX therapy. CONCLUSIONS: These results suggest that the presence of bacteria in Acanthamoeba may be required for the development of AK.

Suppression of fibroblast and bacterial adhesion by MPC coating on acrylic intraocular lenses.

PURPOSE: To investigate cell adhesion to intraocular lens (IOL) surfaces having different properties using bacteria and fibroblasts. SETTING: Department of Ophthalmology, Tokyo Medical University Hospital, Tokyo, Japan. METHODS: The polished acrylic IOLs VA60-BB and VA-60-CB (Hoya) were used with no coating or after coating with poly(2-methacryloyloxyethyl phosphocholine-co-n-butyl-methacrylate) (MPC) or methane gas plasma. Each IOL was placed in a culture of Staphylococcus aureus (5 x 10(7) colony forming units [CFU]/mL) or fibroblasts (SUSM-1, 1 x 10(4) cells/mL), and the cells adhering to the IOL surface were counted after the culture. Fibroblast adhesiveness was evaluated by centrifuging post-culture IOLs in test tubes at up to 15,000 rpm and looking at the ICAM-1 mRNA expression in the adhering fibroblasts using real-time polymerase chain reaction. RESULTS: After 1 minute in the bacterial culture, the mean adhering bacteria count was 0.7 x 10(6) CFU in the MPC-coated IOL group and about 2.0 x 106 CFU in the noncoated IOL group (P = 0.03) and the plasma-coated IOL group (P = 0.02). After 96 hours in the fibroblast culture, the adhering fibroblast count was 2.2/mm2 in the MPC-coated IOL group, significantly lower (P = 0.009) than 57.6/mm2 in the noncoated IOL group and 125.8/mm2 in the plasma-coated IOL group. Cell adhesion and ICAM-1 mRNA expression were weak on the MPC-coated IOL, intermediate on the noncoated IOL, and relatively strong on the plasma-coated IOL. CONCLUSION: The MPC-coated IOL surface inhibited bacterial and fibroblast adhesion, which is an initial stage of cell proliferation and expression, suggesting that MPC coating may provide an effective means of reducing the risk for endophthalimitis in IOL implantation.