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  • Title: Photoreceptor protection after photodynamic therapy using dexamethasone in a rat model of choroidal neovascularization.
    Author: She H, Nakazawa T, Matsubara A, Connolly E, Hisatomi T, Noda K, Kim I, Gragoudas ES, Miller JW.
    Journal: Invest Ophthalmol Vis Sci; 2008 Nov; 49(11):5008-14. PubMed ID: 18421085.
    Abstract:
    PURPOSE: To study whether corticosteroids protect photoreceptors when combined with photodynamic therapy (PDT) in a laser-induced model of choroidal neovascularization (CNV). METHODS: PDT was performed in 36 Brown-Norway rats 2 weeks after laser induction of CNV. The expressional change of several cytokines and chemokines in the CNV lesions after PDT was measured by real-time PCR in combination with laser-capture microdissection. Immunostaining for monocyte chemoattractant protein (MCP)-1, C-C chemokine receptor 2(CCR2), interleukin (IL)-1beta, and myeloperoxidase(MPO) were performed. To study the effect of corticosteroids in combination with PDT, either dexamethasone (100 mg/kg) or control was injected intraperitoneally 1 hour before PDT. Animals were killed 24 hours or 1 week after PDT. CNV was examined by fluorescein angiography and choroidal flatmount. Photoreceptor degeneration was evaluated by TUNEL assay. RESULTS: MCP-1 and IL-1beta was increased in CNV lesions 24 hours after PDT. CCR2 was also expressed in laser-induced CNV but did not increase after PDT. Twenty-four hours after PDT, MPO-positive cells were noted in the CNV lesions. Dexamethasone-treated animals had significantly fewer TUNEL-positive cells in the photoreceptor layer than did the control animals (P < 0.05) after PDT. Fluorescein angiographic grading of CNV closure 6 days after PDT showed a closure rate in the dexamethasone-treated group of 31% (15/48 lesions) compared to 10% (4/42 lesions) in the control group (P < 0.05). CNV size was significantly smaller in the dexamethasone-treated group 1 week after PDT compared with the control (P < 0.05). CONCLUSIONS: Systemic administration of dexamethasone combined with PDT reduces photoreceptor apoptosis, increases angiographic closure, and reduces CNV size compared with PDT alone in a rat model.
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