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Valeriy V. Lyzogubov, Purushottam Jha, Ruslana G. Tytarenko, Nalini S. Bora, Puran S. Bora; Complement Activation and Changes in RPE and Retina after Subretinal Treatment of Polyethylene Glycol (PEG) in Mice. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1647.
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Age-related macular degeneration (AMD) is a leading cause of irreversible blindness worldwide. Recently we reported that polyethylene glycol (PEG) can activate the alternative pathway of the complement system and induce CNV in mice. The aim of this study was to characterize changes in mouse RPE and retina after PEG treatment.
We injected male C57BL/6 mice subretinally with 0.5 mg of PEG. We used 2 μL of solution for injections. Sterile PBS was used as vehicle and was injected in control groups. Eyes were harvested at day 1, 3 and 5 after injection and processed for histological analysis. Semi thin (1 μm) sections of PBS and PEG treated mouse eyes were stained with hematoxylin. Paraffin sections (5 μm) were stained with hematoxylin and eosin and used for morphometry. Sections were stained for complement component C3, membrane attack complex (MAC), proliferating cell nuclear antigen (PCNA) and cytokeratin 18 (CK18) by IHC. Light and laser confocal microscopy was used for image capturing. Measurement and quantification of morphometric parameters was performed using ImageJ program.
PEG increased deposition of C3 and MAC on RPE cells and on all retinal layers. PEG induced loss of cellular contacts between RPE cells, migration of RPE cells in subretinal space at day 1 after PEG injection. Increased size of RPE cells and expression of PCNA was detected at day 3 and 5 after PEG treatment. Apoptotic bodies were observed in ONL at day 3 and 5 after PEG treatment. RPE cells with dark cytoplasm and condensed chromatin were observed. By day 5 after subretinal injection of PEG we found decreased nuclei density in the ONL of the retina (-49%), decreased the length of the photoreceptor outer and inner segments (-61%), increased size of the RPE cells (+133%), and reduced pigmentation of the RPE cells (-33%) compared to PBS injected control group.
Activation the complement system by PEG leads to morphological changes in RPE and retina consistent with dry AMD. PEG is a very useful tool to induce proliferation and death of RPE cells and death of photoreceptors in mice. This simple and fast model may be used to investigate dry AMD pathogenesis.
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