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V Zubaty, G Richard, J Zurdel; Amyloid AA deposition in CNV membranes secondary to ARMD . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2795.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Amyloid AA is derived from the precursor serum amyloid A (SAA)and is present in several chronic inflammatory diseases. Amyloid components, namely amyloid P component have been detected in drusen of early ARMD but no data exist about their possible presence in exudative ARMD. The objective of this study was to investigate the presence of amyloid AA in CNV membranes secondary to ARMD. Methods:CNV membranes were removed by a standard three-port vitrectomy in 16 patients with ARMD. They were fixated in formaline for 1 hour, embedded in paraffin, and were then dissected into 4µm layers. Monoclonal mouse antibody to amyloid AA was titrated and then diluted 1:100. Tissue sections were deparaffinized, rehydrated to water, treated with proteinase K for 10 min and incubated for 15 min with normal goat serum. After this blocking step, slides were incubated with mouse antibody directed specifically against amyloid AA for 30 min. Link antibody was incubated for 10 min, and slides were then washed and incubated with alkaline phosphatase conjugated streptavidine. Finally, slides were stained with substrate chromogene for 10 min. Endogenous alkaline phosphatase was blocked with levamisole and sections were counterstained with haematoxylin. In negative controls, the primary antibody was replaced with normal mouse serum. Human kidney secodary amyloidoses served as positive control. Results:Amyloid AA was present in all but one CNV membranes. No negative control showed any positive staining. The fibrovascular matrix was the most common localization of amyloid AA deposits, this pattern was seen in 11 membranes. In 4 CNV membranes, amyloid AA was detected in close proximity to RPE cells. Conclusion:Our results suggest that CNV membranes in ARMD contain deposits of amyloid AA. Possible explanations for this phenomenon include the following: amyloid AA may be an ocular manifestation of systemic disease. It may also be a remainder of former drusen components incorporated into the neovascular membranes. Furthermore, this may reflect a local form of amyloidosis possibly in association with local inflammatory response. We consider it unlikely that amyloid AA deposits reflect a similar pathway between ARMD and atherosclerosis as proposed recently since atherosclerotic lesions would be expected to contain amyloid P component but no true amyloids like amyloid AA.
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