Toward a new insight of calcium oxalate stones in Drosophila by micro-computerized tomography.

We previously developed an animal model of calcium oxalate (CaOx) deposition on the Malphigian tubules of Drosophila melanogaster as a model of urolithiasis. Here, we introduce a new tool for the study of anatomical structure for Drosophila. As a consequence of technical development, the invention of micro-computerized tomography (CT) has been introduced to the small animal, such as rat and mice. We used Drosophila as a model organism and fed the flies 0.5% lithogenic agent ethylene glycol for 3 weeks. Samples were simply prepared for further scanned by micro-CT to scan samples at 800 nm resolution. CT scanning was performed at 40 kVp of voltage, 250 µA of current, and 1750 ms of exposure time and without filter. Reconstruction of sections was carried out with the GPU-based scanner software. Specific region of interests was further analyzed by DataViewer software. Area with high radiologic density level was defined as CaOx deposition for further 3D analysis. Image of whole lithogenic Drosophila was compared with control. High radiologic density level was detected in the region of Malphigian tubules which can be identified as CaOx stones. There was no stone image in the control group. The image was the same as human non-contrast CT for the diagnosis of stone disease. Micro-CT clearly demonstrated the calcium oxalate calcifications in the Malphigian tubules of fruit fly. The image system provides that a new vision on study animal will facilitate further study of stone disease. With the development of new technology on micro-CT, more delicate and advanced image will be presented in the future.