In Vivo Imaging of the Adult Drosophila melanogaster Heart With Real-Time Optical Coherence Tomography
Over the past century, research involving the fruit fly Drosophila melanogaster has consistently yielded fundamental insights into the nature of complex organisms. The cardiovascular sciences have benefited from these discoveries. Examples include the discovery of the human ether-a-go-go inward rectifying potassium channel, a fly homologue of HERG that is implicated in inherited long-QT syndrome, and the tinman protein, a fly homologue of NKX2.5 that is responsible for certain congential atrial septal defects and conduction abnormalities. More recent results, such as those involving the insulin regulation of heart function in aging fruit flies, suggest that D melanogaster is an emerging model organism in cardiac disease. To date, functional studies of the adult D melanogaster heart have been difficult, and in vivo cross-sectional imaging has been essentially impossible. Here, we present real-time in vivo B- and M-mode optical coherence tomography (OCT) images of wild-type (OreR) D melanogaster heat tubes. Our OCT system has axial and lateral resolution of 10 μm and 23 μm, respectively, a B-mode frame rate of 8 to 20 per second, and an M-mode line rate of 4000 per second. Flies were anesthetized with FlyNap (Carolina Biological, Burlington, NC) for examination. Numbered figures represent different flies. Figure 1 and Movies I and II show transverse and sagittal B-scans of the heat tube during systole and diastole. M-mode images were taken at the landmark indicated by the line in Figure 1C. Figure 2 shows a 1-second M-scan. From the M-scan, the heart rate is determined to be 360 beats per minute (beat-to-beat interval of 167 milliseconds), and the shortening fraction to be 67%. Figure 3 and Movie III show intermittent arrhythmia and asystole occasionally noted immediately after induction of anesthesia. These images suggest that D melanogaster can be readily used as a model organism in genetic and genomic studies of cardiovascular disease including heart failure and arrhythmia.
Sources of Funding
This work was supported by National Institutes of Health grant R24-EB00243, “Partnership for Research in Optical Coherence Tomography.”
Dr J. Izatt is a cofounder, officer, and major stockholder in Bioptigen, Inc, which has commercialized an advanced version of the instrument used in this study. Duke University has licensed intellectual property to and holds equity in Bioptigen, Inc.
The online-only Data Supplement, which contains 3 movies, can be found at http://circ.ahajournals.org/cgi/content/full/114/2/e35/DC1.