Three-Dimensional High-Frequency Ultrasonography for Early Detection and Characterization of Embryo Implantation Site Development in the Mouse

Abstract

Ultrasonography is a powerful tool to non-invasively monitor in real time the development of the human fetus in utero. Although genetically engineered mice have served as valuable in vivo models to study both embryo implantation and pregnancy progression, such studies usually require sacrifice of parous mice for subsequent phenotypic analysis. To address this issue, we used three-dimensional (3-D) reconstruction in silico of high-frequency ultrasound (HFUS) imaging data for early detection and characterization of murine embryo implantation sites and their development in utero. With HFUS imaging followed by 3-D reconstruction, we were able to precisely quantify embryo implantation site number and embryonic developmental progression in pregnant C57BL6J/129S mice from as early as 5.5 days post coitus (d.p.c.) through to 9.5 d.p.c. using a VisualSonics Vevo 2100 (MS550S) transducer. In addition to measurements of implantation site number, location, volume and spacing, embryo viability via cardiac activity monitoring was also achieved. A total of 12 dams were imaged with HFUS with approximately 100 embryos examined per embryonic day. For the post-implantation period (5.5 to 8.5 d.p.c.), 3-D reconstruction of the gravid uterus in mesh or solid overlay format enabled visual representation in silico of implantation site location, number, spacing distances, and site volume within each uterine horn. Therefore, this short technical report describes the feasibility of using 3-D HFUS imaging for early detection and analysis of post-implantation events in the pregnant mouse with the ability to longitudinally monitor the development of these early pregnancy events in a non-invasive manner. As genetically engineered mice continue to be used to characterize female reproductive phenotypes, we believe this reliable and non-invasive method to detect, quantify, and characterize early implantation events will prove to be an invaluable investigative tool for the study of female infertility and subfertility phenotypes based on a defective uterus.

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“…Color Doppler angiography of tumor blood vessels. Murine ultrasonographic imaging was done as previously described, with modifications (45,46). Briefly, breast tumors were visualized by using a Vevo 2100 Imaging System with 550D scan probe (VisualSonics Inc.) at 32 MHz.…”

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“…High-frequency probes have been developed for rodents and zebrafish and have remarkable resolution of the fish heart 9 or for mouse embryos. [10][11][12] Ultrasound methods evaluate anatomy, function, endothelial molecular changes, and blood flow through organs. Advanced ultrasound methods had been developed for ocular imaging, 13 intravascular imaging, and living mouse embryo imaging used for microinjections into the embryo.…”