In Vivo Imaging of Mouse Cardiovascular Development and Disease by High Frequency Ultrasound

Abstract

We developed a noninvasive ultrasound imaging protocol for cardiovascular phenotyping fetal mice. Using Doppler echocardiography, we could evaluate structure and function of the developing fetal mouse heart. With multiple scans of the same fetuses, the progression of cardiovascular development and disease can be followed over time. The ultrasound imaging modalities utilized included 2D, color flow, spectral Doppler and M-mode imaging, and together, all of the major elements of the heart can be systematically assessed. We ultrasound scanned nearly 15,000 ENU (ethylnitrosourea) mutagenized mouse fetuses between embryonic day12.5 to 19.5 and identified 541 with cardiovascular defects. Further analysis by necropsy and histology showed heart defects that included conotruncal anomalies, obstructive lesions, shunt lesions, as well as other complex heart diseases. In addition, ultrasound imaging identified craniofacial/head defects, body wall closure defects, and other anomalies, which necropsy revealed as acrania, microcephaly, encephalocele, holoprosencephaly, omphalocele, gastroschisis, and others. We also could observe limb anomalies such as polydactyly by ultrasound. The incidences of noncardiac anomalies were considerably lower than cardiovascular defects. Some fetuses with cardiac defects also exhibited noncardiac malformations. Overall, these studies show the efficacy of ultrasound phenotyping for the analysis of congenital heart defects and a wide variety of other extracardiac anomalies.