Fetal Mouse Cardiovascular Imaging Using a High-frequency Ultrasound (30/45MHZ) System.

Congenital heart defects (CHDs) are the most common cause of childhood morbidity and early mortality. Prenatal detection of the underlying molecular mechanisms of CHDs is crucial for inventing new preventive and therapeutic strategies. Mutant mouse models are powerful tools to discover new mechanisms and environmental stress modifiers that drive cardiac development and their potential alteration in CHDs. However, efforts to establish the causality of these putative contributors have been limited to histological and molecular studies in non-survival animal experiments, in which monitoring the key physiological and hemodynamic parameters is often absent. Live imaging technology has become an essential tool to establish the etiology of CHDs. In particular, ultrasound imaging can be used prenatally without surgically exposing the fetuses, allowing maintaining their baseline physiology while monitoring the impact of environmental stress on the hemodynamic and structural aspects of cardiac chamber development. Herein, we use the High-Frequency Ultrasound (30/45) system to examine the cardiovascular system in fetal mice at E18.5 in utero at the baseline and in response to prenatal hypoxia exposure. We demonstrate the feasibility of the system to measure cardiac chamber size, morphology, ventricular function, fetal heart rate, and umbilical artery flow indices, and their alterations in fetal mice exposed to systemic chronic hypoxia in utero in real time.