Xenopus Tadpole Craniocardiac Imaging Using Optical Coherence Tomography

Abstract

Optical coherence tomography (OCT) imaging can be used to visualize craniocardiac structures in the Xenopus model system. OCT is analogous to ultrasound, utilizing light instead of sound to create a gray-scale image from the echo time delay of infrared light reflected from the specimen. OCT is a high-speed, cross-sectional, label-free imaging modality, which can outline dynamic in vivo morphology at resolutions approaching histological detail. OCT imaging can acquire 2D and 3D data in real time to assess cardiac and facial structures. Additionally, during cardiac imaging, Doppler imaging can be used to assess the blood flow pattern in relation to the intracardiac structures. Importantly, OCT can reproducibly and efficiently provide comprehensive, nondestructive in vivo cardiac and facial phenotyping. Tadpoles do not require preprocessing and thus can be further raised or analyzed after brief immobilization during imaging. The rapid development of the Xenopus model combined with a rapid OCT imaging protocol allows the identification of specific gene/teratogen phenotype relationships in a short period of time. Loss- or gain-of-function experiments can be evaluated in 4–5 d, and OCT imaging only requires ∼5 min per tadpole. Thus, we find this pairing an efficient workflow for screening numerous candidate genes derived from human genomic studies to in-depth mechanistic studies.