Noninvasive monitoring of embryonic chick eye development in ovo using 7 Tesla MRI

Abstract

Purpose : The avian embryo serves as an excellent model for monitoring embryonic development. Ultrahigh field magnetic resonance imaging (UHF-MRI) is an invaluable tool for noninvasive and high resolution tissue imaging. The purpose of this study was to characterize the embryonic eye development during incubation in ovo and to analyze the putative influence of repetitive UHF-MRI measurement procedure on ocular developments.

Methods : A total population of 38 fertilized chicken eggs has been divided into two sub-groups: 36 eggs were examined pairwise only on one day, starting at embryonic day 3 (E3) to day 20 (E20) and have been sacrificed immediately after MR imaging (Group A). For comparison, the second group of two eggs (Group B) was examined repeatedly on daily manner during the developmental time course E3 to E20 to evaluate the influence of daily MRI-scanning. Moderate cooling of the eggs was performed before and during UHF-MRI at 7.1 Tesla for about 50-70 minutes to reduce possible artifacts due to natural embryo movements. Ganglion cell counting was performed using HE-staining at E20 in both groups.

Results : Using fast T2 weighted MR-sequences, we could provide a biometry of the eye with an in-plane resolution of 74 μm starting from E5. Data show a rapid growth of the chicken eye with a steep increase of intraocular distances and of bulbus volume during initial development until E10, followed by a phase of reduced growth rate in later developmental stages. The length of the pecten, a nutritive structure specific to the bird eye, could be evaluated from E12. No differences in ocular development could be determined comparing the two sub-groups A and B.

Conclusions : We conclude that UHF-MRI provides a powerful imaging technique for noninvasive and longitudinal studies of avian eye development. The technique allows an investigation of the maturation of the chicken eye in ovo from E5 onwards. Daily MR scanning in combination with moderate cooling of chicken eggs during MR imaging does not alter ocular development. The MR based imaging technique could become a routine approach for longitudinal embryonic studies.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.