Noninvasive Ovarian Imaging in the Murine Models Using Ultrasound Biomicroscopy

The laboratory mouse is a well-accepted model for reproductive
biology studies and findings made in mice have been commonly
translated to humans. C57BL/6J and BALB/c strains provide a
robust experimental platform for polycystic ovary syndrome and
ovarian cancer research in women. Serial assessment of ovarian
morphometry and follicle dynamics may be performed non-invasively
and reliably in mice by Ultrasound Biomicroscopy (UBM),
with a near microscopic resolution. Our pilot study focused on
the utility of UBM in murine models to measure size of ovaries
and to count ovarian follicles over time. Three C57Bl/6J and two
BALB/c adult mice (>8 weeks of age) were housed in standard
conditions, with free access to food and water. Spontaneous
estrous cycle was longitudinally evaluated by transcutaneous
UBM (Vevo 770, VisualSonics, Toronto, Canada; center frequency
of 40 MHz; focal depth of 6 mm, spatial resolution of 30 um) on
a time period of 8-15 consecutive days. Mice were anesthetized
with 1.5% isoflurane in oxygen and fixed in sternal recumbency
on a heated stage. Trichotomy was performed over the thoracolumbar
area, and acoustic gel was applied to the skin. Images
of both ovaries were obtained in sagittal and axial scans, and
processed offline using ImageJ software. Ovarian diameters, area,
volume and follicles identification were obtained. To imaging
results comparison, the phase of the estrous cycle was assessed
in BALB/c mice by vaginal cytology. Ovaries were consistently
localized in all mice, with a 10 minutes scan time. The changes of
the follicles pattern and number overtime have wave-like fashion.
In conclusion, UBM is a suitable method for measuring and for
identifying the patterns in follicle development, ovulation and
regression in mice in vivo, and to monitor the potential efficacy
of novel therapies in murine models of ovarian pathologies.

Noninvasive Ovarian Imaging in the Murine Models Using Ultrasound Biomicroscopy