Our laboratory is one of the few Assisted Reproductive Technology (ART) centers in the world that is equipped with the ability to monitor growing equine embryos with a live embryo monitoring system, allowing us to evaluate the embryo formation precisely. Traditional monitoring of embryos includes removing them from the incubator environment for microscopic observation once a day, which can cause stress on the embryo, and does not allow the exact timing for specific embryonic events. Moreover, studies have shown that imaging phenotypes reflect molecular programs of the embryo and of individual blastomeres. It is not known whether equine embryo development follows specific timed division (mitotic)events. An understanding of these events will help improve our understanding of factors affecting blastocyst success rate in mares.
Equine Embryos Growing
Eq Blast 1- This is a Miri time-lapse video of the first 4 days after ICSI of an equine developing embryo. Note the cell divisions from 1-2 cell and 2-4 cell stages and continuing to the 8-16-cell morula stage. Each video frame was captured at 5-minute intervals and compiled in to a movie for review of condensed timing of the equine embryo development.
Eq Blast 2 – Miri time-lapse video of an equine morula developing to a complete normal ICSI blastocyst. Note the regular pulsing of the entire embryo at intervals of approximately 5-10 times per hour.
Embryo Time-Lapse Imaging
Using the MiriTL® time-lapse incubation system in our laboratory at UC Davis, we can determine the normal timeline of mitotic events of developing equine embryos and we can predict which embryos are likely to progress to the blastocyst stage using non-invasive TLM imaging and without removing them from the incubator as most labs must do to check development progress!
We routinely generate ICSI embryos and culture them using a self-contained imaging incubator system (MiriTL® Esco Technologies) that captures brightfield images at 5-min intervals throughout the 7-to 10-day course of equine in vitro embryo development. Movies like the one on this page are then generated and we can define and annotate the mitotic events, including cleavage, time to the 2-,4-, and 8-cell stages, morula formation, and blastocyst development. In our laboratory, all embryos reaching the blastocyst stage will exhibit a rhythmic and repeated pulsation (see pulsation video) lasting approximately 5 min approximately five times per hour which we identified as being highly related to blastocysts that develop successfully and can be transferred to become healthy foal.
The advent of transvaginal aspiration of oocytes (TVA) and ICSI has provided a reliable way to produce foals from stallions with very limited semen reserves (including frozen semen from deceased stallions), as well as from performance and aged mares and from mares with severe uterine, cervical or oviductal disease. The reasons for embryo loss in mares after transfer are not precisely known, but are considered multifactorial and include embryo mortality due to mare age, individual stallion effects (including age), oocyte chromosome abnormalities (known as aneuploidies) that could affect mitotic integrity and variation in pretransfer culture conditions among numerous other potential causes of embryo failure and death.
Visit the Equine Reproduction Center for more info and scheduling for your mares