Researchers Examine the Secret Life of Equine Embryos

A mare's pregnancy might not seem that complicated on the surface, but her relationship with the embryo and its adjacent parts--in total, the conceptus--is remarkably complex. In order to prevent early embryonic loss, the conceptus must interrupt her estrous cycle, signaling her uterus to create a receptive environment for attachment and growth.

Exactly how this "maternal recognition of pregnancy" occurs remains a mystery; however, researchers recently identified some of the genes involved--improving their understanding of early embryonic loss and how it might one day be prevented.

"The domestic horse is one of the few species in which the pregnancy recognition signal has not been established," explained Claudia Klein,, PhD, Dipl. ACT, ECAR, of the University of Kentucky's Gluck Equine Research Center .

Researchers know that among mammals a horse's pregnancy is unique : the conceptus is mobile in the uterus for nine to 18 days following ovulation; and a capsule surrounds the embryo like an egg shell. However, veterinarians are striving for a more comprehensive grasp of the earliest days of pregnancy.

To gain a better understanding of how the dam-to-be's body communicates with her embryo during these early days of pregnancy, Klein and research colleague Mats H.T. Troedsson, DVM, PhD, Dipl. ACT, ECAR, collected embryos from mares at Days 8, 10, 12, and 14 after ovulation and noted which of the embryos' genes were turned on or off at each time point.

During the study, the team identified a multitude of genes with roles in early embryonic survival, including some unique types of genes not previously reported in other species.

"Some of the more important genes expressed by early equine conceptuses were those involved in changing the surface of the embryonic capsule, an event orchestrating the cessation of embryonic mobility," explained Klein. It is crucial that the embryo attaches to the uterine wall in a timely manner so that pregnancy can be maintained.

Simply put, researchers learned that the conceptus appears to change the composition or structure of its own capsule to assist in maintaining pregnancy.

However, this is only one aspect of in the early maintenance of pregnancy, note the scientists.

"This research points us in a new direction to determine 'maternal recognition of pregnancy' which will eventually help us to understand early embryonic loss, a frustrating event for horse breeders," Klein concluded.

The study, "Transcriptional profiling of equine conceptuses reveals new aspects of embryo-maternal communication in the horse," will be published in an upcoming edition of The Biology of Reproduction. The abstract is available for free on PubMed.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.