Sexual Differentiation and Primordial Germ Cell Distribution in the Early Horse Fetus

It was the aim of this study to characterize development gonads and genital ducts in equine fetus around time sexual differentiation. This included identification localization primordial germ cell population. Equine fetuses between 45 60 days gestation were evaluated using a combination micro-computed tomography scanning, immunohistochemistry, multiplex immunofluorescence. Fetal increased size 23-fold from gestation, an even greater increase observed metanephros volume. Signs mesonephros atrophy detected during time. Tubular structures fetal testes present day 50 onwards, whereas clusters dominated ovary. The well-differentiated presented lumen all samples. No sign mesonephric or paramesonephric duct degeneration detected. Expression AMH strong but absent ovaries. Irrespective sex, cells selectively expressed LIN28. Migration gonad at days, not development. Their number distribution within influenced (p < 0.05) by sex. Most (86.8 ± 3.2% females 84.6 4.7% males) characterized as pluripotent according co-localization with CD117. However, only very small percentage proliferating (7.5 1.7% 3.2 1.2% based on Ki67. can be concluded that gonadal differentiation horse occurs asynchronously regard sex already before gestation.