Ostrich (Struthio camelus) primordial germ cells in embryonic blood and presumptive gonad: characterization by PAS and immunohistochemistry

Background: Among the birds, chicken was the model used in the majority of studies on germ cells and other birds like quail, turkey and pheasant had some interest but ostrich has been lacking from these researches. Aims: The present study was conducted to confirm the presence of ostrich primordial germ cells (PGCs) in the embryonic blood and to determine the appropriate time for having them in the blood. Methods: Embryos were extracted in embryonic day (E) 612, their blood was obtained and the rest of the embryos were processed for histological examinations. Staining by periodic acidSchiff (PAS) method and immunohistochemistry (IHC) using stagespecific embryonic antigen 1 (SSEA1) and stagespecific embryonic antigen 4 (SSEA4) antibodies (Abs) were used for identification of the PGCs. Results: While the blood circulating ostrich PGCs were SSEA1negative and SSEA4positive, in the presumptive gonads PGCs showed negative immunoreactivity for both Abs. Although the ostrich PGCs were PASpositive in both blood and presumptive gonad, their PASpositive contents reduced during development from E 10 to E 12. Conclusion: E 9, when the hind limb buds appear, is the best time for detecting PGCs in the ostrich embryonic blood.