Abstract
Our previous studies demonstrated that maternal (oocyte derived) follistatin (FST) expression is positively associated with bovine oocyte competence and exogenous follistatin treatment during the pre-compaction period of development (d 1–3 post insemination) is stimulatory to bovine early embryogenesis in vitro [blastocyst rates and cell numbers/allocation to trophectoderm (TE)]. In the present study, bovine embryos were treated with exogenous follistatin during d 1–3, d 4–7 and d 1–7 post insemination to test the hypothesis that embryotropic effects of exogenous follistatin are specific to the pre-compaction period (d 1–3) of early embryogenesis. Follistatin treatment during d 4–7 (peri-/post-compaction period) of embryo culture increased proportion of embryos reaching blastocyst and expanded blastocyst stage and total cell numbers compared to controls, but blastocyst rates and total cell numbers were lower than observed following d 1–3 (pre-compaction) follistatin treatment. Follistatin supplementation during d 1–7 of embryo culture increased development to blastocyst and expanded blastocyst stages and blastocyst total cell numbers compared to d 1–3 and d 4–7 follistatin treatment and untreated controls. A similar increase in blastocyst CDX2 mRNA and protein (TE cell marker) was observed in response to d 1–3, d 4–7 and d 1–7 follistatin treatment. However, an elevation in blastocyst BMP4 protein (TE cell regulator) was observed in response to d 1–3 and d 1–7, but not d 4–7 (peri-/post-compaction) follistatin treatment. In summary, our study revealed the potential utility of follistatin treatment for increasing the success rate of in vitro embryo production in cattle. Such results also expand our understanding of the embryotropic actions of follistatin and demonstrate that follistatin actions on blastocyst development and cell allocation to the TE layer are not specific to the pre-compaction period.
Highlights
Poor oocyte quality is recognized as a key limiting factor in improving the current low rate of successful assisted reproductive technologies and development of new options in infertility treatments
Given observed positive association of maternal follistatin abundance with oocyte and embryo developmental competence, we have previously investigated the functional role of follistatin in regulation of bovine early embryogenesis. siRNA mediated depletion of oocyte derived follistatin in zygotes reduced the number of embryos developing to the 8–16 cell stage and blastocyst stage and decreased the number of total and TE cells in blastocysts [14]
Blastocyst rates for embryos treated with follistatin during the post compaction period (d 4–7) were lower than observed for embryos treated with follistatin during the pre-compaction period (d 1–3)
Summary
Poor oocyte quality is recognized as a key limiting factor in improving the current low rate of successful assisted reproductive technologies and development of new options in infertility treatments. A large body of evidence suggests that maternal transcripts and proteins accumulated during oogenesis are crucial in determining competence of the oocyte to resume meiosis and develop into a viable embryo after fertilization [1,2,3]. Maternal (oocytederived) follistatin mRNA and protein abundance was greater in embryos that cleaved early and resulted in four times higher rates of blastocyst development compared to their late cleaving counterparts. Results suggested an association of maternal (oocyte-derived) follistatin with bovine oocyte competence
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
