Regulation Mechanisms Of Thyroid Hormone In Porcine Folliculogenesis And Early Embryo Development

In vitro embryo production (IVP) has been successfully used for infertility treatment, farm animal breeding and preservation of endangered species. Embryo culture media and its composition play an important role in the developmental competency of in vitro produced embryos. To optimize IVP it is important to understand the physiology of the in vivo embryo medium. Previously, we confirmed whether the presence of thyroid hormones (THs) in the porcine follicle fluid,expression pattern of TR alpha in different developmental stages of porcine follicules, in vitro matured oocytes and early embryos were systemically investigated in the present study,And their beneficial effect on embryo quality in vitro. The THs concentration of the different diameter sizes of pig follicular was determined by chemiluminescence immunoassay (CLIA) technique. And the localization of TR alpha in pig ovary were determined by immunohistochemieal techniques. The expression pattern of TR alpha in pig oocytes and pre-implantation embryos were determined with immunofluorescence and QRT-PCR.To assess the outcome of supplementation thyroxin(T4)and anti thyroid hormone receptor alpha antibody(Anti-THRA), embryos were followed through standard and T4-supplemented in-vitro procedures, and evaluated for the cleavage rates, blastocyst formation rate. The T3concentration in pig follicles was rised at first and then declined following the increase of follicle diameter. TR alpha-immunoreactive substance was mainly distributed over granular cells,theca cells and oocytes.The quantity of the TR alpha-immunoreactive and TR alpha-immunoreactive cells were increased following the development of follicles.The results of QRT-PCR showed that TR alpha was expressed through out the process of in vitro matured oocytes, and the relative expression level in1-,2-and4-cell stages were significant higher than that of8-cell morula and blastula stage. Immunohistochemical analysis results showed that TR alpha clearly expressed following the increase of follicles, and reached peak at24-36h. TR alpha protein expressed in different stages of early embryos, and its expression level was upregulated at8-cell, morula and blastocyst stage. the lOng/ml T4-treated embryos exhibited significant increases in blastocyst formation and hatching rates (P<0.05).And the Anti-THRA antibody treated embryos exhibited significant decreases in blastocyst formation and hatching rates (P<0.05).Embryo quality was significantly improved in the treated groups as demonstrated by greater total cell counts. THs existed in the pig follicle fluid, TR alpha expressed in different stages of COCs and early embryos,THs may be affected pig folliculogenesis and early embryonic development by banding with the TR alpha.