Expression Of Progesterone-related Genes In Liver Of Sheep During Early Pregnancy And Their Application In Production

Early embryo death is one of the main causes of recessive abortion in livestock.It often causes infertility,fewer litters and lower reproductive performance of livestock,which causes serious economic losses to animal husbandry production.The embryo mortality rate of sheep is about 40%.70% to 80% of the embryos died 8-16 days after mating and fertilization.In infertile sheep,embryo mortality rates were30% and 40% respectively in the 0-7 and 8-17 gestational periods.Therefore,the embryonic death of sheep mainly occurs in the early pregnancy.In order to investigate the causes of early embryo loss and to reduce the rate of embryo loss,we conducted the following three experiments:Experiment 1: This experiment took sheep with normal reproductive function as experimental animals.First,sheep were treated with estrus synchronization,and then they were tested and mated(control group was not mated).Then collect the liver tissue of the sheep that was not pregnant on the 16 th day after estrus,and on the 13 th,16th and 25 th day after pregnancy.The expression of progesterone receptor(PGR)and progesterone-induced blocking factor(PIBF)in the liver of sheep was studied by real-time fluorescence quantitative PCR,Western blotting and immunohistochemical staining.Result: The isoforms of PGR with molecular weights of approximately 60kDa(PGR60)and 89 kDa(PGR89)were strongly expressed in the livers from pregnant ewes(P < 0.05),but there was no expression of the isoform of PIBF with a molecular weight of approximately 55 kDa(PIBF55)on day 13 of pregnancy.The PGR protein was mainly limited to the endothelial cells of the proper hepatic arteries and hepatic portal veins.It was suggested that early pregnancy exerted its effect on the maternal liver,resulted in the up-regulation of PGR89 and PGR60 and down-regulation of PIBF55 on day 13 of pregnancy,which involved in the regulation of maternal hepatic immunoregulatory,hematopoietic and other functions through an endocrine manner during early pregnancy in sheep.Experiment 2:The expression of prostaglandin synthase(PG)in sheep liver was studied by real-time fluorescence quantitative PCR,Western blotting and immunohistochemical staining.Result:There were increases in the expression of mRNAs and the proteins of COX-2,PTGES and AKR1B1 in the livers during earlypregnancy,but COX-1 was decreased in the pregnant groups.AKR1B1 proteins were limited to the endothelial cells of the proper hepatic arteries and hepatic portal veins.In conclusion,the up-regulation of COX-2,PTGES and AKR1B1 and down-regulation of COX-1 involved in the maternal hepatic immune adjustment during early pregnancy in sheep.Experiment 3: The experimental animals were selected from Fuye Animal Husbandry Group of Hebei Province,from which 24 Small-tailed Han sheep ewes with good health and similar reproductive organs were selected.Sheep were randomly divided into two groups,12 in each group,one of which was the control group,the other was the experimental group.Progesterone sponge suppository(dosage: 0.3g)was placed in the vagina of sheep in the experimental group on the 13 th day after oestrus mating,while the control group was not treated.Results: In the control group(without implantation of progesterone),4 embryos were lost,the rate of embryo loss was 33.3%(4/12),while in the experimental group(implantation of progesterone),2embryos were lost,and the rate of embryo loss was 16.7%(2/12).The results showed that implantation of progesterone could reduce the rate of embryo loss,improve the survival rate of embryos,and thus improve economic benefits.In conclusion,early pregnancy in sheep,progesterone acts to reduce embryo loss.The early pregnancy exerted its effect on the maternal liver through P4,PGR and PIBF participated in the regulation of maternal hepatic immunoregulatory,hematopoietic and other functions through blood circulation in sheep.At the same time,the up-regulation of COX-2,PTGES and AKR1B1 and down-regulation of COX-1 may be implicated in the maternal hepatic immunoregulation during early pregnancy in sheep.