Effects Of Prostaglandin D2 On Corpus Luteum Degeneration And Its Regulatory Mechanism In Sheep

Objective:Luteal corpus（CL）is an important temporary reproductive organ for the regulation of fertilized egg implantation,embryo development and pregnancy.Regression of CL is a prerequisite for the initiation of the next reproductive cycle.PGF2αcan effectively promote CL regression,while PGD2 is involved in many physiological responses（mainly including inflammatory responses）,but rarely reported in reproduction.Therefore,this experiment was based on the main luteinizing hormone PGF2αand focused on PGD2,to study the effect of PGD2 on the regression of CL in ewes and the regulatory mechanism involved in the process of PGF2α-induced luteolysis.It provides new ideas for further optimization of high-efficiency breeding technology（especially the PGs scheme）.Methods:Firstly,20 healthy ewes were treated on estrus synchronization.Then PGD2（The PGD2 group）,PGF2α（the PGF2αgroup）,PGD2+PGF2α（the combined group）,and normal saline（the blank group）to treat with uterine muscle in the mid-luteal phase of the second estrus cycle.Then,external observation and H.E staining were used to compare the CL morphological changes in each group before and after treatment.Finally the relative genes and reproductive hormones were detected by ELISA,q RT-PCR and Western blot.（1）The expression of related apoptosis genes BCL-2 and Caspase-3 in CL,the regression effect of CL structure was analyzed.（2）The differential expression of endocrine hormone P₄and E₂,and St AR gene were detected,the effect of each treatment group on the regression of CL endocrine function was analyzed.（3）The expression levels of endocrine PGD2 and PGF2αand the key synthases HPGDS and PGFS in uterus that regulatory relationship between PGD2 and PGF2αwas analyzed.（4）The expression levels of different receptor types DP1,CRTH2 and FP in CL（IF technology was used to detect the expression distribution of different receptors）,to analyze the regulation mechanism of PGD2 and PGF2αon its receptors.Results:（1）The results showed that,PGD2 alone promoted the appearance of multiple follicles in ovary,the structure of CL was cavitated,but the volume of the CL did not change significantly.Additionally,PGD2 could also promote the decrease of P₄and E₂,promoted the down-regulation of St AR expression significantly in CL（P<0.05）.（2）When the PGD2 was used alone,the expressions of uterine-derived HPGDS and PGFS were significantly increased（P<0.05）,the level of PGD2 was increased,and the level of PGF2αwas decreased.In CL,DP1,CRTH2 and FP proteins were distributed in the cytoplasmic membrane.When the PGD2 was used alone,the expressions of DP1 and FP were significantly up-regulated（P<0.05）.When the PGF2αwas used alone,the expressions of CRTH2 and FP were significantly up-regulated（P<0.05）.（3）When the PGD2 combined with PGF2α,multiple follicles appeared in ovary,and the volume of CL was basically ablated.Compared with PGF2αwas used alone,when PGD2 was used in combination with PGF2α,the expression of BCL-2 significantly down-regulated（P<0.05）,and the expression of the Caspase-3 was significantly up-regulated（P<0.05）,the levels of P₄and E₂were significantly decreased（P<0.05）,and the expression of St AR was significantly down-regulated（P<0.05）.（4）Compared with PGF2αwas used alone,when PGD2 was used in combination with PGF2α,the expressions of uterine-derived HPGDS and ovarian-derived receptors DP1 and CRTH2 were significantly down-regulated（P<0.05）,and the expressions of uterine-derived PGFS and ovarian-derived receptors FP were significantly up-regulated（P<0.05）.Conclusion:（1）We found that PGD2 could promote CL regression by analyzing the CL structure（morphology,BCL-2,Caspase-3）and endocrine function（P₄,E₂and St AR）.But the effect was not as good as PGF2α.PGD2 has a synergistic role in the process of PGF2α-induced luteal involution.（2）In the process of luteinizing degeneration,PGD2 and PGF2αcan promote each other（PGD2,PGF2α,HPGDS and PGFS）,which also have a mutual promotion effect on the receptors（DP1,CRTH2 and FP）on the ovarian corpus luteum.