Endometrial receptivity plays a vital role in successful embryo implantation in pigs. MicroRNAs (miRNAs), known as the regulator of gene expression, were implicated in the regulation of embryo implantation. However, the role of miRNAs in the endometrial receptivity during the pre-implantation period remains elusive. In this study, we reported that the expression level of ssc-miR-21-5p in porcine endometrium tissues was significantly increased from day 9 to day 12 of pregnancy. Knockdown of ssc-miR-21-5p inhibited proliferation and migration of endometrial epithelial cells (EECs), while induced their apoptosis. We verified that programmed cell death 4 (PDCD4) was a target gene of ssc-miR-21-5p. Inhibition of PDCD4 rescued the effect of ssc-miR-21-5p repression on EECs. Our results also revealed that knockdown of ssc-miR-21-5p impeded the phosphorylation of AKT by targeting PDCD4, which further up-regulated the expression of Bax and down-regulated the levels of Bcl2 and Mmp9. Furthermore, loss of function of mmu-miR-21-5p in vivo resulted in a decreased number of implanted mouse embryos. Taken together, knockdown of ssc-miR-21-5p hampers endometrial receptivity through modulating the PDCD4/AKT pathway.
Background The exosomes of uterine luminal fluid (ULF) mediate intrauterine communication between conceptus and uterus in pigs. The small RNAs of ULF exosomes are widely recognized as important factors that influence embryonic implantation in humans, mice, cattle and sheep. Therefore, it can be hypothesized that small RNAs of ULF exosomes are essential for implantation in pigs. Results Cup-shaped exosomes (diameters: 40–160 nm) of porcine ULF were isolated and characterized, and then PKH67 stained exosomes were taken up by endometrial epithelial cells and porcine trophectoderm cells. The expression of small RNAs in these exosomes on days 10 (D10), 13 (D13) and 18 (D18) of pregnancy was comprehensively profiled through sequencing. From nine libraries, a total of 152 known microRNAs (miRNAs), 43 novel miRNAs and 145 novel Piwi-interacting RNAs (piRNAs) were identified. Among these small RNAs, ssc-miR-21-5p, ssc-let-7a, ssc-let-7i-5p and ssc-let-7g were differentially and highly expressed during the three stages. Hierarchical cluster analysis and principal component analysis suggested that the expression profiles of small RNAs in D13 group were different from those in D10 and D18 groups. Bioinformatics analysis showed that the miRNAs differentially expressed in the comparisons between D10 and D13, D13 and D18, and D10 and D18 groups were involved in important molecular functions and pathways such as “G-protein coupled receptor activity” and “Insulin signaling pathway”. Conclusions Our results reveal that porcine ULF exosomes contain various small RNAs with potentially vital effects on implantation. This research also provides resources for studies of miRNAs and piRNAs in the cross-talk between embryo and endometrium.
Background The exosomes of uterine luminal fluid (ULF) mediate intrauterine communication between conceptus and uterus in pigs. The small RNAs of ULF exosomes are widely recognized as important factors that influence embryonic implantation in humans, mice, cattle and sheep. Therefore, it can be hypothesized that small RNAs of ULF exosomes are essential for implantation in pigs. Results Cupshaped exosomes (diameters: 40-160 nm) of porcine ULF were isolated and characterized, and then PKH67 stained exosomes were taken up by endometrial epithelial cells and porcine trophectoderm cells. The expression of small RNAs in these exosomes on days 10 (D10), 13 (D13) and 18 (D18) of pregnancy was comprehensively profiled through sequencing. From nine libraries, a total of 152 known microRNAs (miRNAs), 43 novel miRNAs and 145 novel Piwi-interacting RNAs (piRNAs) were identified. Among these small RNAs, ssc-miR-21-5p, ssc-let-7a, ssc-let-7i-5p and ssc-let-7g were differentially and highly expressed during the three stages. Hierarchical cluster analysis and principal component analysis suggested that the expression profiles of small RNAs in D13 group were different from those in D10 and D18 groups. Bioinformatics analysis showed that the miRNAs differentially expressed in the comparisons between D10 and D13, D13 and D18, and D10 and D18 groups were involved in important molecular functions and pathways such as "G-protein coupled receptor activity" and "Insulin signaling pathway". Conclusions Our results reveal that porcine ULF exosomes contain various small RNAs with potentially vital effects on implantation. This research also provides resources for studies of miRNAs and piRNAs in the cross-talk between embryo and endometrium. BackgroundPrevious studies have indicated that the majority of pre-natal losses occur during the periimplantation period in pigs [1,2]. During this period, the porcine blastocyst expands from 0.5-1 mm in diameter at hatching to 2-mm spheres on day 10 of pregnancy (D10) and begins to rapidly elongate into tubular and filamentous shapes on day 11 or 12 [3,4]. The conceptus starts to attach to the surface of maternal endometrium at day 13 of pregnancy (D13) and the attachment is usually completed between days 18 (D18) and 24 of pregnancy [5,6]. The synchronous communication between conceptus and uterus exerts strong influence on embryo implantation [7]. Furthermore, the
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