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  • Author: Kazuya Kusama x
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Kazuya Kusama, Mikihiro Yoshie, Kazuhiro Tamura, Takiko Daikoku, Tsutomu Takarada and Eiichi Tachikawa

The optimal decidualization of endometrial stromal cells (ESCs) following embryo implantation is one of the critical steps to establish pregnancy in rodents and humans. This step is intricately regulated by ovarian hormones. Using in vitro human ESCs model, we previously showed that activation of a cAMP mediator, exchange protein directly activated by cAMP (EPAC), promotes ovarian steroid- or cAMP analog-induced decidualization. However, expressions and functions of EPAC and RAP1 in the uterus during pregnancy have not yet been examined. In this study, we found that the expression of EPAC2 and RAP1 was markedly upregulated in the decidual cells at the implantation sites on days 7 and 9 of pregnancy in rats. Furthermore, both delayed-implantation and artificial decidualization models showed that EPAC2 and RAP1 expression was enhanced in decidual cells. Significant activation of cAMP-responsive element-binding protein (CREB), a central transcriptional factor of cAMP signaling, was observed in decidual cells. These spatiotemporal expressions of protein related EPAC pathway are overlapped by sites with activated cAMP signaling, indicating the association of EPAC signaling with decidualization. Strikingly, further studies in in vitro rat decidualization model showed that the cAMP analog and medroxyprogesterone stimulated the expression of decidual markers, while knockdown of EPAC1/2 and RAP1 attenuated the expressions of these markers. Together, these findings suggest that EPAC and RAP1 are the crucial factors for endometrial decidualization in rat pregnancy.

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Keigo Nakamura, Kazuya Kusama, Atsushi Ideta, Kazuhiko Imakawa and Masatoshi Hori

Extracellular vesicles (EVs) present in uterine lumen are involved in conceptus-endometrial interactions during the pre-implantation period. Despite numerous studies conducted on interferon tau (IFNT), a major protein of maternal recognition of pregnancy, the effect of intrauterine EVs on the endometrium during pre-implantation periods has not been well-characterized. To characterize conceptus-derived intrauterine EVs independent of IFNT, transcripts found from RNA-seq analysis in RNAs extracted from primary bovine endometrial epithelial cells (EECs) treated with cyclic day 17 (C17) EVs, pregnant day 17 (P17) EVs or IFNT were analyzed. These analyses identified 82 transcripts uniquely induced by IFNT-independent P17 EVs, of which a large number of transcripts were associated with ‘the TNF signaling pathway’ and ‘Inflammatory response’. Moreover, high expression of CD40L, a member of the TNF superfamily, and its receptor CD40 were found in P17 EVs and in EECs, respectively. Furthermore, the expression of TNF signaling pathway-related genes was up-regulated by the treatment with P17 EVs, but these increases were down-regulated by NF-kB signaling inhibitor. These findings suggest that P17 EVs could induce a pro-inflammatory response in the endometrium, independent of IFNT, to regulate uterine receptivity, facilitating conceptus implantation.

Free access

Kazuhiko Imakawa, Pramod Dhakal, Kaiyu Kubota, Kazuya Kusama, Damayanti Chakraborty, M A Karim Rumi and Michael J Soares

Trophoblast stem (TS) cells possess the capacity to differentiate along a multi-lineage pathway yielding several specialized cell types. The regulatory network controlling trophoblast cell differentiation is poorly understood. Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain, 2 (CITED2) has been implicated in the regulation of placentation; however, we know little about how CITED2 acts to influence trophoblast cells. Rat Rcho-1 TS cells can be manipulated to proliferate or differentiate into specialized trophoblast lineages and are an excellent model for investigating trophoblast differentiation. CITED2 transcript and protein showed a robust induction during Rcho-1 TS cell differentiation. We used an shRNA knockdown approach to disrupt CITED2 expression in order to investigate its involvement in trophoblast cell differentiation. RNA-sequencing was used to examine the impact of CITED2 on trophoblast cell differentiation. CITED2 disruption affected the differentiating trophoblast cell transcriptome. CITED2 possessed a prominent role in the regulation of cell differentiation with links to several signal transduction pathways and to hypoxia-regulated and coagulation processes. In summary, our findings indicate that CITED2 contributes to the regulation of trophoblast cell differentiation.

Reproduction (2016) 151 1–8