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Endometrial development is a complicated process involving numerous regulatory factors. Circular RNAs (circRNAs) have been known as a member of the naturally occurring non-coding RNA family, and are reportedly crucial for a variety of physiological processes. This study investigated the circRNA landscape of non-pregnant endometrium of dairy goats during estrus. Non-pregnant endometrial samples of goats at estrus day 5 (Ed5) and estrus day 15 (Ed15) were used to methodically analyze the circRNA landscape using strand-specific Ribo-Zero RNA-Seq. A total of 2 331 differentially expressed (P<0.05) circRNAs (DEciRs) between Ed5 and Ed15 were discovered in the goat endometrium. It was found that Nipped-B-like (NIPBL) and calcium responsive transcription factor (CARF) may participate in the development of the endometrium by decreasing (P<0.05) the levels of their circRNA-transcript forms. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of DEciR host genes (hgDEciRs) revealed that tight junctions and GTPases may be involved in endometrial development during the estrus cycle. A total of 2 331 DEciRs were discovered in the endometrium at Ed5 and Ed15. Based on GO and KEGG enrichment analyses, it could be inferred that tight junctions and GTPases are likely to play an important role in the development of goat endometrium during the estrus cycle. This circRNA study greatly enhances our knowledge of global trends in the development of non-pregnant endometrium during the estrus cycle in goats; these results help us to better understand the molecular regulation of endometrial development in dairy goats.

Objective:This study attempted to reconstruct engineered uterine tissues (EUTs) containing smooth muscle layer, akin to the normal uterine wall. Methods: EUTs were reconstructed by seeding epithelial cells on top of the constructed stromal layer over smooth muscle layer. A self-made mold was used to keep the EUTs from contraction. At the same time, it provided static stretch to the EUTs. After 14 days of culture, the structure of the EUTs was analyzed histologically and immunohistochemically, or by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The expression of integrin β3 subunit, heparin-binding epidermal growth factor (EGF)–like growth factor (HB-EGF), and HOXA-10was detected by reverse transcription–polymerase chain reaction (RT-PCR). The ability of the EUTs supporting the development of embryos was estimated by coculturing embryos on the EUTs. We also tried a new method to reconstruct EUTs by mixing epithelial cell and stromal cells (1:2) in collagen/Matrigel to form an endometrial layer and putting it on top of the smooth muscle layer. The self-assembling ability of the endometrial epithelial cells and stromal cells in the reconstructed EUTs was analyzed histologically and immunohistochemically. Results: The results found that the constructed EUTs with the first and the second method showed three-layered structures. The epithelial layer, stromal layer, and smooth muscle layer were stained by cytokeratin 18, vimentin, and α-actin, respectively. TEM showed that the cells in the EUTs reconstructed by the first method were attached to each other by apical tight junctions and rivet-like desmosomes. SEM showed protruded pinopodes, microvilli, and cilium of epithelial cells. The RT-PCR analysis showed that integrin β3 subunit, HB-EGF, and HOXA-10were expressed in EUTs. The coculture system of EUTs improved the development rate and quality of murine embryo significantly in comparison with those of control Chatot Ziomek Bavister culture. In the EUTs reconstructed by the second method, the epithelial cells demonstrated self-assembling ability and formed epithelial cell layer on top of the stromal layer and glandular tube–like structures in the stromal layer. Columnar epithelial cells existed in some parts of the epithelial layer. Conclusion: We engineered EUTs containing smooth muscle layer by two methods. The reconstructed EUTs could support the development of embryos. The epithelial cells showed self-assembling ability in the EUTs.