mmu-mir-21a: Mmu-mir-21a is a microRNA that plays a crucial role in decidual cells by inhibiting cell apoptosis through targeting Pdcd4 [PMC8099688]. The luciferase reporter assay confirmed the targeting relationship between mmu-mir-21a and Pdcd4 [PMC8099688]. The high conservation of the seed sequence of mmu-mir-21a for the 3′-UTR of Pdcd4 across different mammalian species suggests its importance [PMC8099688]. The expression levels of mmu-mir-21a and Dtprp were higher after induced decidualization in vitro, indicating their involvement in decidualization [PMC8099688]. Inhibition of mmu-mir-21a resulted in an upregulation of Pdcd4 expression and an increase in cell apoptosis, suggesting the regulatory role of mmu-mir-21a on decidual cells [PMC8099688]. Previous studies have also shown an inverse correlation between miR-21 and Pdcd4 expression in various cell types, supporting the hypothesis that mmu-mir-21a targets Pdcd4 in decidual cells [PMC8099688]. In artificially induced decidualized cells, a significant increase in mmu-mir-21a expression was observed along with a decrease in Pdcd4 expression [PMC8099688]. Mmu-mir-21a was found to be highly localized in subluminal stromal cells within the endometrium during decidualization [PMC8099688]. Overall, these findings highlight the importance of mmu-mir-21a as a key regulator for the reconstruction and maintenance of decidual areas during pregnancy establishment and maintenance [PMC8099688]. References: [PMC8099688] Hu SJ, Ren G, Liu JL et al. Mmu-MiR-21a-5p Mediates the Anti-Apoptotic Effect of Estrogen in Decidual Cells by Targeting Pdcd4. Int J Mol Sci. 2021;22(4):2021. doi:10.3390/ijms22042021