mmu-mir-21a: mmu-mir-21a, a microRNA, has been shown to play a significant role in the regulation of decidual cell function in mice by targeting the 3′-UTR of the Programmed cell death 4 (Pdcd4) gene [PMC8099688]. The expression of mmu-mir-21a is upregulated in decidualized cells, and its mimicry leads to a reduction in Pdcd4 expression by approximately 33.1%, suggesting an inhibitory role [PMC8099688]. The seed sequence of mmu-mir-21a is highly conserved across mammalian species, and its targeting sites on Pdcd4 mRNA have been predicted using TargetScan databases [PMC8099688]. Inhibition of mmu-mir-21a results in increased Pdcd4 protein levels and is associated with elevated apoptosis markers such as cleaved Caspase-3 and BAX/BCL2 ratio, indicating that mmu-mir-21a may function by inhibiting apoptosis in decidual cells [PMC8099688]. This microRNA's regulatory effect on Pdcd4 has implications for the maintenance and reconstruction of decidual tissues during pregnancy establishment [PMC8099688]. The study's findings underscore the importance of mmu-mir-21a as a key factor for pregnancy maintenance by modulating cell survival pathways through its interaction with Pdcd4 [PMC8099688].