Changes of MicroRNA Expression and Apoptosis in Endometrial Glandular Epithelial Cells under Hypoxic

To explore the changes in the transcription levels of microRNAs(miRNAs) in endometrial glandular epithelial cells (EECs) under hypoxia and their effects on apoptosis.

EECs were seeded into six-well plates in logarithmic growth phase(1×10⁵ cells/well), and divided into two groups: hypoxia group and control group. The cells in both hypoxia group and the control group were placed in a hypoxic environment (the volume ratio of O₂∶N₂∶CO₂ was 1∶94∶5) and cultured in normoxic environment (O₂∶CO₂ volume ratio of 95∶5). All cells were collected after they were cultured 4 h, and Trizol was added into the cells and total RNAs were extracted. High-throughput sequencing was used to detect the changes of miRNAs expression profiles in the two groups of EECs. Subsequently, realtime fluorescence quantitative polymerase chain reaction (RT-PCR) was used to detect the gene expression of miR-7704 and miR-7974. Flow cytometry was used to detect the apoptosis of EECs. The protein expression changes of p53 and apoptosis-related proteins were detected by Western blot.

High-throughput sequencing detected the expression levels of 21 common miRNAs. Compared with the control group, 16 miRNAs were up-regulated and 5 miRNAs were down-regulated in the EECs of the hypoxia group; the expression of miR-7704 and miR-7974 decreased most significantly in the hypoxia group(all P < 0.05). RT-PCR results showed that compared with the control group, the relative expression levels of miR-7704 and miR-7974 in EECs of the hypoxia group decreased by 20% and 80%, respectively. The results of flow cytometry showed that the ratio of early apoptotic cells and late apoptotic cells in the hypoxia group was higher than that in the control group (all P < 0.001). The results of Western blot showed that the expression of p53 in EECs in the hypoxia group increased, and the expression of the anti-apoptotic protein B-cell lymphoma-2 decreased compared with the control group(all P < 0.05).

Hypoxic environment can induce changes in the expression profile of miRNAs in EECs, among which the down-regulation of miR-7974 is the most significant. p53 may be the target protein of miR-7974, and hypoxia-induced EEC apoptosis may be achieved by down-regulating the level of miR-7974 and promoting the expression of p53.