Objective To investigate the expression of miR-31a-5p in myocardial infarction (MI) mice and its potential mechanism. Methods A dataset was downloaded from the gene expression database, and miR-31a-5p and its predicted target gene hypoxia-inducible factor-1α (HIF-1α) were screened using bioinformatics methods. The MI model was established by ligating the left anterior descending branch of the coronary artery in C57BL/6J male mice which were randomly divided into sham and MI groups (n=6 in each group). The in vitro hypoxic cell model was induced by treatment of H9c2 cells with cobalt chloride (CoCl2) and divided into a control group, a model group, a NC group, a miR-31a-5p mimic group and a miR-31a-5p inhibitor group. The degree of myocardial tissue fibrosis was stained by Masson and analyzed. The expression levels of miR-31a-5p and HIF-1α mRNA in mouse myocardial tissues and H9c2 cells were detected by qRT-PCR. Western blotting was used to detect the expression levels of B-cell lymphoma 2 (Bcl-2), cleaved-caspase 3 apoptotic protein in mouse myocardial tissues and HIF-1α and apoptotic protein in H9c2 cells, respectively. The dual luciferase reporter gene assay was used to verify the targeting relationship between miR-31a-5p and HIF-1α. Results Masson staining showed significantly increased fibrosis in MI mice (P<0.000 1); miR-31a-5p, cleaved-caspase 3 were significantly elevated and Bcl-2 was decreased in MI mice and CoCl2 treated H9c2 (P<0.05). The results of dual luciferase reporter assay showed that the relative luciferase activity of miR-31a-5p mimic cotransfected with HIF-1α-3'-UTR WT plasmid was reduced (P<0.000 1); miR-31a-5p mimic decreased HIF-1α expression and increased apoptotic protein levels in CoCl2 induced H9c2 cells (both P<0.05), while miR-31a-5p exerted the opposite effect. Conclusion miR-31a-5p can aggravate apoptosis in myocardial ischemia by targeting HIF-1α.

The aim of the present study was to develop three-dimensional (3D) culture model, a more pathologically relevant model, of human breast cancer for drug resistance study. MCF-7 cells were embedded within collagen gel to establish 3D culture model. Cellular morphology was observed using Carmine and HE staining. Cell proliferation was evaluated by CCK-8 assay, and cell activity was detected by Live/Dead staining kit. Drug sensitivities of the 3D culture to doxorubicin, carboplatin, 5-fluorouracil were assayed and compared with those of monolayer (2D) culture. In addition, the levels of drug resistance-related genes P-glycoprotein (P-gp), mrp2 mRNA expressions were detected by real time RT-PCR. Expression level of P-gp protein was detected by Western blot. The results showed that MCF-7 cells in 3D culture formed a number of cell aggregates, and most of them displayed good cell viability. The IC50 values of doxorubicin, carboplatin, 5-fluorouracil were all increased significantly in 3D culture compared with those in 2D culture. Moreover, compared with MCF-7 cells in 2D culture, the cells in 3D culture showed increased mRNA levels of P-gp and mrp2, as well as up-regulated protein expression of P-gp. These results suggest that in vitro collagen-embedded culture system of human breast cancer cells represents an improved pathologically relevant 3D microenvironment for breast cancer cells, providing a robust tool to explore the mechanism of drug resistance of cancer cells.
ATP-Binding Cassette, Sub-Family B, Member 1 ; Breast Neoplasms ; Cell Culture Techniques ; Cell Proliferation ; Cell Survival ; Doxorubicin ; Drug Resistance, Neoplasm ; Humans ; MCF-7 Cells