Apoptosis-promoting properties of miR-3074-5p in MC3T3-E1 cells under iron overload conditions

Iron overload can promote the development of osteoporosis by inducing apoptosis in osteoblasts. However, the mechanism by which miRNAs regulate apoptosis in osteoblasts under iron overload has not been elucidated. Method: The miRNA expression profile in MC3T3-E1 cells under iron overload was detected by next generation sequencing. qRT-PCR was used to determine the expression of miR-3074-5p in MC3T3-E1 cells under iron overload. The proliferation of MC3T3-E1 cells was tested using CCK-8 assays, and apoptosis was measured using flow cytometry. The miRanda and TargetScan databases were used to predict the target genes of miR-3074-5p. Interaction between miR-3074-5p and the potential target gene was validated by qRT-PCR, luciferase reporter assay and western blotting.

miR-3074-5p functions as an apoptosis promoter in iron-overloaded MC3T3-E1 cells by directly targeting Smad4.

We found that iron overload decreased the cell viability and induced apoptosis of MC3T3-E1 cells. The results of next generation sequencing analysis showed that miR-3074-5p expression was significantly increased in MC3T3-E1 cells under iron overload conditions, which was confirmed by further experiments. The inhibition of miR-3074-5p attenuated the apoptosis of iron-overloaded MC3T3-E1 cells. Furthermore, the expression of Smad4 was decreased and was inversely correlated with miR-3074-5p expression, and overexpression of Smad4 partially reversed the viability inhibition of iron-overloaded MC3T3-E1 cells by relieving the suppression of ERK, AKT, and Stat3 phosphorylation, suggesting its regulatory role in the viability inhibition of iron-overloaded MC3T3-E1 cells. The luciferase reporter assay results showed that Smad4 was the target gene of miR-3074-5p.