MiR-21 promotes fracture healing by activating the PI3K/Akt signaling pathway

This study aims to elucidate the potential mechanism of micro ribonucleic acid (miR)-21 in promoting fracture healing.

30 male Sprague-Dawley rats were randomly divided into group A (phosphate-buffered saline, PBS, n=10), group B (AntagomiR-21, n=10) and group C (AntagomiR-NC, n=10) according to the different treatments. The femoral fracture operation was performed in every rat, which was pathologically diagnosed via X-ray. After the successful modeling, 50 μL (2 nmoL) PBS, 50 μL AntagomiR-21 or 50 μL AntagomiR-NC was intraperitoneally injected into rats in group A, B or C, respectively. The above agents were injected once a week for 6 weeks. At 6 weeks, 3 rats were executed in each group, and the tissue at the fracture end was observed via hematoxylin-eosin (HE) staining. The fracture healing of rats was evaluated via imaging at 1 and 7 weeks. At the same time, the expression of miR-21 in the three groups was detected via Reverse Transcription-Polymerase Chain Reaction (RT-PCR), and the expression of phosphatidylinositol 3-hydroxy kinase (PI3K) and phosphorylated-serine/threonine-protein kinase B (p-Akt) in the three groups was detected via Western blotting.

According to the histological staining, the bone repair at the fracture end of rats in group B was not significant with fracture and poor continuity compared with those in group A and group C. The imaging evaluation revealed that in group B, the callus tissues were significantly reduced, the fracture line had undesirable healing. There were no displacement and loosening of internal fixation compared with group A and group C. Besides, RT-PCR showed that the miR-21 expression declined markedly in group B compared with that in group A and group C, and the differences were statistically significant (p<0.05). Western blotting manifested that the protein levels of PI3K and p-Akt also declined in group B compared with those in group A and group C, and there were statistically significant differences (p<0.05).

MiR-21 promotes the fracture healing in fractured rats by activating the PI3K/Akt signaling pathway.