LncRNA HAGLR Absorbing MiR-214-3p Promotes BMP2 Expression and Improves Tibial Fractures

Objective: To determine whether long-chain non-coding RNA (lncRNA) HAGLR can regulate BMP2 by absorbing microRNA-214-3p (miR-214-3p), and to explore its role and mechanism in tibial fracture (TF) healing.

Methods: The HAGLR, miR-214-3p, and BMP2 expression levels in TF and in adjacent normal tissues were measured using quantitative real-time polymerase chain reaction (qRT-PCR). MC3T3-E1 osteoblasts were used to construct the model. HAGLR was localized subcellularly through RNA-fluorescence in situ hybridization (FISH). A dual-luciferase report experiment confirmed that miR-214-3p has a targeted relationship with HAGLR and BMP2. It was then divided into a HAGLR over-expression group, an miR-214-3p mimic group, a HAGLR+miR-214-3p mimic group, an sh-HAGLR group, a BMP over-expression group, an sh-HAGLR+over-expression BMP2 group, and a negative control group. The proliferation and apoptosis of the MC3T3-E1 osteoblasts were examined using MTT assays and flow cytometry. A TF model was established in male C57BL/6J mice. The serum alkaline phosphatase (ALP) and osteoprotegerin (OPG) levels in the sham group, the TF group, and the TF group that were injected with HAGLR were compared using ELISA. Hematoxylin-eosin (HE) staining was used to confirm the fracture healing in the mouse model.

Results: Compared with the adjacent normal tissues in the TF patients, the HAGLR and BMP2 expressions decreased but the miR-214-3p expressions increased in the TF tissues (<0.05). HAGLR, an endogenous sponge, absorbed the miR-214-3p, and the BMP2 expression was directly regulated by miR-214-3p. HAGLR increased the proliferative activity of the osteoblasts and decreased the apoptosis rate. The over-expression of miR-214-3p partly reversed the effect of HAGLR on the cells, decreased the proliferative activity, and increased the apoptosis rate (all <0.05). The sh-HAGLR decreased the proliferative activity and increased the apoptosis rate. But after the over-expression of BMP2, the proliferative activity of the cells was higher, and the apoptosis rate was lower than it was in the sh-HAGLR group (all <0.05). The over-expression of HAGLR can up-regulate the ALP and OPG levels in mouse models (<0.05).

Conclusion: lncRNA HAGLR can regulate BMP2 to play a protective role in TF by absorbing miR-214-3p, and it is related to promoting the osteoblast proliferation, inhibiting apoptosis, and up-regulating the serum ALP and OPG levels to accelerate bone healing.