LncRNA PVT1 activates HIF-1α/RANKL signal to promote osteoclast differentiation and inflammatory response through post-transcriptional regulation.

Osteoclasts play an essential role as the main functional cells for bone resorption in osteomyelitis (OM). Staphylococcus aureus (SA), a prevalent pathogen causing bone infections, significantly contributes to OM by synthesizing substantial quantities of staphylococcal protein A (SpA). However, the potential mechanisms underlying the effects of SpA on osteoclastogenesis in OM need to be further explored. In our study, we found that SpA promoted the osteoclast differentiation and the inflammatory response in macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-kappa B ligand (RANKL)-treated THP-1 cells in a dose-dependent manner. Additionally, SpA-treated cells exhibited upregulation of the long non-coding RNA (lncRNA) plasmacytoma variant translocation 1 (PVT1). Silencing PVT1 reversed SpA-mediated inhibition of cell viability, and abolished SpA-induced promotion of osteoclast differentiation and the release of pro-inflammatory factors. Mechanistically, the upregulation of lncRNA PVT1 was regulated by methyltransferase-like 3 (METTL3)-mediated RNA N6-methyladenosine (m6A) modification. PVT1 increased the stability of hypoxia-inducible factor-1α (HIF-1α) by binding to its mRNA, thereby activating the HIF-1α/RANKL pathway and the pro-inflammatory NF-κB and MAPK signaling pathways. Furthermore, rescue experiments demonstrated that the silencing of METTL3-mediated upregulation of cell viability, along with the inhibition of osteoclast differentiation and inflammatory response, was reversed by overexpression of PVT1 in the presence of SpA. Meanwhile, the inhibitory effects induced by knockdown of PVT1 on osteoclast differentiation and inflammation were reversed by elevating HIF-1α. These data uncover that elevated expression of PVT1, regulated by METTL3-mediated m6A modification, activates the HIF-1α/RANKL pathway, thereby exacerbating osteoclast activation in SpA-induced OM.