Long non‐coding RNA X‐Inactive Specific Transcript (XIST) interacting with USF2 promotes osteogenic differentiation of periodontal ligament stem cells through regulation of WDR72 transcription

BACKGROUND: Periodontal ligament stem cells (PDLSCs) are the most potential cells in periodontal tissue regeneration and bone tissue regeneration. Our prior work had revealed that WD repeat-containing protein 72 (WDR72) was crucial for osteogenic differentiation of PDLSCs. Here, we further elucidated its underlying mechanism in PDLSC osteogenic differentiation. METHODS: Human PDLSCs, isolated and identified by flow cytometry, were prepared for osteogenic differentiation induction. Levels of WDR72, long non-coding RNA X-Inactive Specific Transcript (XIST), upstream stimulatory factor 2 (USF2), and osteogenic marker genes (Runx2, Osteocalcin, and Collagen I) in human PDLSCs and clinical specimens were detected by RT-qPCR. Protein expressions of WDR72, Runx2, Osteocalcin, and Colla1 were tested by Western blot. The interactions among the molecules were verified by RIP, RNA pull-down, ChIP, and luciferase reporter assays. Osteogenic differentiation was evaluated by alkaline phosphatase (ALP) and alizarin red staining (ARS). RESULTS: WDR72 was decreased in periodontal tissues of periodontitis patients, and overexpression reversed TNF-α-mediated suppressive effects on PDLSC osteogenic differentiation. Mechanically, XIST recruited the enrichment of USF2 to the WDR72 promoter region, thereby positively regulating WDR72. WDR72 silencing overturned XIST-mediated biological effects in PDLSCs. CONCLUSION: WDR72, regulated by the XIST/USF2 axis, enhances osteogenic differentiation of PDLSCs, implying a novel strategy for alleviating periodontitis.