LncRNA ZFAS1 Promotes Alveolar Bone Resorption by Enhancing Osteoclastogenesis in Periodontitis.

Periodontitis is a predominant persistent inflammatory disease marked by consistent destruction of tooth-supporting tissues including periodontal ligament and alveolar bone. Although some cytokines have been identified as key mediators, the upstream regulatory molecules that drives this pathological bone loss remains elusive. This study explores the mechanistic role of lncRNA ZFAS1 in the dysregulated bone remodeling of periodontitis microenvironment. We utilized single-cell and bulk RNA sequencing to profile cellular and molecular landscape in healthy and diseased periodontal tissues. GSEA analysis of bulk transcriptomes confirmed a significant activation of osteoclast-related pathways in disease (NES = 1.7, FDR q = 0.025). Findings were validated through qPCR, histology, and immunohistochemistry. The gain- and loss-of-function models in RAW264.7 and MC3T3-E1 cells to characterize the role of lncRNA ZFAS1 in vitro. The scRNA-seq analysis unveiled a marked 11-fold increase in osteoclast-osteoblast ratio in periodontitis, which was further confirmed histologically. This shift was accompanied by a specific inflammatory profile, and a marked upregulation of lncRNA ZFAS1 in diseased tissues. Notably, ZFAS1 expression showed a robust positive correlation with early osteoclast marker genes NFATC1 (R2 = 0.2056, p = 0.015) and TRAP1 (R2 = 0.784, p < 0.0001) but not the late-stage effector CTSK (R2 = 0.0011, p = 0.792). We confirmed that lncRNA ZFAS1 expression was precisely induced by the synergetic effect of differentiation (RANKL) and inflammatory (LPS) signals. Functionally, lncRNA ZFAS1 overexpression in RAW264.7 potentiated osteoclastogenesis, enhanced TRAP-positive osteoclasts and increased resorptive gene expression (NFATC1, Dcstamp, ACP5, CTSK, V-ATPase d2), while its knockdown exhibited the opposite effect. In contrast, lncRNA ZFAS1 knockdown in MC3T3-E1 boosted differentiation and matrix mineralization, augmented osteoblast-related gene expression (Runx2, ALP, OCN). In summary, lncRNA ZFAS1 is a critical driver of inflammatory bone loss, functioning as a dual-path regulator that promotes osteoclastogenesis and inhibits osteoblastogenesis. Its physiological role as a negative osteogenic regulator is evidenced by its downregulation during normal differentiation, highlighting its therapeutic potential for periodontitis and related conditions.