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Background: Cementoblasts on the tooth-root surface are responsible for cementum formation (cementogenesis) and sensitive to Porphyromonas gingivalis stimulation. We have previously proved transcription factor CXXC-type zinc finger protein 5 (CXXC5) participates in cementogenesis. Here, we aimed to elucidate the mechanism in which CXXC5 regulates P. gingivalis-inhibited cementogenesis from the perspective of mitochondrial biogenesis., Methods: In vivo, periapical lesions were induced in mouse mandibular first molars by pulp exposure, and P. gingivalis was applied into the root canals. In vitro, a cementoblast cell line (OCCM-30) was induced cementogenesis and submitted for RNA sequencing. These cells were co-cultured with P. gingivalis and examined for osteogenic ability and mitochondrial biogenesis. Cells with stable CXXC5 overexpression were constructed by lentivirus transduction, and PGC-1α (central inducer of mitochondrial biogenesis) was down-regulated by siRNA transfection., Results: Periapical lesions were enlarged, and PGC-1α expression was reduced by P. gingivalis treatment. Upon apical inflammation, Cxxc5 expression decreased with Il-6 upregulation. RNA sequencing showed enhanced expression of osteogenic markers, Cxxc5, and mitochondrial biogenesis markers during cementogenesis. P. gingivalis suppressed osteogenic capacities, mitochondrial biogenesis markers, mitochondrial (mt)DNA copy number, and cellular ATP content of cementoblasts, whereas CXXC5 overexpression rescued these effects. PGC-1α knockdown dramatically impaired cementoblast differentiation, confirming the role of mitochondrial biogenesis on cementogenesis., Conclusions: CXXC5 is a P. gingivalis-sensitive transcription factor that positively regulates cementogenesis by influencing PGC-1α-dependent mitochondrial biogenesis. Video Abstract., (© 2023. The Author(s).)

Hypoxia often occurs in inflammatory tissues, such as tissues affected by periodontitis and apical periodontitis lesions. Mitochondrial biogenesis can be disrupted in hypoxia. Peroxisome proliferator‐activated receptor gamma coactivator‐1 alpha (PGC‐1α) is a core factor required for mitochondrial biogenesis. Cementoblasts are root surface lining cells that play an integral role in cementum formation. There is a dearth of research on the effect of hypoxia on cementoblasts and underlying mechanisms, particularly in relation to mitochondrial biogenesis during the hypoxic process. In this study, we found that the expression of hypoxia inducible factor‐1α was elevated in apical periodontitis tissues in vivo. In contrast, periapical lesions exhibited a reduction of PGC‐1α expression. For in vitro experiments, cobalt chloride (CoCl2) was used to induce hypoxia. We observed that CoCl2‐induced hypoxia suppressed the mineralization ability and mitochondrial biogenesis of cementoblasts, accompanied by abnormal mitochondria morphology. Furthermore, we found that CoCl2 blocked the p38 pathway, while it activated the Erk1/2 pathway, with the former upregulating the expression of PGC‐1α, while the latter reversed the effects. Overall, our findings demonstrate that mitochondrial biogenesis, especially via PGC‐1α, is impaired during cementogenesis in the context of CoCl2‐induced hypoxia, dependent on the mitogen‐activated protein kinase signaling pathway. [ABSTRACT FROM AUTHOR]