Betulinic acid promotes the osteogenic differentiation of human periodontal ligament stem cells by upregulating EGR1

Periodontitis is one of the most common chronic inflammations of the oral cavity, which eventually leads to tooth loss. Betulinic acid (BetA) is an organic acid that has anti-inflammatory effects and is derived from fruits and plants, but its effect on the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) is still unclear. This study aimed to explore the effect of BetA on the osteogenic differentiation of hPDLSCs and its mechanism. Our results revealed that BetA not only promoted the viability of hPDLSCs but also induced their osteogenic differentiation in a dose-dependent manner. In addition, RNA sequencing was used to screen the differentially expressed genes (DEGs) after hPDLSCs were treated with BetA, and 127 upregulated and 138 downregulated genes were identified. Gene Ontology enrichment analysis showed that DEGs were mainly involved in the response to lithium ions and the positive regulation of macrophage-derived foam cell differentiation. The Kyoto Encyclopedia of Genes and Genomes analysis results revealed that DEGs were enriched in the nuclear factor-kappa B and interleukin-17 signaling pathways. More importantly, we confirmed that early growth response gene 1 (EGR1), one of the three DEGs involved in bone formation, significantly promoted the expression of osteogenic markers and the mineralization of hPDLSCs. Knockdown of EGR1 obviously limited the effect of BetA on the osteogenic differentiation of hPDLSCs. In conclusion, BetA promoted the osteogenic differentiation of hPDLSCs through upregulating EGR1, and BetA might be a promising candidate in the clinical application of periodontal tissue regeneration.