(PR04) The Effects of Lipopolysaccharide on Stem Cells of the Apical Papilla

Abstract: Stem cells of the apical papilla (SCAP) are vital for the success of regenerative endodontic procedures (REPs). Previous studies have demonstrated the effects of inadequate disinfection and bacteria on the success of REPs. Lipopolysaccharide (LPS) is the major component Gram-negative bacteria and may be present in the canal after bacteria cell lysis and could affect SCAP. However, the direct effect of LPS on SCAP has not yet been elucidated. Hence, the aim of this study is to evaluate the effects of LPS has on the survival and differentiation gene expression of SCAP. Human SCAP were cultured under three different conditions for 24 hours, untreated cells, LPS and a Dexamethasone group. RNA was extracted and reverse transcribed to cDNA. The cDNA was analyzed using Real time-PCR for various osteogenic, transcription and differentiation genes. Data were analyzed using a one-way analysis of variance (ANOVA). Real time-PCR analysis demonstrated that SCAP treated with LPS had downregulation of osteogenic genes (ALPL), genes promoting angiogenesis and endothelial cell growth (VEGFC, FT1), and collagen synthesis (COL5A1, COL10A1). There was an upregulation of genes involved with the breakdown of extracellular matrix (MMP13, MMP7), genes involved in the activation of innate immunity (TLR3, TLR4), apoptosis related genes (FADD, TRADD) and those promoting tissue inflammation (IL1B, CSF2).

Conclusions: SCAP treated with LPS have a downregulation of pathways related to osteogenesis, angiogenesis and cell growth, and an upregulation of pathways related to innate immunity activation, apoptosis and tissue inflammation. This research suggests that LPS can have negative effects on REPs.