Biological properties of stem cells from the apical papilla exposed to lipopolysaccharides: An in vitro study

The aim of this study was to analyze the effect of lipopolysaccharides (LPS) on the biological properties of stem cells from the apical papilla (SCAPs), such as viability, adhesion to dentin, odontoblast-like differentiation, mineralization, and release of immunomodulatory cytokines.

SCAPs were isolated from immature teeth of three donors (10 to 15 years old) and cultured in mineralizing media with or without 1 μg/mL lipopolysaccharide (LPS). Cells were seeded and cultured under standardized conditions; viability was assessed by MTT assay on days 1, 3, 5, and 7; adhesion to dentin was analyzed using an environmental scanning electron microscope after 2 days; the expression of odontogenic and mineralization genes (DSPP, DMP-1, OCN, Col1A1) was evaluated through qPCR after 14 days, mineralization was evaluated with alizarin red staining after 21 days; and the release of immunomodulatory cytokines (IL-6 and IL-10) was measured by ELISA after 1 and 7 days. The Kruskal-Wallis test was performed to detect the effect of LPS on SCAPs, followed by the Dunn-Sidak test.

LPS presence in the culture media affected SCAPs viability on day 5 and increased IL-6 secretion by day 7, however, SCAPs retained the adhesion to dentin and mineralization capacities, as well as the differentiation capacity into a mineralizing phenotype.

In conclusion, within the limitations of this in vitro study, and under the inflammatory microenvironment simulated in this study, stem cells from the apical papilla were found with retained adhesion capacity to dentin, differentiation into a mineralizing phenotype, mineralization, and release of IL-10.