Human Apical Papilla Express Genes of The Endocannabinoid System

Objectives: The Endocannabinoid (ECb) system consists of the main endogenous lipid ligands n-arachidonoyl ethanolamine (AEA) and 2-arachidonoylglycerol (2-AG); cannabinoid receptors (CB1 and CB2); syntetic enzymes: Phospholipase D specific for n-acylphosphatidylethanolamine (NAPE-PLD), Diacylglycerol lipase (DAGL) and degradation enzymes: Fatty acid amide hydrolase (FAAH) and Monoacylglycerol lipase (MAGL). The ECb System is responsible for the modulation of various cellular activities, including physiological and pathological functions such as nociception, immune and endocrine regulation, inflammation, embryogenesis, remodeling of bone tissue and tissue healing. This system has already been characterized in mesenchymal stem cells (MSCs) and dental pulp stem cells (DPSCs), but its presence in stem cells of the apical papilla (SCAP) has not been reported yet. The purpose of this study was to characterize the gene expression of ECb components in SCAPs from human teeth in vitro, in a simulated pro-inflammatory microenvironment (lipopolysaccharide [LPS] treatment).
Methods: Culture of SCAPs were obtained from healthy immature wisdom teeth and characterized by flow citometry and quantitative osteo/odontogenic experiments. Cells were used between the passages 2 and 5 and divided into 4 groups, according to the culture medium (proliferation or differentiation), LPS treatment (10 μg/mL) and experimental period (0, 3, 7 and 14 days). Determination of the expression levels of the genes for CB1, CB2, NAPE-PLD, DAGL, FAAH and MAGL was performed by RT-qPCR.
Results: SCAPs do not expressed genes for CB1, CB2 and FAAH. NAPE-PLD, DAGL and MAGL were expressed in all experimental periods, except at 14 days. Statistical differences were found only for NAPE-PLD at 7 days with decrease for all experimental conditions compared to proliferation medium.
Conclusions: SCAPs express the mRNA for the enzymes of ECb synthesis and MAGL, but not the receptors CB1 and CB2. Only NAPE-PLD was modulated by differentiation and cell activation.