Effects of Glutamine on Proliferation, Migration, and Differentiation of Human Dental Pulp Cells

Introduction: Although glutamine (Gin) is mitogenic in various cell types, little is known about its role in human dental pulp cells (HDPCs). This study investigated the effects of Gin on proliferation, migration, and odontoblastic differentiation of HDPCs and the underlying signal pathway mechanisms. Methods: Growth and migration were assessed by cell counting and colorimetric cell migration kits. Differentiation was measured as alkaline phosphatase activity, calcified nodule formation by alizarin red staining, and marker mRNA expression by reverse transcriptase polymerase chain reaction (RT-PCR). Chemokine expression was also evaluated by RT-PCR. Signal transduction pathways were examined by RT-PCR and Western blot analysis. Results: Gin dose-dependently increased proliferation, migration, alkaline phosphatase activity, mineralized nodule formation, and odontoblast-marker mRNA of HDPCs. Gln also up-regulated expression of interleukin-6, interleukin-8, MCP-1, MIP-3 alpha, CCL2, CCL20, and CXCL1. Gin increased BMP-2 and BMP-4 mRNA, phosphorylation of Smad 1/5/8, beta-catenin, and key proteins of the Wnt signaling pathway. Furthermore, Gin resulted in up-regulation of extracellular signal-regulated kinase, p38, and c-Jun N-terminal kinase. In addition, noggin, DKK1, inhibitors of p38, ERK, and JNK significantly attenuatted Gin-induced growth, migration, and odontoblastic differentiation. Conclusions: Collectively, this study demonstrated that Gln promoted growth, migration, and differentiation in HDPCs through the BMP-2, Wnt, and MAPK pathways, leading to improved pulp repair and regeneration.