Neuregulin-1-β1 influence on expression of major mineralization- or innervation-related genes in tooth pulpal fibroblast-like cells

Neuregulin-1 (NRG-1) proteins are cell-to-cell signalling substances, which interact with ErbB receptors on cell surfaces. During general embryonal organogenesis, NRG-1 – ErbB interactions contribute with essential functions in cardiacand mammary gland development, and in survival and differentiation of Schwann cells. Both NRG-1-β1 and ErbB4 receptors are expressed during tooth development but their functions in this process are not known. ErbB4 receptors are particularly strongly expressed just prior to odontoblast secretion of dentin matrix. This is also a stage when nerve fibres enter the dental papilla. This suggests that NRG-1-β1 might influence ErbB4-expressing pulpal fibroblasts, which are a pool of odontoblast precursors, to differentiate and participate in dentin formation, and possibly also in the establishment of a pulpal innervation. This issue was addressed through investigations if exogenously added NRG-1-β1 affects BSP-, DSP-, OPN-(mineralization related), NGFor GDNF-(innervation related) mRNA expression in fibroblast-like cells from early postnatal rat tooth pulps, in vitro. The cells were stimulated with NRG-1-β1 under non-serum conditions for 48 hours and then harvested for RNA extraction. Reverse transcriptase-polymerase chain reaction was performed and subsequently visualized on agarose gel. The results suggest that NRG-1β1 does not influence the expression of neither innervationnor mineralization-related genes. However, further studies are needed to clarify how NRG-ErbB interactions might contribute to the developmental processes during tooth formation.