Introduction: Melatonin, an endogenous neurohormone, modulates the biological circadian rhythms of vertebrates. It functions have been reported in previous stomatological studies as anti-inflammation, antioxidant, osseointegration of dental implants and stimulation to dental pulp stem cells differentiation, but its role in ameloblastic differentiation and mineralization has been rarely studied.Objective: To reveal the effects of melatonin on the mineralization of ameloblast lineage cells (ALCs), and to identify the change in gene expression and the potential mechanism based on ribonucleic acid sequencing (RNA-seq) analysis.Method: ALCs were induced in melatonin-conditioned medium. After 7-days culture, Western blot, real-time PCR, alkaline phosphatase (ALP) activity test, RNA-seq were accordingly used to detect the change in molecular level. After 1-month odontogenic induction in melatonin medium, Alizarin Red-S (ARS) staining showed the changes of mineral nodules. Differentially expressed genes (DEGs), enrichment of functions and signaling pathways analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) database were performed. The JNK3 antagonist (JNK3 inhibitor IX, SR3576) and β-arrestin1 (Arrb1) overexpression were applied to confirm the fluctuation of melatonin-medicated JNK3 and Arrb1 expression.Results: In this study, we found out melatonin contributed to the ameloblastic mineralization, from which we can observed the elevated expression of enamel matrix protein, and increased ALP activity and mineralized nodules formation. RNA-seq analysis showed the up-regulation of neural JNK3 and down-regulation of Arrb1 in ALCs. Meanwhile, phosphorylated JNK3 deficiency (phosphorylated JNK3 inhibitor---SR3576 added to culture medium) led to mineralization delay, and Arrb1 overexpression proved Arrb1 takes bridge between melatonin receptors (MTNR) and JNK3 in MAPK signaling pathway.

Background: Many studies have found that circRNA plays a part in osteoblast differentiation. However, its mechanism remains unknown. Methods: High-throughput sequencing was used to identifield the different expression of circRNA during osteogenic dental pulp stem cells (DPSCs) differentiation. Luciferase report analysis and RT-qPCR were used to clarify the expression and regulation relationship among circ-FURIN, miR-125 and SOX11. The heterotopic bone formation experiment was further used to confirm the osteoblast differentiation of DPSC with different expression of circ-FURIN, miR-125 and SOX11. Results: Study indicated that circ-FURIN expression remarkably increased during osteoblast differentiation, yet circ-FURIN knockdown suppressed it. Bioinformatics and luciferase results discovered that miR-125 is the downstream target of circ-FURIN. Furthermore, circ-FURIN upregulation decreased miR-125 expression. MiR-125 upregulation restored the promotion effect of circ-FURIN on osteogenic DPSC differentiation. Luciferase report analysis verified that SOX11 is miR-125 downstream target. miR-125 overexpression suppressed osteogenic DPSC differentiation through targeting SOX11. SOX11 overexpression restored miR-125 inhibitory effect on osteogenic DPSC differentiation. In vivo experiments with heterotopic bone model suggested that circ-FURIN overexpression has crucial function to enhance heterotopic bone formation. Conclusions: In summary, circ-FURIN enhances osteoblast DPSC differentiation via the SOX11 signaling pathway by sponging miR-125. These findings suggest a novel therapeutic target for osteoporosis treatment.

Melatonin plays a critical role in promoting the proliferation of osteoblasts and the growth and development of dental papilla cells. However, the effect and mechanism of melatonin on the growth and development of ALCs still need to be explored. CCK8 assay was used for the evaluation of cell numbers. qRT-PCR was used to identify the differentially expressed genes in ALCs after melatonin treatment. The number and morphology of ALCs were investigated by confocal microscopy. Alkaline phosphatase assay and Alizarin red S staining were used for measuring mineralization. Then, we focused on observing the crucial factors of the signaling pathway by RNA-seq and qRT-PCR. Melatonin limited the cell number of ALCs in a dose-dependent manner and promoted the production of actin fibers. A high concentration of melatonin significantly promoted the mRNA levels of enamel matrix proteins and the formation of mineralized nodules. RNA-seq data showed that Wnt signaling pathway may be involved in the differentiation of ALCs under the influence of melatonin. This study suggests that melatonin plays a regulatory role in the cell number, differentiation, and mineralization of the ALCs, and then shows the relationship between the Wnt signaling pathway with the ALCs under melatonin.

Objective: Amelogenesis imperfecta is a common oral disease. In this study, ALC cells were cultured in vitro to study the factors affecting the growth and development of enamel to explore the influencing factors of amelogenesis imperfecta.Methods: The effects of melatonin on the proliferation and differentiation of ALC cells were detected by CCK8, qRT-PCR, and alizarin red staining, etc. RNA-seq and qRT-PCR were used to identify the differentially expressed genes in ALC cells after melatonin treatment. Then, we focused on observing the important factors of the signaling pathway.Results: Melatonin inhibited the proliferation of ALC cells in a dose-dependent manner and promoted the production of actin fibers. High concentration of melatonin significantly promoted the expression of enamel development related proteins and the formation of mineralized nodules. RNA-seq data showed that melatonin may induce transcriptional changes of Wnt signaling pathway in ALC cells.Conclusion: This study suggests that melatonin plays a regulatory role in the proliferation, differentiation, and mineralization of the enamel, which may be one of the causes of enamel hypoplasia. Moreover, the main factors of the Wnt signaling pathway may play an important role in the process of melatonin in the growth and development of ALC lines.