Gestational diabetes mellitus affects odontoblastic differentiation of dental papilla cells via Toll‐like receptor 4 signaling in offspring

The Role of Cellular Metabolism in Maintaining the Function of the Dentine-Pulp Complex: A Narrative Review

The cellular metabolic processes ensure the physiological integrity of the dentine-pulp complex. Odontoblasts and odontoblast-like cells are responsible for the defence mechanisms in the form of tertiary dentine formation. In turn, the main defence reaction of the pulp is the development of inflammation, during which the metabolic and signalling pathways of the cells are significantly altered. The selected dental procedures, such as orthodontic treatment, resin infiltration, resin restorations or dental bleaching, can impact the cellular metabolism in the dental pulp. Among systemic metabolic diseases, diabetes mellitus causes the most consequences for the cellular metabolism of the dentine-pulp complex. Similarly, ageing processes present a proven effect on the metabolic functioning of the odontoblasts and the pulp cells. In the literature, several potential metabolic mediators demonstrating anti-inflammatory properties on inflamed dental pulp are mentioned. Moreover, the pulp stem cells exhibit the regenerative potential essential for maintaining the function of the dentine-pulp complex.

Krüppel-like factor 6 promotes odontoblastic differentiation through regulating the expression of dentine sialophosphoprotein and dentine matrix protein 1 genes

AIM

To investigate the potential role of Krüppel-like factor 6 (KLF6) in the odontoblastic differentiation of immortalized dental papilla mesenchymal cells (iMDP-3) cells.

METHODOLOGY

Alizarin Red S (ARS) and Alkaline phosphatase (ALP) staining was used to examine the mineralization effect of iMDP-3 cells after odontoblastic induction. Real-time PCR and Western blotting were employed to analyse dentine sialophosphoprotein (DSPP), dentine matrix protein 1 (DMP1), RUNX family transcription factor 2 (RUNX2), ALP and KLF6 expression during this process. Co-expression of the KLF6 with DMP1, DSPP and RUNX2 was detected by double immunofluorescence staining to explore their local relationship in the cell. To further investigate KLF6 functions, Klf6 gain- and loss-of-function assays followed by ARS and ALP stainings, real-time PCR and Western blotting were performed using Klf6-overexpression plasmids and Klf6 siRNA to investigate whether changes in Klf6 expression affect the odontoblastic differentiation of iMDP-3 cells. Dual-luciferase reporter assays were used to elucidate the mechanistic regulation of Dspp and Dmp1 expression by Klf6. Means were compared using the unpaired t-test and Kruskal-Wallis one-way anova with P < 0.05 and P < 0.01 defined as statistical significance levels.

RESULTS

The expression levels of Klf6 (P < 0.01), Dspp (P < 0.05), Dmp1 (P < 0.01), Runx2 (P < 0.01) and Alp (P < 0.01) were significantly elevated during odontoblastic differentiation of iMDP-3 cells. KLF6 was co-localized with DSPP, DMP1 and RUNX2 in the cytoplasm and nucleus of iMDP-3 cells. Overexpression of Klf6 promoted the odontoblastic differentiation of iMDP-3, whereas the inhibition of Klf6 prevented this procession. Dual-luciferase assays revealed that Klf6 upregulates Dspp and Dmp1 transcription in iMDP-3 cells during odontoblastic differentiation.

CONCLUSION

Klf6 promoted odontoblastic differentiation by targeting the transcription promoter of Dmp1 and Dspp. This study may offer novel insights into strategies for treating injuries to dental pulp tissue.

Molecular Insight into Odontogenesis in Hyperglycemic Environment: A Systematic Review

Diabetes mellitus is an endocrinal disorder affecting worldwide and the disease incidence is rising alarmingly high. The effects of diabetes on tooth development are explored by limited studies and their molecular insights are very rarely studied. This systematic review is aimed to provide the best scientific literature source on the molecular insights into odontogenesis in hyperglycemic environment caused by diabetes mellitus or by maternal diabetes on the offspring. The literature search was conducted on the databases, namely PubMed, PubMed Central, Cochrane, and Scopus. The original studies exploring the alterations in the molecular pathways of odontogenesis in diabetes mellitus were selected. Data were extracted, chosen, and evaluated by two independent researchers. At the end of thorough data search, four articles were eligible for the review. Three articles brought out the molecular pathways involved in the offspring of gestational diabetes through animal models. Fourth article was an in vitro study, which treated the stem cells in hyperglycemic environment and drafted the molecular pathway. The altered molecular pathways in dental epithelial stem cells (DESCs), dental papilla cells (DPCs), and stem cells from apical papilla were studied and empowered with statistical analysis. Thus with this systematic review, we conclude that apurinic/apyrimidinic endonuclease1 downregulation causing deoxyribonucleic acid hypermethylation and Oct4, Nanog gene silencing, activation of toll-like receptor-4/nuclear factor kappa B (TLR4/NF-κB) pathway are involved in suppressing cell proliferation and accelerated apoptosis in DESCs in high glucose environment. DPCs are suppressed from odonto differentiation by activation of TLR4 signaling and resulting inhibition of SMAD1/5/9 phosphorylation in diabetic condition. NF-κB pathway activation causes decreased cell proliferation and enhanced differentiation in apical papilla stem cells in hyperglycemia. Further studies targeting various stages of odontogenesis can reveal more molecular insight.