Nell-1 attenuates lipopolysaccharide-induced inflammation in human dental pulp cells

Nel-like molecule type 1 (Nell-1) is a secreted protein that plays an important role in osteoinduction in multiple animal models. A previous study has suggested the anti-inflammatory effect of Nell-1 on bone inflammation inhibition. However, its role in pulpitis has not been investigated. The present study aims to explore the effect of human recombinant Nell-1 (Nell-1) on rat pulp inflammation response, and its effect on lipopolysaccharide-induced inflammation in human dental pulp cells and its related intracellular signaling pathways. 30 Wistar rats with healthy non-carious maxillary first molars were chosen, Nell-1 was absorbed onto a sterile collagen sponge and capped onto exposed pulps. The expression of IL-6 and IL-8 were detected by immunohistochemical staining. Human dental pulp cells (hDPCs) were isolated from healthy extracted premolars and third molars. hDPCs were co-cultured with Escherichia coli lipopolysaccharide (LPS), Nell-1 protein, and mitogen-activated protein kinase (MAPK) inhibitors. The expression of pro-inflammatory cytokines and chemokines, such as IL-6 and IL-8, was examined via quantitative real-time PCR and enzyme-linked immunosorbent assay. The results showed that Nell-1 inhibited the inflammatory response of rat pulp. LPS treatment contributed to the expression of inflammatory factors in hDPCs, whereas Nell-1 obviously suppressed the LPS-induced inflammation. p38 MAPK and extracellular signal-regulated kinase (ERK) MAPK inhibitors attenuated the anti-inflammatory effect of hrNell-1, whereas the c-Jun N-terminal kinases (JNK) MAPK inhibitor exerted minimal effect. Therefore Nell-1 could inhibit LPS-induced inflammation in human dental pulp cells, and this effect may be mediated by p38 and ERK MAPK signaling pathways, but not JNK MAPK signaling pathway.

Teneligliptin inhibits lipopolysaccharide-induced cytotoxicity and inflammation in dental pulp cells

Diabetes mellitus is one of the most common health threatening disorders. Patients with chronic diabetes are at high risk of contracting oral diseases, including dental pulp damage. In this study, we reviewed how Teneligliptin, a commonly used anti-diabetic agent, protected dental pulp cells from lipopolysaccharide (LPS)-induced cytotoxicity and improved their viability. The dental pulp cells treated with Teneligliptin were resistant to LPS-induced reactive oxygen species (ROS) and its byproduct 4-hydroxynonenal (4-HNE) generation. The Teneligliptin recovered LPS-induced a reduction of cellular glutathione and produced cytokine including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). Mechanistically, we found that Teneligliptin suppressed LPS- that caused an expression of the cell surface receptor toll like receptor 4 (TLR-4) and the activation of JNK kinase and activator protein 1 (AP1) as well as the nuclear factor-κB (NF-κB) signal pathways. Collectively, our study demonstrates that the molecular mechanism Teneligliptin is a protective anti-diabetic agent in dental pulp cells and it has the potential to treat diabetes-associated dental pulp diseases.

Sclerostin promotes human dental pulp cells senescence

Background

Senescence-related impairment of proliferation and differentiation limits the use of dental pulp cells for tissue regeneration. Deletion of sclerostin improves the dentinogenesis regeneration, while its role in dental pulp senescence is unclear. We investigated the role of sclerostin in subculture-induced senescence of human dental pulp cells (HDPCs) and in the senescence-related decline of proliferation and odontoblastic differentiation.

Methods

Immunohistochemical staining and qRT-PCR analyses were performed to examine the expression pattern of sclerostin in young (20–30-year-old) and senescent (45–80-year-old) dental pulps. HDPCs were serially subcultured until senescence, and the expression of sclerostin was examined by qRT-PCR analysis. HDPCs with sclerostin overexpression and knockdown were constructed to investigate the role of sclerostin in HDPCs senescence and senescence-related impairment of odontoblastic differentiation potential.

Results

By immunohistochemistry and qRT-PCR, we found a significantly increased expression level of sclerostin in senescent human dental pulp compared with that of young human dental pulp. Additionally, elevated sclerostin expression was found in subculture-induced senescent HDPCs in vitro. By sclerostin overexpression and knockdown, we found that sclerostin promoted HDPCs senescence-related decline of proliferation and odontoblastic differentiation potential with increased expression of p16, p53 and p21 and downregulation of the Wnt signaling pathway.

Discussion

The increased expression of sclerostin is responsible for the decline of proliferation and odontoblastic differentiation potential of HDPCs during cellular senescence. Anti-sclerostin treatment may be beneficial for the maintenance of the proliferation and odontoblastic differentiation potentials of HDPCs.

Changes in SIRT gene expression during odontoblastic differentiation of human dental pulp cells

Objectives

The aim of this study was to investigate the expression of 7 different sirtuin genes (SIRT1-SIRT7) in human dental pulp cells (HDPCs), and to determine the role of SIRTs in the odontoblastic differentiation potential of HDPCs.

Materials and Methods

HDPCs were isolated from freshly extracted third molar teeth of healthy patients and cultulred in odontoblastic differentiation inducing media. Osteocalcin (OCN) and dentin sialophosphoprotein (DSPP) expression was analyzed to evaluate the odontoblastic differentiation of HDPCs by reverse transcription-polymerase chain reaction (RT-PCR), while alizarin red staining was used for the mineralization assay. To investigate the expression of SIRTs during odontoblastic differentiation of HDPCs, real time PCR was also performed with RT-PCR.

Results

During the culture of HDPCs in the differentiation inducing media, OCN, and DSPP mRNA expressions were increased. Mineralized nodule formation was also increased in the 14 days culture. All seven SIRT genes were expressed during the odontogenic induction period. SIRT4 expression was increased in a time-dependent manner.

Conclusions

Our study identified the expression of seven different SIRT genes in HDPCs, and revealed that SIRT4 could exert an influence on the odontoblast differentiation process. Further studies are needed to determine the effects of other SIRTs on the odontogenic potential of HDPCs.

Inhibition of odontogenic differentiation of human dental pulp cells by dental resin monomers

Background

Dental resin monomers that are leached from the resin matrix due to incomplete polymerization can affect the viability and various functions of oral tissues and cells. In this study, the effects of triethylene glycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) on odontogenic differentiation of human dental pulp cells (HDPCs) were examined. To mimic clinical situations, dental pulp cells were treated with resin monomers for 24 h prior to the analysis of alkaline phosphatase (ALP) activity and mRNA expression of genes related to pulp cell differentiation. To elucidate the underlying signaling pathways, regulation of mitogen-activated protein (MAP) kinases by resin monomers was also investigated.

Results

The ALP activity of HDPCs was reduced by TEGDMA and HEMA at noncytotoxic concentrations. The mRNA expression of dentin sialophosphoprotein (DSPP), osteocalcin (OCN), and osteopontin (OPN) was also downregulated by resin monomers. However, DSPP expression was not affected by hydrogen peroxide (H₂O₂). Among the MAP kinases examined, ERK activation (ERK phosphorylation) was not affected by either resin monomers or H₂O₂, whereas JNK was phosphorylated by TEGDMA and HEMA. Phospho-p38 was upregulated by HEMA, while TEGDMA and H₂O₂ suppressed p38 phosphorylation.

Conclusions

Exposure to TEGDMA and HEMA for a limited period suppresses differentiation of HDPCs via different signaling pathways.

The different expression profiles of microRNAs in elderly and young human dental pulp and the role of miR-433 in human dental pulp cells

As a kind of endogenous noncoding small RNA, MicroRNA (miRNA) plays important roles of regulation to various physiological functions, while its affections on senescence of human dental pulp cell (HDPCs) are still unknown. Thus, we identified the senescence-associated miRNAs in HDPCs by microarray analysis, predicted their targets and regulatory signaling pathway by gene ontology and Kyoto encyclopedia of genes and genomes pathway database analysis. After validated, the senescence-associated miRNAs' expression level was up- and down-regulated using lentivirus package and cell transfection to find its role in HDPCs' morphology, proliferation, apoptosis, and mineralization. The results showed 27 miRNAs differentially expressed at least 1.5-fold, of which 16 were up-regulated and 11 down-regulated, the function of their targets was mainly focused on signal transduction, cell proliferation, apoptosis, and transcription regulation. According to the change fold, we speculated that miR-433 could be one of the vital senescence-associated miRNAs of HDPCs and found its target (GRB2), validated that miR-433 could negatively regulate GRB2 and the RAS-MAPK signaling pathway, leading to the decline of proliferation and mineralization ability of HDPCs and the acceleration of cell apoptosis, suggesting the regulation of miR-433 might be the potential target to promote repair and regeneration of HDPCs in the elderly.

Odontogenic differentiation of human dental pulp cells by calcium silicate materials stimulating via FGFR/ERK signaling pathway

Bone healing needs a complex interaction of growth factors that establishes an environment for efficient bone formation. We examine how calcium silicate (CS) and tricalcium phosphate (β-TCP) cements influence the behavior of human dental pulp cells (hDPCs) through fibroblast growth factor receptor (FGFR) and active MAPK pathways, in particular ERK. The hDPCs are cultured with β-TCP and CS, after which the cells' viability and odontogenic differentiation markers are determined by using PrestoBlue® assay and western blot, respectively. The effect of small interfering RNA (siRNA) transfection targeting FGFR was also evaluated. The results showed that CS promoted cell proliferation and enhances FGFR expression. It was also found that CS increases ERK and p38 activity in hDPCs, and furthermore, raises the expression and secretion of DSP, and DMP-1. Additionally, statistically significant differences (p<0.05) have been found in the calcium deposition in si-FGFR transfection and ERK inhibitor between CS and β-TCP; these variations indicated that ERK/MAPK signaling is involved in the silicon-induced odontogenic differentiation of hDPCs. The current study shows that CS substrates play a key role in odontoblastic differentiation of hDPCs through FGFR and modulate ERK/MAPK activation.

Analysis of gene expression during odontogenic differentiation of cultured human dental pulp cells

OBJECTIVES

We analyzed gene-expression profiles after 14 day odontogenic induction of human dental pulp cells (DPCs) using a DNA microarray and sought candidate genes possibly associated with mineralization.

MATERIALS AND METHODS

Induced human dental pulp cells were obtained by culturing DPCs in odontogenic induction medium (OM) for 14 day. Cells exposed to normal culture medium were used as controls. Total RNA was extracted from cells and analyzed by microarray analysis and the key results were confirmed selectively by reverse-transcriptase polymerase chain reaction (RT-PCR). We also performed a gene set enrichment analysis (GSEA) of the microarray data.

RESULTS

Six hundred and five genes among the 47,320 probes on the BeadChip differed by a factor of more than two-fold in the induced cells. Of these, 217 genes were upregulated, and 388 were down-regulated. GSEA revealed that in the induced cells, genes implicated in Apoptosis and Signaling by wingless MMTV integration (Wnt) were significantly upregulated.

CONCLUSIONS

Genes implicated in Apoptosis and Signaling by Wnt are highly connected to the differentiation of dental pulp cells into odontoblast.