Influence of rs2228570 on Transcriptional Activation by the Vitamin D Receptor in Human Gingival Fibroblasts and Periodontal Ligament Cells

Human β-defensins are correlated with the immune infiltration and regulated by vitamin D3 in periodontitis

OBJECTIVE

Exploring the correlation between human β-defensins (HBDs) and immune infiltration in periodontitis, and whether it is regulated by vitamin D3 .

BACKGROUND

The human body produces essential antimicrobial peptides called HBDs, which are associated with periodontitis. There is a strong link between periodontal tissue destruction and the immune cell infiltration. Moreover, vitamin D3 has been reported to regulate the expression of immune cell chemokines. However, the relationship between vitamin D3 , HBDs, and immune infiltration in periodontitis remains to be investigated.

METHODS

The Gene Expression Omnibus database was accessed to obtain transcriptomic information of gingival samples taken from periodontitis patients. The expression value of HBD-2 and HBD-3 was calculated. Additionally, using the online program ImmuCellAl, 10 immune cells were scored for immune infiltration in the high-HBDs-expression group and the low-HBDs-expression group, separately. After that, transcriptome sequencing was done based on human gingival fibroblasts that had received vitamin D3 treatment. Furthermore, hGFs were treated by vitamin D3 , tumor necrosis factor-α (TNF-α), and Porphyromonas gingivalis lipopolysaccharide (Pg-LPS). The expressions of HBD-2, HBD-3, interleukin-8 (IL-8), and monocyte chemoattractant protein-1 (MCP-1) were detected. To seek the potential mechanism, CYP27A1 siRNA was employed to reduce the expression of CYP27A1, and nuclear factor-gene binding protein 65 (NF-κB p65) was examined.

RESULTS

In GSE10334, the expressions of HBD-2 and HBD-3 were down-regulated in periodontitis group. Meanwhile, monocyte, macrophage, and CD4_T cell were less infiltrated in low-HBD-2-expression group, while less Gamma-delta T-cell infiltration was found in low-HBD-3-expression group. Transcriptome sequencing found that 21 genes were significantly expressed, of which the function was enriched in response to bacterial origin and TNF signal pathway. Vitamin D3 could significantly up-regulate the expression of HBD-2 and HBD-3, which could be controlled by knocking down CYP27A1 mRNA expression. With prolonged vitamin D3 stimulation, the expression of HBD-2 and HBD-3 increased. TNF-α/Pg-LPS could significantly increase the expression of HBD-2, HBD-3, IL-8, MCP-1, and p65, all of which were reduced by vitamin D3 .

CONCLUSION

HBDs are correlated with immune infiltration in periodontitis. Vitamin D3 inhibits the expression of HBDs and chemokines induced by TNF-α/Pg-LPS, possibly through NF-κB pathway, in human gingival fibroblasts.

The role of vitamin D in periodontal health and disease

Vitamin D plays an essential role in calcium and bone metabolism, immune regulation and possesses profound anti-inflammatory effects. Evidence suggests that low serum vitamin D is associated with increased severity of periodontitis, a chronic inflammatory condition characterised by destruction of the supporting tissues surrounding the tooth, which has several shared risk factors with other chronic non-communicable diseases. The biological functions of vitamin D are mediated by its strong anti-microbial, anti-inflammatory, and host modulatory properties. Experimental periodontitis models involving targeted deletion of 1α-hydroxylase, the enzyme responsible for the conversion of inactive substrate to active 1,25(OH)₂ D₃ (calcitriol), showed augmented alveolar bone loss and gingival inflammation. Vitamin D receptor (VDR) gene polymorphisms have also been associated with increased severity of periodontitis. Thus, the involvement of vitamin D in the pathogenesis of periodontitis is biological plausible. Clinical studies have consistently demonstrated an inverse relationship between serum 25OHD₃ and periodontal disease inflammation. However, due to the paucity of well-designed longitudinal studies, there is less support for the impact of vitamin D status on periodontal disease progression and tooth loss. The evidence emphasises the importance of maintaining vitamin D sufficiency in supporting periodontal health. This review aims to first examine the biological mechanisms by which vitamin D might influence the pathogenesis of periodontal disease and second, discuss the clinical evidence which implicate the role of vitamin D in periodontal disease.

Association between genetic variants in key vitamin-D-pathway genes and external apical root resorption linked to orthodontic treatment

This study evaluated the association between single-nucleotide polymorphisms (SNPs) in vitamin-D-related genes and the amount of external apical root resorption linked to orthodontic treatment. One hundred and forty-three individuals were assessed. The amount of external apical root resorption of upper central incisors (EARR_inc ) and lower first molars (EARR_mol ) were evaluated in radiographs. Seven SNPs were genotyped across four genes including the vitamin D receptor [VDR], group-specific component [GC], cytochrome P450 family 27 subfamily B member 1 [CYP27B1], and cytochrome P450 family 24 subfamily A member 1 [CYP24A1]. Linear regressions were implemented to determine allele-effects on external apical root resorption. Individuals carrying the AA genotype in VDR rs2228570 had a 21% higher EARR_mol than those having AG and GG genotypes (95% CI: 1.03,1.40). EARR_mol in heterozygous rs2228570, was 12% lower than for homozygotes (95%CI: 0.78,0.99). Participants with the CCG haplotype (rs1544410-rs7975232-rs731236) in VDR had an EARR_mol 16% lower than those who did not carry this haplotype. Regarding CYP27B1 rs4646536, EARR_inc in participants who had at least one G allele was 42% lower than for homozygotes AA (95%CI: 0.37,0.93). Although these results did not remain significant after multiple testing adjustment, potential associations may still be suggested. Further replication studies are needed to confirm or refute these findings.

LIPUS as a potential strategy for periodontitis treatment: A review of the mechanisms

Periodontitis is a chronic inflammatory condition triggered by oral bacteria. A sustained inflammatory state in periodontitis could eventually destroy the alveolar bone. The key objective of periodontal therapy is to terminate the inflammatory process and reconstruct the periodontal tissues. The traditional Guided tissue regeneration (GTR) procedure has unstable results due to multiple factors such as the inflammatory environment, the immune response caused by the implant, and the operator's technique. Low-intensity pulsed ultrasound (LIPUS), as acoustic energy, transmits the mechanical signals to the target tissue to provide non-invasive physical stimulation. LIPUS has positive effects in promoting bone regeneration, soft-tissue regeneration, inflammation inhibition, and neuromodulation. LIPUS can maintain and regenerate alveolar bone during an inflammatory state by suppressing the expression of inflammatory factors. LIPUS also affects the cellular behavior of periodontal ligament cells (PDLCs), thereby protecting the regenerative potential of bone tissue in an inflammatory state. However, the underlying mechanisms of the LIPUS therapy are still yet to be summarized. The goal of this review is to outline the potential cellular and molecular mechanisms of periodontitis-related LIPUS therapy, as well as to explain how LIPUS manages to transmit mechanical stimulation into the signaling pathway to achieve inflammatory control and periodontal bone regeneration.

Influence of Single-Nucleotide Polymorphisms on Vitamin D Receptor Expression in Periodontal Ligament Fibroblasts as a Response to Orthodontic Compression

This study aimed to evaluate if single-nucleotide polymorphisms (SNPs) in the vitamin D receptor (VDR) gene are associated with gene expression in human periodontal ligament (hPDL) fibroblasts under simulated orthodontic compressive force. hPDL samples from 57 patients were used. A physiological compressive strain was performed to simulate orthodontic tooth movement in pressure areas under cell culture conditions. The RNA from hPDL fibroblasts was isolated to determine the relative gene expression (mRNA) of the VDR. The DNA was also isolated for the genotyping analysis of five SNPs in the VDR gene: BglI (rs739837, G/T), BsmI (rs1544410, T/C), ApaI (rs7975232, A/C), FokI (rs2228570, A/G), and TaqI (rs731236, A/G). Real-time polymerase chain reaction was used for both analyses. Kruskal−Wallis tests were used to compare VDR expression among genotypes of each SNP. A linear regression analysis was performed to evaluate SNP−SNP interaction. An established alpha of 5% was used. The relative mRNA VDR expression according to the genotypes in the SNPs BglI, BsmI, ApaI, FokI, and TaqI was not statistically significantly different (p > 0.05). The SNP−SNP interaction evaluated by regression analysis did not demonstrate any statistically significant association. No association was observed (p > 0.05). In conclusion, the SNPs BglI (rs739837), BsmI (rs1544410), ApaI (rs7975232), FokI (rs2228570), and TaqI (rs731236) did not show an impact on VDR gene expression in hPDL fibroblasts under simulated orthodontic compressive force.

Effects of DDR1 on migration and adhesion of periodontal ligament cells and the underlying mechanism

BACKGROUND AND OBJECTIVE

As one of the widely expressed cell surface receptors binding to collagen, the most abundant component of the extracellular matrix (ECM), knowledge of the expression, functions, and mechanisms underlying the role of discoidin domain receptor 1 (DDR1) in human periodontal ligament cells (hPDLCs) is incomplete. This study determined the expression of DDR1 in hPDLCs and the effect of DDR1 upon migration and adhesion to hPDLCs, as well as the related regulatory mechanisms.

MATERIALS AND METHODS

The expression of DDR1 and the DDR1 isoforms in hPDLCs from six donors were tested. The migratory ability (horizontal and vertical) and adhesive capacity of hPDLCs with or without specific knockdown of DDR1 were evaluated. After treatment with MEK-ERK1/2 inhibitors (PD98059 and U0126) with or without RNAi, the migratory and adhesive capacity of hPDLCs were re-tested. Western blotting was performed to verify p-MEK1/2 and p-ERK1/2, the key factors of the MEK-ERK1/2 signaling pathways.

RESULTS

DDR1 was detected in hPDLCs in the mRNA and protein level; DDR1b was the dominant isoform. Knockdown of DDR1 almost halved the migratory capacity and significantly downregulated the adhesive capacity of hPDLCs. The use of MEK-ERK1/2 inhibitors caused declined migratory and adhesive capacity of hPDLCs as well. After DDR1 was knocked down, the expression of p-MEK and p-ERK protein declined significantly while total MEK and ERK showed no obvious change, which means the ratio of p-MEK/MEK and p-ERK/ERK was markedly reduced.

CONCLUSIONS

DDR1 plays an important role in the migration and adhesion of hPDLCs and might be regulated via the MEK-ERK1/2 signaling pathway.

The role of 25-hydroxyvitamin-D3 and vitamin D receptor gene in human periodontal ligament fibroblasts as response to orthodontic compressive strain: an in vitro study

Background

This study aimed to investigate, if different physiological concentrations of vitamin D (25(OH)D₃) and single nucleotide polymorphisms in vitamin D receptor (VDR) gene have an impact on gene expression in human periodontal ligament (hPDL) fibroblasts induced by simulated orthodontic compressive strain.

Methods

A pool of hPDL fibroblasts was treated in absence or presence of 25(OH)D₃ in 3 different concentrations (10, 40 and 60 ng/ml). In order to evaluate the role of single nucleotide polymorphisms in the VDR gene, hPDL fibroblasts from 9 patients were used and treated in absence or presence of 40 ng/ml 25(OH)D₃. Each experiment was performed with and without simulated orthodontic compressive strain. Real-time PCR was used for gene expression and allelic discrimination analysis. Relative expression of dehydrocholesterol reductase (DHCR7), Sec23 homolog A, amidohydrolase domain containing 1 (AMDHD1), vitamin D 25-hydroxylase (CYP2R1), Hydroxyvitamin D-1-α hydroxylase, receptor activator of nuclear factor-κB ligand (RANKL), osteoprotegerin (OPG), cyclooxygenase-2 (COX-2) and interleukin-6 (IL6) was assessed. Three single nucleotide polymorphisms in VDR were genotyped. Parametric or non-parametric tests were used with an alpha of 5%.

Results

RANKL, RANKL:OPG ratio, COX-2, IL-6, DHCR7, CYP2R1 and AMDHD1 were differentially expressed during simulated orthodontic compressive strain (p < 0.05). The RANKL:OPG ratio was downregulated by all concentrations (10 ng/ml, 40 ng/ml and 60 ng/ml) of 25(OH)D₃ (mean = 0.96 ± 0.68, mean = 1.61 ± 0.66 and mean = 1.86 ± 0.78, respectively) in comparison to the control (mean 2.58 ± 1.16) (p < 0.05). CYP2R1 gene expression was statistically modulated by the different 25(OH)D₃ concentrations applied (p = 0.008). Samples from individuals carrying the GG genotype in rs739837 presented lower VDR mRNA expression and samples from individuals carrying the CC genotype in rs7975232 presented higher VDR mRNA expression (p < 0.05).

Conclusions

Simulated orthodontic compressive strain and physiological concentrations of 25(OH)D₃ seem to regulate the expression of orthodontic tooth movement and vitamin-D-related genes in periodontal ligament fibroblasts in the context of orthodontic compressive strain. Our study also suggests that single nucleotide polymorphisms in the VDR gene regulate VDR expression in periodontal ligament fibroblasts in the context of orthodontic compressive strain.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01740-8.

Extending the vitamin D pathway to vitamin D3 and CYP27A1 in periodontal ligament cells

BACKGROUND

In periodontal connective tissue cells, the vitamin D pathway has been elucidated, and vitamin D₃ in the main storage form, 25-hydroxy vitamin D₃ (25[OH]D₃ ), and the functional form, 1,25-dihydroxy vitamin D₃ (1,25[OH]₂ D₃ ), have been found to induce the expression of human cationic antimicrobial protein (hCAP-18)/LL-37. Moreover, synergistic effects between Toll-like receptor agonists and 25(OH)D₃ have been reported. This research aimed at extending the vitamin D pathway to vitamin D₃ and CYP27A1 in human periodontal ligament cells (hPDLCs) to further explore its function in periodontal inflammatory reaction.

METHODS

Vitamin D₃ was used to stimulate hPDLCs in the presence or absence of Porphyromonas gingivalis lipopolysaccharide (Pg-LPS). Conversely, CYP27A1 RNA interference was performed to further validate the findings. The mRNA expression of hCAP-18 was determined with real-time polymerase chain reaction. Monocyte chemotactic protein-1 (MCP-1) and interleukin-8 (IL-8) were also detected. The cell supernatant levels of LL-37 were detected with enzyme-linked immunosorbent assay.

RESULTS

Vitamin D₃ significantly enhanced the generation of hCAP-18/LL-37. A combination of Pg-LPS and vitamin D₃ significantly promoted hCAP-18/LL-37 expression. When the expression of CYP27A1 was knocked down with RNA interference, the induction of hCAP-18/LL-37 expression was significantly inhibited. Therefore, the mRNA levels of MCP-1 and IL-8 in hPDLCs were significantly decreased through the vitamin D pathway.

CONCLUSION

The vitamin D pathway from vitamin D₃ to hCAP-18/LL-37 exists in hPDLCs, and CYP27A1 might be involved in periodontal immune defense.

Enhanced wound healing and osteogenic potential of photodynamic therapy on human gingival fibroblasts

BACKGROUND

Photodynamic therapy (PDT) has shown ideal antibacterial effects in clinical treatment of periodontal diseases. However, little is known about the specific potential of PDT on human gingival fibroblasts (HGFs) especially cells in the inflamed state, which may contribute to the repairi of periodontal tissue.

METHODS

The effect of PDT with different concentrations of methylene blue (5 μM, 10 μM, 20 μM) on cell vitality of healthy and inflamed human gingival fibroblasts was evaluated by CCK-8, and cell migration was assessed by cell scratching assay. The gene expression of interleukin-6 (IL-6), interleukin-8 (IL-8), type I collagen (Col I), fibronectin (FN) and basic fibroblast growth factor (bFGF) were measured with real-time fluorescent quantitative polymerase chain reaction. The alkaline phosphatase (ALP) production and alizarin red staining of mineralized nodules in healthy and inflamed human gingival fibroblasts was evaluated to explore the effect on osteogenic differentiation.

RESULTS

PDT with relatively low concentration of methylene blue (5 μM) inhibited the cell vitality of inflamed human gingival fibroblasts (I-HGFs) slightly (P < 0.05), but had no adverse effect on healthy human gingival fibroblasts (H-HGFs) (P > 0.05). As the concentration increased, PDT with 20 μM methylene blue had significantly negative effect on both healthy and inflamed cells. Further, PDT with 5 μM methylene blue was observed to be able to promote the migration of HGFs especially the healthy state, and increases the expression of wound healing related genes including IL-6, COL1, FN, bFGF in healthy and inflamed HGFs (P < 0.05). PDT with 5 μM methylene blue was also capable of increasing the production of ALP and mineralized nodules (P < 0.05), although the better effect was observed in the laser treatment group.

CONCLUSIONS

The relatively low concentration of methylene blue mediated PDT is conducive to the growth of H-HGFs while inhibiting the I-HGFs, and it also has the potential to promote the wound healing and osteogenic related functions of both healthy and inflamed HGFs.