Effects of Sirtuin 1 on the proliferation and osteoblastic differentiation of periodontal ligament stem cells and stem cells from apical papilla

Oxidative stress and inflammation regulation of sirtuins: New insights into common oral diseases

Sirtuins are a family of nicotinamide adenine dinucleotide (NAD)⁺-dependent histone deacetylases, comprising seven members SIRT1-SIRT7. Sirtuins have been extensively studied in regulating ageing and age-related diseases. Sirtuins are also pivotal modulators in oxidative stress and inflammation, as they can regulate the expression and activation of downstream transcriptional factors (such as Forkhead box protein O3 (FOXO3a), nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-kappa B (NF-κB)) as well as antioxidant enzymes, through epigenetic modification and post-translational modification. Most importantly, studies have shown that aberrant sirtuins are involved in the pathogenesis of infectious and inflammatory oral diseases, and oral cancer. In this review, we provide a comprehensive overview of the regulatory patterns of sirtuins at multiple levels, and the essential roles of sirtuins in regulating inflammation, oxidative stress, and bone metabolism. We summarize the involvement of sirtuins in several oral diseases such as periodontitis, apical periodontitis, pulpitis, oral candidiasis, oral herpesvirus infections, dental fluorosis, and oral cancer. At last, we discuss the potential utilization of sirtuins as therapeutic targets in oral diseases.

DNA Methylation and Histone Modification in Dental-derived Mesenchymal Stem Cells

Epigenetic regulation, mainly involving DNA methylation, histone modification, and noncoding RNAs (ncRNAs), is essential for the regulation of multiple cellular processes. Dental-derived mesenchymal stem cells (DMSCs), a kind of multipotent cells derived from dental tissues, are impactful in regenerative medicine. Recent studies have shown that epigenetic regulation plays a major role in DMSCs. Therefore, exploring how epigenetic regulation is involved in DMSCs may be of guiding significance for tissue repair and regeneration or for exploring more effective treatments. A number of research of ncRNAs in DMSCs have been reported. However, little is known about the roles of DNA methylation and histone modifications in DMSCs. In this review, we summarize the important roles of DNA methylation and histone modifications of the fate of DMSCs.

A pilot study on biological characteristics of human CD24(+) stem cells from the apical papilla

Background/purpose

CD24 is a specific cell surface marker for undifferentiated dental stem cells from apical papilla (SCAPs) seen only during root development, before the tooth emerges through gum. But the comprehensive role of CD24 in the SCAPs is unclear. This study aims to clarify the exact roles of CD24 in SCAPs.

Materials and methods

SCAPs were divided into CD24 (+)-SCAPs (high percentage CD24) and CD24 (-)-SCAPs (low percentage CD24) via flow cytometry. The proliferation, migration and osteogenic/adipogenic differentiation of the two groups were detected, RT-PCR was performed to detect the expression of osteogenic/adipogenic related genes and thegene expression were analyzed.

Results

The proliferative and migratory ability of CD24 (-)-SCAPs were significantly stronger than that of CD24 (+)-SCAPs. Although, the mineralization process and the osteogenic genes expression were not significantly difference in the two groups. Both CD24 (+)-SCAPs and CD24 (-)-SCAPs differentiated into adipocytes. The adipogenic differentiation in CD24 (+)-SCAPs was better than that in CD24 (-)-SCAPs, after 3 weeks of adipogenic induction. However, the expression of adipogenic related gene, PPAR γ2 mRNA in CD24 (+)-SCAPs was lower than that in CD24 (-)-SCAPs after 1 week of adipogenic induction. But the trend changed for the opposite after 3 weeks.

Conclusion

The study proposes that CD24 has a regulatory effect on the adipogenic differentiation of SCAPs, and this may be attained by targeting the PPAR γ2 mRNA. Concurrently, it was found that CD24 plays an inhibitory role in the proliferation and migration of SCAPs, which may minimize the manifestation of diseases caused by an abnormal cell growth.

Stem Cells from the Apical Papilla: A Promising Source for Stem Cell-Based Therapy

Stem cells are biological cells that can self-renew and can differentiate into multiple cell lineages. Stem cell-based therapy is emerging as a promising alternative therapeutic option for various disorders. Mesenchymal stem cells (MSCs) are multipotent adult stem cells that are isolated from various tissues and can be used as an alternative to embryonic stem cells. Stem cells from the apical papilla (SCAPs) are a novel population of MSCs residing in the apical papilla of immature permanent teeth. SCAPs present the characteristics of expression of MSCs markers, self-renewal, proliferation, migration, differentiation, and immunosuppression, which support the application of SCAPs in stem cell-based therapy, including the immunotherapy and the regeneration of dental tissues, bone, neural, and vascular tissues. In view of these properties and therapeutic potential, SCAPs can be considered as promising candidates for stem cell-based therapy. Thus the aim of our review was to summarize the current knowledge of SCAPs considering isolation, characterization, and multilineage differentiation. The prospects for their use in stem cell-based therapy were also discussed.

Resveratrol Reverts Epigenetic and Transcription Changes Caused by Smoke Inhalation on Bone-Related Genes in Rats

We investigated the effects of cigarette smoke (CS) and resveratrol intake on the modulation of bone repair-related genes through epigenetic mechanisms at the global and gene-specific levels, after 30 days of calvarial defects were created, in rats. The samples were assigned to three groups as follows: no CS, CS, and CS/resveratrol. After evaluation of global (5 hmC) changes and epigenetic and transcription regulation at gene-specific levels, CS group showed increased 5 hmC and Tets transcripts with demethylation at Rankl and Trap promoters (p ≤ 0.01), linked to their increased gene expression (p ≤ 0.001). These modifications were reverted in the CS/resveratrol group. Opposite patterns were observed among CS and CS/resveratrol for epigenetic enzyme transcripts with higher levels of Dnmts in the CS/resveratrol (p ≤ 0.01). No CS and CS/resveratrol demonstrated similar gene expression levels for all Tets and bone-related genes. Resveratrol reverts epigenetic and transcription changes caused by CS at both global and gene-specific levels in bone-related and epigenetic machinery genes, emphasizing the resveratrol as biological modulator for CS in rats.

SIRT1 regulates macrophage self-renewal

Mature differentiated macrophages can self-maintain by local proliferation in tissues and can be extensively expanded in culture under specific conditions, but the mechanisms of this phenomenon remain only partially defined. Here, we show that SIRT1, an evolutionary conserved regulator of life span, positively affects macrophage self-renewal ability in vitro and in vivo Overexpression of SIRT1 during bone marrow-derived macrophage differentiation increased their proliferative capacity. Conversely, decrease of SIRT1 expression by shRNA inactivation, CRISPR/Cas9 mediated deletion and pharmacological inhibition restricted macrophage self-renewal in culture. Furthermore, pharmacological SIRT1 inhibition in vivo reduced steady state and cytokine-induced proliferation of alveolar and peritoneal macrophages. Mechanistically, SIRT1 inhibition negatively regulated G1/S transition, cell cycle progression and a network of self-renewal genes. This included inhibition of E2F1 and Myc and concomitant activation of FoxO1, SIRT1 targets mediating cell cycle progression and stress response, respectively. Our findings indicate that SIRT1 is a key regulator of macrophage self-renewal that integrates cell cycle and longevity pathways. This suggests that macrophage self-renewal might be a relevant parameter of ageing.

Sirtuin 1 regulates matrix metalloproteinase-13 expression induced by Porphyromonas endodontalis lipopolysaccharide via targeting nuclear factor-κB in osteoblasts

Porphyromonas endodontalis lipopolysaccharide (P.e LPS) is an important initiating factor for periapical inflammation and bone destruction. Matrix metalloproteinase-13 (MMP-13) has been shown to participate in the formation and diffusion of periapical bone lesion in chronic apical periodontitis. Sirtuin 1 (SIRT1) is a key regulator of inflammation in mammalian cells which suppresses the release of inflammatory mediators. This study aimed to explore the role of SIRT1 in regulating MMP-13 expression induced by P.e LPS in osteoblasts. P.e LPS stimulated MMP-13 expression in MC3T3-E1 cells. Knockdown of SIRT1 reinforced the increase of MMP-13mRNA expression induced by P.e LPS. SIRT1 activator resveratrol significantly reduced the expression of MMP-13 and SIRT1 inhibitor EX-527 enhanced the expression of MMP-13. Moreover, SIRT1 activation with resveratrol inhibited acetylation of NF-κB p65 and NF-κB transcriptional activity, which were enhanced by P.e LPS. In addition, NF-κB p65 was involved in P.e LPS-induced MMP-13 expression via directly binding to the MMP-13 promoter. However, SIRT1 activation significantly interfered with this binding. These findings strongly suggest that P.e LPS induces MMP-13 expression in osteoblasts, and SIRT1 suppresses this expression of MMP-13 through targeting NF-κB p65. This provides new insights into understanding the actions of SIRT1 on anti-inflammatory and anti-bone resorption activity.

Sirtuin 1 (Sirt1) Overexpression in BaF3 Cells Contributes to Cell Proliferation Promotion, Apoptosis Resistance and Pro-Inflammatory Cytokine Production

Background

B lymphocyte hyperactivity is a main characteristic of systemic lupus erythematosus (SLE), and B lymphocytes play a prominent pathogenic role in the development and progression of SLE. The aim of this study was to investigate the role of Sirtuin 1 (Sirt1) in B lymphocytes.

Material/Methods

Mouse B lymphocytes BaF3 was transfected with Sirt1 vector or shRNA against Sirt1. Then the transfected cells viability and apoptosis were respectively determined by MTT assay and flow cytometry. In addition, the mRNA levels of three pro-inflammatory cytokines and p53 were detected by RT-PCR. Furthermore, the expression levels of nuclear factor-kappa B (NF-κB) pathway proteins were measured by Western blot.

Results

Overexpression of Sirt1 significantly increased cell proliferation (p<0.05 or p<0.01) and significantly suppressed apoptosis (p<0.05). The mRNA level expressions of interleukin 1 (IL-1), IL-6, and tumor necrosis factor-α (TNF-α) were significantly upregulated (p<0.05 or p<0.01), whereas p53 was significantly downregulated (p<0.05) by Sirt1 overexpression. In addition, the inhibitory subunit of NF-κB (IκBα) and p65 were significantly activated and phosphorylated (p<0.01 or p<0.001), and B-Cell CLL/Lymphoma 3 (Bcl-3) was significantly upregulated (p<0.05) by Sirt1 overexpression.

Conclusions

These results suggested that Sirt1 overexpression could promote BaF3 cell proliferation, inhibit apoptosis, and upregulate pro-inflammatory cytokines. The NF-κB pathway might be involved in these effects of Sirt1 on BaF3 cells, and Sirt1 might be a potential risk factor of SLE.

IGF-1/IGF-1R/hsa-let-7c axis regulates the committed differentiation of stem cells from apical papilla

Insulin-like growth factor-1 (IGF-1) and its receptor IGF-1R play a paramount role in tooth/bone formation while hsa-let-7c actively participates in the osteogenic differentiation of mesenchymal stem cells. However, the interaction between IGF-1/IGF-1R and hsa-let-7c on the committed differentiation of stem cells from apical papilla (SCAPs) remains unclear. In this study, human SCAPs were isolated and treated with IGF-1 and hsa-let-7c over/low-expression viruses. The odonto/osteogenic differentiation of these stem cells and the involvement of mitogen-activated protein kinase (MAPK) pathway were subsequently investigated. Alizarin red staining showed that hsa-let-7c low-expression can significantly promote the mineralization of IGF-1 treated SCAPs, while hsa-let-7c over-expression can decrease the calcium deposition of IGF-1 treated SCAPs. Western blot assay and real-time reverse transcription polymerase chain reaction further demonstrated that the expression of odonto/osteogenic markers (ALP, RUNX2/RUNX2, OSX/OSX, OCN/OCN, COL-I/COL-I, DSPP/DSP, and DMP-1/DMP-1) in IGF-1 treated SCAPs were significantly upregulated in Let-7c-low group. On the contrary, hsa-let-7c over-expression could downregulate the expression of these odonto/osteogenic markers. Moreover, western blot assay showed that the JNK and p38 MAPK signaling pathways were activated in Let-7c-low SCAPs but inhibited in Let-7c-over SCAPs. Together, the IGF-1/IGF-1R/hsa-let-7c axis can control the odonto/osteogenic differentiation of IGF-1-treated SCAPs via the regulation of JNK and p38 MAPK signaling pathways.