Glycosylation end products mediate damage and apoptosis of periodontal ligament stem cells induced by the JNK-mitochondrial pathway.Aging (Albany NY). 2020;12:12850-12868. [PMID: 32611833 DOI: 10.18632/aging.103304]

cGAMP-targeting injectable hydrogel system promotes periodontal restoration by alleviating cGAS-STING pathway activation

The impaired function of periodontal ligament stem cells (PDLSCs) impedes restoration of periodontal tissues. The cGAS-cGAMP-STING pathway is an innate immune pathway that sensing cytosolic double-stranded DNA (dsDNA), but its role in regulating the function of PDLSCs is still unclear. In this study, we found that mitochondrial DNA (mtDNA) was released into the cytoplasm through the mitochondrial permeability transition pore (mPTP) in PDLSCs upon inflammation, which binds to cGAS and activated the STING pathway by promoting the production of cGAMP, and ultimately impaired the osteogenic differentiation of PDLSCs. Additionally, it is first found that inflammation can down-regulate the level of the ATP-binding cassette membrane subfamily member C1 (ABCC1, a cGAMP exocellular transporter) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1, a cGAMP hydrolase), which further aggravated the accumulation of intracellular cGAMP, leading to the persistent activation of the cGAS-STING pathway and thus the impaired the differentiation capacity of PDLSCs. Furthermore, we designed a hydrogel system loaded with a mPTP blocker, an ABCC1 agonist and ENPP1 to promote periodontal tissue regeneration by modulating the production, exocytosis, and clearance of cGAMP. In conclusion, our results highlight the profound effects, and specific mechanisms, of the cGAS-STING pathway on the function of stem cells and propose a new strategy to promote periodontal tissue restoration based on the reestablishment of cGAMP homeostasis.

Mitochondrial dysfunction as a key player in aggravating periodontitis among diabetic patients: review of the current scope of knowledge

Periodontitis is a prevalent inflammatory disease that leads to significant periodontal tissue destruction and compromised dental health, with its severity exacerbated in individuals with Diabetes Mellitus (DM). This review explores the complex relationship between mitochondrial dysfunction and periodontitis in diabetic patients. Recent studies indicate that the excessive production of reactive oxygen species (ROS), primarily generated by dysfunctional mitochondrial electron transport chain (ETC) complexes, contributes to oxidative stress (OS) and subsequent periodontal tissue damage. The interplay between impaired mitochondrial biogenesis, apoptosis of periodontal cells, and ROS accumulation highlights a critical area of concern in understanding the pathophysiology of diabetic periodontitis. Furthermore, altered glycemic control due to inflammatory processes associated with periodontitis may perpetuate a cyclical detriment to oral and systemic health. This review aims to highlight the mechanistic roles of mitochondrial dysfunction in the aggravation of periodontitis among diabetic patients, emphasizing further research to identify potential therapeutic targets and improve treatment efficacy for this dual pathology.

Connection between oral health and chronic diseases

Chronic diseases have emerged as a paramount global health burden, accounting for 74% of global mortality and causing substantial economic losses. The oral cavity serves as a critical indicator of overall health and is inextricably linked to chronic disorders. Neglecting oral health can exacerbate localized pathologies and accelerate the progression of chronic conditions, whereas effective management has the potential to reduce their incidence and mortality. Nevertheless, limited resources and lack of awareness often impede timely dental intervention, delaying optimal therapeutic measures. This review provides a comprehensive analysis of the impact of prevalent chronic diseases-such as diabetes mellitus, rheumatoid arthritis, cardiovascular disorders, and chronic respiratory diseases-on oral health, along with an exploration of how changes in oral health affect these chronic conditions through both deterioration and intervention mechanisms. Additionally, novel insights into the underlying pathophysiological mechanisms governing these relationships are presented. By synthesizing these advancements, this review aims to illuminate the complex interrelationship between oral health and chronic diseases while emphasizing the urgent need for greater collaboration between dental practitioners and general healthcare providers to improve overall health outcomes.

PGC-1α/LDHA signaling facilitates glycolysis initiation to regulate mechanically induced bone remodeling under inflammatory microenvironment

The mechanosensitivity of inflammation can alter cellular mechanotransduction. However, the underlying mechanism remains unclear. This study aims to investigate the metabolic mechanism of inflammation under mechanical force to guide tissue remodeling better. Herein, we found that inflammation hindered bone remodeling under mechanical force, accompanied by a simultaneous enhancement of oxidative phosphorylation (OXPHOS) and glycolysis. The control of metabolism direction through GNE-140 and Visomitin revealed that enhanced glycolysis might act as a compensatory mechanism to resist OXPHOS-induced osteoclastogenesis by promoting osteogenesis. The inhibited osteogenesis induced by inflammatory mechanical stimuli was concomitant with a reduced expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). PGC-1α knockdown impeded osteogenesis under mechanical force and facilitated osteoclastogenesis by enhancing OXPHOS. Conversely, PGC-1α overexpression attenuated the impairment of bone remodeling by inflammatory mechanical signals through promoting glycolysis. This process benefited from the PGC-1α regulation on the transcriptional and translational activity of lactate dehydrogenase A (LDHA) and the tight control of the extracellular acidic environment. Additionally, the increased binding between PGC-1α and LDHA proteins might contribute to the glycolysis promotion within the inflammatory mechanical environment. Notably, LDHA suppression effectively eliminated the bone repair effect mediated by PGC-1α overexpression within inflammatory mechanical environments. In conclusion, this study demonstrated a novel molecular mechanism illustrating how inflammation orchestrated glucose metabolism through glycolysis and OXPHOS to affect mechanically induced bone remodeling.

Mitochondrial Dysfunction in Periodontitis and Associated Systemic Diseases: Implications for Pathomechanisms and Therapeutic Strategies

Periodontitis is a chronic infectious disorder damaging periodontal tissues, including the gingiva, periodontal ligament, cementum, and alveolar bone. It arises from the complex interplay between pathogenic oral bacteria and host immune response. Contrary to the previous view of "energy factories", mitochondria have recently been recognized as semi-autonomous organelles that fine-tune cell survival, death, metabolism, and other functions. Under physiological conditions, periodontal tissue cells participate in dynamic processes, including differentiation, mineralization, and regeneration. These fundamental activities depend on properly functioning mitochondria, which play a crucial role through bioenergetics, dynamics, mitophagy, and quality control. However, during the initiation and progression of periodontitis, mitochondrial quality control is compromised due to a range of challenges, such as bacterial-host interactions, inflammation, and oxidative stress. Currently, mounting evidence suggests that mitochondria dysfunction serves as a common pathological mechanism linking periodontitis with systemic conditions like type II diabetes, obesity, and cardiovascular diseases. Therefore, targeting mitochondria to intervene in periodontitis and multiple associated systemic diseases holds great therapeutic potential. This review provides advanced insights into the interplay between mitochondria, periodontitis, and associated systemic diseases. Moreover, we emphasize the significance of diverse therapeutic modulators and signaling pathways that regulate mitochondrial function in periodontal and systemic cells.

Impaired pulp healing associated with underlying disorders in the dental pulp of rats with type 2 diabetes

Background/purpose

Type 2 diabetes mellitus (T2DM), characterized by hyperglycemia, is a systematic disease affecting structure and healing ability in various tissues. This study aimed to investigate whether T2DM could impair the dental pulp healing and cause underlying pathological changes in the dental pulp before an injury occurred.

Materials and methods

Goto-Kakizaki rats were used as T2DM model animals and performed with direct pulp capping procedures on the first maxillary molars. The molars at 1, 2, 4 weeks after operation and non-injured molars were examined using hematoxylin and eosin staining, immunohistochemical staining, immunofluorescence staining, and Masson's trichrome staining. The fresh dental pulp of maxillary incisors was collected for transmission electron microscopy and glucose content evaluation.

Results

The T2DM rats showed deficient reparative dentin formation compared with the healthy rats. Before the occurrence of an injury, underlying pathological changes of major components in the pulp tissue were observed in T2DM rats, including vasculopathy; collagen abnormalities; decreased proliferation, decreased odontogenetic differentiation and damaged ultrastructure of dental pulp cells. High glucose content and advanced glycation end products accumulation were further found in the pulp tissue in T2DM rats.

Conclusion

T2DM can impede pulp healing process in rats, which is associated with underlying pathological changes in the non-injured pulp caused by the advanced glycation end products accumulation under high-glucose conditions.

Oleanolic acid attenuates hydrogen peroxide-induced apoptosis of IPEC-J2 cells through suppressing c-Jun and MAPK pathway

Oleanolic acid (OA) is a natural triterpenoid with therapeutic potential for a multitude of diseases. However, the precise mechanism by which OA influences stress-induced apoptosis of intestinal epithelial cells remains elusive. Therefore, the effect of OA on intestinal diseases under stressful conditions and its possible mechanisms have been investigated. In a hydrogen peroxide (H2 O2 )-induced oxidative stress model, OA attenuated H2 O2 -induced apoptosis in a concentration-dependent manner. To investigate the underlying mechanisms, the gene expression profile of OA on IPEC-J2 cells was analyzed using an RNA sequencing system. Results from gene ontology and Kyoto encyclopedia of genes and genomes analysis confirmed that OA may mitigate the cytotoxic effects of H2 O2 by downregulating gene expression through the MAPK signaling pathway. Furthermore, Quantitative real-time polymerase chain reaction results validated the differentially expressed genes data. Western blot analysis further demonstrated that OA effectively suppressed the expression level of c-Jun protein induced by H2 O2 in IPEC-J2 cells. Collectively, our results indicate that OA pretreatment significantly attenuated H2 O2 -induced apoptosis in intestinal epithelial cells through suppressing c-Jun and MAPK pathway.

Long non-coding RNA X-Inactive Specific Transcript (XIST) interacting with USF2 promotes osteogenic differentiation of periodontal ligament stem cells through regulation of WDR72 transcription

BACKGROUND

Periodontal ligament stem cells (PDLSCs) are the most potential cells in periodontal tissue regeneration and bone tissue regeneration. Our prior work had revealed that WD repeat-containing protein 72 (WDR72) was crucial for osteogenic differentiation of PDLSCs. Here, we further elucidated its underlying mechanism in PDLSC osteogenic differentiation.

METHODS

Human PDLSCs, isolated and identified by flow cytometry, were prepared for osteogenic differentiation induction. Levels of WDR72, long non-coding RNA X-Inactive Specific Transcript (XIST), upstream stimulatory factor 2 (USF2), and osteogenic marker genes (Runx2, Osteocalcin, and Collagen I) in human PDLSCs and clinical specimens were detected by RT-qPCR. Protein expressions of WDR72, Runx2, Osteocalcin, and Colla1 were tested by Western blot. The interactions among the molecules were verified by RIP, RNA pull-down, ChIP, and luciferase reporter assays. Osteogenic differentiation was evaluated by alkaline phosphatase (ALP) and alizarin red staining (ARS).

RESULTS

WDR72 was decreased in periodontal tissues of periodontitis patients, and overexpression reversed TNF-α-mediated suppressive effects on PDLSC osteogenic differentiation. Mechanically, XIST recruited the enrichment of USF2 to the WDR72 promoter region, thereby positively regulating WDR72. WDR72 silencing overturned XIST-mediated biological effects in PDLSCs.

CONCLUSION

WDR72, regulated by the XIST/USF2 axis, enhances osteogenic differentiation of PDLSCs, implying a novel strategy for alleviating periodontitis.

Advanced glycation end products impair bone marrow mesenchymal stem cells osteogenesis in periodontitis with diabetes via FTO-mediated N6-methyladenosine modification of sclerostin

BACKGROUND

Diabetes mellitus (DM) and periodontitis are two prevalent diseases with mutual influence. Accumulation of advanced glycation end products (AGEs) in hyperglycemia may impair cell function and worsen periodontal conditions. N6-methyladenosine (m6A) is an important post-transcriptional modification in RNAs that regulates cell fate determinant and progression of diseases. However, whether m6A methylation participates in the process of periodontitis with diabetes is unclear. Thus, we aimed to investigate the effects of AGEs on bone marrow mesenchymal stem cells (BMSCs), elucidate the m6A modification mechanism in diabetes-associated periodontitis.

METHODS

Periodontitis with diabetes were established by high-fat diet/streptozotocin injection and silk ligation. M6A modifications in alveolar bone were demonstrated by RNA immunoprecipitation sequence. BMSCs treated with AGEs, fat mass and obesity associated (FTO) protein knockdown and sclerostin (SOST) interference were evaluated by quantitative polymerase chain reaction, western blot, immunofluorescence, alkaline phosphatase and Alizarin red S staining.

RESULTS

Diabetes damaged alveolar bone regeneration was validated in vivo. In vitro experiments showed AGEs inhibited BMSCs osteogenesis and influenced the FTO expression and m6A level in total RNA. FTO knockdown increased the m6A levels and reversed the AGE-induced inhibition of BMSCs differentiation. Mechanically, FTO regulated m6A modification on SOST transcripts, and AGEs affected the binding of FTO to SOST transcripts. FTO knockdown accelerated the degradation of SOST mRNA in presence of AGEs. Interference with SOST expression in AGE-treated BMSCs partially rescued the osteogenesis by activating Wnt Signaling.

CONCLUSIONS

AGEs impaired BMSCs osteogenesis by regulating SOST in an m6A-dependent manner, presenting a promising method for bone regeneration treatment of periodontitis with diabetes.

The onset of adenosine monophosphate-activated protein kinase activity on orthodontic tooth movement in rats with type 2 diabetes

Adenosine monophosphate-activated protein kinase (AMPK) plays pivotal roles in metabolic diseases including type 2 diabetes. However, the specific role of AMPK for orthodontic tooth movement in type 2 diabetes is unclear. In this study, a diabetic rat model was established through dietary manipulation and streptozocin injection. Examinations were conducted to select qualified type 2 diabetic rats. Then, an orthodontic device was applied to these rats for 0, 3, 7, or 14 days. The distance of orthodontic tooth movement and parameters of alveolar bone were analyzed by micro-computed tomography. Periodontal osteoclastic activity, inflammatory status, and AMPK activity were measured via histological analyses. Next, we repeated the establishment of diabetic rats to investigate whether change of AMPK activity was associated with orthodontic tooth movement under type 2 diabetes. The results showed that diabetic rats exhibited an exacerbated alveolar bone resorption, overactive inflammation, and decreased periodontal AMPK activity during orthodontic tooth movement. Injection of the AMPK agonist alleviated type 2 diabetes-induced periodontal inflammation and alveolar bone resorption, thus normalizing distance of orthodontic tooth movement. Our study indicates that type 2 diabetes decreases periodontal AMPK activity, leading to excessive inflammation elevating osteoclast formation and alveolar bone resorption, which could be reversed by AMPK activation.

Diabetes mellitus promotes susceptibility to periodontitis-novel insight into the molecular mechanisms

Diabetes mellitus is a main risk factor for periodontitis, but until now, the underlying molecular mechanisms remain unclear. Diabetes can increase the pathogenicity of the periodontal microbiota and the inflammatory/host immune response of the periodontium. Hyperglycemia induces reactive oxygen species (ROS) production and enhances oxidative stress (OS), exacerbating periodontal tissue destruction. Furthermore, the alveolar bone resorption damage and the epigenetic changes in periodontal tissue induced by diabetes may also contribute to periodontitis. We will review the latest clinical data on the evidence of diabetes promoting the susceptibility of periodontitis from epidemiological, molecular mechanistic, and potential therapeutic targets and discuss the possible molecular mechanistic targets, focusing in particular on novel data on inflammatory/host immune response and OS. Understanding the intertwined pathogenesis of diabetes mellitus and periodontitis can explain the cross-interference between endocrine metabolic and inflammatory diseases better, provide a theoretical basis for new systemic holistic treatment, and promote interprofessional collaboration between endocrine physicians and dentists.

Programmed cell death of periodontal ligament cells

The periodontal ligament is a crucial tissue that provides support to the periodontium. Situated between the alveolar bone and the tooth root, it consists primarily of fibroblasts, cementoblasts, osteoblasts, osteoclasts, periodontal ligament stem cells (PDLSCs), and epithelial cell rests of Malassez. Fibroblasts, cementoblasts, osteoblasts, and osteoclasts are functionally differentiated cells, whereas PDLSCs are undifferentiated mesenchymal stem cells. The dynamic development of these cells is intricately linked to periodontal changes and homeostasis. Notably, the regulation of programmed cell death facilitates the clearance of necrotic tissue and plays a pivotal role in immune response. However, it also potentially contributes to the loss of periodontal supporting tissues and root resorption. These findings have significant implications for understanding the occurrence and progression of periodontitis, as well as the mechanisms underlying orthodontic root resorption. Further, the regulation of periodontal ligament cell (PDLC) death is influenced by both systemic and local factors. This comprehensive review focuses on recent studies reporting the mechanisms of PDLC death and related factors.

FUT2 Facilitates Autophagy and Suppresses Apoptosis via p53 and JNK Signaling in Lung Adenocarcinoma Cells

Lung cancer is the most common cancer with high morbidity and mortality worldwide. Our previous studies showed that fucosyltransferase 2 (FUT2) is highly expressed in lung adenocarcinoma (LUAD) and plays a vital role in the tumorigenesis of LUAD. However, the underlying mechanism is not fully understood. Autophagy has recently attracted increasing attention due to its pro-survival role in cancer progression and metastasis. Here, we found that FUT2 was up-regulated and had an AUC (Area Under Curve) value of 0.964 in lung adenocarcinoma based on the TCGA dataset. Knockdown of FUT2 weakened the autophagy response, as evidenced by a degradation of LC3-II and Beclin1. The phosphorylation levels of AMPK, ULK1, and PI3K III were significantly reduced by FUT2 knockdown. FUT2 promoted the translocation of p53 from the cytoplasm into the nucleus, which triggered the DRAM1 pathway and enhanced autophagy. Meanwhile, the knockdown of FUT2 increased the phosphorylation of JNK and promoted mitochondrial-mediated apoptosis. Furthermore, the knockdown of FUT2 inhibited the autophagy induced by Z-VAD-FMK and promoted the apoptosis suppressed by rapamycin. The autophagy and apoptosis regulated by FUT2 antagonized each other. Taken together, these findings provide a mechanistic understanding of how FUT2 mediated the crosstalk between autophagy and apoptosis, which determine lung cancer cell death and survival, leading to the progression of lung adenocarcinoma.

The effect of low-level laser irradiation on the proliferation, osteogenesis, inflammatory reaction, and oxidative stress of human periodontal ligament stem cells under inflammatory conditions

Periodontitis often causes damage to the periodontal tissue and affects the function of human periodontal ligament stem cells (hPDLSCs). Low-level laser therapy (LLLT) has been used for periodontal treatment and can upregulate the proliferation and osteogenesis of hPDLSCs. The purpose of this study was to investigate the effects of LLLT on the proliferation, osteogenic differentiation, inflammatory reaction, and oxidative stress of hPDLSCs in an inflammatory environment (pPDLSCs). We designed one control group and three testing groups (treated with Nd:YAG laser at 4, 8, and 16 J/cm2) of hPDLSCs from periodontitis patients who were diagnosed with stable phase periodontitis. Cell proliferation was measured by colony-forming unit fibroblast (CFU-F) assays and 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assays. The osteogenic capacity of the cells was determined by alkaline phosphatase (ALP) staining, ALP activity assays, Alizarin Red S staining and the mRNA transcript levels of runt-related transcription factor 2 (Runx2), ALP, and osteocalcin (OCN). The effects of LLLT on the secretion of tumor necrosis factor-α (TNF-α) and interleukin (IL)-1β by PDLSCs were measured by enzyme-linked immunosorbent assay (ELISA). We also evaluated the oxidative stress of hPDLSCs and pPDLSCs by measuring the reactive oxygen species (ROS) level, malondialdehyde (MDA) level, and superoxide dismutase (SOD) activity after treatment with LLLT at 4, 8, and 16 J/cm2. Our results demonstrated that LLLT could modulate the osteogenic potential of pPDLSCs at 8 J/cm2. Inflammatory stimuli induced excess ROS release, and LLLT at 4-8 J/cm2 promoted oxidative stress levels in hPDLSCs but decreased the expression of inflammatory cytokines and ROS levels in pPDLSCs. Moreover, LLLT at 16 J/cm2 could significantly suppress proliferation and osteogenic differentiation and promote inflammatory cytokines and ROS levels in pPDLSCs. In conclusion, LLLT could regulate proliferation, osteogenesis, inflammatory reaction, and oxidative stress of human periodontal ligament stem cells under inflammatory conditions.

Erythropoietin Activates Autophagy to Regulate Apoptosis and Angiogenesis of Periodontal Ligament Stem Cells via the Akt/ERK1/2/BAD Signaling Pathway under Inflammatory Microenvironment

Background. Angiogenic tissue engineering is a vital problem waiting to be settled for periodontal regeneration. Erythropoietin, a multieffect cytokine, has been reported as a protective factor for cell fate. According to our previous study, erythropoietin has a significantly angiogenic effect on periodontal ligament stem cells. To further explore its potential effects and mechanism, we studied biological behaviors of periodontal ligament stem cells under inflammatory microenvironment induced by different concentrations (0, 10, 20, 50, and 100 ng/mL) of tumor necrosis factor-α (TNF-α) and examined how different concentrations (0, 5, 10, 20, and 50 IU/mL) of erythropoietin changed biological behaviors of periodontal ligament stem cells. Materials and Methods. Cell Counting Kit-8 was used for cell proliferation assay. Annexin V-PI-FITC was used for cell apoptosis through flow cytometry. Matrigel plug was adopted to measure the angiogenic capacity in vitro. RNA sequencing was used to detect the downstream signaling pathway. Quantitative real-time polymerase chain reaction was conducted to examine mRNA expression level. Western blot and immunofluorescence were applied to testify the protein expression level. Results. Periodontal ligament stem cells upregulated apoptosis and suppressed autophagy and angiogenesis under inflammatory microenvironment. Erythropoietin could activate autophagy to rescue apoptosis and angiogenesis levels of periodontal ligament stem cells through the Akt/Erk1/2/BAD signaling pathway under inflammatory microenvironment. Conclusions. Erythropoietin could protect periodontal ligament stem cells from inflammatory microenvironment, which provided a novel theory for periodontal regeneration.

Oxidative Stress in the Oral Cavity before and After Prosthetic Treatment

BACKGROUND: Metal ions emitted from dental alloys may induce oxidative stress leading to numerous pathological changes. Lipid peroxidation may cause disturbance of structure and function of cell membranes, apoptosis, autophagy, and formation of potentially mutagenic compounds. Products of interaction between reactive oxygen species and biomolecules may be used for evaluation of oxidative stress level. AIM: The aim of this study was to evaluate the influence of the prosthetic dental treatment with metal ceramic restorations on the level of oxidative stress in the oral cavity. MATERIALS AND METHODS: Metal ceramic crowns with copings fabricated by direct metal laser sintering were produced for 35 patients. CoCr dental alloy EOS CobaltChrome SP2 (EOS) was used. Non-stimulated and stimulated saliva samples were collected from the patients before and after the prosthetic treatment. For evaluation of oxidative stress concentration of 8-isoPGF2-alpha was measured by liquid chromatography tandem mass spectrometry. For statistical processing, non-parametric Wilcoxon signed-rank test and Mann–Whitney test were applied. RESULTS: The concentration of isoprostane 8-isoPGF2-alpha in non-stimulated saliva was lower 2 h after fixing the crowns compared to the initial level and statistically significant difference was observed. On the 7th day the concentration of isoprostanes remained significantly lower than the initial one. No significant differences were found in isoprostane concentration in stimulated saliva before and after prosthetic treatment. CONCLUSION: Prosthetic dental treatment leads to decrease in oral oxidative stress.

Diabetic oxidative stress-induced telomere damage aggravates periodontal bone loss in periodontitis

Periodontitis, one of the most common oral complications of diabetes mellitus (DM), causes a reduction in alveolar bone height and loss of alveolar bone mass. It has been shown that DM aggravates the progression of periodontitis, but the mechanism remains inconclusive. The hyperglycemic environment of DM has been proven to generate reactive oxygen species (ROS). Since telomeres, guanine-rich repeats, are highly susceptible to oxidative attack, we speculate that the excessive accumulation of ROS in DM could induce telomere damage resulting in dysfunction of periodontal ligament cells, especially periodontal ligament stem cells (PDLSCs), which reduces the ability of tissue repair and reconstruction in diabetic periodontitis. In this study, our current data revealed that oxidative telomere damage occurred in the periodontal ligaments of diabetic mice. And Micro-CT scans showed reduced alveolar bone height and impaired alveolar bone mass in a diabetic periodontitis model. Next, cultured mouse PDLSCs (mPDLSCs) were treated with the oxidant tert-butyl hydroperoxide (t-BHP) in vitro, as we expected telomere damage was observed and resulted in cellular senescence and dysfunction. Taken together, oxidative stress in DM causes telomere dysfunction and PDLSCs senescence, which influences periodontal bone tissue regeneration and reconstruction and ultimately exacerbates bone loss in periodontitis.

Nanorepairers Rescue Inflammation-Induced Mitochondrial Dysfunction in Mesenchymal Stem Cells

Mitochondrial dysfunction in tissue-specific mesenchymal stem cells (MSCs) plays a critical role in cell fate and the morbidity of chronic inflammation-associated bone diseases, such as periodontitis and osteoarthritis. However, there is still no effective method to cure chronic inflammation-associated bone diseases by physiologically restoring the function of mitochondria and MSCs. Herein, it is first found that chronic inflammation leads to excess Ca2+ transfer from the endoplasmic reticulum to mitochondria, which causes mitochondrial calcium overload and further damage to mitochondria. Furthermore, damaged mitochondria continuously accumulate in MSCs due to the inhibition of mitophagy by activating the Wnt/β-catenin pathway under chronic inflammatory conditions, impairing the differentiation of MSCs. Based on the mechanistic discovery, intracellular microenvironment (esterase and low pH)-responsive nanoparticles are fabricated to capture Ca2+ around mitochondria in MSCs to regulate MSC mitochondrial calcium flux against mitochondrial dysfunction. Furthermore, the same nanoparticles are able to deliver siRNA to MSCs to inhibit the Wnt/β-catenin pathway and regulate mitophagy of the originally dysfunctional mitochondria. These precision-engineered nanoparticles, referred to as "nanorepairers," physiologically restore the function of mitochondria and MSCs, resulting in effective therapy for periodontitis and osteoarthritis. The concept can potentially be expanded to the treatment of other diseases via mitochondrial quality control intervention.

Pathogenic Molecular Mechanisms in Periodontitis and Peri-Implantitis: Role of Advanced Glycation End Products

Advanced Glycation End Products (AGEs), the products of the non-enzymatic oxidation of proteins, nucleic acids, and lipids, are accumulated in periodontal tissues under hyperglycemic conditions such as Diabetes Mellitus (DM) and are responsible for sustained periodontal destruction. AGEs mediate their intracellular effects either directly or indirectly through receptor binding (via RAGE) in all types of periodontal ligament cells (osteocytes, gingival fibroblasts, stem cells, epithelial cells), indicating an important target for intervention. In combination with lipopolysaccharides (LPS) from Porphyromonas gingivalis (Pg), the negative impact of AGEs on periodontal tissue is further enhanced and accentuated. In addition, AGE accumulation is evident in peri-implantitis, yet through different underlying molecular mechanisms. Novel therapeutic approaches targeting the effects of AGEs in periodontal ligament cells show beneficial effects in pre-clinical studies. Herein, we provide evidence on the detrimental role of AGE accumulation in oral cavity tissues and their associated signaling pathways in periodontitis and peri-implantitis to further highlight the significance of oral or topical use of AGE blockers or inhibitors along with dental biofilms’ removal and DM regulation in patients’ management.

The Effect of Diabetes Mellitus on IGF Axis and Stem Cell Mediated Regeneration of the Periodontium

Periodontitis and diabetes mellitus (DM) are two of the most common and challenging health problems worldwide and they affect each other mutually and adversely. Current periodontal therapies have unpredictable outcome in diabetic patients. Periodontal tissue engineering is a challenging but promising approach that aims at restoring periodontal tissues using one or all of the following: stem cells, signalling molecules and scaffolds. Mesenchymal stem cells (MSCs) and insulin-like growth factor (IGF) represent ideal examples of stem cells and signalling molecules. This review outlines the most recent updates in characterizing MSCs isolated from diabetics to fully understand why diabetics are more prone to periodontitis that theoretically reflect the impaired regenerative capabilities of their native stem cells. This characterisation is of utmost importance to enhance autologous stem cells based tissue regeneration in diabetic patients using both MSCs and members of IGF axis.

Role and mechanism of necrostin-1 in promoting oxidative stress response of macrophages in high glucose condition

OBJECTIVES

To investigate the role and molecular mechanism of necrostatin-1 (Nec-1), a specific programmed cell necrosis inhibitor, in promoting the oxidative stress response of macrophages under high glucose (HG) environment.

METHODS

Macrophages were cultured in control (5.5 mmol·L^-1 glucose) or HG (25 mmol·L^-1 glucose) medium for 72 h. The HG+Nec-1 group was given HG and 5 μmol·L^-1 Nec-1. Reactive oxygen species (ROS) level, malondialdehyde (MDA) activity, and superoxide dismutase (SOD) activity were measured by 2'-7'dichlorofluorescin diacetate, MDA, and SOD enzyme linked immunosorbent assay kits, respectively. Moreover, receptor interacting protein 1 (RIP1) expression was assessed through real-time quantitative polymerase chain reaction (qRT-PCR) and Western blot (WB). Finally, after the expression of RIP1 in macrophages was silenced, the effect of HG environment on oxidative stress response was evaluated in the gene-deficient cells.

RESULTS

The HG group had increased ROS level and MDA activity (P<0.000 1) and decreased SOD activity (P<0.000 1) compared with the control group. The HG+Nec-1 group had higher ROS level and MDA activity (P<0.000 1) and lower SOD activity (P<0.01) than the HG group. The qRT-PCR and WB results showed that RIP1 mRNA level (P<0.001) and protein expression level (P<0.000 1) in the HG group were significantly higher than those in the control group, and RIP1 mRNA and protein expression levels in the HG+Nec-1 group were significantly lower than those in the HG group (P<0.000 1). After RIP1 was silenced effectively (P<0.001) with si-RNA, the ROS level and MDA activity of the HG+si-RIP1 group decreased compared with those of the HG+si-negative control (si-NC) group (P<0.001), and SOD activity in the HG+si-RIP1 group increased than that in the HG+si-NC group (P<0.000 1).

CONCLUSIONS

HG promotes oxidative stress on macrophages by upregulating RIP1 expression.

Epithelial Cell Rests of Malassez Provide a Favorable Microenvironment for Ameliorating the Impaired Osteogenic Potential of Human Periodontal Ligament Stem Cells

Human periodontal ligament stromal/stem cells (PDLSCs) are ideal candidates for periodontal regeneration and are of significant importance in clinical practice. However, PDLSCs derived from diseased microenvironments exert impaired behavior, which leads to the failure of periodontal regeneration. The epithelial cell rests of Malassez (ERM), which are involved in periodontal homeostasis, are residual cells from Hertwig's epithelial root sheath (HERS). However, the function of ERM remains largely unknown. Therefore, the aim of this study was to evaluate the effect of ERM on the osteogenic potential of PDLSCs from an impaired microenvironment. PDLSCs from healthy donors (H-PDLSCs), periodontitis donors (P-PDLSCs) and human ERM were harvested. Osteogenic evaluation showed a lower osteogenic potential of P-PDLSCs compared to that of H-PDLSCs. Then, we co-cultured ERM with P-PDLSCs, and the data showed that ERM promoted the expression of osteogenic genes and proteins in P-PDLSCs. In addition, we collected the PDLSCs from aged donors (A-PDLSCs) and analyzed the osteogenesis capacity of the A-PDLSCs and A-PDLSCs + ERM groups, which displayed similar results to P-PDLSCs. Finally, we evaluated the Wnt pathway, which is associated with osteogenic differentiation of stromal/stem cells, in A-PDLSCs + ERM and P-PDLSCs + ERM groups, which indicated that suppression of the Wnt pathway may result in an increase in the osteogenic properties of A-PDLSCs + ERM and P-PDLSCs + ERM groups. Taken together, the above findings shed new light on the function of ERM and provide a novel therapeutic for optimizing PDLSCs-based periodontal regeneration.

Advanced glycation end productions and tendon stem/progenitor cells in pathogenesis of diabetic tendinopathy

Tendinopathy is a challenging complication observed in patients with diabetes mellitus. Tendinopathy usually leads to chronic pain, limited joint motion, and even ruptured tendons. Imaging and histological analyses have revealed pathological changes in various tendons of patients with diabetes, including disorganized arrangement of collagen fibers, microtears, calcium nodules, and advanced glycation end product (AGE) deposition. Tendon-derived stem/ progenitor cells (TSPCs) were found to maintain hemostasis and to participate in the reversal of tendinopathy. We also discovered the aberrant osteochondrogenesis of TSPCs in vitro. However, the relationship between AGEs and TSPCs in diabetic tendinopathy and the underlying mechanism remain unclear. In this review, we summarize the current findings in this field and hypothesize that AGEs could alter the properties of tendons in patients with diabetes by regulating the proliferation and differentiation of TSPCs in vivo.

Diabetes Mellitus and Periodontitis Share Intracellular Disorders as the Main Meeting Point

Diabetes and periodontitis are two of the most prevalent diseases worldwide that negatively impact the quality of life of the individual suffering from them. They are part of the chronic inflammatory disease group or, as recently mentioned, non-communicable diseases, with inflammation being the meeting point among them. Inflammation hitherto includes vascular and tissue changes, but new technologies provide data at the intracellular level that could explain how the cells respond to the aggression more clearly. This review aims to emphasize the molecular pathophysiological mechanisms in patients with type 2 diabetes mellitus and periodontitis, which are marked by different impaired central regulators including mitochondrial dysfunction, impaired immune system and autophagy pathways, oxidative stress, and the crosstalk between adenosine monophosphate-activated protein kinase (AMPK) and the renin-angiotensin system (RAS). All of them are the shared background behind both diseases that could explain its relationship. These should be taken in consideration if we would like to improve the treatment outcomes. Currently, the main treatment strategies in diabetes try to reduce glycemia index as the most important aspect, and in periodontitis try to reduce the presence of oral bacteria. We propose to add to the therapeutic guidelines the handling of all the intracellular disorders to try to obtain better treatment success.

Effects of REDOX in Regulating and Treatment of Metabolic and Inflammatory Cardiovascular Diseases

Reduction oxidation (REDOX) reaction is crucial in life activities, and its dynamic balance is regulated by ROS. Reactive oxygen species (ROS) is associated with a variety of metabolic diseases involving in multiple cellular signalling in pathologic and physiological signal transduction. ROS are the by-products of numerous enzymatic reactions in various cell compartments, including the cytoplasm, cell membrane, endoplasmic reticulum (ER), mitochondria, and peroxisome. ROS signalling is not only involved in normal physiological processes but also causes metabolic dysfunction and maladaptive responses to inflammatory signals, which depends on the cell type or tissue environment. Excess oxidants are able to alter the normal structure and function of DNA, lipids, and proteins, leading to mutations or oxidative damage. Therefore, excessive oxidative stress is usually regarded as the cause of various pathological conditions, such as cancer, neurodegeneration, cardiovascular diseases (CVDs), diabetes, and kidney diseases. Currently, it has been possible to detect diabetes and other cardiac diseases by detecting derivatives accompanied by oxidative stress in vivo as biomarkers, but there is no effective method to treat these diseases. In consequence, it is essential for us to seek new therapy targeting these diseases through understanding the role of ROS signalling in regulating metabolic activity, inflammatory activation, and cardiac diseases related to metabolic dysfunction. In this review, we summarize the current literature on REDOX and its role in the regulation of cardiac metabolism and inflammation, focusing on ROS, local REDOX signalling pathways, and other mechanisms.

The Impact of Advanced Glycation End-Products (AGEs) on Proliferation and Apoptosis of Primary Stem Cells: A Systematic Review

Stem cell-based regenerative therapies hold great promises to treat a wide spectrum of diseases. However, stem cell engraftment and survival are still challenging due to an unfavorable transplantation environment. Advanced glycation end-products (AGEs) can contribute to the generation of these harmful conditions. AGEs are a heterogeneous group of glycated products, nonenzymatically formed when proteins and/or lipids become glycated and oxidized. Our typical Western diet as well as cigarettes contain high AGEs content. AGEs are also endogenously formed in our body and accumulate with senescence and in pathological situations. Whether AGEs have an impact on stem cell viability in regenerative medicine remains unclear, and research on the effect of AGEs on stem cell proliferation and apoptosis is still ongoing. Therefore, this systematic review provides a clear overview of the effects of glycated proteins on cell viability in various types of primary isolated stem cells used in regenerative medicine.