Macrophage M2 polarization promotes pulpal inflammation resolution during orthodontic tooth movement.

Mechanical force induces hypoxia in the pulpal area by compressing the apical blood vessels of the pulp, triggering pulpal inflammation during orthodontic tooth movement. However, this inflammation tends to be restorable. Macrophages are recognized as pivotal immunoreactive cells in the dental pulp. Whether they are involved in the resolution of pulpal inflammation in orthodontic teeth remains unclear. In this study, we investigated macrophage polarization and its effects during orthodontic tooth movement. It was demonstrated that macrophages within the dental pulp polarized to M2 type and actively participated in the process of pulpal inflammation resolution. Inflammatory reactions were generated and vascularization occurred in the pulp during orthodontic tooth movement. Macrophages in orthodontic pulp show a tendency to polarize towards M2 type as a result of pulpal hypoxia. Furthermore, by blocking M2 polarization, we found that macrophage M2 polarization inhibits dental pulp-secreting inflammatory factors and enhances VEGF production. In conclusion, our findings suggest that macrophages promote pulpal inflammation resolution by enhancing M2 polarization and maintaining dental health during orthodontic tooth movement.

Periapical bacterial disinfection is critical for dental pulp regenerative cell therapy in apical periodontitis in dogs.

BACKGROUND: Application of pulp regenerative cell therapy for mature teeth with periapical lesions is a critical clinical challenge. The bacterial infection in inaccessible location within the root canal system and in the periapical lesions could cause resistance and impediment, leading to limitations in successful therapy. Thus, the aim of this study was to examine the effect of residual bacteria on the outcome of pulp regeneration in mature teeth with apical periodontitis in dogs. METHODS: Periapical lesions were induced in 32 root canals of 4 dogs in two different models in severities, model A and model B. Model A (moderate infection): the canal exposed to the oral cavity for 2 weeks and then closed for 2 weeks. Model B (severe infection): the canal exposed to the oral cavity for 2 months and then closed for 5 months. All root canals were irrigated with 6% sodium hypochlorite, and 3% EDTA and further with 0.015% levofloxacin-containing nanobubbles, which was also used as an intracanal medicament. The aseptic conditions were examined by bacterial anaerobic culture and/or PCR analyses. The root canal treatment was repeated several times, and allogeneic dental pulp stem cells were transplanted into the root canals. The radiographic evaluation of periapical lesions was performed by cone-beam computed tomography before the first treatment, just after cell transplantation, and after 2 months and 6 months in both model A, model B, respectively. The animals were then sacrificed and the jaw blocks were harvested for histological and histobacteriological evaluations of pulp regeneration and periapical tissue healing. Furthermore, the DiI-labelled DPSCs were transplanted into the root canals after complete disinfection (n = 4) or without root canal treatment (n = 4) in the apical periodontitis model (model A) in one dog, and cell localization was compared 72 h after transplantation. RESULTS: In 8 out of 12 canals from model A, and 10 out of 15 canals from model B, pulp regeneration with good vascularization, innervation, and a significant reduction in the radiolucent area of the periapical lesions were observed. However, in the other 4 canals and 5 canals from model A and model B, respectively, no pulp tissue was regenerated, and inflammation in the periapical tissue, and external resorption or healed external resorption were detected. The presence of residual bacteria in the periapical tissues and severe inflammation were significantly associated with inhibition of regenerated pulp tissue in these 9 unsuccessful canals (P < 0.05, each) (OR = 0.075, each) analyzed by multiple logistic regression analysis. For cellular kinetics, transplanted cells remained in the disinfected root canals, while they were not detected in the infected root canals, suggesting their migration through the apical foramen under the influence of inflammation. CONCLUSIONS: A true pulp-dentin complex was regenerated in the root canal by the pulp regenerative therapy in mature teeth with apical lesions. The successful pulp regeneration was negatively associated both with residual bacteria and inflammation in the periapical tissue.

Allogeneic Bone Marrow Mesenchymal Stromal Cell Transplantation Induces Dentin Pulp Complex-like Formation in Immature Teeth with Pulp Necrosis and Apical Periodontitis.

INTRODUCTION: Dental pulp regeneration is challenging in endodontics. Cellular therapy is an alternative approach to induce dental pulp regeneration. Mesenchymal stromal cells (MSCs) have the capacity to induce dental pulp-like tissue formation. In this study, we evaluated the capacity of allogeneic bone marrow MSCs (BM-MSCs) to regenerate pulp following necrosis and apical periodontitis in children's permanent immature apex teeth. METHODS: Patients aged 8 to 12 years with pulp necrosis and apical periodontitis were evaluated. The study included 15 teeth (13 incisors and 2 molars) from 14 patients (8 boys and 6 girls). Radiographic evaluation showed periapical radiolucency and immature apex teeth. There was no response to cold or electric pulp testing. The root canal of each tooth was cleaned, shaped, and Ca(OH)2 used as an interappointment medication. Cryopreserved allogeneic BM-MSCs were thawed, expanded, incorporated into preclotted platelet-rich plasma, and implanted into the tooth's pulp cavity. They were sealed with bioceramic cement and composite. Sensibility, apical foramen, calcium deposits within the root canal, and resolution of periapical lesions were evaluated in each tooth over the following 12 months. RESULTS: Based on 9 variables established for dental pulp-like tissue regeneration, all MSC-treated teeth showed evidence of successful regeneration. Clinical and radiographic evaluation of the treated teeth showed periapical lesion healing, sensitivity to cold and electricity, decreased width of the apical foramen, and mineralization within the canal space. CONCLUSIONS: Transplantation of allogeneic MSCs induces the formation of dental pulp-like tissue in permanent immature apex teeth with pulp necrosis and apical periodontitis. Implant of MSCs constitutes a potential therapy in regenerative endodontics in pediatric dentistry. Future studies incorporating a larger sample size may confirm these results.

Cell-Based Regenerative Endodontics for the Treatment of Irreversible Pulpitis: AnIn VivoInvestigation.

INTRODUCTION: This study aims to investigate the ability of umbilical cord mesenchymal stem cells (UC-MSC) to enhance the regeneration of pulp-dentin complex in immature permanent teeth with irreversible pulpitis. METHODS: A total of 32 mandibular premolar teeth with immature apices in 5 dogs were used in this in-vivo randomized controlled trial (RCT). Eight healthy teeth without pre-existing pathosis served as the positive control samples and received no treatment, while in another 8 teeth, the pulp was completely extirpated (negative control). Class V cavities were prepared to induce inflammation in the remaining 16 teeth (groups 3 and 4) and the pulp was extirpated 2-4 mm short of the radiographic apex. Of the 16, the 8 teeth in group 4 received 1 mL of cord blood stem cells with a hydrogel scaffold. Blood clots were covered with mineral trioxide aggregates at the cementoenamel junction in the experimental groups, and teeth were filled with RMGI and composite. Three months later, block sections were removed for histologic evaluations for the evaluation of postoperative apical closure, degree of inflammation, and presence of normal pulp tissue. The data were statistically analyzed with the chi-square test (P < .05). RESULTS: All teeth with complete pulp extirpation demonstrated pulpal necrosis with no postoperative closure of their apices, while apical closure was seen in all the teeth in the remaining groups. There was a statistically significant (P < .001) difference in the presence of inflammation and normal pulp tissue between the experimental groups. The teeth in group 3 showed normal pulp tissue extending to the level of MTA, but there was inflammation within the canal space. In contrast, the teeth in the UC-MSC group demonstrated organized, normal pulp tissue with no inflammation. CONCLUSION: Based on these results, the regeneration of the pulp-dentin complex is possible with no inflammation when UC-MSCs are used and 2-4 mm of the apical pulp remains intact in immature teeth with irreversible pulpitis.

Inhibitory effects of the nanoscale lysate derived from xenogenic dental pulp stem cells in lung cancer models.

BACKGROUND: Lung cancer is a highly prevalent malignancy and has the highest mortality rate among all tumors due to lymph node metastasis. Bone marrow and umbilical cord-derived mesenchymal stem cells (MSCs) have demonstrated tumor-suppressive effects on lung cancer. This study investigated the effects of DPSC lysate on proliferation, apoptosis, migration and invasion of cancer cells were studied in vivo and in vitro. METHODS: The proliferation, apoptosis, and migration/metastasis were evaluated by cell counting kit-8 assay, Annexin-V and propidium iodide staining, and the transwell assay, respectively. The expression levels of apoptosis-, cell cycle-, migration-, and adhesion-related mRNA and proteins were measured by qRT-PCR and western blot. The level and mRNA expression of tumor markers carcino embryonic antigen (CEA), neuron-specific enolase (NSE), and squamous cell carcinoma (SCC) were measured by Enzyme-linked immunosorbent assay (ELISA) and qRT-PCR. Finally, a tumor-bearing mouse model was constructed to observe the tumor-suppressive effect of DPSC lysate after intraperitoneal injection. RESULTS: DPSC lysate decreased the viability of A549 cells and induced apoptosis in lung cancer cells. Western blot confirmed that levels of Caspase-3, Bax, and Bad were increased, and Bcl-2 protein levels were decreased in A549 cells treated with DPSC lysate. In addition, DPSC lysate inhibited the migration and invasion of A549 cells; downregulated key genes of the cell cycle, migration, and adhesion; and significantly suppressed tumor markers. Xenograft results showed that DPSC lysate inhibited tumor growth and reduced tumor weight. CONCLUSIONS: DPSC lysate inhibited proliferation, invasion, and metastasis; promoted apoptosis in lung cancer cells; and suppressed tumor growth- potentially providing a cell-based alternative therapy for lung cancer treatment.

Reparative Dentin Formation Following Dental Pulp Capping is Mediated by TNFR1 In Vivo.

INTRODUCTION: Tumor necrosis factor (TNF)-α is a pro-inflammatory cytokine that promotes biomineralization in vitro in dental pulp cells. However, the role of TNF-α-TNF receptor 1 (TNFR1) signaling in reparative dentin formation and related inflammatory pathways is not known. Therefore, the aim of this study was to evaluate the role of the TNF-α-TNFR1 axis in dental pulp repair following pulp capping in vivo. METHODS: Dental pulp repair response of genetically deficient TNF-α receptor-1 mice (TNFR1-/-; n = 20) was compared with that of C57Bl6 mice (wild type [WT]; n = 20). Pulp capping was performed with mineral trioxide aggregate on the mandibular first molars of mice. After 7 and 70 days, tissues were collected and stained with hematoxylin and eosin for histopathological and histometric evaluation, and assessed by the Brown and Brenn methods for histomicrobiological analysis and by immunohistochemistry to localize TNF-α, Runt-related transcription factor 2, Dentin Sialoprotein (DSP) and Osteopontin (OPN) expression. RESULTS: Compared with WT mice, TNFR1-/- mice showed significantly decreased reparative dentin formation with a lower mineralized tissue area (P < .0001). Unlike WT mice, TNFR1-/- mice also exhibited significant dental pulp necrosis, neutrophil recruitment, and apical periodontitis formation (P < .0001) without bacterial tissue invasion. TNFR1-/- animals further exhibited decreased TNF-α, DSP, and OPN expression (P < .0001), whereas Runt-related transcription factor 2 expression was unchanged (P > .05). CONCLUSION: The TNF-α-TNFR1 axis is involved in reparative dentin formation following dental pulp capping in vivo. Genetic ablation of TNFR1 modified the inflammatory process and inhibited the expression of the DSP and OPN mineralization proteins, which culminated in dental pulp necrosis and development of apical periodontitis.

Quantitative analysis of culturable bacteria, levels of endotoxins, inflammatory mediators and substance P in teeth with symptomatic irreversible pulpitis and in teeth with vital normal pulp tissues.

AIM: To comparatively analyse the levels of culturable bacteria, endotoxins (LPS), tumour necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1ß) and substance P in teeth with symptomatic irreversible pulpitis (SIP) and vital normal pulp (VNP) tissues. METHODOLOGY: Thirty-two patients were included (20 teeth with SIP and 12 teeth with VNP tissues) in this cross-sectional study. Samples were collected from the full length of the root canals (microbial analysis) and periapical tissues (2 mm beyond the apex for immunological analysis), using sterile absorbent paper points. The levels of culturable bacteria (culture method), endotoxins (LAL Pyrogent 5000), TNF-α, IL-1ß and substance P (ELISA) were assessed. The Mann-Whitney test was used for comparisons between the levels of CFU/mL, LPS, TNF-α, IL-1ß and substance P in the SIP and VNP groups. The statistical analysis was performed with the significance level set at 5%. RESULTS: Culturable bacteria were recovered from all teeth with SIP. On the other hand, no positive cultures were observed in the VNP tissues group (p > .05). The levels of LPS were approximately four times higher in teeth with SIP than in teeth with VNP tissues (p < .05). Higher levels of TNF-α and substance P were detected in teeth with SIP (p < .05). On the other hand, no difference in the levels of IL-1ß was detected between the two groups (p > .05). CONCLUSION: Teeth with symptomatic irreversible pulpitis present higher levels of culturable bacteria, endotoxins, TNF-α and substance P than those with vital normal pulp tissues. On the other hand, the levels of IL-1ß were similar in teeth from both groups suggesting reduced implications of this inflammatory mediator in the early stages of infection.

Insights into the protective capacity of human dental pulp stem cells and its secretome in cisplatin-induced nephrotoxicity: effects on oxidative stress and histological changes.

OBJECTIVES: Acute renal injury (AKI) is a major limiting factor for cisplatin administration. Recent evidence suggests the potential contribution of mesenchymal stem cells (MSCs) to rehabilitation from several disorders via both direct and indirect routes. Thus, the present study aimed, for the first time, to explore and compare the reno-protective potential of human dental pulp-derived stem cells (hDPSCs) vs. hDPSC-conditioned medium (hDPSC-CM) in recovery of impaired kidney tissues in a rat animal model of cisplatin-induced AKI. METHODS: AKI was induced via cisplatin injection (n=36). One day after, 24 rats were treated with either hDPSCs or hDPSC-CM (n=12). An extra set of rats (n=12) served as sham group. On days 2 or 7 (n=6), rats were humanly sacrificed for further analysis. Renal injury was explored via measuring serum creatinine and BUN. Renal level of oxidative stress was assessed by determining malondialdehyde, and enzymatic activities of superoxide dismutase and catalase. Renal histopathological changes were scored for comparison among different experimental groups. RESULTS: A single dose of cisplatin resulted in considerable renal dysfunction and oxidative stress. Treatment with hDPSCs or hDPSC-CM resulted in significantly restored renal function, reduced level of oxidative stress, and improved histopathological manifestations. Furthermore, as compared to hDPSC-CM, administration of hDPSCs led to superior results in AKI-induced animals. CONCLUSIONS: The current study described the first comparative evidence of reno-protective potential of hDPSCs and their CM against cisplatin-induced nephrotoxicity in an AKI rat model, proposing them as useful adjunctive therapy in AKI. Yet, future explorations are still needed.

Accelerating Wound Healing of Traumatic Ulcer with Topical Application of Dental Pulp Mesenchymal Stem Cell Secretome and Robusta Green Coffee Bean Extract Combination in vivo

ABSTRACT Objective: To investigate the ability of a combination dental pulp mesenchymal stem cell secretome (DPMSCS), robusta green coffee bean extract (RGCBE), and Carboxymethylcellulose-Natrium (CMC-Na) in a Wistar rats model of traumatic ulcers. Material and Methods: Twenty-eight young, male, healthy Wistar rats (Rattus norvegicus) were divided into seven groups randomly: Group K0, group K1-3 (traumatic ulcer rats that received CMC-Na gel for three days), group K1-7 (traumatic ulcer rats that received CMC-Na gel for seven days), group K2-3 (traumatic ulcer rats that received RGCBE for three days), group K2-7 (traumatic ulcer rats that received RGCBE for seven days), group K3-3 (traumatic ulcer rats that received DPMSCS for three days), and group K3-7 (traumatic ulcer rats that received DPMSCS for seven days). An ulcer was made with an amalgam stopper on the right buccal mucosa of the rats. DPMSCS 50% gel was applied to the ulcer on the left buccal mucosa. The ulcer diameter was measured on day 3 and day 7. Results: There was a significant difference in the diameter of the ulcer, the number of neutrophils, and fibroblasts in the treatment group compared to the control group on day 7. Conclusion: A combination of DPMSCS and RGCBE 50% accelerates traumatic ulcer wound healing by lowering ulcer diameter, decreasing neutrophil counts, and increasing fibroblast proliferation in vivo.

Novel strategy for dental caries by physiologic dentin regeneration with CPNE7 peptide.

OBJECTIVE: CPNE7-derived functional peptide (CPNE7-DP) has been introduced as a bioactive therapeutics for dentin diseases. CPNE7-DP regenerates tubular dentin on the pulpal side and occlude dentinal tubules. CPNE7-DP was capable to treat dentin hypersensitivity typically associated with dentinal wear at the neck of the tooth. However, the role of CPNE7-DP in another common dentin disease, dental caries, remains uninvestigated. In this study, we evaluated the potential application of CPNE7-DP in dentin caries using an experimental dentin caries model in rats. DESIGN: The stability of CPNE7-DP in caries-like environments including pathologic bacteria of caries or low pH was tested. We established a nutrition-time/hyposalivation-based dental caries rat model by inoculating caries-inducing bacteria and diet for sufficient time. Glycopyrrolate has been treated to induce reversible hyposalivation for accelerating caries progression. Then the tubular dentin regeneration was investigated with histologic methods. Also, modulation of inflammation or autophagy by CPNE7-DP was investigated with marker gene expression in human dental pulp cells (hDPCs) and immunohistochemistry. RESULTS: CPNE7-DP was stable with caries-inducing bacteria and low pH. Establishment of dentin caries was confirmed with radiographic and histologic evaluation. CPNE7-DP regenerated a substantial amount of tubular tertiary dentin and alleviated the pulp inflammation of dentin caries. Under inflammatory conditions, CPNE7-DP reduced the expression of inflammatory cytokines. These phenomena could be the consequence of the modulation of autophagy by CPNE7-DP, which reactivates inflamed odontoblasts. CONCLUSIONS: Overall, CPNE7-DP, which repairs caries through physiological dentin regeneration, might help overcoming the limitations of current restorative caries treatments.

Unusual Lesion Caused by Food Displacement Into the Oral Mucosa, Mimicking a Sinus Tract.

This article reports an unusual case of foreign body lesion on the oral mucosa. A 61-year-old man, with no previous traumatic episode, presented with a small swelling resembling a sinus tract on the mucosa in the anterior mandible, adjacent to the left central and lateral incisors. Because of a discrete drainage of serous/purulent exudate, the clinician initially suspected endodontic involvement; however, the adjacent teeth were caries-free, responded positively to pulp tests, and the periapical tissues were radiographically normal. Exploration of the lesion opening under an operating microscope revealed a small seed associated with a dark filamentous structure; both were removed and processed for histologic examination. The seed was from a fig, and was germinating under the mucosa conditions. Bacterial colonization of the vegetable structures and polymorphonuclear leukocyte accumulations were histologically observed. The mucosa healed completely and uneventfully over the following weeks.

Dental Pulp Stem Cell Therapy in Ischemic Stroke: A Meta-Analysis of Preclinical Studies.

OBJECTIVE: More preclinical research evidence has shown that dental pulp stem cells (DPSCs) transplantation is expected to promote the recovery of ischemic stroke (IS), but it still lacks an evidence-based analysis. The purpose of this study was to investigate the effects of DPSCs on neurological function and infarct size in Sprague-Dawley (SD) rats with middle cerebral artery embolization (MCAO). METHODS: According to PRISMA guidelines, the preclinical study of DPSCs in the treatment of IS was screened according to the inclusion and exclusion criteria, and the relevant data and quality were evaluated by two independent researchers; A meta-analysis of histological and behavioral results was performed. RESULTS: Seven studies were finally included, with quality evaluation scores ranging from 8 to 9. Four articles reported modified Neurological Severity Scores (mNSS), three studies reported rotarod test, and six studies reported infarct volume. Meta-analysis showed that the mNSS score decreased by 1.17 times, the rotarod test increased by 1.11 times and the volume of cerebral infarction decreased by 1.91 times in the DPSC group compared with the blank control group. CONCLUSION: Transplantation of DPSCs can significantly improve the neurological function of ischemic stroke and reduce the infarct volume.

Efecto de la hipoxia sobre los tejidos de la cavidad oral: revisión de la literatura / Effect of hypoxia on oral tissues: a review of the literature

La exposición a hipoxia es considerada un estímulo estresante, por lo que el organismo desarrolla meca-nismos de aclimatación para asegurar la homeosta-sis. Si bien el efecto de la hipoxia sobre los distintos sistemas de tejidos y órganos ha sido bien documen-tado, el rol de los bajos niveles de O2 en la cavidad oral no ha recibido el mismo análisis. En este trabajo se revisaron los datos bibliográficos disponibles sobre el efecto de la hipoxia sobre el tejido periodontal, las glándulas salivales, la pulpa dental y el hueso mandi-bular y alveolar. De lo analizado en la bibliografía, re-sulta evidente que los bajos niveles de O2 aumentan el número de mediadores inflamatorios que inducen la progresión de la enfermedad periodontal y, a su vez, la inflamación establecida durante dicha enfermedad agrava aún más las condiciones de hipoxia tisular. Las glándulas salivales también se encuentran afectadas durante la exposición a hipoxia, disminuyendo la can-tidad de saliva secretada, observándose alteraciones ultraestructurales en el parénquima glandular. Por otra parte, se ha establecido que la hipoxia puede te-ner efectos deseados para el cultivo de células madre de la pulpa dental, lo cual resulta útil en el campo de la odontología reparativa y también para el movimien-to dental durante los tratamientos ortodónticos. En conclusión, para determinar los efectos de la hipoxia en la cavidad oral se debe analizar no sólo el tipo de tejido involucrado sino también las condiciones de hi-poxia a las cuales éste es sometido, así también como la duración de la exposición y la modalidad de hipoxia (AU)

Exposure to hypoxia is considered a stressful stimulus, therefore the organism develops acclimation mechanisms to try to ensure homeostasis. Although the effect of hypoxia on different tissues and organs has been very well documented, the role of low levels of O2 in the oral cavity has not received the same analysis. In this review, we analyzed the available bibliographic data concerning the effects of hypoxia on periodontal tissue, salivary glands, and dental pulp. The published evidence demonstrates that low O2 levels increase the number of inflammatory mediators that induce the progression of periodontal disease, and, in turn, the inflammation established during the progression of periodontitis aggravates tissue hypoxia conditions. Salivary glands are also affected during hypoxic exposure, decreasing salivary secretion, and leading to ultrastructural alterations in the glandular parenchyma. On the other hand, hypoxia could also be beneficial in some scenarios. It has been established that dental pulp cells grow better in culture under hypoxic conditions than they do in normoxia. Furthermore, mild hypoxia seems to stimulate periodontal ligament cells proliferation and matrix degradation, key events during for orthodontic treatments. In conclusion, to determine the effects of hypoxia in the oral cavity, it is necessary to analyze not only the type of tissue involved but also the hypoxic conditions to which it is subjected, as well as its duration and modality (AU)

TRPA1 triggers hyperalgesia and inflammation after tooth bleaching.

Hyperalgesia has become a major problem restricting the clinical application of tooth bleaching. We hypothesized that transient receptor potential ankyrin 1 (TRPA1), a pain conduction tunnel, plays a role in tooth hyperalgesia and inflammation after bleaching. Dental pulp stem cells were seeded on the dentin side of the disc, which was cut from the premolar buccal tissue, with 15% (90 min) or 40% (3 × 15 min) bleaching gel applied on the enamel side, and treated with or without a TRPA1 inhibitor. The bleaching gel stimulated intracellular reactive oxygen species, Ca2+, ATP, and extracellular ATP in a dose-dependent manner, and increased the mRNA and protein levels of hyperalgesia (TRPA1 and PANX1) and inflammation (TNFα and IL6) factors. This increment was adversely affected by TRPA1 inhibitor. In animal study, the protein levels of TRPA1 (P = 0.0006), PANX1 (P < 0.0001), and proliferation factors [PCNA (P < 0.0001) and Caspase 3 (P = 0.0066)] increased significantly after treated rat incisors with 15% and 40% bleaching gels as detected by immunohistochemistry. These results show that TRPA1 plays a critical role in sensitivity and inflammation after tooth bleaching, providing a solid foundation for further research on reducing the complications of tooth bleaching.

Effect of treatment with resiniferatoxin in an experimental model of pulpal inflammatory in mice.

AIM: To evaluate whether treatment with resiniferatoxin (RTX) is capable of lowering the plasma levels of PGE2 and TNF-α, as well as histopathological parameters in inflammation of pulp tissue in a mouse experimental model. METHODOLOGY: Ten groups of six BALB/c mice were formed as follows: healthy group (HC ), healthy group treated with RTX (HRTX ), two groups with pulp inflammation at 14 and 18 hours (PI14 /PI18 ), six groups with pulpal inflammation plus treatment with Ibuprofen (IBU14 /IBU18 ), dexamethasone (DEX14 /DEX18 ) and resiniferatoxin (RTX14 /RTX18 ) at 14 and 18 hours, respectively. Pulpal inflammation was induced through occlusal exposure of the pulp of the maxillary first molar. The plasma levels of PGE2 and TNF-α and the histological parameters of the pulp tissue of the HC and HRTX groups were evaluated at the time of acquiring the animals. In the other groups, the plasma levels of PGE2 and TNF-α and the histopathological parameters were evaluated at 14 and 18 hours after pulp damage. Plasma levels of PGE2 and TNF-α were quantified by ELISA, and the histopathological parameters were evaluated by H/E staining. Statistical significance was determined by one-way analysis of variance (ANOVA) to test for overall differences between group means. RESULTS: A significant increase (*p < .05) in plasma levels of PGE2 and TNF-α occurred 14 and 18 hours after pulp damage. In addition, treatment with RTX significantly decreased (*p < .05) the plasma levels of PGE2 and TNF-α at 14 and 18 hours after pulp damage, as well as the infiltrate of inflammatory cells at 18 hours after pulp damage, similarly to treatment with ibuprofen and dexamethasone. CONCLUSION: It was possible to detect systemic levels of PGE2 and TNF-α at 14 and 18 hours after pulp damage. Likewise, treatment with RTX was associated with an anti-inflammatory effect similar to treatment with ibuprofen and dexamethasone. These findings place resiniferatoxin as a therapeutic alternative in the treatment of inflammatory diseases in Dentistry.

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.

Nuclear receptor coactivator 4-mediated ferritinophagy drives proliferation of dental pulp stem cells in hypoxia.

Nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy has been implicated in the ferroptosis in cancer cells and hematopoiesis in the bone marrow. However, the role of iron metabolism, especially NCOA4-mediated degradation of ferritin, has not been explored in the proliferation of mesenchymal stem cells. The present study was designed to explore the role of NCOA4-mediated ferritinophagy in hypoxia-treated dental pulp stem cells (DPSCs). Hypoxia treatment increased ROS generation, boosted cytosolic labile iron pool, increased expression of transferrin receptor 1 and NCOA4. Moreover, colocalization of LC3B with NCOA4 and ferritin was observed in hypoxia-treated DPSCs, indicating the development of ferritinophagy. Hypoxia promoted the proliferation of DPSCs, but not ferroptosis, under normal serum supplement and serum deprivation. NCOA4 knock-down reduced ferritin degradation and inhibited proliferation of DPSCs under hypoxia. Furthermore, the activation of hypoxia inducible factor 1α and p38 mitogen-activated protein kinase signaling pathway was involved in the upregulation of NCOA4 in hypoxia. Therefore, our present study suggested that NCOA4-mediated ferritinophagy promoted the level of labile iron pool, leading to enhanced iron availability and elevated cell proliferation of DPSCs. Our present study uncovered a physiological role of ferritinophagy in the proliferation and growth of mesenchymal stem cells under hypoxia.

Inflammatory Response Mechanisms of the Dentine-Pulp Complex and the Periapical Tissues.

The macroscopic and microscopic anatomy of the oral cavity is complex and unique in the human body. Soft-tissue structures are in close interaction with mineralized bone, but also dentine, cementum and enamel of our teeth. These are exposed to intense mechanical and chemical stress as well as to dense microbiologic colonization. Teeth are susceptible to damage, most commonly to caries, where microorganisms from the oral cavity degrade the mineralized tissues of enamel and dentine and invade the soft connective tissue at the core, the dental pulp. However, the pulp is well-equipped to sense and fend off bacteria and their products and mounts various and intricate defense mechanisms. The front rank is formed by a layer of odontoblasts, which line the pulp chamber towards the dentine. These highly specialized cells not only form mineralized tissue but exert important functions as barrier cells. They recognize pathogens early in the process, secrete antibacterial compounds and neutralize bacterial toxins, initiate the immune response and alert other key players of the host defense. As bacteria get closer to the pulp, additional cell types of the pulp, including fibroblasts, stem and immune cells, but also vascular and neuronal networks, contribute with a variety of distinct defense mechanisms, and inflammatory response mechanisms are critical for tissue homeostasis. Still, without therapeutic intervention, a deep carious lesion may lead to tissue necrosis, which allows bacteria to populate the root canal system and invade the periradicular bone via the apical foramen at the root tip. The periodontal tissues and alveolar bone react to the insult with an inflammatory response, most commonly by the formation of an apical granuloma. Healing can occur after pathogen removal, which is achieved by disinfection and obturation of the pulp space by root canal treatment. This review highlights the various mechanisms of pathogen recognition and defense of dental pulp cells and periradicular tissues, explains the different cell types involved in the immune response and discusses the mechanisms of healing and repair, pointing out the close links between inflammation and regeneration as well as between inflammation and potential malignant transformation.

RANKL/OPG ratio regulates odontoclastogenesis in damaged dental pulp.

Bone-resorbing osteoclasts are regulated by the relative ratio of the differentiation factor, receptor activator NF-kappa B ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG). Dental tissue-localized-resorbing cells called odontoclasts have regulatory factors considered as identical to those of osteoclasts; however, it is still unclear whether the RANKL/OPG ratio is a key factor for odontoclast regulation in dental pulp. Here, we showed that odontoclast regulators, macrophage colony-stimulating factor-1, RANKL, and OPG were detectable in mouse pulp of molars, but OPG was dominantly expressed. High OPG expression was expected to have a negative regulatory effect on odontoclastogenesis; however, odontoclasts were not detected in the dental pulp of OPG-deficient (KO) mice. In contrast, damage induced odontoclast-like cells were seen in wild-type pulp tissues, with their number significantly increased in OPG-KO mice. Relative ratio of RANKL/OPG in the damaged pulp was significantly higher than in undamaged control pulp. Pulp damages enhanced hypoxia inducible factor-1α and -2α, reported to increase RANKL or decrease OPG. These results reveal that the relative ratio of RANKL/OPG is significant to pulpal odontoclastogenesis, and that OPG expression is not required for maintenance of pulp homeostasis, but protects pulp from odontoclastogenesis caused by damages.

ODONTOLOGICAL EFFECTS OF IONIZING RADIATION (review). / ODONTOLOGIChNI EFEKTY IONIZUIuChOGO VYPROMINIuVANNIa (ogliad).

BACKGROUND: Odontological effects of ionizing radiation (IR) as a result of radiotherapy, the consequences of accidents at nuclear power plants and industry, individual occupational exposure, etc. deserve significant attention interns of radiation medicine and radiation safety. OBJECTIVE: to analyze and summarize clinical and experimental data on the odontological radiation effects. OBJECT: the pathological changes in the hard tissues of teeth, pulp, periodontium, mucousmembranes of the mouth and jaws due to exposure to IR. METHOD: search in the PubMed / MEDLINE, Google Scholarabstract medical and biological databases, scientific libraries of the relevant sources of scientific information. RESULTS: Radiobiological effects of IR due to its direct and indirect action are manifested throughout the period ofodontogenesis and formation of the facial skeleton. Experimental and clinical data (in children and adults) indicatethe increased risk of dental caries, reduction of pain threshold and vascularization of tooth pulp along with its fibrosis and atrophy, periodontal dysfunction, which predispose to a high probability of tooth loss. Abnormalities in theactivity of osteoblasts and cementoblasts of dental periosteum and osteoblasts of alveolar process in combinationwith circulatory disorders due to endothelial cell death, hyalinization, thrombosis and vascular obliteration increasethe risk of jaw osteoradionecrosis. Children who have undergone a prenatal exposure to IR as a result of theChornobyl NPP accident have a premature change of teeth. Deterioration of periodontal tissues and early development of acute and complicated dental caries are typical for children and adults affected by the Chornobyl disaster. CONCLUSIONS: Summarized data on the effects of radiation exposure under different conditions on teeth primordia(i.e. immature teeth), their formation and eruption in experimental and clinical settings, as well as on the odontological radiation effects in adults are summarized. Condition of the teeth in the Chornobyl NPP accident survivorsis described. Understanding and taking into account the radiobiological odontological effects is necessary in thelight of planning, preparing, and conducting local radiation therapy and developing the standards of radiation safety and measures to protect professionals and the public in the event of possible radiation accidents at the nuclearpower plants and industry facilities.