The role of interleukin-1α in the pathogenesis of periapical bone destruction in a rat model system

To identify the mediators that stimulate periapical bone resorption following infection, a rat model system was used in which active (rapid) and chronic (slow) phases of bone destruction can be distinguished. Extracts of inflammatory tissues from active lesions contained high levels of bone-resorbing activity, which was destroyed by proteinase K and heat (70°C), but was unaffected by polymyxin B, indicating the presence of protein mediator(s) rather than lipopolysaccharide. Fast-performance liquid chromatography gel filtration of extracts of active lesions demonstrated that most activity was associated with macromolecules of MW 30–60 kDa and 15–20 kDa, consistent with bone resorptive cytokines, including interleukin 1 (IL-I) and tumor necrosis factor (TNF). Inhibition with cytokine-specific antisera demonstrated that resorbing activity in active lesions was significantly neutralized by anti-IL-1β, whereas anti-IL-1/α, anti-TNFα and anti-TNFα had only slight effect. A lower amount of resorbing activity was present in extracts of chronic lesions, which was also neutralized only by anti-IL-1α. Inflammatory tissue explants produced more IL-1α than 1L-1β in vitro , confirming findings with extracts, and high levels of IL-1α were present in active lesions by radioimmunoassay. These data indicate that bone resorption stimulated by bacterial infection is primarily mediated by IL-1α in this model. The similarity of cytokines in active and chronic lesions suggests that quantitative rather than qualitative differences in these mediators may account for lesion progression.     

Interleukin-1beta and tumour necrosis factor-alpha levels in periapical exudates

AIM: The aim of this study was to determine IL-1beta and TNF-alpha levels in periapical exudates and to evaluate their relationship with clinical and radiological findings. METHODOLOGY: Periapical exudates were collected from root canals of 35 single-rooted teeth using absorbent paper points. IL-1beta and TNF-alpha levels were determined by enzyme-linked immunosorbent assays. The samples were divided into two groups according to the presence or absence of clinical signs including swelling and/or fistula, pain on palpation and/or percussion, and pus discharge from canals. Periapical exudate samples were divided into two groups according to size of periapical radiolucent area. RESULTS: The mean concentration of IL-1beta (72.79 ng mL-1) in periapical exudates was approximately 12-fold higher than TNF-alpha(6.17 ng mL-1). There was no significant correlation between these cytokines (P > 0.05). IL-1beta levels in canals with larger radiolucent areas (long axis > or =1 cm) were significantly higher than those with small areas (P < 0.05). There was a tendency toward higher levels of IL-1beta in groups with clinical signs, but the differences were not significant (P > 0.05). CONCLUSIONS: Periapical exudate levels of both cytokines failed to reflect periapical disease state.     

免疫抑制鼠根尖周炎的组织病理学研究

目的 :了解免疫抑制对根尖周炎致病作用的影响。方法 :32只SD大鼠分成两组 ,实验组每周 1次环磷酰胺 (70mg/kg)腹腔注射 ,并作尾静脉血白细胞计数 ;白细胞总数明显下降时 ,行下颌磨牙开髓术 ,术后 1、2、3、4周取材 ,摄X线牙片 ,测X线片所示根尖周稀疏区面积 ;制作组织切片 ,HE染色。结果 :用药前外周血白细胞密度为 (1132 0± 3882 )× 10 6/L ,用药后 (12 70± 4 4 9)× 10 6/L ,下降非常显著。术后 1、2、3、4周根尖阴影面积与对照组呈相似的动态过程。组织学观察 :两组呈相似的非特异性炎症反应过程。结论 :免疫抑制剂致外周血白细胞减少 ,对鼠根尖周炎病程无明显影响。     

The role of immune cytokines in the pathogenesis of periapical lesions

Abstract Bacterial infection of the dental pulp results in pulpal destruction, and subsequently stimulates an inflammatory cell response and destruction of bone in the periapex. Bacterial components, including lipopolysaccharides, induce the production of many polypeptide mediators, or cytokines, by inflammatory cells. These cytokines, which include macrophage-derived interleukin-1 beta, interleukin-1 alpha and tumor necrosis factor, and lymphocyte-derived lymphotoxin, have been shown to potently stimulate bone resorption and to inhibit reparative bone formation in vitro and in vivo. This review presents the hypothesis that immune cytokines play a major role in the pathogenesis of periapical lesions.     

Interactions between immune system and mesenchymal stem cells in dental pulp and periapical tissues

The recent isolation and characterization of mesenchymal stem cells (MSCs) in dental tissues constitutes a major step forward in the development of new treatment strategies. MSCs are essential for dental pulp repair and the success of regenerative endodontic procedures. It is important to understand that immune cells and cytokines can affect stem cell function, which can impact their healing potential. On the other hand, stem cells are immunoprivileged and have the ability to modulate immune and inflammatory responses, which can be utilized to improve treatments outcome. This review addresses both aspects of this interaction and suggests that any change on both sides can tip the balance in favour of either persistence of inflammation or healing. Finally, the therapeutic relevance of the interaction between MSCs and immune system relative to current treatments is discussed, and future research and treatment perspectives are suggested.     

Detection of interleukin-6 in human dental pulp and periapical lesions

Abstract— Pulpal and periapical diseases are characterized by inflammation. The cytokine IL-6 is a major mediator of the host response to tissue injury and infection. This study examined the level of interleukin-6 (IL-6) in six inflamed human pulps and six human periapical lesions of endodontic origin using ELISA. Pulp samples from eight clinically impacted teeth were used as controls. The periapical samples exhibited significant levels of IL-6 (mean= 78.1 ± 9 pg/mg protein) as did inflamed pulpal tissues (mean= 36±3.9 pg/mg protein) compared to healthy pulp (mean= 0.01±0.02 pg/mg protein). These data indicated that IL-6 was produced and released locally in the inflamed pulpal and periapical lesions.     

Repair of large periapical radiolucent lesions of endodontic origin without surgical treatment

The aim of this paper is to present two case reports of pulp necrosis and radiolucent periapical lesions, which were treated without surgical treatment. The first was a mandibular molar with periapical lesion of endodontic origin extending towards the furcation in a 20-year-old woman, and the second affected a maxillary right lateral incisor with a large periapical lesion in a 22-year-old woman. The endodontic treatments were carried out in two sessions, with crown-down instrumentation, irrigation with 2.5% sodium hypochlorite and intracanal medication with calcium hydroxide paste. After 30 days, the root canals were filled with gutta-percha and Sealapex sealer by the lateral condensation technique. The clinical and radiographic examination after 1 year revealed complete repair. The appropriate diagnosis of lesions of endodontic origin and the treatment and obturation of the infected canals allowed complete repair of these large radiolucent periapical lesions without surgical treatment.     

根尖大面积病变手术治疗的临床疗效观察

目的评估根尖手术治疗大面积根尖病变患牙的疗效。方法选择存在大面积根尖病变的59例患者（59处根尖病变,91颗患牙）为研究对象,根尖病变范围6~21 mm,在根管治疗后进行根尖手术。术后1、3、6、9、12、24个月复诊,对患牙及根尖病变进行临床及影像学评估,综合二者结果进行疗效评估,并对可能影响其术后疗效的各种因素进行统计学分析。结果59例患者中52例（88.1%）被评估为成功,6例（10.2%）被评估为失败,1例（1.7%）被评估为有效。老年组患者的成功率（63.6%）明显比青年组（87.5%）和中青年组（95.0%）低,具有统计学差异（P=0.037,P=0.017）;磨牙的成功率（75.0%）比前牙（92.6%）和前磨牙（90.0%）均低,具有统计学差异（P=0.041,P=0.047）;性别、根尖病变侵及牙齿数量、根尖病变范围等因素对成功率的影响未见统计学差异（P>0.05）。结论对于存在大面积根尖病变的患牙,根管治疗后配合根尖手术治疗是一项可选择的治疗方式。     

Production of proinflammatory and immunoregulatory cytokines by inflammatory cells from periapical lesions in culture

Background:  The role of cytokines in pathogenesis of periapical lesions is not well understood. The aim of this study was to study the correlation between proinflammatory and immunoregulatory cytokines in periapical lesions and their relationship with cellular composition and clinical presentation.
Methods:  Inflammatory cells were isolated from 67 human periapical lesions and cultivated for 24 h. The levels of proinflammatory cytokines: interleukin-1 beta (IL-1β), IL-6, IL-8 and tumour necrosis factor alpha (TNF-α) and immunoregulatory cytokines: transforming growth factor-beta (TGF-β) and IL-10 were determined in culture supernatants using a fluorescent bead immunoassay or ELISA. The phenotype of cells was analysed by immunocytochemistry.
Results:  Inflammatory cells from symptomatic lesions which contained higher proportion of granulocytes, secreted higher levels of IL-1, IL-6 and IL-8 compared with asymptomatic lesions. Large-size lesions contained lower percentages of mononuclear phagocytes, higher percentages of CD8⁺ T cells and produced higher levels of TNF-α, IL-6 and IL-10 compared with small-size lesions. There were negative correlations between the concentrations of TGF-β and proinflammatory cytokines. TGF-β, added to cultures, downregulated the levels of proinflammatory cytokines more strongly than IL-10, independently of clinical presentation of the lesions. By contrast, exogenous IL-10 was mainly immunosuppressive in cultures of asymptomatic lesions.
Conclusion:  Symptomatic lesions are characterized by higher production of proinflammatory cytokines. Immunoregulatory cytokines are more important for suppression of inflammation in asymptomatic lesions and in this context the effect of TGF-β is more potent and different from IL-10.     

Changes in root canal microbiota during the development of rat periapical lesions

Periapical lesions are reproducibly induced in rats by pulp exposure and infection from the oral cavity. Lesions expand rapidly between day 7 and day 15-20 (active phase), with slowed expansion thereafter. In the present study we characterized the root canal microbiota present during the active phase of lesion development in this system. The mandibular first molars of Sprague-Dawley rats were exposed on day 0. The teeth were extracted after 7 days ( n = 10 animals) and 15 days ( n = 10), and the microbiota present in roots was isolated and characterized. The number of colonies isolated per tooth was similar on day 7 (1.53 ± 0.64 colony-forming units × 10³) and day 15 (1.49 ± 0.37 colony-forming units × 10³). No colonies were isolated from unexposed control teeth. Anaerobic bacteria increased significantly between day 7 (24.3 ± 5.7%) and day 15 (47.3 ± 7.5%), and the proportion of gram-negative organisms increased from day 7 (24.3 ± 6.1) to day 15 (46.9 ± 6.8). The predominant bacteria included, on day 7: Streptococcus and Bacteroides species; on day 15: species of Streptococcus, Bacieroides, Prevotclla, Neisseria and Peptostreptococcus. Streptococcus oralis, Streptococcus mitis, Streptococcus rattus, Bacteroides pneumosinles and Bacteroides ureolyticus were frequently isolated at both points. Although approximately the same mean number of different species (∼3.5) was isolated per tooth on both day 7 and 15, the overall diversity of the isolates increased on day 15. These results demonstrate that the root canal microbiota becomes increasingly gram-negative and anaerobic with the emergence of Peptostreptococcus, Bacteroides, Prevotella and Neisseria during the period of rapid lesion expansion in this model.     

Effects and interactions of tumour necrosis factor α and bradykinin on interleukin-1 production in gingival fibroblasts

Effects of and interactions between tumour necrosis factor α (TNFα) and bradykinin (BK) on production of interleukin-1 (IL-lα, IL-lβ) in human gingival fibroblasts were studied. The cytokine TNFα induced production of cell-associated IL-lα and IL-1β in gingival fibroblasts, with IL-lβ being most abundant. Addition of BK, in the presence of TNFα, for 1 h and 6 h, respectively, synergistically enhanced the TNFα induced IL-lβ production, whereas BK alone did not induce 1L-1 production. Similar to BK, two phorbol esters, phorbol 12,13 dibutyrate (PDBu) and phorbol 12-myristate-13-acetate (PMA) which are known to stimulate protein kinase C (PKC), synergistically enhanced the TNFα induced IL-lβ production in the gingival fibroblasts. On the contrary, a phorbol ester which does not activate protein kinase C, 13-phorbolacetate (13-PA), did not potentiate the TNFα induced IL-lβ production. Similar to BK, the phorbol esters (PMA, PDBu, 13-PA) alone did not induce IL-1β production in the gingival fibroblasts. The results indicate that TNFα induces production of cell-associated IL-1 in gingival fibroblasts, which can be upregulated by a PKC dependent pathway.     

Localization of substance P-induced upregulated interleukin-8 expression in human dental pulp explants

AIM: To localize ex vivo expression of interleukin-8 (IL-8) induced by substance P (SP) in human dental pulps. METHODOLOGY: Intact caries-free, freshly extracted third molars (n = 20) were collected from patients (15-25 years old). The teeth were split and pulpal tissue was obtained and stored in Dulbecco's modified Eagle medium. Human dental pulp tissue explants were stimulated with SP. Expression of IL-8 in pulp explants was detected and localized by immunohistochemistry. RESULTS: Moderated IL-8 immunoreactivities were detected mainly in the cell-rich zone in pulp tissues 12 h after tumour necrosis factor alpha (TNF-alpha) stimulation (positive controls), whereas only weak IL-8 expression was observed in tissues stimulated with SP at the same time interval. These data did not differ from those in negative controls. Increased IL-8 expression in pulp explants after 24 h of SP stimulation was noted compared with negative controls and located in fibroblast-like cells, blood vessel-associated cells and extracellular matrix in the central zone and cell-rich zone of pulp explants. Tissues stimulated with TNF-alpha for 24 h (positive controls) revealed weak IL-8 immunoreactivities with altered cell morphology. CONCLUSIONS: Substance P induces IL-8 expression and was located in fibroblast-like pulp cells, blood vessel-associated cells and extracellular matrix of human dental explants. These data support the hypothesis that neuropeptide (SP) coordinates the modulation of pulpal inflammation via up-regulating chemokine IL-8.     

Correlation between clinical and histopathological diagnoses in periapical inflammatory lesions

Aim: The purpose of the present study was to evaluate the correlation between clinical and histopathological diagnoses of periapical inflammatory lesions, focusing mainly on cystic conditions. Methods: Files dating from 1998 to 2006 at the Oral Pathology Laboratory, School of Dentistry, Alfenas Federal University, Brazil, were reviewed to identify cases with histopathological diagnoses of periapical inflammatory lesions. A total of 1788 files were analyzed, and 255 cases were identified with clinical diagnoses of periapical inflammatory lesions. Results: The most prevalent clinical diagnosis was apical periodontal cyst (59%), followed by periapical granuloma (20%), and dentoalveolar abscess (2%). After histopathological analysis, 53% of the cases represented apical periodontal cyst, 42% periapical granuloma, and 5% dentoalveolar abscess. Conclusions: The outcomes of the present study show a high prevalence of periapical cysts among periapical inflammatory lesions. Moreover, this study highlights the importance of histopathological evaluation for the correct diagnosis of periapical inflammatory lesions.     

Characterization of lymphocyte subpopulations in periapical lesions by flow cytometry

The mechanisms by which the bacterial root-canal infection leads to periapical bone destruction (cysts or granulomas) are not yet well understood. Previous works have shown elements of an active immune response in the lesions. In the present study, flow cytometry was used to improve the characterization of immune cells. Semiquantitative immunohistochemical analysis showed the presence of plasma cells, macrophages and B and T cells. The simultaneous use of several antibodies in flow cytometry allowed a more precise phenotype of the lymphocytes. The cysts displayed an abundance of B lymphocytes at the same time as a relative scarcity of CD8+ cells. CD4+ lymphocytes were the dominant lymphocyte population in most cases. A small number of gamma delta T lymphocytes and natural killer cells was found. These preliminary results show that flow cytometry may be used to characterize immune cells from inflamed tissue and opens the possibility for further functional studies.     

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提要：糖尿病是一种内分泌-代谢类疾病,其发病率在我国逐渐增高,发病年龄也渐趋向年轻化,已成为严重的社会公共卫生问题。另外,糖尿病还是一种全身性疾病,其对口腔疾病也有明显的影响。本文就糖尿病与牙髓病及根尖周病的关系进行综述,以期对今后的相关研究有所帮助。     

Immnohistochemical examination on the localization of macrophages and plasma cells in induced rat periapical lesions

Abstract – To investigate the role of plasma cells and macro-phages in the development of periapical lesions, we immunohistochemically examined the distribution of these inflammatory cells in experimental induced rat periapical lesions after pulpectomy. The number of EDI-positive mononuclear cells increased rapidly, reached a plateau which remained stable between days 10 and 60, and subsequently decreased. Immunoglobulin (Ig)-bearing plasma cells appeared alter 60 days, and, of these, IgG-bearing plasma cells were predominant after 90 days. The radio-graphic and histopathological findings indicated the develop-ment of bone destruction at 10 days which continued until 60 days; tissue repair began to take place after 90 days. The results suggested that macrophages had a close relation to bone destruc-tion and that plasma cells might participate in tissue repair rather than the development of periapical lesions.