Differential patterns of receptor activator of nuclear factor kappa B ligand/osteoprotegerin expression in human periapical granulomas: possible association with progressive or stable nature of the lesions

Receptor activator of nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG) are expressed in apical periodontitis, suggesting a role for these molecules during lesion development. However, the profiles of RANKL/OPG expression in periapical lesions remain unknown. In this study we investigated the patterns of RANKL and OPG mRNA expression by real-time polymerase chain reaction in human periapical granulomas (N = 44) and compared them with sites presenting characteristic bone resorbing activity: healthy (n = 14) and orthodontically stretched and compressed periodontal ligament (n = 26), healthy gingiva (n = 24), chronic gingivitis (n = 32), and chronic periodontitis (n = 34) samples. Both RANKL and OPG mRNA expression was higher in periapical granulomas when compared with healthy periodontal ligament. Distinct patterns of RANKL and OPG expression ratio were found in the granulomas and in different physiologic and pathologic conditions, with characteristic bone resorption activity potentially being indicative of the stable or progressive nature of the lesions. Lesions with radiographic image smaller than 5 mm showed higher RANKL/OPG expression than images greater than 5 mm. Periapical granulomas presented heterogeneous patterns of RANKL and OPG expression, ranging from samples with RANKL/OPG ratio similar to that seen in sites with minimal or absent bone resorption to samples with RANKL/OPG expression pattern comparable with active bone resorption sites.     

破骨细胞核因子κB受体活化因子配体和骨保护素在根尖周囊肿和肉芽肿中的表达及意义

目的检测破骨细胞核因子κB受体活化因子配体（RANKL）和骨保护素（OPG）在根尖周囊肿及根尖周肉芽肿中的表达水平,探讨RANKL和OPG在不同根尖周疾病周围骨质破坏机制中的作用。方法收集根尖周囊肿组织20例为囊肿组,根尖周肉芽肿组织20例为肉芽肿组,正常牙的牙周膜组织20例为对照组。采用免疫组织化学法检测RANKL和OPG在根尖周囊肿、根尖周肉芽肿和正常牙周膜组织中的阳性表达。结果在囊肿组、肉芽肿组、对照组中,RANKL的表达分别为75.00±7.54、68.40±6.74和29.40±2.46,OPG的表达分别为38.10±7.09、47.65±13.85和58.60±5.88,3组间的差异均有统计学意义（P<0.01）。相关性分析表明,囊肿组中RANKL与OPG呈负相关关系（r=-0.56,P=0.01）,肉芽肿组和对照组中RANKL和OPG无相关关系（P>0.05）。结论RANKL与OPG参与了根尖周病变引起的骨吸收过程。在根尖周病变中,RANKL和OPG的表达失调,RANKL增加而OPG减少,骨吸收活跃,导致溶骨性病变。根尖周囊肿的骨吸收活动较根尖周肉芽肿更活跃。     

Involvement of substance P, mast cells, TNF-α and ICAM-1 in the infiltration of inflammatory cells in human periapical granulomas

BACKGROUND: Substance P (SP), a potent proinflammatory peptide present in sensory neurons, is believed to be a major mediator of neurogenic inflammation. The aim of this study was to examine the localization and involvement of SP, mast cells and tumor necrosis factor-alpha (TNF-alpha)-positive cells in human periapical granulomas. METHODS: Sections from seven periapical granulomas were stained using a variety of immunohistochemical methods. RESULTS: SP-immunoreactive nerve fibers, mast cells and TNF-alpha-positive cells were found localized in the vicinity of blood vessels in all the samples of periapical granulomas. The vascular endothelial cells stained positively for E-selectin and intercellular adhesion molecule-1. SP, TNF-alpha-positive cells and E-selectin could not be detected in clinically healthy periodontal ligament, and served as a negative control. CONCLUSION: Our findings suggest that SP, mast cells, TNF-alpha-positive cells and E-selectin may modulate the pathogenesis of apical periodontitis and may be responsible for stimulating the formation of granuloma with the resorption of periapical bone.     

RANKL/OPG比值变化在根尖肉芽肿骨质破坏中的意义

目的 检测核因子kappa B受体活化因子配体（RANKL）和骨保护素（OPG）的蛋白表达,探讨RANKL/OPG比值在根尖肉芽肿骨质破坏中的意义.方法 采用免疫组织化学技术检测30例慢性根尖肉芽肿和10例健康牙周膜组织中RANKL和OPG的表达.分析RANKL/OPG比值与炎症浸润、骨质破坏及临床症状之间的关系.结果 与正常对照组相比,根尖肉芽肿病损组织中的RANKL蛋白表达和RANKL/OPG比值显著升高（P＜0.05）.RANKL和OPG的蛋白表达无相关性（P＞0.05）.与小病损相比,RANKL/OPG比值在大病损中显著升高（P＜0.05）.RANKL/OPG比值与病损炎症浸润程度和有无临床症状均无关（P＞0.05）.结论 RANKL/OPG比值与根尖肉芽肿的病损大小密切相关,提示RANKL和OPG在根尖肉芽肿骨质破坏进程中发挥重要作用.     

白细胞介素-21和核因子κB受体活化因子配体在人根尖囊肿和肉芽肿中的表达及临床意义

目的 检测白细胞介素-21（IL-21）和破骨细胞核因子κB受体活化因子配体（RANKL）在根尖囊肿和根尖肉芽肿中的表达,分析两者在根尖周病中的关系,探讨IL-21在根尖周炎发病机制中的作用。方法 收集根尖囊肿23例和根尖肉芽肿32例作为实验组,记录相关病例的病损大小及有无叩痛表现;10例健康牙龈组织为对照组。利用免疫组织化学法检测所有样本中IL-21和RANKL蛋白的表达水平,分析IL-21的表达水平与RANKL表达、根尖病灶大小及叩痛的相关性。结果 所有病变组织均可检测到IL-21阳性细胞,而健康牙龈组织则未检测到IL-21的表达。根尖囊肿和肉芽肿中IL-21的表达强度分别为59.92±6.57和36.80±6.81,RANKL的表达强度分别为68.81±18.59和36.12±14.87。根尖囊肿组两种蛋白的表达水平均高于肉芽肿组（P<0.05）。相关性分析表明,IL-21的表达水平与RANKL及根尖病灶大小均呈正相关关系（P<0.05）。结论 IL-21存在于人慢性根尖周炎病损组织中,其表达水平与RANKL的表达量及病损大小呈正相关关系;IL-21可能通过促进RANKL蛋白的表达参与慢性根尖周炎的发病机制。     

Expression and immunohistochemical localization of leptin in human periapical granulomas

Background

Leptin, initially described as an adipocyte-derived hormone to regulate weight control, is expressed in normal and inflamed human dental pulp, being up-regulated during pulp experimental inflammation. Leptin receptor (LER) has been identified in human periapical granulomas. The aim of this study was to analyze and characterize the expression of leptin in human periapical granulomas.

Material and Methods

Fifteen periapical inflammatory lesions were obtained from extracted human teeth and teeth which underwent periapical surgery. After their morphological categorization as periapical granulomas and gradation of the inflammatory infiltrate, they were examined by immunohistochemistry using human leptin policlonal antibodies. Leptin mRNA expression was also determined by quantitative real-time PCR (qRT-PCR) and the amount of leptin protein was analyzed by immunoblot.

Results

All periapical lesions exhibited the characteristic of chronic granulomatous inflammatory process with inflammatory infiltrate grade III. Leptin+ cells were detected in 13 periapical granulomas (86.6%). The median number of Leptin+ cells in periapical granulomas was 1.70 (0.00-7.4). Amongst the inflammatory cells in the periapical granulomas, only macrophages were reactive to leptin antibodies. Western blot analysis revealed the presence in all samples of a protein with apparent molecular weight of approximately 16 kDa, corresponding to the estimated molecular weights of leptin. The expression of leptin mRNA was confirmed by qRT-PCR analysis and the size of the amplified fragment (296 bp for leptin and 194 bp for cyclophilin) was assessed by agarose gel electrophoresis.

Conclusions

For the first time, it has been demonstrated that human periapical granuloma expresses the adipokine leptin. Key words: Apical granuloma, dental pulp, endodontics, leptin, leptin receptor, immune system, immunohistochemistry, periapical inflammatory response.     

核因子кB受体激动子配体在慢性根尖周炎病损组织中的表达

目的:探讨核因子кB受体激动子配体(receptor activator of nuclear factorκB ligand,RANKL)在慢性根尖周炎发病中的作用。方法:采用RT-PCR法,从mRNA水平检测RANKL在10例慢性根尖肉芽肿及3例根尖囊肿中的表达,分析RANKLmRNA的表达与慢性根尖周炎病损的病理学表现(包括病损的病理分型、炎症细胞浸润程度)之间的关系,采用免疫组化的方法,对RANKL的表达进行细胞定位。结果:RANKLmRNA在根尖肉芽肿病损组和根尖囊肿组明显增高,但根尖肉芽肿和根尖囊肿组之间差异无显著性。RANKL mRNA在轻、重度炎症细胞浸润组较中度炎症细胞浸润组明显增高(P<0.05)。RANKL mRNA水平与病损大小无关。免疫组化结果显示,RANKL主要表达于浸润的炎症细胞中及增生的上皮细胞中。结论:RANKL在慢性根尖周炎的发病中具有重要的作用,但也提示存在其它细胞因子的协同作用。     

Interferon-γ-producing cells and inducible nitric oxide synthase-producing cells in periapical granulomas

Periapical granulomas contain a large number of T lymphocytes and monocytes/macrophages and a small number of B lymphocytes and polymorphonuclear leukocytes. Sections from eight periapical granulomas were stained by a variety of immunohistochemical methods. The vascular endothelial cells stained positively for intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. Helper T cells were identified by immunostaining for CD4 and stained positively for interferon-γ (IFN-γ). However, CD4-positive T cells did not stain for interleukin-4 (IL-4). Monocytes/macrophages were identified by immunostaining for CD68 and stained positively for IL-lγ or inducible nitric oxide synthase (iNOS). IL-1β could not be detected in the same samples. No cytokine expression was observed in B cells identified by immunostaining for CD20. IFN-γ-and iNOS-positive cells could not be detected in clinically healthy periodontal ligament being used as a negative control. These results suggest that the IFN-γ-producing T cells and iNOS-positive cells may modulate the progress of disease in local inflammation sites such as in periapical granulomas.     

The role of iNOS and PHOX in periapical bone resorption

Nitric oxide (NO) and reactive oxygen species (ROS) are key molecules in resistance to pathogens. Little is known about their role in pathogenesis of periapical lesions. To address this issue, we induced periapical lesions in mice lacking nitric oxide synthase (iNOS(-/-)) or phagocyte oxidase (PHOX(-/-)). iNOS(-/-) mice expressed higher levels of IL-1β, TNF-α, RANK, RANKL, and MCP-1 than C57BL/6 and PHOX(-/-). Apical thickening of the periodontal ligament was also greater in iNOS(-/-) compared with other groups. Interestingly, ROS production did not interfere in periapical lesion progression, but seemed to be essential for the appearance of multinucleated TRAP-positive cells. Thus, periapical lesion progression in iNOS(-/-) was associated with an imbalance of pro-inflammatory cytokines (IL-1β and TNF-α), bone-resorptive modulators (RANK and RANKL), and MCP-1. We conclude that NO, but not ROS, controls progression of bone resorption in a murine experimental model of apical periodontitis.     

Macrophages in periapical lesions

Abstract – Macrophages are major constituents of periapical granulomas. They have a central protective role in both innate immunity and adoptive, antigen‐specific immune response. Macrophage activation may occur in periapical granulomas by cytokines produced by antigen‐activated T‐lymphocytes; by bacterial endotoxin, as part of the innate immunity; or by both these processes. Recent studies in athymic animals have shown that periapical granulomas may develop independently of T‐lymphocytes. This observation reveals the major role that the activated macrophage may have in the formation of periapical lesions. Only a few of the macrophages in the periapical granuloma are activated. Current studies indicate that these activated cells are the source of the bone‐resorbing cytokines in the periapical granuloma. Understanding the central role of the activated macrophage in the formation as well as the perpetuation of periapical lesions may lead to the development of new diagnostic and therapeutic tools in endodontics.     

IL-1β对人牙周膜成纤维细胞OPG、RANKL mRNA表达的影响

目的:以体外培养的人牙周膜成纤维细胞(HPDLF)为研究对象,观察不同浓度的白细胞介素-1β(IL-1β)对人牙周膜成纤维细胞(HPDLF)中骨保护素(OPG)、核因子κB受体活化剂配体(RANKL)mR-NA表达的影响。方法:组织块法体外原代培养HPDLF并鉴定,以第5代HPDLF作为实验靶细胞,分别用不同浓度(0、0.01、0.1、1、10、100 ng/mL)的IL-1β进行干预,半定量逆转录聚合酶链反应(RT-PCR)检测HPDLF中OPG、RANKL mRNA的表达。结果:IL-1β在0.01～10 ng/mL浓度范围内能明显上调HPDLF中OPG mRNA的表达(P<0.05),并在0.1 ng/mL时上调作用达到最大(P<0.05)。此后,随着IL-1β浓度的增加,OPG mRNA的表达量逐渐减少。IL-1β在0.01～100 ng/mL浓度范围内均可明显上调HPDLF中RANKL、RANKL/OPGmRNA的表达(P<0.05),且呈剂量依赖性,即随着IL-1β浓度增加,HPDLF中RANKL、RANKL/OPG mRNA的表达也逐渐增加,各浓度组两两比较除10 ng/mL与100 ng/mL相比无显著性差异外,其余各组间差异均有统计学意义(P<0.05)。结论:IL-1β可促进HPDLF中RANKL mRNA的表达,上调RANKL/OPG mRNA的比值。     

高迁移率族蛋白B1对牙周膜成纤维细胞表达细胞因子影响的研究

目的观察高迁移率族蛋白B1（HMGB1）对人牙周膜成纤维细胞表达白细胞介素-6（IL-6）、破骨细胞核因子κB受体活化因子（RANKL）、骨保护因子（OPG）的影响,初步探讨HMGB1在牙周疾病的作用。方法采用原代组织块培养法,培养人牙周膜成纤维细胞,用第4~6代的细胞进行实验。分别用10、30、100 ng·mL-1质量浓度的HMGB1孵育牙周膜成纤维细胞24 h后,RT-PCR检测IL-6、RANKL、OPG的mRNA表达;Western blot法检测RANKL、OPG的蛋白表达。均以0 ng·mL-1质量浓度组为对照,所得数据用单因素方差分析处理。结果HMGB1在10、30、100 ng·mL-1质量浓度时,细胞中的RANKL/OPG mRNA的比值增高（P<0.05）,100 ng·mL-1质量浓度时细胞中的IL-6 mRNA的表达量增高（P<0.05）。Western blot检测结果显示10 ng·mL-1质量浓度组的RANKL/OPG的比值有明显增高。结论一定浓度的HMGB1可使牙周膜细胞中的RANKL/OPG比值增高,还会诱导炎症因子IL-6 mRNA表达上调。提示HMGB1可能会在牙周炎的发病以及炎症进展中发挥作用。     

Macrophages in periapical lesions

Macrophages are major constituents of periapical granulomas. They have a central protective role in both innate immunity and adoptive, antigen-specific immune response. Macrophage activation may occur in periapical granulomas by cytokines produced by antigen-activated T-lymphocytes; by bacterial endotoxin, as part of the innate immunity; or by both these processes. Recent studies in athymic animals have shown that periapical granulomas may develop independently of T-lymphocytes. This observation reveals the major role that the activated macrophage may have in the formation of periapical lesions. Only a few of the macrophages in the periapical granuloma are activated. Current studies indicate that these activated cells are the source of the bone-resorbing cytokines in the periapical granuloma. Understanding the central role of the activated macrophage in the formation as well as the perpetuation of periapical lesions may lead to the development of new diagnostic and therapeutic tools in endodontics.