Bacteria associated with apical periodontitis promotes in vitro the differentiation of macrophages to osteoclasts

Impact of Wine Polyphenols on the Inflammatory Profile of Induced Apical Periodontitis in Rats

INTRODUCTION

This study evaluated the impact of dealcoholized red wine polyphenols on the inflammation and lesion volume associated with apical periodontitis (AP) in rats.

METHODS

Thirty-two Wistar rats receiving AP induction were arranged as follows: Control Group, Dealcoholized Red Wine Group (DRW), Red Wine Group, and Alcohol Group (ALC). Solutions were administered daily in a volume of 4.28 mL/kg via gavage for 45 days. Mandibles and maxillae were removed for histologic, immunohistochemical (IL-1β, IL-10, tumor necrosis factor-alpha, receptor activator of nuclear factor κB ligand, osteoprotegerin [OPG], and tartrate-resistant acid phosphatase), and micro-computed tomography analyses of the AP site. A statistical analysis was performed with a significance level of 5%.

RESULTS

Inflammation and TRAP-positive cell count were similar for DRW and Red Wine Group, but lower when compared to Control Group and ALC (P < .001). The immunohistochemical expression of OPG was higher for DRW than for ALC (P < .05). A larger lesion volume was observed in ALC compared to other groups (P < .001).

CONCLUSIONS

Prophylactic administration of dealcoholized red wine significantly reduced inflammation, decreased the number of TRAP-positive cells, enhanced OPG expression, and reduced lesion volume compared to water and alcohol solutions.

Metabolic syndrome and its effect on immune cells in apical periodontitis- a narrative review

OBJECTIVES

Apical periodontitis (AP) is an inflammatory immune response in periapical tissues caused by microbial infections. Failure of root canal treatment or delayed healing is often due to intracanal or extra-radicular bacteria. However, beyond microbial factors, the patient's systemic health can significantly influence the progression and healing of AP. Metabolic syndrome is a risk factor and it is characterized by a cluster of interconnected metabolic risk factors, including abdominal obesity, hyperlipidemia, hypertension, and hyperglycemia.

MATERIALS AND METHODS

A comprehensive literature review was conducted on apical periodontitis and metabolic syndrome, and their impact on the roles of different immune cell populations.

RESULTS

Both AP and metabolic syndrome are inflammatory diseases that involve complex and interwoven immune responses. The affected immune cells are categorized into the innate (neutrophils, macrophages, and dendritic cells) and adaptive immune systems (T cells and B cells).

CONCLUSIONS

Metabolic diseases and AP are closely correlated, possibly intertwined in a two-way relationship driven by a shared dysregulated immune response.

CLINICAL RELEVANCE

Understanding the pathophysiology and immune mechanisms underlying the two-way relationship between metabolic syndrome and AP can help improve treatment outcomes and enhance the overall well-being of patients with endodontic disease complicated by metabolic syndrome.

A review of bacterial and osteoclast differentiation in bone infection

Bone infections are characterized by bacterial invasion of the bone microenvironment and subsequent bone structure deterioration. This holds significance because osteoclasts, which are the only cells responsible for bone resorption, are abnormally stimulated during bone infections. Multiple communication factors secreted by bone stromal cells regulate the membrane of osteoclast progenitor cells, thereby maintaining bone homeostasis through the expression of many types of receptors. During infection, the immunoinflammatory response triggered by bacterial invasion and multiple virulence factors of bacterial origin can disrupt osteoclast homeostasis. Therefore, clarifying the pathways through which bacteria affect osteoclasts can offer a theoretical basis for preventing and treating bone infections. This review summarizes studies investigating bone destruction caused by different bacterial infections. In conclusion, bacteria can affect osteoclast metabolic activity through multiple pathways, including direct contact, release of virulence factors, induction of immunoinflammatory responses, influence on bone stromal cell metabolism, and intracellular infections.

Single-cell RNA sequencing combined with proteomics of infected macrophages reveals prothymosin-α as a target for treatment of apical periodontitis

INTRODUCTION

Chronic apical periodontitis (CAP) is a common infectious disease of the oral cavity. Immune responses and osteoclastogenesis of monocytes/macrophages play a crucial role in CAP progression, and this study want to clarify role of monocytes/macrophages in CAP, which will contribute to treatment of CAP.

OBJECTIVES

We aim to explore the heterogeneity of monocyte populations in periapical lesion of CAP tissues and healthy control (HC) periodontal tissues by single-cell RNA sequencing (scRNA-seq), search novel targets for alleviating CAP, and further validate it by proteomics and in vitro and in vivo evaluations.

METHODS

ScRNA-seq was used to analyze the heterogeneity of monocyte populations in CAP, and proteomics of THP-1-derived macrophages with porphyromonas gingivalis infection were intersected with the differentially expressed genes (DEGs) of macrophages between CAP and HC tissues. The upregulated PTMA (prothymosin-α) were validated by immunofluorescence staining and quantitative real time polymerase chain reaction. We evaluated the effect of thymosin α1 (an amino-terminal proteolytic cleavage product of PTMA protein) on inflammatory factors and osteoclast differentiation of macrophages infected by P. gingivalis. Furthermore, we constructed mouse and rat mandibular bone lesions caused by apical periodontitis, and estimated treatment of systemic and topical administration of PTMA for CAP. Statistical analyses were performed using GraphPad Prism software (v9.2) RESULTS: Monocytes were divided into seven sub-clusters comprising monocyte-macrophage-osteoclast (MMO) differentiation in CAP. 14 up-regulated and 21 down-regulated genes and proteins were intersected between the DEGs of scRNA-seq data and proteomics, including the high expression of PTMA. Thymosin α1 may decrease several inflammatory cytokine expressions and osteoclastogenesis of THP-1-derived macrophages. Both systemic administration in mice and topical administration in the pulp chamber of rats alleviated periapical lesions.

CONCLUSIONS

PTMA upregulation in CAP moderates the inflammatory response and prevents the osteoclastogenesis of macrophages, which provides a basis for targeted therapeutic strategies for CAP.

The balance between helper T 17 and regulatory T cells in osteoimmunology and relevant research progress on bone tissue engineering

BACKGROUND

Bone regeneration is a well-regulated dynamic process, of which the prominent role of the immune system on bone homeostasis is more and more revealed by recent research. Before fully activation of the bone remodeling cells, the immune system needs to clean up the microenvironment in facilitating the bone repair initiation. Furthermore, this microenvironment must be maintained properly by various mechanisms over the entire bone regeneration process.

OBJECTIVE

This review aims to summarize the role of the T-helper 17/Regulatory T cell (Th17/Treg) balance in bone cell remodeling and discuss the relevant progress in bone tissue engineering.

RESULTS

The role of the immune response in the early stages of bone regeneration is crucial, especially the impact of the Th17/Treg balance on osteoclasts, mesenchymal stem cells (MSCs), and osteoblasts activity. By virtue of these knowledge advancements, innovative approaches in bone tissue engineering, such as nano-structures, hydrogel, and exosomes, are designed to influence the Th17/Treg balance and thereby augment bone repair and regeneration.

CONCLUSION

Targeting the Th17/Treg balance is a promising innovative strategy for developing new treatments to enhance bone regeneration, thus offering potential breakthroughs in bone injury clinics.

α-IRAK-4 Suppresses the Activation of RANK/RANKL Pathway on Macrophages Exposed to Endodontic Microorganisms

Periapical lesions are common pathologies affecting the alveolar bone, often initiated by intraradicular lesions resulting from microbial exposure to dental pulp. These microorganisms trigger inflammatory and immune responses. When endodontic treatment fails to eliminate the infection, periapical lesions persist, leading to bone loss. The RANK/RANKL/OPG pathway plays a crucial role in both the formation and the destruction of the bone. In this study, the objective was to inhibit the RANK/RANKL pathway in vitro within exposed Thp-1 macrophages to endodontic microorganisms, specifically Enterococcus faecalis, which was isolated from root canals of 20 patients with endodontic secondary/persistent infection, symptomatic and asymptomatic, and utilizing an α-IRAK-4 inhibitor, we introduced endodontic microorganisms and/or lipoteichoic acid from Streptococcus spp. to cellular cultures in a culture plate, containing thp-1 cells and/or PBMC from patients with apical periodontitis. Subsequently, we assessed the percentages of RANK+, RANKL+, and OPG+ cells through flow cytometry and measured the levels of several inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-8, IL-10, and IL-12p70) in the cellular culture supernatant through a CBA kit and performed analysis by flow cytometry. A significant difference was observed in the percentages of RANK+RANKL+, OPG+ RANKL+ cells in thp-1 cells and PBMCs from patients with apical periodontitis. The findings revealed significant differences in the percentages of the evaluated cells, highlighting the novel role of the IRAK-4 inhibitor in addressing this oral pathology, apical periodontitis, where bone destruction is observed.