Specialized pro-resolving lipid mediators in endodontics: a narrative review

Resolution of inflammation in oral diseases

The resolution of inflammation is an essential endogenous process that protects host tissues from an exaggerated chronic inflammatory response. Multiple interactions between host cells and resident oral microbiome regulate the protective functions that lead to inflammation in the oral cavity. Failure of appropriate regulation of inflammation can lead to chronic inflammatory diseases that result from an imbalance between pro-inflammatory and pro-resolution mediators. Thus, failure of the host to resolve inflammation can be considered an essential pathological mechanism for progression from the late stages of acute inflammation to a chronic inflammatory response. Specialized pro-resolving mediators (SPMs), which are essential polyunsaturated fatty acid (PUFA)-derived autacoid mediators, aid in regulating the endogenous inflammation resolving process by stimulating immune cell-mediated clearance of apoptotic polymorphonuclear neutrophils, cellular debris, and microbes, restricting further neutrophil tissue infiltration, and counter-regulating pro-inflammatory cytokine production. The SPM superfamily contains four specialized lipid mediator families: lipoxins, resolvins, protectins, and maresins that can activate resolution pathways. Understanding the crosstalk between resolution signals in the tissue response to injury has therapeutic application potential for preventing, maintaining, and regenerating chronically damaged tissues. Here, we discuss the fundamental concepts of resolution as an active biochemical process, novel concepts demonstrating the role of resolution mediators in tissue regeneration in periodontal and pulpal diseases, and future directions for therapeutic applications with particular emphasis on periodontal therapy.

Recent Advances in Apical Periodontitis Treatment: A Narrative Review

Apical periodontitis is an inflammatory response caused by pulp infection. It induces bone resorption in the apical and periapical regions of the tooth. The most conservative approach to treat this condition is nonsurgical endodontic treatment. However, clinical failure has been reported with this approach; thus, alternative procedures are required. This review highlights recent literature regarding advanced approaches for the treatment of apical periodontitis. Various therapies, including biological medications, antioxidants, specialized pro-resolving lipid mediators, and stem cell therapy, have been tested to increase the success rate of treatment for apical periodontitis. Some of these approaches remain in the in vivo phase of research, while others have just entered the translational research phase to validate clinical application. However, a detailed understanding of the molecular mechanisms that occur during development of the immunoinflammatory reaction in apical periodontitis remains unclear. The aim of this review was to summarize advanced approaches for the treatment of apical periodontitis. Further research can confirm the potential of these alternative nonsurgical endodontic treatment approaches.

Wnt4 prevents apoptosis and inflammation of dental pulp cells induced by LPS by inhibiting the IKK/NF‑κB pathway

Wnt4 has been shown to promote the recovery of odontogenic differentiation of dental pulp stem cells under inflammatory conditions, but its role in inflammation and apoptosis of pulpitis remains to be elucidated. Lipopolysaccharide (LPS) (10 µg/ml) was applied to treat the human dental pulp cells (HDPCs) for 24 h. Western blotting measured the expressions of inflammatory cytokines and apoptosis-related proteins. Cell apoptosis was measured by flow cytometry. The level of Wnt4 was evaluated by reverse transcription-quantitative PCR and western blotting. The results indicated that LPS could promote inflammatory response and apoptosis in HDPCs and downregulated Wnt4 expression was found in LPS-HDPCs. Overexpression of Wnt4 ameliorated cell inflammatory response and apoptosis, presented by reduced expressions of IL-8, IL-6, TNF-α, IL-1β, Bax, cleaved-caspase 3 and enhanced Bcl-2 expression as well as decreased apoptosis rate. Moreover, overexpression of Wnt4 reduced the phosphorylation levels of IKK2, IκBα and p65 proteins upregulated by LPS. Finally, overexpression of IKK2 reversed the effects of Wnt4 on inflammation and apoptosis of LPS-HDPCs and NF-κB inhibitor reversed the effect of IKK2 overexpression in LPS-HDPCs. Wnt4 inhibited LPS-triggered inflammation and apoptosis in HDPCs via regulating the IKK/NF-κB signaling pathway, which provided a new viewpoint for understanding the pathological mechanism of pulpitis.

Lipoxins in inflammation

Lipoxins and ATL appear to be the first recognized members of a new class of endogenous mediator that are anti-inflammatory or serve for the "pro-resolution" of inflammation. PGE2 can and may display anti-inflammatory properties in certain settings, but in most cases, it enhances inflammation in vivo. This is likely the result of numerous receptor isoforms and differential coupled mechanisms for PGE2 and its diverse role in human physiology. Since the integrated response of the host is essential to health and disease, it is important to achieve a more complete understanding of the molecular and cellular events governing the formation and actions of endogenous mediators of resolution that appear to control the magnitude and duration of inflammation. In view of the present body of evidence, it is not surprising that a protective action for inhibition of COX-2 was found in cardiovascular disease. Characterizing useful experimental systems with clinically relevant endpoints will also take a multidisciplinary approach and require a shift in our current thinking about inflammation and the role of lipid mediators.

Analysis of circRNAs profile in TNF-α treated DPSC

Background

Pulpitis often are characterized as sustained inflammation and impaired pulp self-repair. Circular RNAs (circRNAs) have been reported to be involved in the development of inflammation, but their influence in pulpitis is still unidentified, which was examined in our research.

Methods

In this study, TNF-α (20 ng/mL) was used to treat DPSCs, then MTS identified cell proliferation. The circRNAs profile in DPSCs with or without TNF-α treatment was evaluated using RNA sequencing and subsequently by bioinformatics analysis. After that, the circular structure was assessed using agarose gel electrophoresis, followed by Sanger sequencing. And the circRNAs expression was ratified using quantitative real-time polymerase chain reaction in cell and tissues samples. Additionally, the plausible mechanism of circRNAs was envisaged, and the circRNA-miRNA-mRNA linkage was plotted using Cytoscape.

Results

The treatment of TNF-α inhibited cell proliferation capabilities in DPSCs, which also made 1195 circRNA expressions undergo significant alterations. Among these changes, 11 circRNAs associated with inflammation were chosen for circular structure verification, and only seven circRNAs (hsa_circ_0001658, hsa_circ_0001978, hsa_circ_0003910, hsa_circ_0004314, hsa_circ_0004417, hsa_circ_0035915, and hsa_circ_0002545) had circular structure. Additionally, five circRNAs expressions (hsa_circ_0001978, hsa_circ_0003910, hsa_circ_0004314, hsa_circ_0004417, and hsa_circ_0035915) had significantly altered between with or without TNF-α treated DPSCs. Furthermore, hsa_circ_0001978 and hsa_circ_0004417 were increased in patients suffering from pulpitis. Furthermore, their ceRNA linkage and Kyoto Encyclopedia of Genes and Genomes analysis suggested that these two circRNAs may participate in the inflammation development of pulpitis via mitogen-activated protein kinase and the Wnt signaling pathway.

Conclusion

This study revealed that the circRNAs profile was altered in TNF-α treated DPSCs. Also, hsa_circ_0001978 and hsa_circ_0004417 may be involved in the inflammation progress of pulpitis. These outcomes provided the latest information for additional research on pulpitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02267-2.

Local Drug Delivery Systems for Vital Pulp Therapy: A New Hope

Vital pulp therapy (VPT) is deliberated as an ultraconservative/minimally invasive approach for the conservation of vital pulpal tissues, preservation of dental structure, and maintenance of tooth function in the oral cavity. In VPT, following the exposure of the dental pulp, the environment is prepared for the possible healing and probable refunctionalisation of pulpal connective tissue. However, to succeed in VPT, specific biomaterials are used to cover and/or dress the exposed pulp, lower the inflammation, heal the dental pulp, provoke the remaining odontoblastic cells, and induce the formation of a hard tissue, i.e., the dentinal bridge. It can be assumed that if the employed biomaterial is transferred to the target site using a specially designed micro-/nanosized local drug delivery system (LDDS), the biomaterial would be placed in closer proximity to the connective tissue, may be released in a controlled and sustained pattern, could properly conserve the remaining dental pulp and might appropriately enhance hard-tissue formation. Furthermore, the loaded LDDS could help VPT modalities to be more ultraconservative and may minimise the manipulation of the tooth structure as well as pulpal tissue, which could, in turn, result in better VPT outcomes.