Maresin-1 and Resolvin E1 Promote Regenerative Properties of Periodontal Ligament Stem Cells Under Inflammatory Conditions

Specialized pro-resolution mediators in the bladder: effects of resolvin E1 on diabetic bladder dysfunction in the type 1 diabetic male Akita mouse model

BACKGROUND

One of the most common, but least studied, diabetic complication is diabetic bladder dysfunction. Current therapies include glucose control and symptom-based interventions. However, efficacy of these therapies is mixed and often have undesirable side effects. Diabetes is now known to be a chronic inflammatory disease. Specialized pro-resolving mediators are a class of compounds that promote the resolution of inflammation and have been shown to be effective in treating chronic inflammatory conditions. In this study we examine the ability of resolvin E1 to improve signs of diabetic bladder dysfunction.

METHODS

Male Akita mice (Type 1 diabetic) develop hyperglycemia at 4 weeks and signs of bladder underactivity by 15 weeks. Starting at 15 weeks, mice were given one or two weeks of daily resolvin E1 and compared to age-matched wild type and untreated Akita mice.

RESULTS

Resolvin E1 did not affect diabetic blood glucose after one week, although there was a slight decrease after two weeks. Diabetes decreased body weight and increased bladder weights and this was not affected by resolvin E1. Evan's blue dye extravasation (an indirect index of inflammation) was dramatically suppressed after one week of resolvin E1 treatment, but, surprisingly, had returned to diabetic levels after two weeks of treatment. Using cystometry, untreated Akita mice showed signs of underactivity (increased void volumes and intercontraction intervals). One week of resolvin E1treatment restored these cystometric findings back to control levels. After two weeks of treatment, cystometric changes were changed from controls but still significantly different from untreated levels, indicating a durable treatment effect even in the presence of increased inflammation at 2 weeks.

CONCLUSIONS

Resolvin E1 has a beneficial effect on diabetic bladder dysfunction in the type 1 diabetic male Akita mouse model.

Impact of Resolvin-E1 and Maresin-1 on Bone Marrow Stem Cell Osteogenesis under Inflammatory Stress

Periodontal disease is characterized by inflammation and bone loss. Central to its pathogenesis is the dysregulated inflammatory response, complicating regenerative therapies. Mesenchymal stem cells (MSCs) hold significant promise in tissue repair and regeneration. This study investigated the effects of specialized pro-resolving mediators (SPMs), Resolvin E1 (RvE1) and Maresin 1 (MaR1), on the osteogenic differentiation of human bone marrow-derived MSCs under inflammatory conditions. The stem cells were treated with SPMs in the presence of lipopolysaccharide (LPS) to simulate an inflammatory environment. Osteogenic differentiation was assessed through alkaline phosphatase activity and alizarin red staining. Proteomic analysis was conducted to characterize the protein expression profile changes, focusing on proteins related to osteogenesis and osteoclastogenesis. Treatment with RvE1 and MaR1, both individually and in combination, significantly enhanced calcified deposit formation. Proteomic analysis revealed the differential expression of proteins associated with osteogenesis and osteoclastogenesis, highlighting the modulatory impact of SPMs on bone metabolism. RvE1 and MaR1 promote osteogenic differentiation of hBMMSCs in an inflammatory environment, with their combined application yielding synergistic effects. This study provides insights into the therapeutic potential of SPMs in enhancing bone regeneration, suggesting a promising avenue for developing regenerative therapies for periodontal disease and other conditions characterized by inflammation-induced bone loss.

Fusobacterium nucleatum triggers senescence phenotype in gingival epithelial cells

The prevalence of periodontitis increases with physiological aging. However, whether bacteria associated with periodontal diseases foster aging and the mechanisms by which they may do so are unknown. Herein, we hypothesize that Fusobacterium nucleatum, a microorganism associated with periodontitis and several other age-related disorders, triggers senescence, a chief hallmark of aging responsible to reduce tissue repair capacity. Our study analyzed the senescence response of gingival epithelial cells and their reparative capacity upon long-term exposure to F. nucleatum. Specifically, we assessed (a) cell cycle arrest by analyzing the cyclin-dependent kinase inhibitors p16INK4a and p14ARF and their downstream cascade (pRb, p53, and p21) at both gene and protein levels, (b) lysosomal mediated dysfunction by using assays targeting the expression and activity of the senescence-associated β-galactosidase (SA-β-Gal) enzyme, and (c) nuclear envelope breakdown by assessing the expression of Lamin-B1. The consequences of the senescence phenotype mediated by F. nucleatum were further assessed using wound healing assays. Our results revealed that prolonged exposure to F. nucleatum promotes an aging-like phenotype as evidenced by the increased expression of pro-senescence markers (p16INK4a , p21, and pRb) and SA-β-Gal activity and reduced expression of the counter-balancing cascade (p14ARF and p53) and Lamin-B1. Furthermore, we also noted impaired wound healing capacity of gingival epithelial cells upon prolong bacterial exposure, which was consistent with the senescence-induced phenotype. Together, our findings provide a proof-of-concept evidence that F. nucleatum triggers a pro-senescence response in gingival epithelial cells. This might affect periodontal tissue homeostasis by reducing its repair capacity and, consequently, increasing susceptibility to periodontitis during aging.

Novel lipid mediator 7S,14R-docosahexaenoic acid: biogenesis and harnessing mesenchymal stem cells to ameliorate diabetic mellitus and retinal pericyte loss

Introduction: Stem cells can be used to treat diabetic mellitus and complications. ω3-docosahexaenoic acid (DHA) derived lipid mediators are inflammation-resolving and protective. This study found novel DHA-derived 7S,14R-dihydroxy-4Z,8E,10Z,12E,16Z,19Z-docosahexaenoic acid (7S,14R-diHDHA), a maresin-1 stereoisomer biosynthesized by leukocytes and related enzymes. Moreover, 7S,14R-diHDHA can enhance mesenchymal stem cell (MSC) functions in the amelioration of diabetic mellitus and retinal pericyte loss in diabetic db/db mice. Methods: MSCs treated with 7S,14R-diHDHA were delivered into db/db mice i.v. every 5 days for 35 days. Results: Blood glucose levels in diabetic mice were lowered by 7S,14R-diHDHA-treated MSCs compared to control and untreated MSC groups, accompanied by improved glucose tolerance and higher blood insulin levels. 7S,14R-diHDHA-treated MSCs increased insulin+ β-cell ratio and decreased glucogan+ α-cell ratio in islets, as well as reduced macrophages in pancreas. 7S,14R-diHDHA induced MSC functions in promoting MIN6 β-cell viability and insulin secretion. 7S,14R-diHDHA induced MSC paracrine functions by increasing the generation of hepatocyte growth factor and vascular endothelial growth factor. Furthermore, 7S,14R-diHDHA enhanced MSC functions to ameliorate diabetes-caused pericyte loss in diabetic retinopathy by increasing their density in retina in db/db mice. Discussion: Our findings provide a novel strategy for improving therapy for diabetes and diabetic retinopathy using 7S,14R-diHDHA-primed MSCs.

Single-Cell Transcriptomic Analysis of Dental Pulp and Periodontal Ligament Stem Cells

The regeneration of periodontal, periapical, and pulpal tissues is a complex process requiring the direct involvement of cells derived from pluripotent stem cells in the periodontal ligament and dental pulp. Dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PDLSCs) are spatially distinct with the potential to differentiate into similar functional and phenotypic cells. We aimed to identify the cell heterogeneity of DPSCs and PDLSCs and explore the differentiation potentials of their specialized organ-specific functions using single-cell transcriptomic analysis. Our results revealed 7 distinct clusters, with cluster 3 showing the highest potential for differentiation. Clusters 0 to 2 displayed features similar to fibroblasts. The trajectory route of the cell state transition from cluster 3 to clusters 0, 1, and 2 indicated the distinct nature of cell differentiation. PDLSCs had a higher proportion of cells (78.6%) at the G1 phase, while DPSCs had a higher proportion of cells at the S and G2/M phases (36.1%), mirroring the lower cell proliferation capacity of PDLSCs than DPSCs. Our study suggested the heterogeneity of stemness across PDLSCs and DPSCs, the similarities of these 2 stem cell compartments to be potentially integrated for regenerative strategies, and the distinct features between them potentially particularized for organ-specific functions of the dental pulp and periodontal ligament for a targeted regenerative dental tissue repair and other regeneration therapies.

RvE1 Promotes Axin2+ Cell Regeneration and Reduces Bacterial Invasion

Vital pulp therapy and root canal therapy (RCT) are the dominant treatment for irreversible pulpitis. While the success rate of these procedures is favorable, they have some limitations. For instance, RCT leads to removing significant dentin in the coronal third of the tooth that increases root-fracture risk, which forces tooth removal. The ideal therapeutic goal is dental pulp regeneration, which is not achievable with RCT. Specialized proresolving mediators (SPMs) are well known for inflammatory resolution. The resolution of inflammation and tissue restoration or regeneration is a dynamic and continuous process. SPMs not only have potent immune-modulating functions but also effectively promote tissue homeostasis and regeneration. Resolvins have been shown to promote dental pulp regeneration. The purpose of this study was to explore further the cellular target of Resolvin E1 (RvE1) therapy in dental pulp regeneration and the impact of RvE1 in infected pulps. We investigated the actions of RvE1 on experimentally exposed pulps with or without microbial infection in an Axin2Cre-Dox;Ai14 genetically defined mouse model. Our results showed RvE1 promoted Axin2-tdTomato+ cell expansion and odontoblastic differentiation after direct pulp capping in the mouse, which we used to mimic reversible pulpitis cases in the clinic. In cultured mouse dental pulp stem cells (mDPSCs), RvE1 facilitated Axin2-tdTomato+ cell proliferation and odontoblastic differentiation and also rescued impaired functions after lipopolysaccharide stimulation. In infected pulps exposed to the oral environment for 24 h, RvE1 suppressed inflammatory infiltration, reduced bacterial invasion in root canals, and prevented the development of apical periodontitis, while its proregenerative impact was limited. Collectively, topical treatment with RvE1 facilitated dental pulp regenerative properties by promoting Axin2-expressing cell proliferation and differentiation. It also modulated the resolution of inflammation, reduced infection severity, and prevented apical periodontitis, presenting RvE1 as a novel therapeutic for treating endodontic diseases.

Characterization of the soft-tissue wall lining residual periodontal pockets and implications in periodontal wound healing

AIM

To characterize the soft-tissue wall of remaining periodontal pockets for wound healing-related parameters versus healthy gingival crevices in the same individuals.

MATERIALS AND METHODS

Gingival tissues collected from the diseased interface of pockets (GT biopsies) and from healthy gingival crevices (G biopsies) were subjected to RT2-profiler PCR Array for wound healing-related markers and network analysis of differentially expressed genes. Lymphangiogenesis-related gene expression was determined by qRT-PCR. The migration potential of mesenchymal stem cells isolated from GT biopsies (GT-MSCs) and G biopsies (G-MSCs) was evaluated by the scratch- and the transwell migration assays. The total collagen protein content was determined in GT-MSCs and G-MSCs homogenates.

RESULTS

Gene-ontology analysis on significantly upregulated genes expressed in GT biopsies revealed enrichment of several genes involved in processes related to matrix remodeling, collagen deposition, and integrin signaling. No significantly expressed genes were seen in G biopsies. Regarding lymphangiogenesis-related genes, GT biopsies demonstrated greater expression for PROX1 than G biopsies (p = 0.05). Lower migration potential (p < 0.001), yet greater production of collagen protein (p = 0.05), was found for GT-MSCs over G-MSCs.

CONCLUSION

Differential expression patterns of various molecular pathways in biopsies and cell cultures of diseased versus healthy gingival tissues indicate a potential of the former for tissue remodeling and repair.

CLINICAL RELEVANCE

In the course of periodontitis, granulation tissue is formed within a periodontal defect in an attempt to reconstruct the site. Following treatment procedures periodontal granulation tissue remains inflamed but appears to retain healing potential.

Roles of specialized pro-resolving mediators and omega-3 polyunsaturated fatty acids in periodontal inflammation and impact on oral microbiota

Periodontitis is a chronic inflammatory disease induced by dysbiotic dental biofilms. Management of periodontitis is primarily anti-bacterial via mechanical removal of bacterial biofilm. The successful resolution requires wound healing and tissue regeneration, which are not always achieved with these traditional methods. The discovery of specialized pro-resolving mediators (SPMs), a class of lipid mediators that induce the resolution of inflammation and promote local tissue homeostasis, creates another option for the treatment of periodontitis and other diseases of chronic inflammation. In this mini-review, we discuss the host-modulatory effects of SPMs on periodontal tissues and changes in the taxonomic composition of the gut and oral microbiome in the presence of SPMs and SPM precursor lipids. Further research into the relationship between host SPM production and microbiome-SPM modification has the potential to unveil new diagnostic markers of inflammation and wound healing. Expanding this field may drive the discovery of microbial-derived bioactive therapeutics to modulate immune responses.

Maresin: Macrophage Mediator for Resolving Inflammation and Bridging Tissue Regeneration-A System-Based Preclinical Systematic Review

Maresins are lipid mediators derived from omega-3 fatty acids with anti-inflammatory and pro-resolving properties, capable of promoting tissue regeneration and potentially serving as a therapeutic agent for chronic inflammatory diseases. The aim of this review was to systematically investigate preclinical and clinical studies on maresin to inform translational research. Two independent reviewers performed comprehensive searches with the term "Maresin (NOT) Review" on PubMed. A total of 137 studies were included and categorized into 11 human organ systems. Data pertinent to clinical translation were specifically extracted, including delivery methods, optimal dose response, and specific functional efficacy. Maresins generally exhibit efficacy in treating inflammatory diseases, attenuating inflammation, protecting organs, and promoting tissue regeneration, mostly in rodent preclinical models. The nervous system has the highest number of original studies (n = 25), followed by the cardiovascular system, digestive system, and respiratory system, each having the second highest number of studies (n = 18) in the field. Most studies considered systemic delivery with an optimal dose response for mouse animal models ranging from 4 to 25 μg/kg or 2 to 200 ng via intraperitoneal or intravenous injection respectively, whereas human in vitro studies ranged between 1 and 10 nM. Although there has been no human interventional clinical trial yet, the levels of MaR1 in human tissue fluid can potentially serve as biomarkers, including salivary samples for predicting the occurrence of cardiovascular diseases and periodontal diseases; plasma and synovial fluid levels of MaR1 can be associated with treatment response and defining pathotypes of rheumatoid arthritis. Maresins exhibit great potency in resolving disease inflammation and bridging tissue regeneration in preclinical models, and future translational development is warranted.

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.

Maresin1: A multifunctional regulator in inflammatory bone diseases

Inflammation plays a crucial role in the physical response to danger signals, the elimination of toxic stimuli, and the restoration of homeostasis. However, dysregulated inflammatory responses lead to tissue damage, and chronic inflammation can disrupt osteogenic-osteoclastic homeostasis, ultimately leading to bone loss. Maresin1 (MaR1), a member of the specialized pro-resolving mediators (SPMs) family, has been found to possess significant anti-inflammatory, anti-allergic, pro-hemolytic, pro-healing, and pain-relieving properties. MaR1 is synthesized by macrophages (Mφs) and omega-3 fatty acids, and it may have the potential to promote bone homeostasis and treat inflammatory bone diseases. MaR1 has been found to stimulate osteoblast proliferation through leucine-rich repeat G protein-coupled receptor 6 (LGR6). It also activates Mφ phagocytosis and M2-type polarization, which helps to control the immune system. MaR1 can regulate T cells to exert anti-inflammatory effects and inhibit neutrophil infiltration and recruitment. In addition, MaR1 is involved in antioxidant signaling, including nuclear factor erythroid 2-related factor 2 (NRF2). It has also been found to promote the autophagic behavior of periodontal ligament stem cells, stimulate Mφs against pathogenic bacteria, and regulate tissue regeneration and repair. In summary, this review provides new information and a comprehensive overview of the critical roles of MaR1 in inflammatory bone diseases, indicating its potential as a therapeutic approach for managing skeletal metabolism and inflammatory bone diseases.

Mediterranean diet component oleic acid increases protective lipid mediators and improves trabecular bone in a Porphyromonas gingivalis inoculation model

AIM

Therapeutic modulation of bacterial-induced inflammatory host response is being investigated in gingival inflammation and periodontal disease pathology. Therefore, dietary intake of the monounsaturated fatty acid (FA) oleic acid (OA (C18:1)), which is the main component of Mediterranean-style diets, and saturated FA palmitic acid (PA (C16:0)), which is a component of Western-style diets, was investigated for their modifying potential in an oral inoculation model of Porphyromonas gingivalis.

MATERIALS AND METHODS

Normal-weight C57BL/6-mice received OA- or PA-enriched diets (PA-ED, OA-ED, PA/OA-ED) or normal standard diet for 16 weeks and were inoculated with P. gingivalis/placebo (n = 12/group). Gingival inflammation, alveolar bone structure, circulating lipid mediators, and in vitro cellular response were determined.

RESULTS

FA treatment of P. gingivalis-lipopolysaccharide-incubated gingival fibroblasts (GFbs) modified inflammatory activation, which only PA exacerbated with concomitant TNF-α stimulation. Mice exhibited no signs of acute inflammation in gingiva or serum and no inoculation- or nutrition-associated changes of the crestal alveolar bone. However, following P. gingivalis inoculation, OA-ED improved oral trabecular bone micro-architecture and enhanced circulating pro-resolving mediators resolvin D4 (RvD4) and 4-hydroxydocosahexaenoic acid (4-HDHA), whereas PA-ED did not. In vitro experiments demonstrated significantly improved differentiation in RvD4- and 4-HDHA-treated primary osteoblast cultures and reduced the expression of osteoclastogenic factors in GF. Further, P. gingivalis infection of OA-ED animals led to a serum composition that suppressed osteoclastic differentiation in vitro.

CONCLUSIONS

Our results underline the preventive impact of Mediterranean-style OA-EDs by indicating their pro-resolving nature beyond anti-inflammatory properties.

Anti-Inflammatory Effect of Specialized Proresolving Lipid Mediators on Mesenchymal Stem Cells: An In Vitro Study

An interconnection between tissue inflammation and regeneration has been established through the regulation of defense and repair mechanisms within diseased dental tissue triggered by the release of immune-resolvent mediators. To better our understanding of the role of specific pro-resolving mediators (SPMs) in inflamed human bone marrow-derived mesenchymal stem cells (hBMMSCs), we studied the effects of Resolvin E1 (RvE1) and Maresin 1 (MaR1) in lipopoly-saccharide (LPS) stimulated hBMMSCs. The hBMMSCs were divided into five different groups, each of which was treated with or without SPMs. Group-1: negative control (no LPS stimulation), Group-2: positive control (LPS-stimulated), Group-3: RvE1 100 nM + 1 μg/mL LPS, Group-4: MaR1 100 nM + 1 µg/mL LPS, and Group-5: RvE1 100 nM + MaR1100 nM + 1 μg/mL LPS. Cell proliferation, apoptosis, migration, colony formation, Western blotting, cytokine array, and LC/MS analysis were all performed on each group to determine the impact of SPMs on inflammatory stem cells. According to our data, RvE1 plus MaR1 effectively reduced inflammation in hBMMSCs. In particular, IL-4, 1L-10, and TGF-β1 activation and downregulation of RANKL, TNF-α, and IFN-γ compared to groups receiving single SPM were shown to be significantly different (Group 3 and 4). In addition, the LC/MS analysis revealed the differentially regulated peptide's role in immunological pathways that define the cellular state against inflammation. Inflamed hBMMSCs treated with a combination of Resolvin E1 (RvE1) and Maresin 1 (MaR1) promoted the highest inflammatory resolution compared to the other groups; this finding suggests a potential new approach of treating bacterially induced dental infections.

α-Cyperone Ameliorates Lipopolysaccharide-Induced Inflammation and Apoptosis of Periodontal Ligament Stem Cells via Blocking the Toll-Like Receptor 4/NF-κB Signaling

Periodontitis is a long-lasting inflammatory microbial sickness that could cause damage to the periodontal ligament, gums, cementum and alveolar bone directly. Cyperus rotundus is a common traditional Chinese medicine clinically with many pharmacological activities, α-Cyperone is a bioactive ingredient abundant in Cyperus rotundus, few studies have focused on its anti-fungal and anti-oxidative stress activities in mice, during this research, we firstly investigated the impact of α-Cyperone on PDLSCs inflammatory by LPS stimulation. Our findings illustrated that α-Cyperone exerted no influence on PDLSCs viability at concentrations lower than 60 μM, and the release of inflammatory cytokines decreased with an increase in LPS concentration. Meanwhile, we found that α-Cyperone effectively restrained LPS-induced PDLSC cell apoptosis by CCK-8 cell viability assay and TUNEL-positive staining. Furthermore, the TLR4 expression and NF-κB kinase activation were greatly repressed by α-Cyperone treatment in LPS-induced PDLSCs inflammatory model. Subsequently, enhanced TLR4 expression was observed to reverse the suppressed release of inflammatory cytokines and decreased apoptosis effects mediated by α-Cyperone in LPS-cotreated PDLSCs, indicating that the deactivation of TLR4 and downstream NF-κB were implicated in favoring α-Cyperone-triggered protective effects of LPS in PDLSCs.

Maresin 1 enhances osteogenic potential of mesenchymal stem cells by modulating macrophage peroxisome proliferator-activated receptor-γ-mediated inflammation resolution

Inflammation resolution plays a significant role in attenuating bone injury aggravated by acute inflammation and maintaining bone homeostasis. Maresin 1 (MaR1), a specialized pro-resolving mediators (SPMs), is biosynthesised in macrophages (Mφs) that regulates acute inflammation. Strategies to accelerate the resolution of inflammation in bone repair include not only promoting vanish of acute inflammation, also improving osteogenic microenvironment. Here, previously prepared difunctional demineralized bone matrix (DBM) scaffold was used to study thoroughly the "cross-talk" between Mφs lipid metabolism and mesenchymal stem cells (MSCs) behaviors in vitro. The pro-resolving mechanism in Mφs treated with MaR1 was elaborated. Furthermore, the biological behaviors of MSCs in co-culture system were evaluated. The results indicated that MaR1 had an enhanced capability and performance in peroxisome proliferator-activated receptor-γ (PPAR-γ) activation, M2-type Mφs polarization, and lipid droplets (LDs) biogenesis in Mφs in vitro. The nuclear receptor PPAR-γ enhanced the anti-inflammatory proteins expression and the polarization of Mφs toward M2 subtype, thereby favoring the proliferation, migration, and osteogenesis of MSCs. Overall, the results verified that MaR1 facilitated MSCs behaviors by regulating PPAR-γ-mediated inflammatory response, which implied that PPAR-γ exhibited a significant role in the dialogue between MSCs behaviors and Mφs lipid metabolism.

Lipid emulsion rich in n-3 polyunsaturated fatty acids elicits a pro-resolution lipid mediator profile in mouse tissues and in human immune cells

BACKGROUND

Lipid emulsions are a key component of total parenteral nutrition (TPN) and are administered to patients who are unable to ingest their daily required calories orally. Lipid emulsions rich with n-6 (ω-6) PUFAs are known to cause parenteral nutrition-associated liver disease and have inflammatory side effects, whereas n-3 PUFA-rich emulsions have favourable clinical outcomes.

OBJECTIVES

The present study used targeted lipid mediator analysis to investigate the metabolism of a n-3 PUFA-rich lipid emulsion and a n-6 PUFA-rich lipid emulsion in a mouse model of TPN and in primary human monocyte-derived macrophages (MDMs) and CD4+ T cells.

RESULTS

Mice given n-3 PUFA-based TPN for 7 d had a less proinflammatory lipid mediator profile compared with those receiving n-6 PUFA-based TPN. This was characterized by higher concentrations of specialized pro-resolving mediators (SPMs) and endocannabinoids, including resolvin D (RvD) 1, maresin (MaR) 1, MaR2, protectin D1 (PD1), protectin DX (PDX), and the endocannabinoids eicosapentaenoyl ethanolamide (EPEA) and docosahexaenoyl ethanolamide (DHEA) in the liver and RvD1, 17R-RvD1, RvD2, RvD3, RvD5, MaR1, MaR2, PD1, PDX, and EPEA and DHEA in the spleen. The spleen was identified as a source of high lipid mediator and SPM formation as lipid mediator concentrations were on average 25-fold higher than in the liver. Additionally, n-3 PUFA-treated primary human MDMs produced RvD5 and the endocannabinoids EPEA and DHEA, which was associated with an increased IL-10 secretion. In contrast, primary human CD4+ T cells showed only an increase in SPM precursors and an increase in the endocannabinoids EPEA and DHEA, which was associated with reduced cytokine expression.

CONCLUSIONS

This demonstrates that lipid mediators, particularly SPMs and endocannabinoids from spleen, could play a key role in facilitating the favorable clinical outcomes associated with the use of n-3 PUFA-rich lipid emulsions in TPN.

Host Response Modulation Therapy in the Diabetes Mellitus—Periodontitis Conjuncture: A Narrative Review

The inflammatory response of the host in periodontitis is the phenomenon that underlies the onset and evolution of periodontal destructive phenomena. A number of systemic factors, such as diabetes mellitus (DM), can negatively affect the patient with periodontitis, just as the periodontal disease can aggravate the status of the DM patient. Host response modulation therapy involves the use of anti-inflammatory and anti-oxidant products aimed at resolving inflammation, stopping destructive processes, and promoting periodontal healing, all important aspects in patients with high tissue loss rates, such as diabetic patients. This paper reviews the data available in the literature on the relationship between DM and periodontitis, the main substances modulating the inflammatory response (nonsteroidal anti-inflammatory drugs, sub-antimicrobial doses of doxycycline, or omega-3 fatty acids and their products, specialized pro-resolving mediators), as well as their application in diabetic patients.

A cell-free difunctional demineralized bone matrix scaffold enhances the recruitment and osteogenesis of mesenchymal stem cells by promoting inflammation resolution

The dialogue between host macrophages (Mφs) and endogenous mesenchymal stem cells (MSCs) promotes M2 Mφs polarization to resolve early-stage inflammation, thereby effectively guiding in situ bone regeneration. Once inflammation is unresolved/incontrollable, it will induce the impediment of MSCs homing at bone defect site, implying the seasonable resolution of inflammation in balancing bone homeostasis. Repeatedly, evidence elucidated that specialized pro-resolving mediators (SPMs) could conduce to proper resolve inflammation and promote the repairing of bone defect. A difunctional demineralized bone matrix (DBM) scaffold co-modified by maresin 1 (MaR1) and aptamer 19S (Apt19S) was fabricated to facilitate the osteogenesis of MSCs. To confirm the osteogenesis and immunomodulatory role of the difunctional DBM scaffold, the proliferation, recruitment, and osteogenic differentiation of MSCs and the Mφs M2 subtype polarization were evaluated in vitro. Then, the DBM scaffolds were implanted into mice model with critical size calvarial defect to evaluate bone repair efficiency. Finally, the specific resolution mechanism in Mφs cultured on the difunctional DBM scaffold was further in-depth investigated. This difunctional DBM scaffold exhibited an enhanced function on the recruitment, proliferation, migration, osteogenesis of MSCs and the resolution of inflammation, finally improved bone-scaffold integration. At the same time, MaR1 modified on the difunctional DBM scaffold increased the biosynthesis of 12-lipoxygenase (12-LOX) and 12S-hydroxy-eicosatetraenoic acid (12S-HETE), and also directly stimulated lipid droplets (LDs) biogenesis in Mφs, which suggested that MaR1 regulated Mφ lipid metabolism at bone repair site. Findings based on this synergy strategy demonstrated that Mφ lipid metabolism was essential in bone homeostasis, which might provide a theoretical direction for the treatment-associated application of MaR1 in inflammatory bone disease.

Targeting chronic inflammation as a potential adjuvant therapy for osteoporosis

Systemic, chronic, low-grade inflammation (SCLGI) underlies the pathogenesis of various widespread diseases. It is often associated with bone loss, thus connecting chronic inflammation to the pathogenesis of osteoporosis. In postmenopausal women, osteoporosis is accompanied by SCLGI development, likely owing to estrogen deficiency. We propose that SCGLI persistence in osteoporosis results from failed inflammation resolution, which is mainly mediated by specialized, pro-resolving mediators (SPMs). In corroboration, SPMs demonstrate encouraging therapeutic effects in various preclinical models of inflammatory disorders, including bone pathology. Since numerous data implicate gut dysbiosis in osteoporosis-associated chronic inflammation, restoring balanced microbiota by supplementing probiotics and prebiotics could contribute to the efficient resolution of SCGLI. In the present review, we provide evidence for this hypothesis and argue that efficient SCGLI resolution may serve as a novel approach for treating osteoporosis, complementary to traditional anti-osteoporotic medications.

Expression and function of resolvin RvD1n-3 DPA receptors in oral epithelial cells

Chronic inflammatory responses can inflict permanent damage to host tissues. Specialized pro‐resolving mediators downregulate inflammation but also can have other functions. The aim of this study was to examine whether oral epithelial cells express the receptors FPR2/ALX and DRV1/GPR32, which bind RvD1_{n‐3 DPA}, a recently described pro‐resolving mediator derived from omega‐3 docosapentaenoic acid (DPA), and whether RvD1_{n‐3 DPA} exposure induced significant responses in these cells. Gingival biopsies were stained using antibodies to FPR2/ALX and DRV1/GPR32. Expression of FPR2/ALX and DRV1/GPR32 was examined in primary oral epithelial cells by qRT‐PCR, flow cytometry, and immunofluorescence. The effect of RvD1_{n‐3 DPA} on intracellular calcium mobilization and transcription of beta‐defensins 1 and 2, and cathelicidin was evaluated by qRT‐PCR. FPR2/ALX and DRV1/GPR32 were expressed by gingival keratinocytes in situ. In cultured oral epithelial cells, FPR2/ALX was detected on the cell surface, whereas FPR2/ALX and DRV1/GPR32 were detected intracellularly. Exposure to RvD1_{n‐3 DPA} induced intracellular calcium mobilization, FPR2/ALX internalization, DRV1/GPR32 translocation to the nucleus, and significantly increased expression of genes coding for beta‐defensin 1, beta‐defensin 2, and cathelicidin. This shows that the signal constituted by RvD1_{n‐3 DPA} is recognized by oral keratinocytes and that this can strengthen the antimicrobial and regulatory potential of the oral epithelium.

Maresin 1 intervention Reverses Experimental Pulmonary Arterial Hypertension in mice

BACKGROUND AND PURPOSE

Pulmonary arterial hypertension (PAH) is a pulmonary vasculature obstructive disease that leads to right heart failure and death. Maresin 1 is an endogenous lipid mediator known to promote inflammation resolution. However, the effect of Maresin 1 on PAH remains unclear.

EXPERIMENTAL APPROACH

The serum Maresin 1 concentration was assessed using UPLC. A mouse model of PAH was established by combining the Sugen 5416 injection and hypoxia exposure (SuHx). After treatment with Maresin 1, the right ventricular systolic pressure (RVSP) and right ventricular function were measured by hemodynamic measurement and echocardiography, respectively. Vascular remodeling was evaluated by histological staining. Confocal and western blot were used to test related protein expression. In vitro, cell migration, proliferation and apoptosis assays were performed in primary rat pulmonary artery smooth muscle cells (PASMCs). Western blotting and siRNA transfection were used to clarify the mechanism of Maresin 1.

KEY RESULTS

Endogenous serum Maresin 1 was decreased in PAH patients and mice. Maresin 1 treatment decreased RVSP and attenuated the right ventricular dysfunction (RVD) in murine PAH model. Maresin 1 reversed abnormal changes in pulmonary vascular remodeling, attenuating endothelial to mesenchymal transformation (EndoMT) and enhancing apoptosis of α-SMA positive cells. Furthermore, Maresin 1 inhibited PASMC proliferation and promoted apoptosis by inhibiting STAT, AKT, ERK and FoxO1 phosphorylation via LGR6.

CONCLUSION AND IMPLICATIONS

Maresin 1 improved abnormal pulmonary vascular remodeling and right ventricular dysfunction in PAH mice, targeting aberrant PASMC proliferation. This suggests Maresin 1 may have a potent therapeutic effect in vascular disease.

Does the use of omega-3 fatty acids as an adjunct to non-surgical periodontal therapy provide additional benefits in the treatment of periodontitis? A systematic review and meta-analysis

This review aimed to assess the impact of dietary omega-3 fatty acids as an adjunct to non-surgical periodontal treatment when compared with periodontal treatment alone on periodontal clinical parameters of periodontitis patients. We included only randomized clinical trials (RCTs) with at least 3-months follow-up of non-surgical periodontal therapy, in combination with dietary omega-3 fatty acids. The MEDLINE, EMBASE, and LILACS databases were searched for articles published up to October 2021. Random-effects meta-analyses were conducted to determine the change in clinical attachment level (CAL), probing pocket depth (PPD), bleeding on probing (BOP), and gingival index (GI) after therapy. Of the eight hundred eighty-four potentially relevant papers retrieved from the electronic databases, 10 RCTs were selected for qualitative analysis, and of these, 8 RCTs were included in meta-analysis. RCTs showed a significant PPD reduction/CAL gain associated with the use of omega-3 fatty acids. The pooled estimates revealed significant overall PPD reduction of 0.42 mm (95% CI 0.15, 0.68) and CAL gain 0.58 mm (95% CI 0.24, 0.92). In individuals with periodontitis, the use of omega-3 fatty acid dietary supplementation as an adjunct to non-surgical periodontal treatment can provide additional benefits in CAL gain and PPD reduction, compared with non-surgical periodontal treatment alone.

Combination of resolvin E1 and lipoxin A4 promotes the resolution of pulpitis by inhibiting NF-κB activation through upregulating sirtuin 7 in dental pulp fibroblasts

Objectives

To determine whether the combination of resolvin E1 (RvE1) and lipoxin A4 (LXA4) could promote resolution of pulpitis and to investigate the mechanism.

Materials and Methods

Preliminary screening was first conducted in four specialized pro‐resolving mediators (SPMs). Real‐time quantitative polymerase chain reaction, western blotting, enzyme‐linked immunosorbent assay and double‐immunofluorescence labelling were employed to assess the expression of RelA, SIRT1, SIRT6, SIRT7 and pro‐inflammatory factors. Dental pulp fibroblasts (DPFs) were transfected with siRNA to assess the biological role of SIRT7. A pulpitis model was utilized to evaluate the in vivo curative effect.

Results

Preliminary results showed that RvE1 and LXA4 reduced the expression of RelA more markedly than other two SPMs. Both RvE1 and LXA4 treatment downregulated nuclear factor kappa B (NF‐κB) activation and increased the expression of SIRT1, SIRT6 and SIRT7, more so in combination than alone. Double‐immunofluorescence labelling showed that SIRT7 co‐localized with p‐p65 and Ac‐p65 in the nucleus. Inhibiting ChemR23 and ALX reversed the expression of RelA mRNA, p‐p65 and Ac‐p65 proteins, pro‐inflammatory factors, SIRT1, SIRT6 and SIRT7. Silencing SIRT7 significantly increased p‐p65 and Ac‐p65 protein levels and decreased SIRT1 and SIRT6 expression. In vivo experiments showed that combined administration of RvE1 and LXA4 promoted pulpitis markedly to resolution.

Conclusions

Combination of RvE1 and LXA4 effectively inhibited NF‐κB activation by upregulating SIRT7 expression in DPFs, leading to reduced production of pro‐inflammatory factors and promotion of pulpitis resolution.

Specialized pro-resolution mediators in the bladder: Receptor expression and recovery of bladder function from cystitis

Inflammation is a central process in most benign bladder disorders, and its control is a delicate balance between initiating factors and resolving factors. While recent discoveries have shown a central role for the NLRP3 inflammasome in initiation, the resolving pathways remain unexplored. Resolution is controlled by specialized pro-resolution mediators (SPMs) functioning through seven receptors (six in rodents). Here we demonstrate expression of all seven in humans (six in mice) through immunocytochemistry. Expression was universal in urothelia with most also expressed in smooth muscle. We next explored the therapeutic potential of three SPMs; Resolvin E1 (RvE1), Maresin 1 (MaR1), and Protectin D1 (PD1). SPMs promote epithelial wound/barrier repair and RvE1 triggered dose-dependent wound closure in urothelia in vitro (scratch assay) (EC90 = 12.5 nM). MaR1 and PD1 were equally effective at this concentration. In vivo analyses employed a cyclophosphamide (CP) model of bladder inflammation (Day 0-CP [150 mg/kg], Day 1 to 3 SPM [25 µg/kg/day], Day 4 - analysis). All three SPMs reduced bladder inflammation (Evans blue) and bladder weights to control levels. Effects of RvE1 were also examined by urodynamics. CP decreased void volume, increased frequency and decreased bladder capacity while RvE1 restored values to control levels. Finally, SPMs reduce fibrosis and RvE1 reduced urothelial expression of TGF-β and collagen I to control values. Together these results expand the known SPMs active in the bladder tissue and provide promising therapeutic targets for controlling inflammation in a wide variety of inflammation-associated benign bladder diseases.

Liposomal Formulations Enhance the Anti-Inflammatory Effect of Eicosapentaenoic Acid in HL60 Cells

Dietary omega 3 polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), have been reported to be beneficial for cardiovascular diseases and cancer. Such diseases share a common pathophysiological feature of inflammation responses, such as unbalanced oxidative stress and increased cytokine release. PUFAs show anti-inflammatory effects, and thus, they are potential therapeutics to treat inflammatory disorders. Here, we proposed a novel liposomal formulation of EPA (EPA-liposomes), and the liposome was PEGylated to increase their stability. In the study, we measured the physicochemical characteristics of EPA-liposomes and their anti-inflammatory effects in neutrophil-like cells (HL 60 cells). The results showed that EPA-liposomes dramatically decreased the production of NO, ROS, and cytokines compared to EPA alone, and the molecular mechanism is associated with biosynthesis of RvE1 from EPA, and RvE1 binds to GPCRs to mediate the anti-inflammatory effects.

Maresins: The Mainstay in Periodontal Resolution

Not much was known about the resolution of inflammation until the recent past when significant breakthroughs led to the unveiling of the exact mechanism of this. It is now known that the resolution of inflammation involves specific mediators of resolution such as lipoxins, protectins, resolvins, and maresins, making it an active process. Of these mediators, maresins are the latest discovery. Maresins are macrophage-derived mediators that are involved in the resolution of inflammation. Various studies on what maresins do to resolve periodontitis are ongoing. Reportedly, maresins help in periodontal regeneration and wound healing. Having known the numerous roles of these mediators, our current focus is shifting from anti-inflammatory pharmacotherapy to resolution pharmacotherapy.

Resolvins as a Treatment Modality in Experimental Periodontitis: A Systematic Review of Preclinical Studies

This systematic review aimed to assess scientific data of existing literature to identify the efficacy of resolvins (Rv) in the treatment of periodontitis. The electronic databases, Web of Science (WOS), Medline/PubMed, The Cochrane Library, Scopus, and Saudi digital library (SDL), were searched for eligible studies in the field of periodontics. A thorough analysis of the retrieved literature provided five articles that were assessed and included in this systematic review. The quality of these studies was assessed by updated Essential Animal Research: Reporting of In-Vivo Experiments (ARRIVE) guidelines. The five included studies were published between 2005 and 2018 and investigated resolvins as a treatment approach in experimental periodontitis of animals. Among the study animals employed, New Zealand white rabbits were used in three studies, Wistar rats and Albino mice in two studies, respectively. Four studies have evaluated eicosapentaenoic acid-derived RvE1, and one study evaluated docosahexaenoic acid-derived RvD2. Oral-topical application of Rv was followed in four studies, and intra-peritoneal Rv injection was administered in one study. The study duration in these studies have ranged between 4-12 weeks, and the Rv dose was between 0.1 μg to 0.5 μg. One study evaluated the influence of RvE1 topical application on both the prevention and treatment of experimental periodontitis. Resolvins (RvE1 and RvD2) have been studied in periodontitis-induced animal models to assess their potential role in periodontal inflammation resolution. There are promising preclinical data of using resolvins as a treatment modality in experimental periodontitis. Resolvins have been demonstrated to inhibit the destructive inflammatory process and alveolar bone loss in laboratory-induced periodontitis under controlled experimental conditions.

E-series resolvin metabolome, biosynthesis and critical role of stereochemistry of specialized pro-resolving mediators (SPMs) in inflammation-resolution: Preparing SPMs for long COVID-19, human clinical trials, and targeted precision nutrition

The COVID-19 pandemic has raised international awareness of the importance of rigorous scientific evidence and the havoc caused by uncontrolled excessive inflammation. Here we consider the evidence on whether the specialized pro-resolving mediators (SPMs) are ready to meet this challenge as well as targeted metabololipidomics of the resolution-inflammation metabolomes. Specific stereochemical mechanisms in the biosynthesis of SPMs from omega-3 essential fatty acids give rise to unique local-acting lipid mediators. SPMs possess stereochemically defined potent bioactive structures that are high-affinity ligands for cognate G protein-coupled surface receptors that evoke the cellular responses required for efficient resolution of acute inflammation. The SPMs biosynthesized from the major omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are coined Resolvins (resolution phase interaction products; E series and D-series), Protectins and Maresins (macrophage mediators in resolving inflammation). Their biosynthesis and stereochemical assignments are established and confirmed (>1,441 resolvin publications in PubMed.gov) as well as their functional roles on innate immune cells and adaptive immune cells (both lymphocyte T-cell subsets and B-cells). The resolution of a protective acute inflammatory response is governed mainly by phagocytes that actively clear apoptotic cells, debris, blood clots and pathogens. These resolution phase functions of the acute inflammatory response are enhanced by SPMs, which together prepare the inflammatory loci for homeostasis and stimulate tissue regeneration via activating stem cells and the biosynthesis of novel cys-SPMs (e.g. MCTRs, PCTRs and RCTRs). These cys-SPMs also activate regeneration, are organ protective and stimulate resolution of local inflammation. Herein, we review the biosynthesis and functions of the E-series resolvins, namely resolvin E1 (the first n-3 resolvin identified), resolvin E2, resolvin E3 and resolvin E4 biosynthesized from their precursor eicosapentaenoic acid (EPA), and the critical role of total organic synthesis in confirming SPM complete stereochemistry, establishing their potent functions in resolution of inflammation, and novel structures. The physical properties of each biologically derived SPM, i.e., ultra-violet (UV) absorbance, chromatographic behavior, and tandem mass spectrometry (MS2) fragmentation, were matched to SPMs biosynthesized and prepared by stereospecific total organic synthesis. We briefly review this approach, also used with the endogenous D-series resolvins, protectins and maresins confirming their potent functions in resolution of inflammation, that paves the way for their rigorous evaluation in human tissues and clinical trials. The assignment of complete stereochemistry for each of the E and D series Resolvins, Protectins and Maresins was a critical and required step that enabled human clinical studies as in SPM profiling in COVID-19 infections and experimental animal disease models that also opened the promise of resolution physiology, resolution pharmacology and targeted precision nutrition as new areas for monitoring health and disease mechanisms.

Polarized Macrophages in Periodontitis: Characteristics, Function, and Molecular Signaling

Periodontitis (PD) is a common chronic infectious disease. The local inflammatory response in the host may cause the destruction of supporting periodontal tissue. Macrophages play a variety of roles in PD, including regulatory and phagocytosis. Moreover, under the induction of different factors, macrophages polarize and form different functional phenotypes. Among them, M1-type macrophages with proinflammatory functions and M2-type macrophages with anti-inflammatory functions are the most representative, and both of them can regulate the tendency of the immune system to exert proinflammatory or anti-inflammatory functions. M1 and M2 macrophages are involved in the destructive and reparative stages of PD. Due to the complex microenvironment of PD, the dynamic development of PD, and various local mediators, increasing attention has been given to the study of macrophage polarization in PD. This review summarizes the role of macrophage polarization in the development of PD and its research progress.

Inflammation and Periodontal Regeneration

Technological innovations in cellular and molecular aspects of tissue engineering --scaffolds, stem cells and 3D printed tissues --have been dramatically increased in the last decade. However, regenerative treatment still has challenges in translation to clinic. This is partly due to failure of addressing an essential element of wound healing, inflammation. It is now well-recognized that inflammation is an active process. This paradigm shift opened up a new avenue of therapeutic approaches called "host-modulation." Host-modulation therapies capable of modulating inflammatory response at multiple levels and mimicking the natural sequence of wound healing offer a new direction and promising clinical translation.

Biological Basis of Periodontal Regeneration

The ultimate goal of periodontal therapy is homeostatic regeneration of lost attachment of alveolar bone and gingival connective tissue to the exposed root surfaces with a fully functional and healthy periodontal ligament that is covered with a healthy epithelium. This goal needs a complete understanding of the biological mechanisms inherent to healing and inflammatory processes.

Specialized Proresolving Mediators Facilitate the Immunomodulation of the Periodontal Ligament Stem Cells

Recent investigations into the regulation of the inflammation in the periodontitis have revealed that chronic inflammatory diseases such as periodontitis are characterized by an imbalance in the proinflammatory and proresolution mediators and can be characterized by a failure of the resolution pathways in the late stages of the acute inflammatory response. The proresolution mediators, termed as specialized proresolving mediators (SPMs), comprise the lipoxins, resolvins, protectins, and maresins that are derived from the arachidonic acid or omega-3 polyunsaturated fatty acids. In the animal studies, treatment of the periodontitis with the topical SPMs return the inflammatory lesion to the homeostasis with the regeneration of all the components of the periodontal organ lost to the disease. In this article, the study investigates the immunomodulatory role of SPMs in the periodontal ligament stem cells (PDLSCs). Primary porcine PDLSCs (pPDLSCs) were stimulated with interleukin-1β (IL-1β) and interleukin-17 (IL-17) in vitro to simulate the periodontal inflammation in the presence or absence of SPMs. This study found that IL-1β and IL-17 synergistically activated the proinflammatory genes of pPDLSCs and altered the immune phenotype of pPDLSCs including the key signaling pathways. Addition of SPMs rescued the pPDLSCs phenotype and induced further production of the additional SPMs, which was reflected by upregulation of the requisite enzymes 12- and 15-lipoxygenase by pPDLSCs. This study interrogated the immunomodulatory actions of pPDLSCs on the monocytes/macrophages, focusing on the porcine CD14/CD16/CD163 markers by using flow cytometry. This study utilized the CD14+CD16+/CD14+CD16− ratio and CD163 on the monocytes/macrophages to differentiate between a proinflammation phenotype (lower ratio) and a resolution of the inflammation phenotype (higher ratio). This study also found that the conditioned medium from pPDLSCs treated with the cytokines and Maresin1 increased the CD14+CD16+/CD14+CD16− ratio and had the highest CD163 expression. This study concludes that in an inflammatory environment, pPDLSCs become proinflammatory and exert immunomodulatory functions. Maresin 1 resolves the inflammation by acting on pPDLSCs directly and by shifting the monocytes/macrophages phenotype to the proresolution dominance.

Specialized pro-resolving mediators: biosynthesis and biological role in bacterial infections

Acute inflammation caused by bacterial infections is an essential biological defence mechanism of the host in order to neutralize and clear the invaders and to return to homeostasis. Despite its protective function, inflammation may become persistent and uncontrolled, resulting in chronic diseases and tissue destruction as consequence of the unresolved inflammatory process. Therefore, spatiotemporal induction of endogenous inflammation resolution programs that govern bacterial clearance as well as tissue repair and regeneration, are of major importance in order to enable tissues to restore functions. Lipid mediators that are de-novo biosynthesized from polyunsaturated fatty acids (PUFAs) mainly by lipoxygenases and cyclooxygenases, critically regulate the initiation, the maintenance but also the resolution of infectious inflammation and tissue regeneration. The discovery of specialized pro-resolving mediators (SPMs) generated from omega-3 PUFAs stimulated intensive research in inflammation resolution, especially in infectious inflammation elicited by bacteria. SPMs are immunoresolvents that actively terminate inflammation by limiting neutrophil influx, stimulating phagocytosis, bacterial killing and clearance as well as efferocytosis of apoptotic neutrophils and cellular debris by macrophages. Moreover, SPMs prevent collateral tissue damage, promote tissue repair and regeneration and lower antibiotic requirement. Here, we review the biosynthesis of SPMs in bacterial infections and cover specific mechanisms of SPMs that govern the resolution of bacteria-initiated inflammation.

Identification of docosahexaenoic and eicosapentaenoic acids multiple targets facing periodontopathogens

The eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) play a substantial role in Periodontal Disease (PD) due to their antimicrobial and immunomodulatory actions. However, their antimicrobial mechanism of action against bacteria involved in PD remains unclear. We aimed to estimate the probable targets of EPA and DHA against the seven periodontopathogens. Through in silico analyses, the protein-acids interactions, protein characterization, and molecular docking were performed. We identified 165 proteins from periodontopathogens that may interact with EPA and DHA. Fusobacterium nucleatum has the highest number of predicted proteins among analyzed bacteria (n = 43, 26.06%). The EPA shows more interactions than DHA. The EPA and DHA interact mainly with proteins involved in the metabolism (n = 69, 41.81%). Also, the EPA and DHA interact with proteins located in any subcellular location. The affinities between acids and pathogenic proteins were moderate (binding energy was lower than -4.0 kcal/mol). The interactions between EPA and DHA and periodontopathogens occur in multiples proteins. There is not a predilection about the functional class of pathogenic proteins targeting EPA and DHA. However, there are moderate binding affinities between EPA or DHA and essential pathogenic proteins (TolC, CRISPR, FusA).

Controlled Release of the α-Tocopherol-Derived Metabolite α-13'-Carboxychromanol from Bacterial Nanocellulose Wound Cover Improves Wound Healing

Inflammation is a hallmark of tissue remodeling during wound healing. The inflammatory response to wounds is tightly controlled and well-coordinated; dysregulation compromises wound healing and causes persistent inflammation. Topical application of natural anti-inflammatory products may improve wound healing, in particular under chronic pathological conditions. The long-chain metabolites of vitamin E (LCM) are bioactive molecules that mediate cellular effects via oxidative stress signaling as well as anti-inflammatory pathways. However, the effect of LCM on wound healing has not been investigated. We administered the α-tocopherol-derived LCMs α-13'-hydroxychromanol (α-13'-OH) and α-13'-carboxychromanol (α-13'-COOH) as well as the natural product garcinoic acid, a δ-tocotrienol derivative, in different pharmaceutical formulations directly to wounds using a splinted wound mouse model to investigate their effects on the wounds' proinflammatory microenvironment and wound healing. Garcinoic acid and, in particular, α-13'-COOH accelerated wound healing and quality of the newly formed tissue. We next loaded bacterial nanocellulose (BNC), a valuable nanomaterial used as a wound dressing with high potential for drug delivery, with α-13'-COOH. The controlled release of α-13'-COOH using BNC promoted wound healing and wound closure, mainly when a diabetic condition was induced before the injury. This study highlights the potential of α-13'-COOH combined with BNC as a potential active wound dressing for the advanced therapy of skin injuries.

Effects of collagen membranes and bone substitute differ in periodontal ligament cell microtissues and monolayers

BACKGROUND

Barrier membranes and bone substitute are major tools of guided tissue regeneration (GTR) after periodontal disease. Integrity of the periodontal ligament plays a key role in periodontal health, but its functionality fails to be fully re-established by GTR after disease or trauma. Microtissue models suggest an in vivo-like model to develop novel GTR approaches due to its three-dimensionality. This study aims to assess the effects of collagen membranes and bone substitute on cell viability, adhesion and gene expression of regenerative and inflammatory biomarkers by periodontal ligament cell (PDLC) microtissues.

METHODS

Human PDLC microtissues and monolayers were cultured on collagen membranes or bone substitute. After 24 hours incubation, metabolic activity, focal adhesion, mRNA and protein production of collagen-type-I (COL1A1), periostin (POSTN), vascular endothelial growth factor (VEGF), angiogenin (ANG), interleukin (IL)6 and IL8 were measured by resazurin-based toxicity assay, focal adhesion staining, quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.

RESULTS

PDLC microtissues and monolayers were viable on collagen membranes and bone substitute, but microtissues were less metabolically active. Dominant staining of actin filaments was found in PDLC microtissues on collagen membranes. COL1A1, POSTN, VEGF, ANG and IL6 were modulated in PDLC microtissues on bone substitute, while there were no significant changes on collagen membranes. PDLC monolayers showed a different character of gene expression changes.

CONCLUSIONS

PDLC microtissues and monolayers react diversely to collagen membranes and bone substitute. Further descriptive and mechanistic tests will be required to clarify the potential of PDLC microtissues as in vivo-like model for GTR.

Therapeutic potential of periodontal ligament stem cells

Inflammatory periodontal disease known as periodontitis is one of the most common conditions that affect human teeth and often leads to tooth loss. Due to the complexity of the periodontium, which is composed of several tissues, its regeneration and subsequent return to a homeostatic state is challenging with the therapies currently available. Cellular therapy is increasingly becoming an alternative in regenerative medicine/dentistry, especially therapies using mesenchymal stem cells, as they can be isolated from a myriad of tissues. Periodontal ligament stem cells (PDLSCs) are probably the most adequate to be used as a cell source with the aim of regenerating the periodontium. Biological insights have also highlighted PDLSCs as promising immunomodulator agents. In this review, we explore the state of knowledge regarding the properties of PDLSCs, as well as their therapeutic potential, describing current and future clinical applications based on tissue engineering techniques.

Selective Antimicrobial Therapies for Periodontitis: Win the "Battle and the War"

Traditional antimicrobial therapies for periodontitis (PD) have long focused on non-selective and direct approaches. Professional cleaning of the subgingival biofilm by instrumentation of dental root surfaces, known as scaling and root planning (SRP), is the mainstay of periodontal therapy and is indisputably effective. Non-physical approaches used as adjuncts to SRP, such as chemical and biological agents, will be the focus of this review. In this regard, traditional agents such as oral antiseptics and antibiotics, delivered either locally or systemically, were briefly reviewed as a backdrop. While generally effective in winning the “battle” against PD in the short term, by reducing its signs and symptoms, patients receiving such therapies are more susceptible to recurrence of PD. Moreover, the long-term consequences of such therapies are still in question. In particular, concern about chronic use of systemic antibiotics and their influence on the oral and gut microbiota is warranted, considering antibiotic resistance plasmids, and potential transfer between oral and non-oral microbes. In the interest of winning the “battle and the war”, new more selective and targeted antimicrobials and biologics for PD are being studied. These are principally indirect, blocking pathways involved in bacterial colonization, nutrient acquisition, inflammation or cellular invasion without directly killing the pathogens. This review will focus on current and prospective antimicrobial therapies for PD, emphasizing therapies that act indirectly on the microbiota, with clearly defined cellular and molecular targets.

Subgingival Microbiome and Specialized Pro-Resolving Lipid Mediator Pathway Profiles Are Correlated in Periodontal Inflammation

Failure of resolution pathways in periodontitis is reflected in levels of specialized pro-resolving lipid mediators (SPMs) and SPM pathway markers but their relationship with the subgingival microbiome is unclear. This study aimed to analyze and integrate lipid mediator level, SPM receptor gene expression and subgingival microbiome data in subjects with periodontitis vs. healthy controls. The study included 13 periodontally healthy and 15 periodontitis subjects that were evaluated prior to or after non-surgical periodontal therapy. Samples of gingival tissue and subgingival plaque were collected prior to and 8 weeks after non-surgical treatment; only once in the healthy group. Metabololipidomic analysis was performed to measure levels of SPMs and other relevant lipid mediators in gingiva. qRT-PCR assessed relative gene expression (2-ΔΔCT) of known SPM receptors. 16S rRNA sequencing evaluated the relative abundance of bacterial species in subgingival plaque. Correlations between lipid mediator levels, receptor gene expression and bacterial abundance were analyzed using the Data Integration Analysis for Biomarker discovery using Latent cOmponents (DIABLO) and Sparse Partial Least Squares (SPLS) methods. Profiles of lipid mediators, receptor genes and the subgingival microbiome were distinct in the three groups. The strongest correlation existed between lipid mediator profile and subgingival microbiome profile. Multiple lipid mediators and bacterial species were highly correlated (correlation coefficient ≥0.6) in different periodontal conditions. Comparing individual correlated lipid mediators and bacterial species in periodontitis before treatment to healthy controls revealed that one bacterial species, Corynebacterium durum, and five lipid mediators, 5(S)6(R)-DiHETE, 15(S)-HEPE, 7-HDHA, 13-HDHA and 14-HDHA, were identified in both conditions. Comparing individual correlated lipid mediators and bacterial species in periodontitis before treatment to after treatment revealed that one bacterial species, Anaeroglobus geminatus, and four lipid mediators, 5(S)12(S)-DiHETE, RvD1, Maresin 1 and LTB4, were identified in both conditions. Four Selenomonas species were highly correlated with RvD1, RvE3, 5(S)12(S)-DiHETE and proinflammatory mediators in the periodontitis after treatment group. Profiles of lipid mediators, receptor gene and subgingival microbiome are associated with periodontal inflammation and correlated with each other, suggesting inflammation mediated by lipid mediators influences microbial composition in periodontitis. The role of correlated individual lipid mediators and bacterial species in periodontal inflammation have to be further studied.

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

Endodontics is the branch of dentistry concerned with the morphology, physiology, and pathology of the human dental pulp and periradicular tissues. Human dental pulp is a highly dynamic tissue equipped with a network of resident immunocompetent cells that play major roles in the defense against pathogens and during tissue injury. However, the efficiency of these mechanisms during dental pulp inflammation (pulpitis) varies due to anatomical and physiological restrictions. Uncontrolled, excessive, or unresolved inflammation can lead to pulp tissue necrosis and subsequent bone infections called apical periodontitis. In most cases, pulpitis treatment consists of total pulp removal. Although this strategy has a good success rate, this treatment has some drawbacks (lack of defense mechanisms, loss of healing capacities, incomplete formation of the root in young patients). In a sizeable number of clinical situations, the decision to perform pulp extirpation and endodontic treatment is justifiable by the lack of therapeutic tools that could otherwise limit the immune/inflammatory process. In the past few decades, many studies have demonstrated that the resolution of acute inflammation is necessary to avoid the development of chronic inflammation and to promote repair or regeneration. This active process is orchestrated by Specialized Pro-resolving lipid Mediators (SPMs), including lipoxins, resolvins, protectins and maresins. Interestingly, SPMs do not have direct anti-inflammatory effects by inhibiting or directly blocking this process but can actively reduce neutrophil infiltration into inflamed tissues, enhance efferocytosis and bacterial phagocytosis by monocytes and macrophages and simultaneously inhibit inflammatory cytokine production. Experimental clinical application of SPMs has shown promising result in a wide range of inflammatory diseases, such as renal fibrosis, cerebral ischemia, marginal periodontitis, and cancer; the potential of SPMs in endodontic therapy has recently been explored. In this review, our objective was to analyze the involvement and potential use of SPMs in endodontic therapies with an emphasis on SPM delivery systems to effectively administer SPMs into the dental pulp space.

Impact of resolvin mediators in the immunopathology of diabetes and wound healing

Introduction: Wound healing in diabetes may be delayed by persistent wound infection due to deficient immune and cellular response to tissue injury. Hyperglycemia due to decreased insulin availability and increased insulin resistance affects the immune response of the body. Accumulation of inflammatory immune cells and pro-inflammatory cytokines results in chronic inflammation and an altered resolution and remodeling phase of wound healing.Areas covered: Pro-resolving mediators called 'resolvins' target the resolution phase of wound healing and are becoming an area of increased interest. Resolvins stimulate self-limited innate immune responses and enhance innate microbial killing and clearance. Resolvins resolve inflammation by decreasing neutrophil infiltration and transmigration, increasing the phagocytic activity of macrophages, decreasing adipose tissue macrophages, downregulating platelet activation, suppressing nuclear factor-kappa beta activation, promoting the apoptosis of polymorphonuclear leukocytes, and improving insulin sensitivity. This review discusses the role of resolvins in diabetic wound healing and potential therapeutic strategies. The review is based on a literature search of PubMed and the Web of Science restricted to publications between January 2001 and October 2020.Expert opinion: There is increasing support for the use of resolvins in clinical applications related to diabetes and wound healing. Further research will help clarify this potential.

Host Modulation and Treatment of Periodontal Disease

Periodontitis is the sixth-most prevalent disease in the world and the first cause for tooth loss in adults. With focus shifted to the inflammatory/immune response in the pathogenesis of periodontitis, there is a critical need to evaluate host modulatory agents. Synthetic and biological disease-modifying antirheumatic drugs are a cornerstone for the treatment of inflammatory diseases. Recent prospective cohort studies showed that synthetic disease-modifying antirheumatic drugs improved periodontal clinical parameters following nonsurgical periodontal treatment in patients with rheumatoid arthritis. Treatment with recombinant humanized monoclonal antibodies against CD20 (rituximab) and IL-6 receptor (tocilizumab), the latter also in clinical trials for the treatment of COVID-19 pneumonia, resulted in decreased periodontal inflammation and improved periodontal status. Studies on the effect of TNF-α inhibitors in patients with periodontitis yielded inconsistent results. Recent data suggest that probiotics provide anti-inflammatory clinical benefit, as do nutritional supplements, such as n-3 fatty acids, when combined with periodontal therapy. Probiotics reduce the production of proinflammatory cytokines/chemokines by suppressing NF-κB pathways and promote the accumulation of T regulatory cells. Statins, like aspirin, have been shown to exhibit anti-inflammatory and bone-preserving actions by upregulating production of Specialized Proresolving Mediators (SPMs). Currently, there is insufficient scientific support for the topical delivery of statins or bisphosphonates as adjuncts to periodontal therapy. Here, we present a critical review of the most recent host modulatory agents applied in humans and the key immune pathways that they target. Emerging evidence from novel drug candidates, including SPMs and complement inhibitors as previously studied in animal models and currently in human clinical trials, suggests future availability of adjunctive therapeutic strategies for the management of periodontitis.

A New E-Series Resolvin: RvE4 Stereochemistry and Function in Efferocytosis of Inflammation-Resolution

The resolution of the acute inflammatory response is governed by phagocytes actively clearing apoptotic cells and pathogens. Biosynthesis of the specialized pro-resolving mediators (SPMs) is pivotal in the resolution of inflammation via their roles in innate immune cells. Resolvin E4 (RvE4: 5S,15S-dihydroxy-eicosapentaenoic acid) is a newly uncovered member of the E-series resolvins biosynthesized from eicosapentaenoic acid (EPA) recently elucidated in physiologic hypoxia. This new resolvin was termed RvE4 given its ability to increase efferocytosis of apoptotic cells by macrophages. Herein, we report on the total organic synthesis of RvE4 confirming its unique structure, complete stereochemistry assignment and function. This synthetic RvE4 matched the physical properties of biogenic RvE4 material, i.e. ultra-violet (UV) absorbance, chromatographic behavior, and tandem mass spectrometry (MS²) fragmentation, as well as bioactivity. We confirmed RvE4 potent responses with human M2 macrophage efferocytosis of human apoptotic neutrophils and senescent red blood cells. Together, these results provide direct evidence for the assignment of the complete stereochemistry of RvE4 as 5S,15S-dihydroxy-6E,8Z,11Z,13E,17Z-eicosapentaenoic acid and its bioactions in human phagocyte response.

Angiogenic Effects of Secreted Factors from Periodontal Ligament Stem Cells

Periodontal disease is a chronic inflammation of tooth-supporting tissues, and the destruction of these tissues results in tooth loss. Regeneration of periodontal tissues is the ultimate goal of periodontal treatment. We previously reported that transplantation of conditioned medium (CM) of periodontal ligament stem cells (PDLSCs) demonstrated the enhancement of periodontal tissue regeneration, compared to CM from fibroblasts (Fibroblast-CM). We hypothesized that the angiogenic effects of PDLSC-CM might participate in the enhanced wound healing of periodontal tissues. The aim of this study was to investigate the effect of PDLSC-CM on the functions of endothelial cells. PDLSCs were cultured from periodontal ligament tissues obtained from healthy volunteers. Human gingival epithelial cells, dermal fibroblasts, osteoblasts, and umbilical vein endothelial cells (HUVECs) were purchased from commercial sources. The functions of endothelial cells were examined using immunostaining of Ki67, observation of nuclear fragmentation and condensation (apoptosis), and network formation on Matrigel. Vascular endothelial cell growth factor (VEGF) level was measured using an ELISA kit. HUVECs demonstrated higher cell viability in PDLSC-CM when compared with those in Fibroblast-CM. HUVECs demonstrated a higher number of Ki67-positive cells and lower apoptosis cells in PDLSC-CM, compared to Fibroblast-CM. Additionally, HUVECs formed more capillary-like structures in PDLSC-CM than Fibroblast-CM. PDLSC-CM contained higher levels of angiogenic growth factor, VEGF, than Fibroblast-CM. Our results showed that PDLSC-CM increased cell viability, proliferation, and capillary formation of HUVECs compared to Fibroblast-CM, suggesting the angiogenic effects of PDLSC-CM, and the effect is a potential regenerative mechanism of periodontal tissues by PDLSC-CM.