Peri-implantitis fibroblasts respond to host immune factor C1q

Single-cell sequencing identifies inflammation-promoting fibroblast-neutrophil interaction in peri-implantitis

AIM

To reveal the cellular composition and molecular environment of the periodontal and peri-implant inflammatory infiltrates through a single-cell sequencing technique, which may explain the pathological difference between these two diseases. A special focus was placed on the phenotypes and potential roles of neutrophils and fibroblasts in peri-implant/periodontal tissue immunity.

MATERIALS AND METHODS

High-throughput single-cell transcriptomic profiling of peri-implant tissues from patients with peri-implantitis as well as periodontal tissues from patients with periodontitis and healthy donors was performed. Immunofluorescence analysis was carried out to further validate the identified cell subtypes and their involvement in peri-implantitis and periodontitis.

RESULTS

Based on our single-cell resolution analysis, a quantified proportional increase of neutrophil (Neu) subtypes was shown in peri-implantitis. Among these, a predominance of Neutro_CXCR2 was revealed. We also found the involvement of inflammation-promoting fibroblasts as well as a predominance of CXCL8+ fibroblast-CXCR2+ neutrophil interaction in peri-implantitis.

CONCLUSIONS

Our study indicated that the predominance of CXCL8+ fibroblast-CXCR2+ neutrophil interaction might underline the enhanced host response in peri-implantitis compared with periodontitis. This information offers a molecular basis by which fibroblast and neutrophil subtypes might be diagnostically and therapeutically targeted in peri-implantitis.

C3-targeted host-modulation approaches to oral inflammatory conditions

Periodontitis is an inflammatory disease caused by biofilm accumulation and dysbiosis in subgingival areas surrounding the teeth. If not properly treated, this oral disease may result in tooth loss and consequently poor esthetics, deteriorated masticatory function and compromised quality of life. Epidemiological and clinical intervention studies indicate that periodontitis can potentially aggravate systemic diseases, such as, cardiovascular disease, type 2 diabetes mellitus, rheumatoid arthritis, and Alzheimer disease. Therefore, improvements in the treatment of periodontal disease may benefit not only oral health but also systemic health. The complement system is an ancient host defense system that plays pivotal roles in immunosurveillance and tissue homeostasis. However, complement has unwanted consequences if not controlled appropriately or excessively activated. Complement overactivation has been observed in patients with periodontitis and in animal models of periodontitis and drives periodontal inflammation and tissue destruction. This review places emphasis on a promising periodontal host-modulation therapy targeting the complement system, namely the complement C3-targeting drug, AMY-101. AMY-101 has shown safety and efficacy in reducing gingival inflammation in a recent Phase 2a clinical study. We also discuss the potential of AMY-101 to treat peri-implant inflammatory conditions, where complement also seems to be involved and there is an urgent unmet need for effective treatment.

Peri-Implantitis: Application of a Protocol for the Regeneration of Deep Osseous Defects. A Retrospective Case Series

Background and aims: Peri-implantitis is a complex pathology, both in its diagnosis and in the identification of etiological causes. Although we have been studying more and more over the years to try to answer the many questions that remain regarding everything that circulates around this disease which affects implants, nothing has yet been taken as an official consensus regarding its surgical treatment. There are still many proposed protocols, each of which has been shown to have comforting results and promising prospects, but no total predictability. The aim of this case series is to assess the clinical outcomes of a mixed protocol for the regeneration of deep osseous defects. Materials and methods: The data and clinical records of 23 patients, with 29 implants affected by peri-implantitis treated surgically in private practice, were analyzed retrospectively. The method used for the surgical treatment was a mixed protocol of mechanical–chemical decontamination and bone regeneration with bovine xenograft. Results: All patients were followed for at least 2 years, averaging 28.9 months (a range of 24–38 months) with a reduction in the probing depth (PD) at one year from the initial 8.14 ± 1.156 mm to 3.72 ± 0.649 mm, and to 4.14 ± 1.093 mm at the final assessment. The differences between assessment time points were always statistically significant. The data regarding bleeding on probing (BoP) and suppuration also showed a statistically significant reduction at the final time point compared to the baseline. Only one patient, at 24 months, still showed BoP, suppuration, and a PD deeper than 5 mm, indicating a recurrence of the disease compared to the initial improvement of the PD (5 mm) at one year. Conclusions: In conclusion, within the limits of this retrospective analysis, it can be affirmed that this combined mechanical–chemical and regenerative decontamination therapy is effective in the treatment of peri-implantitis.

Histological evaluation of peri-implant mucosal and gingival tissues in peri-implantitis, peri-implant mucositis and periodontitis patients: a cross-sectional clinical study

Objective: Aim of present study was to evaluate gingival tissue samples obtained from healthy and diseased sites of teeth and dental implants in terms of hypoxia and collagenase activity.Methods: Four study groups were created as Group-1; healthy individuals (H), Group-2; periodontitis patients with stage 3 grade B (P), Group-3; patients with peri-implant mucositis. Group-4; patients with peri-implantitis (P-IMP). Plaque index (PI), gingival index (GI) and probing pocket depth (PPD) were recorded. Gingival and peri-implant mucosal biopsies were obtained. Fibroblast and inflammatory cells were counted. Hypoxia-inducible factor (HIF)-1α, prolyl hydroxylase (PH), matrix metalloproteinase (MMP)-8, tissue inhibitor of MMPs (TIMP)-1, cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) levels were determined via immunohistochemistry.Results: Healthy controls had highest fibroblast cell counts and lowest inflammatory cell counts compared to other groups. Peri-implantitis and periodontitis samples had similar fibroblast and inflammatory cell counts, while peri-implant mucositis had higher fibroblast cells and lowered inflammatory cells compared to periodontitis and peri-implantitis samples. HIF-1α, COX-2 and iNOS levels were lowest in healthy controls and increased in other groups. Peri-implant mucositis samples had significantly lower expressions of HIF-1α, COX-2 and iNOS compared to peri-implantitis and periodontitis groups. PH expressions were lower in periodontitis and peri-implantitis groups compared to healthy controls and peri-implant mucositis groups. MMP-8 levels were lower in healthy group compared to other groups while levels were similar in periodontitis, peri-implant mucositis and peri-implantitis groups. TIMP levels were similar in groups.Conclusion: Periodontitis, peri-implantitis, and peri-implant mucositis samples exhibited higher inflammation and lower fibroblast cell counts and tend to have increased tissue collagenase activity, hypoxia and inflammation compared to healthy samples.

Novel Yttria-Stabilized Zirconium Oxide and Lithium Disilicate Coatings on Titanium Alloy Substrate for Implant Abutments and Biomedical Application

This study aimed to create novel bioceramic coatings on a titanium alloy and evaluate their surface properties in comparison with conventional prosthetic materials. The highly polished titanium alloy Ti6Al4V (Ti) was used as a substrate for yttria-stabilized zirconium oxide (3YSZ) and lithium disilicate (LS2) coatings. They were generated using sol-gel strategies. In comparison, highly polished surfaces of Ti, yttria-stabilized zirconium oxide (ZrO2), polyether ether ketone (PEEK) composite, and poly(methyl methacrylate) (PMMA) were utilized. Novel coatings were characterized by an X-ray diffractometer (XRD) and scanning electron microscope (SEM). The roughness by atomic force microscope (AFM), water contact angle (WCA), and surface free energy (SFE) were determined. Additionally, biocompatibility and human gingival fibroblast (HGF) adhesion processes (using a confocal laser scanning microscope (CLSM)) were observed. The deposition of 3YSZ and LS2 coatings changed the physicochemical properties of the Ti. Both coatings were biocompatible, while Ti-3YSZ demonstrated the most significant cell area of 2630 μm2 (p ≤ 0.05) and the significantly highest, 66.75 ± 4.91, focal adhesions (FAs) per cell after 24 h (p ≤ 0.05). By contrast, PEEK and PMMA demonstrated the highest roughness and WCA and the lowest results for cellular response. Thus, Ti-3YSZ and Ti-LS2 surfaces might be promising for biomedical applications.

[Osteoimmunological aspects of periodontal inflammatory destructive changes at periimplantitis, chronic periodontitis and oncological diseases of the oral cavity]

THE AIM OF THE STUDY

Was to analyze possible correlation between the concentration of the pro-inflammatory cytokine interleukin-6 and the activation marker of osteoclasts cathepsin K in the gingival fluid during osteoresorption of inflammatory (periimplantitis, chronic generalized periodontitis) and malignant oncological origin (malignant neoplasm of gums).

MATERIALS AND METHODS

The study comprised 87 individuals of both sexes aged 30 to 60: 20 patients (group 1) with periimplantitis, 30 people with chronic generalized periodontitis (CGP) (group 2), 22 patients with squamous cell carcinoma of the upper and lower alveolar bone gingiva (group 3), 15 healthy individuals without periodontal disease.

RESULTS

The concentration of interleukin-6 (IL-6) and cathepsin K was determined in the gingival fluid by enzyme-linked immunosorbent assay. The examination revealed that during CGP and peri-implantitis the accumulation of IL-6 in the contents of periodontal and peri-implantation pockets was a pathogenetic factor for the activation of osteoclasts and their secretion of proteolytic enzymes osteoresorption. In cancer the increase of cathepsin K expression was a lot higher than the accumulation of IL-6 in the gingival fluid reducing the dependence of the activation of osteoclasts on the local accumulation of pro-inflammatory cytokines. Conclusion. To formulate the prognosis of progressive bone loss in patients with peri-implantitis it is necessary to control the concentration of IL-6 and cathepsin K in the peri-implantation pocket, in case of CGP the concentration of IL-6 in the exudate of the periodontal pocket and in patients with cancer of the alveolar processes the content of cathepsin K of gingival fluid.

VEGF, Microvessel Density, and CD44 as Inflammation Markers in Peri-implant Healthy Mucosa, Peri-implant Mucositis, and Peri-implantitis: Impact of Age, Smoking, PPD, and Obesity

Several biologic processes affect the supporting peri-implant tissue leading to implant failure and complications, mainly referred to inflammation that is still poorly investigated in the peri-implant soft tissues. Our aim was to investigate in peri-implant healthy mucosa, peri-implant mucositis, and peri-implantitis the expression of some angiogenesis markers highly associated with inflammation, and evaluate its relationships with age, smoking, peri-implant pocket depth (PPD), and body max index (BMI). Moreover, we wanted to study the impact of these clinical parameters in the disease pathogenesis. Forty-eight total patients were recruited. Sixteen had at least one successfully osteointegrated dental implant (group A) and 32 had at least one osseointegrated implant in need of a peri-implant treatment for inflammatory/infectiveous reasons: precisely 16 for mucositis (group B) and 16 for peri-implantitis (group C). VEGF, CD34, and CD44 immunohistochemical expression was evaluated in the interproximal biopsies of marginal peri-implant tissue and correlated with the clinical parameters. A significant difference between groups in mean PPD was found, while the distribution by age, gender, smoking, and BMI resulted similar. Group C had significantly higher levels of VEGF, CD34, and CD44 expression compared to the other groups. VEGF, CD34, CD44, and peri-implant pocket depth were all positively correlated. Our study revealed that peri-implantitis is a condition characterized by unique and distinctive features. Our results supported that PPD has a great impact on the peri-implantitis and it is closely related to the inflammation marker expression. The identification of specific biomarkers might help in choosing distinct treatment approaches for target individuals.

Globular C1q receptor (p33) binds and stabilizes pro-inflammatory MCP-1: a novel mechanism for regulation of MCP-1 production and function

The protein gC1qR (globular C1q receptor), also named p33, was originally identified as a binding partner of the globular heads of C1q in the complement system. gC1qR/p33 is abundantly expressed in many cell types, but the functional importance of this protein is not completely understood. Here, we investigate the impact of gC1qR/p33 on the production and function of the pathophysiologically important chemokine monocyte chemoattractant protein-1 (MCP-1) and the underlying molecular mechanisms. Knockdown of gC1qR/p33 negatively regulated the production of MCP-1, but had no effect on the expression of transcript for MCP-1 in human periodontal ligament cells, suggesting a translational/post-translational mechanism of action. Laser scanning confocal microscopy showed considerable cytosolic co-localization of gC1qR/p33 and MCP-1, and co-immunoprecipitation disclosed direct physical interaction between gC1qR/p33 and MCP-1. Surface plasmon resonance analysis revealed a high-affinity binding (K_D = 10.9 nM) between gC1qR/p33 and MCP-1. Using a transwell migration assay, we found that recombinant gC1qR/p33 enhances MCP-1-induced migration of human THP-1 monocytes, pointing to a functional importance of the interaction between gC1qR/p33 and MCP-1. An in vitro assay revealed a rapid turnover of the MCP-1 protein and that gC1qR/p33 stabilizes MCP-1, hence preventing its degradation. We propose that endogenous gC1qR/p33 physically interacts with MCP-1 causing stabilization of the MCP-1 protein and stimulation of its activity in human periodontal ligament cells, suggesting a novel gC1qR/p33-mediated pro-inflammatory mechanism of action.

Silver-doped keratin nanofibers preserve a titanium surface from biofilm contamination and favor soft-tissue healing

Peri-implantitis is a severe condition affecting the success of transmucosal dental implants: tissue healing is severely limited by the inflammatory processes that come about to control homeostasis in the surrounding tissues. The main cause of peri-implantitis is bacterial biofilm infection; gingival fibroblasts play a pivotal role in regulating the inflammatory cascades. A new technology aimed at preventing bacterial colonization of titanium (Ti) implants, and enhancing the spread of gingival fibroblasts, is presented. Using electro-spinning, mirror-polished Ti disks were uniformly coated with keratin fibers obtained from discarded wool via sulfitolysis. The keratin-coated surfaces were then doped with silver (Ag) to introduce antibacterial properties, using different concentrations of silver nitrate as a precursor (0.01, 0.05 and 0.1 M). The resulting specimens were characterized in terms of morphology and chemical composition by FESEM, FTIR and XPS, revealing silver concentrations between 1.7 and 1.9%. Silver release into the medium was evaluated in the presence of cells (α-MEM) or bacteria (LB) by ICP; release was 0.2-1.4 mg l^-1 for α-MEM, and 10-40 mg l^-1 for LB. The antibacterial properties of the Ag-doped specimens were tested against a multidrug-resistant Staphylococcus aureus biofilm through morphology (FESEM) and metabolic assay (XTT); reduction in viability was significant (p < 0.05; >80% reduction within 72 h). Lastly, the cytocompatibility of the specimens was confirmed using human primary gingival fibroblasts, whose viability, spread and matrix deposition were found to be comparable to those of untreated Ti polished controls (p > 0.05). Thus, Ag surface enrichment was effective in reducing viability and maturation of S. aureus biofilm, without compromising human cell viability. Moreover, cell spread was found to be very sensitive to keratin fiber stimulation. The strategy thus appears to be very promising to introduce surface features in line with the main requirements for transmucosal dental implants.

Differences between inflammatory and catabolic mediators of peri-implantitis and periodontitis lesions following initial mechanical therapy: An exploratory study

BACKGROUND AND OBJECTIVE

The aim of this study was to analyze the differences in inflammatory and catabolic mediators expressed in peri-implantitis compared to periodontitis lesions after non-surgical therapy. Peri-implantitis is associated with a faster rate of bone loss when compared with periodontitis, and peri-implant non-surgical therapy is ineffective to cure peri-implantitis. This may be due to persistent inflammation in peri-implantitis tissues after initial mechanical treatment.

MATERIAL AND METHODS

Eleven patients with peri-implantitis and 10 with severe chronic periodontitis received non-surgical therapy. They were included at re-evaluation (8 weeks) if they presented pocket depth ≥6 mm with bleeding on probing, and the indication for open flap debridement surgery. Connective tissues were harvested during surgery from diseased sites. Healthy gingiva were harvested during third molar extraction in a third group of healthy patients (n=10). Explants were incubated for 24 hours in media culture and the release of cytokines, chemokines, growth factors, osteoprotegerin, receptor activator of nuclear factor kappa-B ligand (RANKL), matrix metalloproteinase and tissue inhibitors of matrix metalloproteinase (TIMP) in the conditioned media was analyzed by an exploratory multiplex immunoassay. When difference was found in the conditioned media, an immunohistochemistry was performed to compare expression in the tissues.

RESULTS

Connective tissues from non-stabilized peri-implantitis exhibited a distinct cytokine profile compared to periodontitis lesions that did not respond to initial therapy. Indeed, TIMP-2 was significantly increased in media from peri-implantitis (P≤.05). In addition, the in situ expression of TIMP-2, interleukin-10 and RANKL was also significantly increased in peri-implantitis tissues (P≤.05). However, the ratio of RANKL/osteoprotegerin-positive cells did not vary (P≥.05).

CONCLUSION

This study suggests that peri-implantitis and periodontitis connective tissues exhibit differences in response to non-surgical treatment, which may contribute to a different pattern of disease evolution.

Microbiological and immuno-pathological aspects of peri-implant diseases

Peri-implant diseases are a cluster of "contemporary" oral infections in humans that have emerged as a result of the routine application of osseointegrated dental implants in clinical practice. They are characterized by the inflammatory destruction of the implant-supporting tissues, as a result of biofilm formation on the implant surface. Peri-implant mucositis and peri-implantitis are analogous to gingivitis and periodontitis that affect natural teeth. The aim of this comprehensive review was to provide insights into the infectious aetiology and immuno-pathology of peri-implant diseases, and to identify similarities and differences with periodontal diseases. The microbial composition of peri-implantitis-associated biofilms is mixed, non-specific and very similar to that of periodontitis. A considerable exception is the frequent presence of high numbers of staphylococci and enteric bacteria in peri-implantitis. The sequence of immuno-pathological events and the qualitative composition of the immune cells in peri-implant infections are similar to that of periodontal infections. The lesions are characterized predominantly by neutrophils, macrophages, T- and B-cells. Nevertheless, compared to periodontitis, peri-implantitis is marked by a more extensive inflammatory infiltrate and innate immune response, a greater severity of tissue destruction and a faster progression rate. This could well account for the structural differences between the two tissue types, predominantly the lack of periodontal ligament and Sharpey's fibres around implants. In order to support the early diagnosis and prevention of peri-implantitis, it is crucial to explain its fast progression rate by elucidating the underlying molecular mechanisms. This could be achieved, for instance, by utilizing the non-invasive collection and analysis of peri-implant crevicular fluid.

Cytokine and matrix metalloproteinase expression in fibroblasts from peri-implantitis lesions in response to viable Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

To assess inflammatory reactions of fibroblasts in the pathophysiology of peri-implantitis, we compared the pro-inflammatory and matrix-degrading responses of gingival and granulation tissue fibroblasts from periodontally healthy controls, peri-implantitis, and periodontitis lesions to an in vitro challenge with Porphyromonas gingivalis.

METHODS

Fibroblasts from periodontally healthy, peri-implantitis and periodontitis donors were challenged with viable P. gingivalis. The inflammatory reactions of fibroblasts were analyzed before and after 6 h P. gingivalis challenge, and 2.5 and 18 h after removal of the challenge. Gene expression and induction of pro-inflammatory mediators, and matrix metalloproteinases (MMPs) were assessed by real-time polymerase chain reaction. Protein expression was measured by enzyme-linked immunosorbent assay.

RESULTS

Non-challenged fibroblasts from peri-implantitis and periodontitis lesions expressed higher levels of interleukin (IL)-1β, IL-8, and monocyte chemotactic protein (MCP)-1 than fibroblasts from periodontally healthy individuals. The P. gingivalis challenge induced expression of IL-1β, IL-8, IL-6, MCP-1, and MMP-1 in periodontitis and peri-implantitis fibroblasts, but not in fibroblasts from periodontally healthy individuals. MMP-8 expression was higher in non-challenged peri-implantitis fibroblasts than in fibroblasts from periodontally healthy individuals. However, the P. gingivalis challenge downregulated MMP-8 gene expression in peri-implantitis fibroblasts. After removal of the P. gingivalis challenge, peri-implantitis fibroblasts sustained higher induction of IL-1β, MCP-1, and MMP-1 compared to periodontitis fibroblasts.

CONCLUSIONS

Fibroblasts from peri-implantitis and periodontitis lesions gave a more pronounced inflammatory response to the P. gingivalis challenge than fibroblasts from healthy donors. They may therefore be involved in the development of inflammation in peri-implantitis and periodontitis. Moreover, the sustained upregulation of inflammatory mediators and MMP-1 in peri-implantitis fibroblasts may play a role in the pathogenesis of peri-implantitis.