Effects of titanium dioxide microparticles and nanoparticles on cytoskeletal organization, cell adhesion, migration, and proliferation in human gingival fibroblasts in the presence of lipopolysaccharide

Biological Processes in Gingival Tissue Integration Around Dental Implants

Peri-implant gingival tissue integration (GTI) is pivotal in determining the long-term success and functionality of dental implants. To enhance GTI, researchers have increasingly focused during the past decade on unraveling the response of gingival tissues to implant surfaces. This increased focus on soft instead of hard tissue integration has led to the development of various models, including in vitro cell culture systems and in vivo animal models, designed to predict and assess GTI around dental implants. However, inconsistent study outcomes between the different models have created confusion, highlighting the need for a comprehensive review. Therefore, the main objective of this review is to present a comprehensive overview of existing in vitro models, ranging from 2D to 3D, specifically designed to investigate cellular behavior relevant to peri-implant GTI. To facilitate a better comprehension of the utility of these models, the review initiates an elucidation of the histological characteristics of gingival tissues surrounding natural dentition, offering insights into the healing dynamics and histological adaptation processes occurring in gingival tissues adjacent to dental implants. In addition, through a critical evaluation of the strengths and limitations inherent in each model, our aim is to contribute to a more profound understanding of their applicability and effectiveness in GTI research.

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.

Effect of functionalized titanium particles with dexamethasone-loaded nanospheres on macrophage polarization and activity

OBJECTIVE

The aim of this study was to determine the effect of titanium micro particles (TiP) previously functionalized with nanoparticles doped with dexamethasone (Dex) and doxycycline (Dox), on macrophage polarization and activity.

METHODS

Macrophages RAW264.7 were cultured in the presence TiP loaded with dexamethasone -NPs (Dex)- and doxycycline -NPs (Dox)-, and as control, TiP with or without doped NPs. Cells were tested with and without previous bacterial lipopolysaccharide endotoxin (LPS) stimulation. Their morphology, proliferation, cytotoxicity, phenotypic change, and cytokines release were assessed by LIVE/DEAD, DNA release, metabolic activity, brightfield and scanning electron microscopy. The test Kruskall-Wallis was used for comparisons, while the cytokine expression profiles were examined by hierarchical clustering (p < 0.05).

RESULTS

Upon exposure with TiP macrophages were activated and polarized to M1, but without depicting cytotoxic effects. The particles were phagocytised, and vacuolized. When exposed to functionalised TiP with NPs(Dex) and NPs(Dox), the ratio M1/M2 was up to forty times lower compared to TiP alone. When exposed to LPS, TiP reduced cell viability in half. Functionalised TiP with NPs(Dex) inhibited the cytokine release exerted by TiP on macrophages. When macrophages were exposed to functionalised TiPs with NPs(Dex) with and without LPS, the effect of TiP on cytokine secretion was inhibited.

SIGNIFICANCE

Functionalised TiPs with NPs(Dex) and NPs(Dox) may potentially have beneficial effects on modulating titanium and LPS-related inflammatory reactions.

Free titanium particles and P. gingivalis lipopolysaccharide create a potentially synergistical effect in a periimplantitis model

OBJECTIVE

Our aim was to examine the effect of titanium particles and lipopolysaccharide (LPS) from P. gingivalis on the inflammatory profile expression of human gingival fibroblasts (hGFs), cultured on rough titanium discs, in an in vitro peri-implantitis simulation.

DESIGN

Human gingival fibroblasts cultured on SLA and TCP surfaces were challenged with LPS, titanium particles or both. At 24, 48 and 72 h after treatment, MTT assay was performed to assess cell proliferation. FDA/PI staining was performed for the same time periods, in order to evaluate cell viability/apoptosis. At 5 and 7 days after the treatment, qPCR was performed to assess gene expressions of IL-6, IL-8 and COL1A1, as well as SEM on titanium discs.

RESULTS

All groups presented a significant increase of their population between the time periods of examination. Regarding the interleukin gene expression, the combination of LPS and particles significantly increased the levels of Interleukin-8. Treatment with LPS and particles also induced a significant increase of Interleukin-6 and collagen. FDA/PI microscopy has revealed several apoptotic cells in the treatment groups. SEM micrographs have shown the difficulty of hGFs to adhere on rough surfaces.

CONCLUSIONS

The combination of titanium particles and LPS significantly upregulated the expression of IL-6, IL-8 and Col-1a. It appears that particles may arouse similar reactions to the endotoxin, while synergistically intensifying it.