BACKGROUND: Regulatory dendritic cell (DCreg) subset exhibits a unique capacity for inducing immune tolerance among the variety subsets of dendritic cells (DCs) within gut-associated lymphoid tissues (GALTs). Fms-like tyrosine kinase 3 ligand (FLT3L) is involved in the differentiation of DCregs and the subsequent expansion of regulatory T-cells (Tregs) mediated by DCregs, though the precise mechanism remains poorly understood. This study aimed to explore the expansion mechanism of Treg induced by DCreg and the role of FLT3L in this process. METHODS: DCregs were distinguished from other DC subsets isolated from GALTs of BALB/c mice through a mixed lymphocyte reaction assay. The functions and mechanisms by which FLT3L promoted Treg expansion via DCregs were investigated in vitro through co-culture experiments involving DCregs and either CD4 + CD25 - T-cells or CD4 + CD25 + T-cells. Additionally, an in vivo experiment was conducted using a dextran sulfate sodium (DSS)-induced colitis model in mice. RESULTS: CD103 + CD11b + DC exhibited DCreg-like functionality and was identified as DCreg for subsequent investigation. Analysis of Foxp3 + Treg percentages within a co-culture system of CD4 + CD25 - T-cells and DCregs, with or without FLT3L, demonstrated the involvement of the FLT3/FLT3L axis in driving the differentiation of precursor T-cells into Foxp3 + Tregs induced by DCregs. Cell migration and co-culture assays revealed that the FLT3/FLT3L axis enhanced DCreg migration toward Tregs via the Rho pathway. Additionally, it was observed that DCregs could promote Treg proliferation through the Notch pathway, as inhibition of Notch signaling by DAPT (N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester) suppressed Treg expansion within the co-culture system of DCregs and CD4 + T-cells or CD4 + CD25 + T-cells. Furthermore, the FLT3/FLT3L axis influenced JAG1 expression in DCregs, indirectly modulating Treg expansion. In vivo experiments further established that FLT3L promoted DCreg expansion and restored Treg balance in DSS-induced colitis models, thereby ameliorating colitis symptoms in mice. CONCLUSION The FLT3/FLT3L axis is integral to the maintenance of DCreg function in Treg expansion.
Animals ; T-Lymphocytes, Regulatory/immunology* ; Dendritic Cells/immunology* ; Mice ; Mice, Inbred BALB C ; Membrane Proteins/metabolism* ; Receptors, Notch/metabolism* ; Lymphoid Tissue/metabolism* ; Signal Transduction/physiology* ; Coculture Techniques ; Flow Cytometry

OBJECTIVE: To investigate the antioxidant and osteogenic induction capabilities of calcium phosphate nanoflowers (hereinafter referred to as nanoflowers) in vitro at different concentrations. METHODS: Nanoflowers were prepared using gelatin, tripolyphosphate, and calcium chloride. Their morphology, microstructure, elemental composition and distribution, diameter, and molecular constitution were characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive spectroscopy. Femurs and tibias were harvested from twelve 4-week-old Sprague Dawley rats, and bone marrow mesenchymal stem cells (BMSCs) were isolated and cultured using the whole bone marrow adherent method, followed by passaging. The third passage cells were identified as stem cells by flow cytometry and then co-cultured with nanoflowers at concentrations of 0, 0.4, 0.8, 1.2, 1.6, 2.0, 2.4, 2.8, 3.2, and 3.6 mg/mL. Cell counting kit 8 (CCK-8) assay was performed to screen for the optimal concentration that demonstrated the best cell viability, which was subsequently used as the experimental concentration for further studies. After co-culturing BMSCs with the screened concentration of nanoflowers, the biocompatibility of the nanoflowers was verified through live/dead cell staining, scratch assay, and cytoskeleton staining. The antioxidant capacity was assessed by using reactive oxygen species (ROS) fluorescence staining. The in vitro osteoinductive ability was evaluated via alkaline phosphatase (ALP) staining, alizarin red staining, and immunofluorescence staining of osteocalcin (OCN) and Runt-related transcription factor 2 (RUNX2). All the above indicators were compared with the control group of normally cultured BMSCs without the addition of nanoflowers. RESULTS: Scanning electron microscopy revealed that the prepared nanoflowers exhibited a flower-like structure; transmission electron microscopy scans discovered that the nanoflowers possessed a multi-layered structure, and high-magnification images displayed continuous atomic arrangements, with the nanoflower diameter measuring (2.00±0.25) μm; energy-dispersive spectroscopy indicated that the nanoflowers contained elements such as C, N, O, P, and Ca, which were uniformly distributed across the flower region; Fourier transform infrared spectroscopy analyzed the absorption peaks of each component, demonstrating the successful preparation of the nanoflowers. Through CCK-8 screening, the concentrations of 0.8, 1.2, and 1.6 mg/mL were selected for subsequent experiments. The live/dead cell staining showed that nanoflowers at different concentrations exhibited good cell compatibility, with the 1.2 mg/mL concentration being the best (P<0.05). The scratch assay results indicated that the cell migration ability in the 1.2 mg/mL group was superior to the other groups (P<0.05). The cytoskeleton staining revealed that the cell morphology was well-extended in all concentration groups, with no significant difference compared to the control group. The ROS fluorescence staining demonstrated that the ROS fluorescence in all concentration groups decreased compared to the control group after lipopolysaccharide induction (P<0.05), with the 1.2 mg/mL group showing the weakest fluorescence. The ALP staining showed blue-purple nodular deposits around the cells in all groups, with the 1.2 mg/mL group being significantly more prominent. The alizarin red staining displayed orange-red mineralized nodules around the cells in all groups, with the 1.2 mg/mL group having more and denser nodules. The immunofluorescence staining revealed that the expressions of RUNX2 and OCN proteins in all concentration groups increased compared to the control group, with the 1.2 mg/mL group showing the strongest protein expression (P<0.05). CONCLUSION The study successfully prepares nanoflowers, among which the 1.2 mg/mL nanoflowers exhibits excellent cell compatibility, antioxidant properties, and osteogenic induction capability, demonstrating their potential as an artificial bone substitute material.
Animals ; Osteogenesis/drug effects* ; Mesenchymal Stem Cells/drug effects* ; Calcium Phosphates/pharmacology* ; Rats, Sprague-Dawley ; Rats ; Antioxidants/chemistry* ; Cells, Cultured ; Cell Differentiation/drug effects* ; Nanostructures/chemistry* ; Tissue Engineering/methods* ; Bone Marrow Cells/cytology* ; Coculture Techniques ; Tissue Scaffolds/chemistry* ; Male ; Biocompatible Materials/chemistry* ; Cell Survival ; Core Binding Factor Alpha 1 Subunit/metabolism* ; Cell Proliferation

Objective To investigate the effects of hyaluronic acid and proteoglycan-linked protein 1 (HAPLN1) secreted by synovial fibroblasts (FLS) on the polarization of macrophages (Mϕ) in rheumatoid arthritis (RA). Methods Human monocytic leukemia cells (THP-1) were differentiated into Mϕ, which were subsequently exposed to recombinant HAPLN1 (rHAPLN1). RA-FLS were transfected separately with HAPLN1 overexpression plasmid (HAPLN1^OE) or small interfering RNA targeting HAPLN1 (si-HAPLN1), and then co-cultured with Mϕ to establish a co-culture model. The viability of Mϕ was assessed using the CCK-8 assay, and the proportions of pro-inflammatory M1-type and anti-inflammatory M2-type Mϕ were analyzed by flow cytometry. Additionally, the expression levels of inflammatory markers, including interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), and inducible nitric oxide synthase (iNOS), were quantified using quantitative real-time PCR and Western blot analysis. Results The viability of Mϕ was increased in the rHAPLN1 group compared to the control group. Furthermore, both the M1/Mϕ ratio and inflammatory factor levels were elevated in the rHAPLN1 and HAPLN1^OE groups. In contrast, the si-HAPLN1 group exhibited a decrease in the M1/Mϕ ratio and inflammatory factor expression. Notably, the introduction of rHAPLN1 in rescue experiments further promoted Mϕ polarization towards the M1 phenotype. Conclusion HAPLN1, secreted by RA fibroblast-like synoviocytes (RA-FLS), enhances Mϕ polarization towards the M1 phenotype.
Humans ; Arthritis, Rheumatoid/genetics* ; Macrophages/immunology* ; Fibroblasts/metabolism* ; Phenotype ; Extracellular Matrix Proteins/genetics* ; Proteoglycans/genetics* ; Synovial Membrane/cytology* ; Tumor Necrosis Factor-alpha/genetics* ; Interleukin-1beta/genetics* ; Nitric Oxide Synthase Type II/genetics* ; Cell Differentiation ; Coculture Techniques ; THP-1 Cells

Objective To observe the effect of m⁶A methylation regulation on Notch1 pathway on the homing of BMSCs in asthma, and the intervention study of traditional Chinese medicine compound Yanghe Pingchuan Granules. Methods Rat bone mesenchymal stem cells(BMSC)and bronchial epithelial cells were cocultured. The extracted cells were divided into: bronchial epithelial cell group, asthma bronchial epithelial cell+mesenchymal stem cell co-culture group (co-culture group), co-culture cell+normal serum group, coculture cell+serum containing optimal drug group, siRNA FTO+normal serum group, siRNA FTO-NC+normal serum group, and siRNA FTO+serum containing optimal drug group. The vitality and cell cycle changes of co-cultured cells were detected. The level and markers of homing BMSC were detected by immunofluorescence staining. The expression of Notch1 pathway related genes were detected by qRT-PCR. The expression of Notch1 pathway related proteins were detected by Western blot. Results Compared with bronchial epithelial cell group, the co-cultured cell group showed an increase in the homing level of BMSCs and the expression of C-X-C motif chemokine receptor 4 (CXCR4), stromal cell-derived factor 1 (SDF-1), Notch1, transcription factor recombination signal binding protein-J (RBP-J), and hairy enhancer of split 1 (Hes1) proteins. Compared with the co-cultured cell group and co-cultured cell+normal serum group, the co-cultured cell+serum containing optimal drug group showed an increase in the homing level of BMSCs and the expressions of CXCR4 and SDF-1, while the protein and mRNA levels of Notch1 and Hes1 decreased. Compared with the siRNA FTO-NC+normal serum group, the siRNA FTO+normal serum group showed an increase in the levels of Notch1, activated Notch1, RBP-J, Hes1 protein, and cell viability, while the level of homing BMSC decreased. Compared with siRNA FTO+normal serum group, the levels of Notch1, RBP-J mRNA, activated Notch1, and Hes1 protein decreased, while the level of homing BMSCs increased in siRNA FTO+serum containing optimal drug group. The levels of Notch1, RBP-J, and Hes1 mRNA were reduced in the co-cultured cells+serum containing optimal drug group. Compared with siRNA FTO+serum containing optimal drug group, the expressions of Notch1, activated Notch1, RBP-J, Hes1 protein and cell viability decreased, while the level of homing BMSCs increased in the co-cultured cells+serum containing optimal drug group. Conclusion Yanghe Pingchuan Granules may promote the homing of BMSCs in asthma and alleviate asthma inflammation by upregulating the expression of FTO and inhibiting the expression of downstream genes in the Notch1 signaling pathway.
Animals ; Receptor, Notch1/genetics* ; Mesenchymal Stem Cells/cytology* ; Asthma/genetics* ; Drugs, Chinese Herbal/pharmacology* ; Signal Transduction/drug effects* ; Rats ; Coculture Techniques ; Alpha-Ketoglutarate-Dependent Dioxygenase FTO/genetics* ; Epithelial Cells/metabolism* ; Rats, Sprague-Dawley ; Cells, Cultured ; Male

Objective To investigate the regulatory effect of tumor necrosis factor-α-induced protein-8-like factor 2 (TIPE2) on the phenotype of lung cancer tumor-associated macrophages (TAM) and its influence on the stemness of lung cancer cells. Methods Mouse macrophage cell line RAW264.7 was cultured and infected with either LV-TIPE2 lentivirus or negative control LV-NC lentivirus. The TIPE2 expression in infected cells was assessed by real-time quantitative PCR (RT-qPCR) and Western blotting to verify transfection efficiency. The infected RAW264.7 cells were co-cultured with lung cancer cell line A549, and were divided into four groups: control group (RAW264.7 cells or A549 cells cultured alone), TAM group (RAW264.7 cells co-cultured with A549 cells), LV-NC group (RAW264.7 cells infected with LV-NC and co-cultured with A549 cells), LV-TIPE2 group (RAW264.7 cells infected with LV- TIPE2 and co-cultured with A549 cells). The RAW264.7 cells were collected after co-culture, and the expression of mannose receptor (CD206) protein of M2 macrophages was detected by cellular immunofluorescence staining. The proportions of M1 and M2 macrophages were detected by flow cytometry. After co-culture, A549 cells were collected, and their activity was assessed by CCK-8 assay. Self-renewal ability was evaluated using tumor cell pelleting experiment. The expression of stemness marker proteins-including cluster of differentiation 133 (CD133), transmembrane adhesion molecule (CD44), sex-determining region Y-box protein 2 (SOX2) and octamer-binding transcription factor 4 (OCT4)-was detected by Western blot. Results Compared with the control group or LV-NC group, the relative mRNA and protein expression levels of TIPE2 in RAW264.7 cells from the LV-TIPE2 group were significantly upregulated. Compared with the control group, the fluorescence intensity of M2-type macrophage marker CD206 protein in RAW264.7 cells from the TAM group was significantly increased, the proportion of M1-type macrophages was significantly decreased, and the proportion of M2-type macrophages was significantly increased. In contrast, compared with the TAM group, the fluorescence intensity of CD206 protein in RAW264.7 cells from the LV-TIPE2 group was significantly decreased, the proportion of M1-type macrophages was significantly increased, and the proportion of M2-type macrophages was significantly decreased. Compared with the control group, the proliferation activity of A549 cells in TAM group was significantly increased, the number of tumor pellet formation was significantly increased, and the relative expression levels of CD133, CD44, SOX2 and OCT4 were significantly up-regulated. However, compared with the TAM group, the proliferation activity of A549 cells from the LV-TIPE2 group was significantly decreased, the number of tumor pellet formation was significantly decreased, and the relative expression levels of CD133, CD44, SOX2 and OCT4 were significantly decreased. Conclusion TIPE2 can suppress the stemness of lung cancer cells by inhibiting the polarization of macrophages to M2-type, thereby exerting an anticancer effect.
Animals ; Mice ; Humans ; Tumor-Associated Macrophages/metabolism* ; Lung Neoplasms/genetics* ; Intracellular Signaling Peptides and Proteins/metabolism* ; RAW 264.7 Cells ; A549 Cells ; Phenotype ; Coculture Techniques ; Receptors, Cell Surface/metabolism* ; Neoplastic Stem Cells/metabolism* ; Mannose Receptor ; Mannose-Binding Lectins/metabolism* ; Lectins, C-Type/metabolism* ; Cell Polarity ; Macrophages/metabolism*

OBJECTIVE: To investigate the role of extracellular vesicles (EVs) derived from placental tissue and placental mesenchymal stem cells in supporting the growth and function of adult hematopoietic stem and progenitor cells (HSPCs), so as to optimize their culture system. METHODS: EVs were isolated from mouse placental tissue (PL-EV) and placental mesenchymal stem cells (PL-MSC-EV). These EVs were co-cultured with 3 000 adult bone marrow LKS⁺ (lineage^- c-Kit⁺ Sca-1⁺ ) cells for 72 hours at concentrations of 0, 1, 10, 50, 100, and 200 μg/ml. The proportion and absolute count of LKS⁺ cells after co-culture were analyzed by flow cytometry, while their self-renewal and multi-lineage differentiation potential were evaluated using colony-forming unit (CFU) assays. RESULTS: Compared to the blank control group, the proportion of LKS⁺ cells were significantly increased in PL-EV groups at concentrations ≥10 μg/ml after 72 hours of co-culture. Notably, LKS⁺ cells co-cultured at the concentration of 10 μg/ml exhibited the highest absolute count (899±171) and the highest proportion of LT-HSCs (LKS⁺ CD135^- CD34^-) (0.67%±0.07%). In the PL-MSC-EV co-culture system, the absolute count of LKS⁺ cells peaked at the concentration of 1 μg/ml (1011±99 cells), though the proportion of LT-HSCs was relatively low (0.15%±0.05%). The comparison between these two culture systems revealed that PL-EV at 10 μg/ml and PL-MSC-EV at 1 μg/ml displayed the most pronounced effects on LKS⁺ cell proliferation, but with no significant difference between them. CFU assays showed that, in the PL-EV culture system, the number of LKS⁺ colony formed in 1 and 10 μg/ml groups was not significantly different compared with the blank control group. In contrast, in the PL-MSC-EV system, the highest LKS⁺ colony-forming capacity was observed when co-cultured with 1 μg/ml PL-MSC-EV, while a significant reduction was noted at concentrations above 10 μg/ml. CONCLUSION PL-EV and PL-MSC-EV effectively support the growth and function of HSPCs. And PL-MSC-EV exhibits a superior efficacy in preserving the stemness of LKS⁺ cells, thus suggesting its potential for optimizing culture systems of HSPCs.
Mesenchymal Stem Cells/cytology* ; Extracellular Vesicles ; Placenta/cytology* ; Female ; Animals ; Mice ; Pregnancy ; Hematopoietic Stem Cells/cytology* ; Coculture Techniques ; Cell Differentiation ; Cell Proliferation ; Cells, Cultured

OBJECTIVES: To investigate the mechanism by which transforming growth factor‑β (TGF‑β) regulates major histocompatibility complex class I (MHC-I) expression in hepatocellular carcinoma (HCC) cells and its role in immune evasion of HCC. METHODS: HCC cells treated with TGF‑β alone or in combination with SB-431542 (a TGF-β type I receptor inhibitor) were examined for changes in MHC-I expression using RT-qPCR and Western blotting. A RNA interference experiment was used to explore the role of miR-23a-3p/IRF1 signaling in TGF‑β‑mediated regulation of MHC-I. HCC cells with different treatments were co-cultured with human peripheral blood mononuclear cells (PBMCs), and the changes in HCC cell proliferation was assessed using CCK-8 and colony formation assays. T-cell cytotoxicity in the co-culture systems was assessed with lactate dehydrogenase (LDH) release and JC-1 mitochondrial membrane potential assays, and T-cell activation was evaluated by flow cytometric analysis of CD69 cells and ELISA for TNF-α secretion. RESULTS: TGF‑β treatment significantly suppressed MHC-I expression in HCC cells and reduced T-cell activation, leading to increased tumor cell proliferation and decreased HCC cell death in the co-culture systems. Mechanistically, TGF-β upregulated miR-23a-3p, which directly targeted IRF1 to inhibit MHC-I transcription. Overexpression of miR-23a-3p phenocopied TGF‑β‑induced suppression of IRF1 and MHC-I. CONCLUSIONS We reveal a novel immune escape mechanism of HCC, in which TGF‑β attenuates T cell-mediated antitumor immunity by suppressing MHC-I expression through the miR-23a-3p/IRF1 signaling axis.
Humans ; MicroRNAs/genetics* ; Carcinoma, Hepatocellular/metabolism* ; Liver Neoplasms/metabolism* ; Interferon Regulatory Factor-1/metabolism* ; Transforming Growth Factor beta/metabolism* ; Signal Transduction ; Histocompatibility Antigens Class I/metabolism* ; Cell Line, Tumor ; Tumor Escape ; Coculture Techniques

OBJECTIVES: To investigate the effect of cardiomyocytes-derived exosomes on lipopolysaccharide (LPS)-induced cardiomyocyte injury and its mechanism. METHODS: Exosomes isolated from rat cardiomyocytes with or without LPS treatment were co-cultured with rat lymphocytes. The lymphocytes with or without exosome treatment were co-cultured with LPS-induced rat cardiomyocytes for 48 h. Cardiomyocyte apoptosis was detected using flow cytometry, and the expressions of apoptosis marker proteins and the PI3K/AKT pathway proteins were detected using Western blotting. The effects of human recombinant IL-38 protein on apoptosis and protein expressions in LPS-induced cardiomyocytes were examined. RESULTS: Compared with normal cardiomyocyte-derived exosomes, the exosomes from LPS-induced cardiomyocytes significantly enhanced proliferation and increased mRNA and protein expression levels of IL-38 in rat lymphocytes. Bioinformatics analysis suggested that miR-1275 in the exosome played a key role in LPS-induced cardiomyocyte injury, and in dual luciferase reporter gene assay, miR-1275 mimics significantly increased luciferase activity of WT-IL-38. Co-culture with lymphocytes treated with exosomes from LPS-induced cardiomyocytes significantly inhibited apoptosis of LPS-induced cardiomyocytes. Treatment with recombinant IL-38 also effectively lowered apoptosis rate of LPS-induced cardiomyocytes, reduced cellular expression of Bax protein, and increased the protein expression levels of Bcl-2, p-PI3K and p-AKT. CONCLUSIONS miR-1275 in exosomes derived from LPS-induced cardiomyocytes mediates IL-38 up-regulation expression in lymphocytes to activate the PI3K/AKT pathway and inhibit LPS-induced cardiomyocyte apoptosis.
Apoptosis/drug effects* ; MicroRNAs/metabolism* ; Myocytes, Cardiac/metabolism* ; Animals ; Lipopolysaccharides ; Rats ; Exosomes/metabolism* ; Up-Regulation ; Interleukins/metabolism* ; Lymphocytes/cytology* ; Cells, Cultured ; Signal Transduction ; Coculture Techniques ; Phosphatidylinositol 3-Kinases/metabolism* ; Rats, Sprague-Dawley ; Humans ; Proto-Oncogene Proteins c-akt/metabolism*

Infiltration and activation of peripheral immune cells are critical in the progression of multiple sclerosis and its experimental animal model, experimental autoimmune encephalomyelitis (EAE). This study investigates the role of high mobility group box 1 (HMGB1) in oligodendrocyte precursor cells (OPCs) in modulating pathogenic T cells infiltrating the central nervous system through the blood-brain barrier (BBB) by using OPC-specific HMGB1 knockout (KO) mice. We found that HMGB1 released from OPCs promotes BBB disruption, subsequently allowing increased immune cell infiltration. The migration of CD4+ T cells isolated from EAE-induced mice was enhanced when co-cultured with OPCs compared to oligodendrocytes (OLs). OPC-specific HMGB1 KO mice exhibited lower BBB permeability and reduced immune cell infiltration into the CNS, leading to less damage to the myelin sheath and mitigated EAE progression. CD4+ T cell migration was also reduced when co-cultured with HMGB1 knock-out OPCs. Our findings reveal that HMGB1 secretion from OPCs is crucial for regulating immune cell infiltration and provides insights into the immunomodulatory function of OPCs in autoimmune diseases.
Animals ; Encephalomyelitis, Autoimmune, Experimental/metabolism* ; HMGB1 Protein/deficiency* ; Mice, Knockout ; Oligodendrocyte Precursor Cells/immunology* ; Mice, Inbred C57BL ; CD4-Positive T-Lymphocytes/immunology* ; Cell Movement ; Blood-Brain Barrier/immunology* ; Mice ; Myelin Sheath/pathology* ; Disease Models, Animal ; Coculture Techniques ; Oligodendroglia/metabolism* ; Female ; Cells, Cultured

Understanding microbial-host interactions in the oral cavity is essential for elucidating oral disease pathogenesis and its systemic implications. In vitro bacteria-host cell coculture models have enabled fundamental studies to characterize bacterial infection and host responses in a reductionist yet reproducible manner. However, existing in vitro coculture models fail to establish conditions that are suitable for the growth of both mammalian cells and anaerobes, thereby hindering a comprehensive understanding of their interactions. Here, we present an asymmetric gas coculture system that simulates the oral microenvironment by maintaining distinct normoxic and anaerobic conditions for gingival epithelial cells and anaerobic bacteria, respectively. Using a key oral pathobiont, Fusobacterium nucleatum, as the primary test bed, we demonstrate that the system preserves bacterial viability and supports the integrity of telomerase-immortalized gingival keratinocytes. Compared to conventional models, this system enhanced bacterial invasion, elevated intracellular bacterial loads, and elicited more robust host pro-inflammatory responses, including increased secretion of CXCL10, IL-6, and IL-8. In addition, the model enabled precise evaluation of antibiotic efficacy against intracellular pathogens. Finally, we validate the ability of the asymmetric system to support the proliferation of a more oxygen-sensitive oral pathobiont, Porphyromonas gingivalis. These results underscore the utility of this coculture platform for studying oral microbial pathogenesis and screening therapeutics, offering a physiologically relevant approach to advance oral and systemic health research.
Coculture Techniques/methods* ; Humans ; Fusobacterium nucleatum/physiology* ; Gingiva/microbiology* ; Keratinocytes/microbiology* ; Host Microbial Interactions ; Mouth/microbiology* ; Host-Pathogen Interactions ; Epithelial Cells/microbiology* ; Cells, Cultured ; Porphyromonas gingivalis