Effect of LPS and IFN-γ transient inflammatory priming on periodontal ligament cells and Schwann cellsAbstract:
This study investigated the effects of Escherichia coli lipopolysaccharide (LPS; 2,000 ng/mL) and interferon-γ (IFN-γ; 50 ng/mL) on human periodontal ligament cells (PDLCs) and mouse Schwann cells (SCs). After a transient inflammatory priming (5 hours), cell migration/proliferation and viability (n = 4) were assessed with scratch and MTT assays, respectively, while inflammatory markers were quantified by real-time quantitative polymerase chain reaction (RT-qPCR; n = 3). Mineralized matrix formation was induced for 12 days and analyzed via Alizarin Red staining (ARS; n = 4) and osteogenesis-related gene expression (RT-qPCR; n = 3). Because of their distinct origins, the two cell lineages were assessed independently. Exposure to LPS+IFN-γ did not affect the viability or migration/proliferation of PDLCs or SCs. In PDLCs, LPS+IFN-γ exposure upregulated interleukin-1α (IL-1α) and interleukin-6 (IL-6), interferon-γ (IFN-γ), IFN-γ receptor (IFN-γR), and tumor necrosis factor (TNF). In SCs, IL-6 and IFN-γR were upregulated, whereas TNF was downregulated compared to the untreated control. Following mineral matrix induction, exposed PDLCs showed increased expression of alkaline phosphatase (ALPL) and runt-related transcription factor 2 (RUNX-2). SCs upregulated ALPL, RUNX-2, and osteocalcin (OCN). Quantitative ARS data indicated that calcium deposition in PDLCs exposed to LPS+IFN-γ was similar to that in the untreated group. SCs exposed to LPS+IFN-γ exhibited significant mineralized matrix formation. Overall, PDLCs responded to LPS+IFN-γ priming with an inflammatory transcriptional response. SCs were unresponsive or showed a downregulated response to inflammatory markers (TNF and IL-1α). Both cell lineages demonstrated mineralized matrix formation after LPS and IFN-γ transient priming.
Descriptors:
Periodontal ligament; Lipopolysaccharides; Schwann cells; Inflammation; In vitro techniques
Introduction
Periodontitis is a chronic inflammatory condition triggered by a shift from a symbiotic to a dysbiotic microbial community.1 It affects over 60% of adults worldwide, with nearly 24% presenting with a severe form.2 The disease is driven by a dysregulated host response, leading to connective tissue damage, irreversible alveolar bone loss, and a systemic inflammatory burden.1 Conventional clinical treatments, including surgical and nonsurgical procedures and antibiotic-based approaches, effectively control disease progression but have limited ability to reverse alveolar bone loss.3 To overcome these limitations, regenerative strategies that combine stem cells with biomaterials have emerged as promising approaches for restoring the PDL and alveolar bone.4,5 Successful tooth preservation is critical for reducing health inequalities and maintaining quality of life.6 However, the success of regenerative therapies depends on how transplanted cells respond to the inflammatory microenvironment.
During the course of periodontal disease, bacterial products such as LPS penetrate periodontal tissues and activate the host innate immune response, stimulating cytokine production.7 Identifying key cellular players that modulate the periodontal disease (PD) milieu is therefore essential for regenerative dentistry. Schwann cells (SCs) and their progenitors have emerged as promising candidates for tissue engineering due to their plasticity and secretome profile.8–10 Originating from the neural crest, these cells are required for peripheral nerve myelination and also serve as precursors during odontogenesis,11 giving rise to dental pulp cells, odontoblasts, and osteoblasts.12 Beyond their developmental roles, SCs orchestrate repair by secreting neurotrophic and growth factors, such as Platelet-derived growth factor AA (PDGF-AA) and Oncostatin M (OSM), thereby promoting the renewal of mesenchymal progenitor cells.8
The therapeutic potential of SCs is well documented in several tissues, including the skin.8–10 In the alveolar bone, SCs may promote tissue repair through paracrine signaling.13,14 Furthermore, their ability to modulate immune responses makes them promising candidates for the treatment of inflammatory diseases.15 Given that the periodontal ligament (PDL) is derived from the neural crest-derived ectomesenchyme of the dental follicle,16 SCs within the PDL and alveolar bone may promote homeostasis.17 However, how SCs respond to a chronic pro-inflammatory microenvironment remains unclear. The extent to which pathogen byproducts, such as LPS, influence SCs’ pro-inflammatory response and mineral matrix formation is underexplored. Moreover, for other cell types, such as periodontal ligament cells (PDLCs), evidence regarding their response to LPS remains conflicting.18–20 Therefore, we aimed to investigate the inflammatory and mineralized matrix formation responses of human PDLCs and mouse SCs following exposure to LPS from Escherichia coli and interferon-gamma (IFN-γ), as a transient inflammatory priming.
Methodology
Cell lineages and culture
PDLCs were isolated from PDL tissue from healthy patients according to previously published protocols.5,21 The tissue was digested in a solution containing 3 mg/mL type I collagenase and 4 mg/mL dispase for 1 hour at 37°C. PDL samples and single cells were obtained by passing the suspensions through a 70-μm cell strainer. The cells were seeded in Petri culture dishes, expanded in Dulbecco's Modified Eagle Medium (DMEM) supplemented with 15% fetal bovine serum, 1% penicillin, and 1% streptomycin (all from Thermo Fisher Scientific, Waltham, USA), and incubated at 37°C in 5% CO2. PDLC characterization was performed as previously described23. Briefly, PDLCs were incubated with CD105, CD146, CD45, and IgG antibodies and then subjected to flow cytometry, as described in previous reports.5,21 All procedures were approved by the Institutional Review Board of the University of California, Los Angeles (UCLA) under IRB#18-001947, and PDLCs between passages 4 and 8 were used for all experiments. A commercially available mouse SC line (ATCC-SW-10) was used for experimentation and expanded in the regular cell culture medium described above.
LPS+ IFN-γ priming media
LPS+IFN-γ priming medium consisted of DMEM supplemented with 15% fetal bovine serum, 1% penicillin, and 1% streptomycin, supplemented with 2,000 ng/mL of LPS from Escherichia coli (Sigma Aldrich, Burlington, USA) and 50 ng/mL interferon gamma (IFN-γ; Sigma Aldrich, Burlington, USA) for 5 hours.22
Migration/proliferation and viability
PDLCs and SCs were seeded in quadruplicate for each group at a density of 2 x 104 cells/well in a 48-well plate. After reaching confluence, a scratch was created at the center of each well using a P200 pipette tip in both untreated and LPS+IFN-γ-treated cells. Bright-field images were obtained after scratching (0 h) using a Leica DMi8 microscope (Wetzlar, Germany), after which the cells were cultured in regular DMEM. Additional images were obtained after 24 and 48 hours to assess cell migration/proliferation. Wound areas were quantified using ImageJ (NIH, Bethesda, USA). The software was calibrated using the microscope scale bar, and the wound area was outlined at all time points by a single calibrated examiner using the freehand selection tool. The percentage of wound closure was calculated as follows: (initial wound area – wound area at 24 or 48 h) / initial area ×100.
At 96 hours, cell viability was assessed using the MTT assay (Sigma-Aldrich, St. Louis, USA) according to the manufacturer's instructions. Absorbance was read at 540 nm using a spectrophotometer (BioTek Synergy H1, BioTek Instruments, Winooski, USA).
Inflammatory assessment in a microenvironment containing LPS and IFN-γ
PDLCs and SCs were seeded in triplicate for each group in 12-well plates at a density of 1 × 105 cells/well. Upon reaching confluence, the LPS+IFN-γ group was exposed. At 24 hours, SCs or PDLCs were collected in TRIzol (Invitrogen, Waltham, USA) for real-time quantitative polymerase chain reaction (RT-qPCR) of pro-inflammatory markers: interleukin-1-alpha (IL1-μ), interleukin-6 (IL-6), tumor necrosis factor (TNF), IFN-γ, interferon-gamma receptor (IFN-γR). Primer sequences for human (PDLCs) or mouse (SCs) were obtained from PrimerBank (https://pga.mgh.harvard.edu/primerbank/) and synthesized by Thermo Fisher (Thermo Fisher Scientific, Waltham, USA). Primer sequences are described in Table 1.
Total mRNA was extracted using the PureLink RNA kit (Thermo Fisher Scientific, Waltham, MA, USA) following the TRIzol protocol. Subsequently, 0.37 μg of total RNA was reverse transcribed using the qScript cDNA kit (Quantabio, Beverly, USA). The obtained cDNA was used for qPCR with SYBR Green PCR Master Mix (Thermo Fisher Scientific, Waltham, USA). Ct values for pro-inflammatory markers, obtained in triplicate, were normalized to the endogenous control, glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) and compared with the reference control group (untreated with LPS+IFN-γ) for analysis of inflammatory gene expression using the 2−ΔΔCt method.
Mineral matrix formation
For the calcium deposition assay, PDLCs and SCs were seeded in triplicate onto 12-well plates at a density of 1 × 105 cells/well for each experimental group. Cells were cultured in mineralization induction medium (DMEM supplemented with 15% FBS, 1% penicillin, and streptomycin, 0.1 mM L-ascorbic acid, 0.01 μM dexamethasone, 1.8 mM KH2PO4). Cells cultured in regular conditions were also evaluated. The medium was changed every 48 hours.
After 12 days, calcium deposition nodules and mineralized matrix were evaluated by Alizarin Red staining (ARS). Cells were washed with PBS, fixed in 75% isopropanol, rehydrated with Milli-Q water (Merck, Darmstadt, Germany), and incubated with ARS solution (pH 7.2) for 5 minutes. After washing with PBS and air-drying, bright-field images were acquired using a Leica DMi8 microscope (Wetzlar, Germany). Mineral deposits were dissolved in a 10% acetic acid-methanol solution (4:1, v/v). Absorbance was measured using a spectrophotometer at 490 nm (BioTek Synergy H1, BioTek Instruments, Winooski, VT, USA). The values were normalized to the total protein absorbance of each well.
Cells were also collected for RT-qPCR analysis of osteogenesis-related genes, including alkaline phosphatase (ALPL), runt-related transcription factor 2 (RUNX-2), and osteocalcin (OCN), using the primer sequences listed in Table 2. RT-qPCR was conducted as described above. The untreated group cultured in regular media served as the reference control.
Statistical analysis
Data were checked for normality using the Shapiro-Wilk test, and homogeneity of variances was assessed with Levene's test (p > 0.05). For comparison between two groups, normally distributed data were analyzed using an unpaired Student's t-test (p < 0.05). For multiple group comparisons across different time points and conditions, a repeated-measures two-way ANOVA followed by Tukey's post-hoc test was used. For comparison among multiple groups, a one-way ANOVA followed by Tukey's post-hoc test was used. Data are presented as mean ± standard error of the mean (SEM). Statistical analyses were performed using GraphPad Prism 9.0 (GraphPad Software, Version 9.0, La Jolla, USA). Statistical significance was set at p < 0.05 (95% confidence level). All experiments were analyzed using the number of biological replicates specified for each assay.
Results
Because of the distinct origins of the PDLCs and SCs used in this study, the results are presented separately.
Effect of LPS+IFN-γ priming on migration/proliferation and viability
LPS+IFN-γ exposure did not impair PDLC (1b) migration/proliferation, assessed as the percentage of remaining wound area at 24 and 48 hours (Figure 1a) (p > 0.05). The treatment numerically reduced SC migration/proliferation (1c), with no statistical difference compared with the control group (p > 0.05).
At 96 hours, cell viability was unaffected by LPS+IFN-γ treatment (Figures 2a and b). The differences between the control and treated groups were not significant for any cell type analyzed (p > 0.05).
Effect of LPS+IFN-γ priming on expression of pro-inflammatory markers
LPS+IFN-γ-treated PDLCs showed a significant upregulation of IL-1 a, IL-6, IFN-γ, IFN-γR, and TNF at 24 h compared to the untreated group (p < 0.05) (Figures 3a–e).
Expression of pro-inflammatory genes by PDLCs or SCs cultured within a microenvironment containing LPS+IFN-γ.
In SCs, IL-1a expression was downregulated (Figure 3f), and IFN-γ expression was slightly increased (Figure 3h), but without a significant difference when compared to the untreated group (p > 0.05). SCs showed significant upregulation of IL-6 and IFN-γR, while TNF expression was downregulated after LPS+IFN-γ exposure (p < 0.05) (Figures 3g, i, and j).
Effect of LPS+IFN-γ priming on mineral matrix formation
When evaluating the ARS color bright-field images, PDLCs cultured in regular media showed minimal staining, whereas PDLCs cultured in mineral-induction media exhibited an increased mineralized matrix and nodule formation after LPS+IFN-γ priming (Figure 4a). Quantitative analysis showed that mineral matrix formation was similar between the untreated and LPS+IFN-γ groups of PDLCs (p>0.05) (Figure 4b).
Alizarin Red staining bright-field images and quantification of PDLCs and SCs cultured in a microenvironment containing LPS+IFN-γ for 12 days.
For SCs, ARS staining revealed enhanced mineral deposition when cells were cultured in mineral-induction media and exposed to LPS + IFN-γ compared to the untreated control (Figure 4c and d). Groups cultured in regular media showed no significant mineral matrix formation.
Effect of LPS+IFN-γ priming on osteogenesis-related gene expression
When evaluating the effect of LPS+IFN-γ on osteogenesis-related markers, PDLCs cultivated in mineral-induction media upregulated ALPL and RUNX-2 (p < 0.05), while downregulated OCN (p < 0.05) (Figures 5a-c).
Expression of osteogenesis-related genes in PDLCs and SCs cultured in a microenvironment containing LPS+IFN-γ for 12 days.
SCs cultivated in mineral-induction media upregulated all assessed osteogenesis-related genes (ALPL, RUNX-2, and OCN) when exposed to LPS+IFN-γ (p < 0.05) (Figures 5d-f)
Discussion
Upon injury, neural crest-derived stem cells respond by secreting growth factors and undergoing differentiation, which may help prevent tissue loss. Mechanisms such as increased blood supply and neural response are activated to promote tissue repair.9 In the present study, we evaluated the effect of LPS derived from E. coli and IFN-γ on PDLC and SC functions. The inflammatory priming consisted of a transient challenge, a standardized method for inducing a pro-inflammatory response.22,23 E. coli LPS enhances the expression of inflammatory cytokines and TLR4.23 Moreover, LPS in the presence of IFN-γ induces TNF production and upregulates CD14 receptors, thereby enhancing immune activation in monocytes and macrophages.22 This association increases inflammation through cytokine receptor expression, autocrine and paracrine signaling, and activation of downstream response genes,22 enabling the in vitro simulation of several inflammatory aspects of periodontal inflammation. Our data demonstrated that LPS+IFN-γ increased the inflammatory response in PDLCs but did not alter their mineral matrix formation capacity, viability, or migration/proliferation. In SCs, transient inflammatory priming elicited only a mild inflammatory response while enhancing mineral matrix formation, without compromising viability or migration/proliferation.
Cell proliferation and migration are essential for tissue repair.24 Our results demonstrated that PDLC and SC migration/proliferation and viability were not affected by the inflammatory microenvironment containing LPS at 2,000 ng/mL. Consistent with our findings for PDLCs, a previous study showed that the proliferation and viability of PDLCs were not affected by E. coli LPS at concentrations of 100 and 1,000 ng/mL immediately after treatment (0 h) and after 24, 48, or 72 hours. Moreover, the percentage of viable cells exposed to LPS was similar to that in the untreated group.20 Another study reported that E. coli LPS at higher concentrations (1,000 ng or 10,000 ng/mL) over 10 days did not affect PDLC proliferation.18 Likewise, a previous study reported no significant changes in SC viability when treated with LPS (10 μg/μL).25
During the progression of periodontal disease, LPS, a component of the outer membrane of gram-negative bacteria, triggers an inflammatory response in cells within or surrounding the affected tissue.26,27 Our data showed that PDLCs stimulated with LPS+IFN-γ upregulated IL-1β, IL-6, IFN-γ, IFN-γR, and TNF. Other studies are consistent with this finding, as E. coli LPS induces a pro-inflammatory response in PDLCs, with increased expression of cytokines such as IL-1, TNF, IL-6, and IL-8.19,28 Based on the current literature, this response is likely related to the physiological role of PDLCs gin the periodontal ligament, which primes these cells to respond to the inflammatory microenvironment by activating nuclear factor-kappa (NF-κβ) and MAPK pathways, and their sensitivity to TLRs.29
SCs primarily regulate neural response; however, they also participate in immune responses by recognizing and presenting antigens and secreting cytokines.30 Following nerve injury, SCs have been shown to produce pro-inflammatory cytokines such as IL-1β, IL-6, and TNF,31 through the activation of the NF-κβ pathway.25 In our study, SCs upregulated the expression of IL-6, IFN-γ, IFN-γR and downregulated IL1-α and TNF. Although these results should be interpreted cautiously because they were obtained following a transient priming challenge, the downregulation of cytokines by SCs might reflect an attempt to control inflammation. SCs can modulate local immune responses through major histocompatibility complex class II (MHC-II) during inflammation32 and contribute to the restoration of neural homeostasis during tissue repair.33,34
Cytokines produced during inflammatory conditions such as periodontitis affect cell poptions, leading to either decreased or increased bone remodeling.35 We therefore analyzed the mineralized matrix formation and osteogenesis-related genes in PDLCs and SCs after LPS+IFN-γ transient inflammatory priming. We observed that PDLCs upregulated ALPL and RUNX-2. Previous data on mineralization properties of PDLCs when exposed to LPS are inconsistent.19,20 Downregulation of RUNX-2, ALPL, and OCN, along with decreased ARS staining indicating reduced mineralized matrix deposition, was reported when PDLCs were stimulated with E. coli LPS. These findings suggest that LPS-induced inflammation can alter the PDLC phenotype and affect their osteogenic differentiation capacity.20 Consistent with our data, another study showed mineralized matrix formation as detected by ARS at 21 days when periodontal ligament progenitor cells were stimulated with E. coli LPS, and reported upregulation of RUNX-2, ALPL, and OCN after seven days.19 In contrast, another study reported that stimulation of PDLCs with Porphyromonas gingivalis LPS had no effect on mineral matrix formation.18
All marker genes evaluated in this study were upregulated in SCs following LPS+IFN-γ priming. To our knowledge, no studies have examined the effects of LPS+IFN-γ or LPS alone on the osteogenic potential or mineralized matrix formation of SCs. SCs cultured with pre-osteoblasts exhibit increased mineralization activity, suggesting that they may contribute to bone repair.13,14 Further evidence shows that SC activation could play a role in periodontitis by modulating alveolar bone loss and inflammation.36 However, the mechanisms underlying SCs’ mineral matrix formation in response to inflammatory stimuli are largely underexplored and deserve further investigation.
This study has several limitations. First, it used E. coli-derived LPS instead of P. gingivalis-derived LPS. The choice of stimulus, whether a typical endotoxin, such as E. coli LPS, or to LPS from another gram-negative pathogen, such as P. gingivalis, can differentially affect the cellular response. LPS from P. gingivalis primarily activates Toll-like receptor 2 (TLR2), whereas LPS from E. coli is a well-established and reproducible agonist of TLR4-mediated signaling pathways. Second, although PDLCs were isolated from healthy individuals and characterized as in our previous publications, there is no information on the number of donors, age, sex, tooth source, or whether the cells were pooled. Accordingly, as a primary cell culture, the results cannot be generalized to other PDLC populations. Another limitation is the distinct cellular origin of PDLCs and SCs. As such, PDLCs and SCs are presented and discussed as independent, complementary arms of the study rather than as a direct comparison, their results should be considered separately.
Finally, LPS+IFN-γ stimulation does not fully reflect the complexity of PD pathogenesis, as it represents only a transient pro-inflammatory microenvironment. Further characterization of the cellular response is needed over the long term, including protein-level validation and the examination of other cytokines.
Conclusions
PDLCs exhibited a pro-inflammatory transcriptional response to LPS+IFN-γ, whereas SCs were unresponsive or showed downregulated expression of pro-inflammatory markers. Both cell lineages independently maintained their viability and wound-closure capacity. SCs formed increased mineralized matrix after transient inflammatory priming with LPS and IFN-γ. Further studies are needed to investigate additional cellular functions of PDLCs and SCs, including their immunoregulatory, anti-inflammatory, and osteoclastogenic capacities.
Financial support:
Data availability:
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
References
-
1 Hajishengallis G. Periodontitis: from microbial immune subversion to systemic inflammation. Nat Rev Immunol. 2015 Jan;15(1):30-44. https://doi.org/10.1038/nri3785
» https://doi.org/10.1038/nri3785 -
2 Trindade D, Carvalho R, Machado V, Chambrone L, Mendes JJ, Botelho J. Prevalence of periodontitis in dentate people between 2011 and 2020: a systematic review and meta-analysis of epidemiological studies. J Clin Periodontol. 2023 May;50(5):604-26. https://doi.org/10.1111/jcpe.13769
» https://doi.org/10.1111/jcpe.13769 -
3 Sun L, Du X, Kuang H, Sun H, Luo W, Yang C. Stem cell-based therapy in periodontal regeneration: a systematic review and meta-analysis of clinical studies. BMC Oral Health. 2023 Jul;23(1):492. https://doi.org/10.1186/s12903-023-03186-6
» https://doi.org/10.1186/s12903-023-03186-6 -
4 Wang M, Xie J, Wang C, Zhong D, Xie L, Fang H. Immunomodulatory properties of stem cells in periodontitis: current status and future prospective. Stem Cells Int. 2020 Jul;2020:9836518. https://doi.org/10.1155/2020/9836518
» https://doi.org/10.1155/2020/9836518 -
5 Ansari S, Diniz IM, Chen C, Aghaloo T, Wu BM, Shi S, et al. Alginate/hyaluronic acid hydrogel delivery system characteristics regulate the differentiation of periodontal ligament stem cells toward chondrogenic lineage. J Mater Sci Mater Med. 2017 Sep;28(10):162. https://doi.org/10.1007/s10856-017-5974-8
» https://doi.org/10.1007/s10856-017-5974-8 -
6 Gamonal J, Bravo J, Malheiros Z, Stewart B, Morales A, Cavalla F, et al. Periodontal disease and its impact on general health in Latin America. Section I: Introduction part I. Braz Oral Res. 2020;34(suppl 1):e024. https://doi.org/10.1590/1807-3107bor-2020.vol34.0024
» https://doi.org/10.1590/1807-3107bor-2020.vol34.0024 -
7 Liu J, Kang R, Tang D. Lipopolysaccharide delivery systems in innate immunity. Trends Immunol. 2024 Apr;45(4):274-87. https://doi.org/10.1016/j.it.2024.02.003
» https://doi.org/10.1016/j.it.2024.02.003 -
8 Johnston AP, Yuzwa SA, Carr MJ, Mahmud N, Storer MA, Krause MP, et al. Dedifferentiated Schwann cell precursors secreting paracrine factors are required for regeneration of the mammalian digit tip. Cell Stem Cell. 2016 Oct;19(4):433-48. https://doi.org/10.1016/j.stem.2016.06.002
» https://doi.org/10.1016/j.stem.2016.06.002 -
9 Parfejevs V, Debbache J, Shakhova O, Schaefer SM, Glausch M, Wegner M, et al. Injury-activated glial cells promote wound healing of the adult skin in mice. Nat Commun. 2018 Jan;9(1):236. https://doi.org/10.1038/s41467-017-01488-2
» https://doi.org/10.1038/s41467-017-01488-2 -
10 Tanaka EM. The molecular and cellular choreography of appendage regeneration. Cell. 2016 Jun;165(7):1598-608. https://doi.org/10.1016/j.cell.2016.05.038
» https://doi.org/10.1016/j.cell.2016.05.038 -
11 Kaukua N, Shahidi MK, Konstantinidou C, Dyachuk V, Kaucka M, Furlan A, et al. Glial origin of mesenchymal stem cells in a tooth model system. Nature. 2014 Sep;513(7519):551-4. https://doi.org/10.1038/nature13536
» https://doi.org/10.1038/nature13536 -
12 Solovieva T, Bronner M. Schwann cell precursors: where they come from and where they go. Cells Dev. 2021 Jun;166:203686. https://doi.org/10.1016/j.cdev.2021.203686
» https://doi.org/10.1016/j.cdev.2021.203686 -
13 Itoyama T, Yoshida S, Tomokiyo A, Hasegawa D, Hamano S, Sugii H, et al. Possible function of GDNF and Schwann cells in wound healing of periodontal tissue. J Periodontal Res. 2020 Dec;55(6):830-9. https://doi.org/10.1111/jre.12774
» https://doi.org/10.1111/jre.12774 -
14 Zhang X, Xiong Q, Lin W, Wang Q, Zhang D, Xu R, et al. Schwann cells contribute to alveolar bone regeneration by promoting cell proliferation. J Bone Miner Res. 2023 Jan;38(1):119-30. https://doi.org/10.1002/jbmr.4735
» https://doi.org/10.1002/jbmr.4735 -
15 Li P, Ou Q, Shi S, Shao C. Immunomodulatory properties of mesenchymal stem cells/dental stem cells and their therapeutic applications. Cell Mol Immunol. 2023 Jun;20(6):558-69. https://doi.org/10.1038/s41423-023-00998-y
» https://doi.org/10.1038/s41423-023-00998-y -
16 Mohebichamkhorami F, Fattahi R, Niknam Z, Aliashrafi M, Khakpour Naeimi S, Gilanchi S, et al. Periodontal ligament stem cells as a promising therapeutic target for neural damage. Stem Cell Research and Therapy. BioMed Central Ltd; 2022. https://doi.org/10.1186/s13287-022-02942-9
» https://doi.org/10.1186/s13287-022-02942-9 - 17 Pitaru S, Narayanan AS, Etikala A, Treves-Manusevitz S. Periodontal stem cells: a historical background and current perspectives. Current Oral Health Reports. Springer Science and Business Media B.V.; 2014. p. 26-33.
-
18 Albiero ML, Amorim BR, Casati MZ, Sallum EA, Nociti FH, Silvério KG. Osteogenic potential of periodontal ligament stem cells are unaffected after exposure to lipopolysaccharides. Braz Oral Res. 2017 Jan;31(0):e17. https://doi.org/10.1590/1807-3107bor-2017.vol31.0017
» https://doi.org/10.1590/1807-3107bor-2017.vol31.0017 -
19 Albiero ML, Amorim BR, Martins L, Casati MZ, Sallum EA, Nociti FH Jr, et al. Exposure of periodontal ligament progenitor cells to lipopolysaccharide from Escherichia coli changes osteoblast differentiation pattern. J Appl Oral Sci. 2015;23(2):145-52. https://doi.org/10.1590/1678-775720140334
» https://doi.org/10.1590/1678-775720140334 -
20 Kukolj T, Trivanović D, Djordjević IO, Mojsilović S, Krstić J, Obradović H, et al. Lipopolysaccharide can modify differentiation and immunomodulatory potential of periodontal ligament stem cells via ERK1,2 signaling. J Cell Physiol. 2018 Jan;233(1):447-62. https://doi.org/10.1002/jcp.25904
» https://doi.org/10.1002/jcp.25904 -
21 Seo BM, Miura M, Gronthos S, Bartold PM, Batouli S, Brahim J, et al. Investigation of multipotent postnatal stem cells from human periodontal ligament. Lancet. 2004 Jul;364(9429):149-55. https://doi.org/10.1016/S0140-6736(04)16627-0
» https://doi.org/10.1016/S0140-6736(04)16627-0 -
22 Lee JY, Sullivan KE. Gamma interferon and lipopolysaccharide interact at the level of transcription to induce tumor necrosis factor alpha expression. Infect Immun. 2001 May;69(5):2847-52. https://doi.org/10.1128/IAI.69.5.2847-2852.2001
» https://doi.org/10.1128/IAI.69.5.2847-2852.2001 -
23 Lan C, Chen S, Jiang S, Lei H, Cai Z, Huang X. Different expression patterns of inflammatory cytokines induced by lipopolysaccharides from Escherichia coli or Porphyromonas gingivalis in human dental pulp stem cells. BMC Oral Health. 2022 Apr;22(1):121. https://doi.org/10.1186/s12903-022-02161-x
» https://doi.org/10.1186/s12903-022-02161-x -
24 Gurtner GC, Werner S, Barrandon Y, Longaker MT. Wound repair and regeneration. Nature. 2008 May;453(7193):314-21. https://doi.org/10.1038/nature07039
» https://doi.org/10.1038/nature07039 -
25 Qin Y, Hua M, Duan Y, Gao Y, Shao X, Wang H, et al. TNF-α expression in Schwann cells is induced by LPS and NF-κB-dependent pathways. Neurochem Res. 2012 Apr;37(4):722-31. https://doi.org/10.1007/s11064-011-0664-2
» https://doi.org/10.1007/s11064-011-0664-2 -
26 Page MJ, Kell DB, Pretorius E. The Role of Lipopolysaccharide-Induced Cell Signalling in Chronic Inflammation. Chronic Stress (Thousand Oaks). 2022 Feb;6:24705470221076390. https://doi.org/10.1177/24705470221076390
» https://doi.org/10.1177/24705470221076390 -
27 Nativel B, Couret D, Giraud P, Meilhac O, d’Hellencourt CL, Viranaïcken W, et al. Porphyromonas gingivalis lipopolysaccharides act exclusively through TLR4 with a resilience between mouse and human. Sci Rep. 2017 Nov;7(1):15789. https://doi.org/10.1038/s41598-017-16190-y
» https://doi.org/10.1038/s41598-017-16190-y -
28 Yamaji Y, Kubota T, Sasaguri K, Sato S, Suzuki Y, Kumada H, et al. Inflammatory cytokine gene expression in human periodontal ligament fibroblasts stimulated with bacterial lipopolysaccharides. Infect Immun. 1995 Sep;63(9):3576-81. https://doi.org/10.1128/iai.63.9.3576-3581.1995
» https://doi.org/10.1128/iai.63.9.3576-3581.1995 -
29 Kato H, Taguchi Y, Tominaga K, Umeda M, Tanaka A. Porphyromonas gingivalis LPS inhibits osteoblastic differentiation and promotes pro-inflammatory cytokine production in human periodontal ligament stem cells. Arch Oral Biol. 2014 Feb;59(2):167-75. https://doi.org/10.1016/j.archoralbio.2013.11.008
» https://doi.org/10.1016/j.archoralbio.2013.11.008 -
30 Meyer zu Hörste G, Hu W, Hartung HP, Lehmann HC, Kieseier BC. The immunocompetence of Schwann cells. Muscle Nerve. 2008 Jan;37(1):3-13. https://doi.org/10.1002/mus.20893
» https://doi.org/10.1002/mus.20893 -
31 Ydens E, Lornet G, Smits V, Goethals S, Timmerman V, Janssens S. The neuroinflammatory role of Schwann cells in disease. Neurobiol Dis. 2013 Jul;55:95-103. https://doi.org/10.1016/j.nbd.2013.03.005
» https://doi.org/10.1016/j.nbd.2013.03.005 -
32 Hartlehnert M, Derksen A, Hagenacker T, Kindermann D, Schäfers M, Pawlak M, et al. Schwann cells promote post-traumatic nerve inflammation and neuropathic pain through MHC class II. Sci Rep. 2017 Oct;7(1):12518. https://doi.org/10.1038/s41598-017-12744-2
» https://doi.org/10.1038/s41598-017-12744-2 -
33 Diogenes A. Trigeminal sensory neurons and pulp regeneration. J Endod. 2020 Sep;46(9 9S):S71-80. https://doi.org/10.1016/j.joen.2020.06.038
» https://doi.org/10.1016/j.joen.2020.06.038 -
34 Duan Y, Liang Y, Yang F, Ma Y. Neural regulations in tooth development and tooth-periodontium complex homeostasis: a literature review. Int J Mol Sci. 2022 Nov;23(22):14150. https://doi.org/10.3390/ijms232214150
» https://doi.org/10.3390/ijms232214150 -
35 Pan W, Wang Q, Chen Q. The cytokine network involved in the host immune response to periodontitis. Int J Oral Sci. 2019 Nov;11(3):30. https://doi.org/10.1038/s41368-019-0064-z
» https://doi.org/10.1038/s41368-019-0064-z -
36 Ribeiro AB, Brognara F, da Silva JF, Castania JA, Fernandes PG, Tostes RC, et al. Carotid sinus nerve stimulation attenuates alveolar bone loss and inflammation in experimental periodontitis. Sci Rep. 2020 Nov;10(1):19258. https://doi.org/10.1038/s41598-020-76194-z
» https://doi.org/10.1038/s41598-020-76194-z
