In an effort to re-establish tissue with odontogenic potential in the pulp space of immature permanent teeth, stimulated human dental pulp stem/progenitor cells (hDPSCs) have shown potential to differentiate and form mineralized matrix, marked by high expression of dentin sialophosphoprotein (DSPP) and osteocalcin (OCN). Bacterial by-products have been shown to adversely affect cell differentiation. This study investigated the effect of P. gingivalis, a putative endodontic pathogen, and blockage of its host recognition on hDPSCs. Stimulated hDPSCs were exposed to varying concentrations of P. gingivalis by-product and gene expression of DSPP and OCN was measured. Cells were exposed to TLR2 blocking agents prior to exposure to the by-product. P. gingivalis affected dose-dependent suppression of the measured gene expression. Blockade of TLR2 inhibited the by-product derived suppression of gene expression. The immune-potential of by-product was confirmed to be detrimental to the differentiation of hDPSCs, and this effect could be moderated by TLR2-blockade.

In an effort to re-establish tissue with odontogenic potential in the pulp space of immature permanent teeth, stimulated human dental pulp stem/progenitor cells (hDPSCs) have shown potential to differentiate and form mineralized matrix, marked by high expression of dentin sialophosphoprotein (DSPP) and osteocalcin (OCN). Bacterial by-products have been shown to adversely affect cell differentiation. This study investigated the effect of P. gingivalis, a putative endodontic pathogen, and blockage of its host recognition on hDPSCs. Stimulated hDPSCs were exposed to varying concentrations of P. gingivalis by-product and gene expression of DSPP and OCN was measured. Cells were exposed to TLR2 blocking agents prior to exposure to the by-product. P. gingivalis affected dose-dependent suppression of the measured gene expression. Blockade of TLR2 inhibited the by-product derived suppression of gene expression. The immune-potential of by-product was confirmed to be detrimental to the differentiation of hDPSCs, and this effect could be moderated by TLR2-blockade.

Les cellules souches de la pulpe dentaire humaine (DPSCs) sont des cellules souches mésenchymateuses (MSCs) isolées de la pulpe dentaire. Les DPSCs sont capables de s’auto-renouveler et se différencier en plusieurs types cellulaires tel que les odontoblastes, les ostéoblastes, les chondrocytes, les neuroblastes et les adipocytes. Les propriétés immunitaires des DPSCs sont de plus en plus étudiées, elles hébergent des récepteurs de types Toll à la surface, possedent une activité immuno-modulatrice.Cependant, les propriétés immunitaires comme celles décrites dans les cellules immunitaires professionnelles telles que la phagocytose, la production de composés anti-microbiens et le nouveau concept « Trained immunity » pourraient être étudiées. une brève revue a été élaborée pour mettre en évidence l'ensemble des propriétés immunitaires des DPSCs décrites dans la littérature. Ensuite, expérimentalement, nous avons montré que les DPSCs pouvaient internaliser le pathogène bactérien Bartonella quintana. En outre, nous avons décrit la capacité des DPSCs à développer une immunité entrainée “trained immunity”. Il s’agit d’une mémoire inflammatoire concernant deux cytokines IL-6 et MCP-1. La stimulation des DPSCs avec le ligand bactérien LPS ou PGN induit une augmentation de l’expression et de la production de l'IL-6 et du PGN après un second stimulus. Dans l'ensemble, l'étude des propriétés immunitaires des DPSCs montre que ces dernières peuvent agir comme des cellules immunitaires. / Dental pulp Stem cells (DPSCs) are mesenchymal stem cells (MSCs) isolated from the dental pulp. DPSCs are able to self-renew and differentiate into several cell types such as odontoblasts, osteoblasts, chondrocytes, neuroblasts and adipocytes.The immune properties of DPSCs are being studied more and more, they harbor Toll-like receptor on the surface and have an immunomodulatory activity.However, immune properties such as those described in professional immune cells such as phagocytosis, production of antimicrobial compounds and the new concept "Trained immunity" could be studied.A brief review has been developed to highlight the set of immune properties of DPSCs described in the literature. Then, experimentally, we showed that DPSCs could internalize the bacterial pathogen Bartonella quintana.In addition, we have described the ability of DPSCs to develop trained immunity. It is an inflammatory memory concerning two cytokines IL-6 and MCP-1. Priming DPSCs with the bacterial ligand LPS or PGN induces an increase in the expression and production of IL-6 and PGN after a second stimulus.Overall, the study of the immune properties of DPSCs shows that DPSCs can act as immune cells.

Indiana University-Purdue University Indianapolis (IUPUI) / The effects of hydroxyapatite in a DAP-loaded MC carrier on dental pulp stem cells Introduction: Regenerative endodontic procedures (REP) require disinfection techniques to eliminate bacteria from the infected immature root canal system and promote new growth of the pulp-dentin complex. Double antibiotic paste (DAP), a mixture of ciprofloxacin and metronidazole, has shown efficacy in doing so while minimizing cytotoxicity on dental pulp stem cells (DPSC). Stem cells, scaffolding, and growth factors are necessary in the maturation, proliferation, and differentiation of mesenchymal stem cells into the root canal system. Nano-hydroxyapatite (n-HA) has a history of biocompatibility and, in addition, has shown promising effects as a tissue bioengineering material. Objective: The aim of this in vitro study was to investigate the proliferation and mineralization of DPSC in the presence of 1% DAP and methylcellulose (MC) with varying concentrations of nano-hydroxyapatite. Materials and Methods: DPSC were plated in 24-well plates containing culture media. The next day, semi-permeable 0.1 mm Transwell chambers were inserted into the wells to separate the reservoirs for medicaments. Treatment paste composed of methylcellulose containing 1% DAP with either 0.25%, 0.50%, or 1.0% nano-hydroxyapatite was added along with culture media. Methylcellulose alone and calcium hydroxide (Ultracal) were used as control groups. After 3 days, cells were evaluated for cytotoxic effects using an MTS proliferation assay (n = 10, in triplicate). DPSCs were also cultured with these medicaments for 7 days in osteogenic media and evaluated for alkaline phosphatase (ALP) activity and mineralization activity (n = 13, in triplicate). Comparisons between groups for differences in mineralization, BSA, and ALP activity were performed using analysis of variance (ANOVA), with different variances allowed for each group and a random effect included in the model to account for correlation within each of the three trials. A simulation-based model was used to adjust for multiple comparisons. Results: Addition of n-HA treatment groups increased mineralization significantly greater than calcium hydroxide, with MC alone and MC+DAP+0.5% HA providing the greatest effect. Regarding ALP, all HA concentrations performed significantly greater than MC and DAP concentrations. Proliferation demonstrated similar metabolic activity in all experimental groups with few comparisons significant. Conclusion: The challenge in REPs is to maintain survival, and preferably promote the proliferation and development of DPSCs into the pulp-dentin complex with a consistent treatment outcome. The combination of DAP with hydroxyapatite may allow for both disinfection and improved mineralization and cellular differentiation. This contribution has shown significant ability to increase stem cell differentiation into an osteogenic lineage as well as calcium deposition, indicating end goal results of regenerative procedures.