A Novel Role of Ascorbic Acid in Anti-Inflammatory Pathway and ROS Generation in HEMA Treated Dental Pulp Stem Cells

Resin (co)monomers issued from restorative dental materials are able to distribute in the dental pulp or the gingiva, to get to the saliva and to the flowing blood. Many authors have recently shown that methacrylate-based resins, in particular 2-hydroxyethylmethacrylate (HEMA), are responsible of inflammatory and autophagic processes in human dental pulp stem cells (hDPSCs) while ascorbic acid (AS), an antioxidant molecule, can assume a protective role in cell homeostasis. The purpose of the current work was to study if 50 µg/mL AS can affect the inflammatory status induced by 2 mM HEMA in hDPSCs, a tissue–specific cell population. Cell proliferation, cytokine release, morphological arrangement and reactive oxygen species (ROS) formation were determined respectively by MTT, ELISA, morphological analysis and dichlorofluorescein assay. The hDPSCs exposed to HEMA let to an increment of ROS formation and in the expression of high levels of inflammatory mediators such as nuclear factor-κB (NFkB), inflammatory cytokines such as interleukin IL6, IL8, interferon (IFN)ɣ and monocyte chemoattractant protein (MCP)1. Moreover, HEMA induced the up-regulation of pospho-extracellular signal–regulated kinases (pERK)/ERK signaling pathway associated to the nuclear translocation. AS treatment significantly down-regulated the levels of pro-inflammatory mediators. Then, the natural product AS reduced the detrimental result promoted by methacrylates in clinical dentistry, in fact restore cell proliferation, reduce the pro-inflammatory cytokine, downregulate ROS production and of NFkB/pERK/ERK signaling path. In synthesis, AS, could improve the quality of dental care and play a strategic role as innovative endodontic compound easy to use and with reasonable cost.

NF-kB mediated down-regulation of collagen synthesis upon HEMA (2-hydroxyethyl methacrylate) treatment of primary human gingival fibroblast/Streptococcus mutans co-cultured cells

PURPOSE

In vitro studies have evidenced the cytotoxic effect of HEMA (2-hydroxyethyl methacrylate), the most common component of dental resin-based restorative material, which is released within the oral cavity, on eukaryotic cells such as gingival fibroblast and epithelial cells. However, since the presence of microorganisms within the oral cavity cannot be excluded and little is known about the interactions occurring between eukaryotic cells and the human oral microbiota, our attention has been addressed to investigate the effect of 3 mM HEMA on the molecular mechanisms driving the response of human gingival fibroblasts (HGFs) co-cultured with Streptococcus mutans.

METHODOLOGY

HGF/S. mutans co-culture has been set up in our lab, and upon HEMA treatment, S.mutans and HGF cells' viability and adhesion along with type I collagen gene and pro-collagen I, Bax, Bcl2, nuclear factor kB (NF-kB), IkBα, pIkBα protein expression by PCR, Western blotting and ELISA assays have been investigated.

RESULTS

HEMA treatment determines a significant decrease of type I collagen protein production, even in the presence of S. mutans, in parallel to a decrease of cell viability and adhesion, which seem to be regulated by NF-kB activation. In fact, when SN50, NF-kB-specific pharmacological inhibitor, is added to the culture, cell proliferation along with collagen synthesis is restored.

CONCLUSION

The modulation exerted by S. mutans on the cytotoxic effect of HEMA suggests that within the oral cavity, the eukaryotic/prokaryotic cell interactions, maintaining the balance of the environment, allow HEMA to perform its adhesive and bonding function and that the use of a co-culture system, which simulates the oral cavity organization, improves the knowledge concerning the biocompatibility of this dental material.

Anti-adhesive and pro-apoptotic effects of 2-hydroxyethyl methacrylate on human gingival fibroblasts co-cultured with Streptococcus mitis strains

AIM

To evaluate and observe the cellular reactions that occur during the interaction/integration between 2-hydroxyethyl methacrylate/host tissue/microbial environment, in a co-culture of human gingival fibroblasts (HGF) and Streptococcus mitis strains.

METHODOLOGY

Streptococcus mitis were cultured with strains in the presence of 3 mmol L(-1) HEMA for 48 h and 72 h. Cytotoxicity was evaluated by the trypan blue dye exclusion test. Apoptosis was evaluated by TUNEL analysis. Adhesion was evaluated by immunofluorescence and western blot analyses. Quantitative analyses of the results were acquired by Qwin Plus 3.5 and QuantityOne I-D analysis software, respectively. The statistical significance of the results was evaluated using t-tests and linear regression tests.

RESULTS

The trypan blue dye test revealed 47.3% and 46.5% of dead fibroblasts after 48 and 72 h HEMA treatment, respectively, while bacterial viability was not influenced by the presence of HEMA and fibroblasts. The expression of pro-collagen I, involved in fibroblast adhesion, in untreated samples ranged from 12.49% to 6.91% of the positive area after 48 and 72 h, respectively, dropping to below 2% of the positive area in the other experimental conditions. Unlike the trypan blue test, co-cultured samples treated with HEMA showed 20% and 25% versus 17% and 21% (after 48 and 72 h, respectively) of apoptotic cells.

CONCLUSIONS

The evidence for HEMA toxicity and anti-adhesive effects against eukaryotic cells was reduced in the presence of bacteria, suggesting that dental resins should be well polymerized to avoid the spread of toxic monomers within the mouth.

Liquid-liquid two-phase systems for the production of porous hydrogels and hydrogel microspheres for biomedical applications: A tutorial review

Macroporous hydrogels may have direct applications in regenerative medicine as scaffolds to support tissue formation. Hydrogel microspheres may be used as drug-delivery vehicles or as building blocks to assemble modular scaffolds. A variety of techniques exist to produce macroporous hydrogels and hydrogel microspheres. A subset of these relies on liquid-liquid two-phase systems. Within this subset, vastly different types of polymerization processes are found. In this review, the history, terminology and classification of liquid-liquid two-phase polymerization and crosslinking are described. Instructive examples of hydrogel microsphere and macroporous scaffold formation by precipitation/dispersion, emulsion and suspension polymerizations are used to illustrate the nature of these processes. The role of the kinetics of phase separation in determining the morphology of scaffolds and microspheres is also delineated. Brief descriptions of miniemulsion, microemulsion polymerization and ionotropic gelation are also included.