Relevance of Cellular Redox Homeostasis for Vital Functions of Human Dental Pulp Cells

Abstract

Odontogenic MSCs are vulnerable to LPS-triggered bacterial infections, and they respond by secreting inflammatory mediators, such as IL-6, and with mineralization. Since both processes might be prone to a disturbance of the redox homeostasis, the oxidative stress influence on vital functions of human dental pulp cells (HPCs) was investigated. With these aims, a model of LPS-stimulated primary HPCs was established, and anti- and pro-oxidant substances were administered up to 21 days to measure inflammation and mineralization parameters. LPS-stimulated HPCs retained mineralization potential, which was decreased with the antioxidants NAC and fisetin and the pro-oxidant BSO. The expression of surface markers related to odontogenic commitment was influenced accordingly but counteracted by the enhanced expression of BMP2 and ALP at the transcriptional level. LPS triggers an early IL-6 production in non-odontogenic conditions, while it can be measured only after 15 days in the presence of the differentiation medium. The present study shows that HPCs functions causally depend on a tightly regulated cellular redox balance. Our data demonstrate a redox control of pulp MSC odontogenic commitment along with a potential association between an IL-6 late secretion and mineralization. These findings lay the groundwork for investigations on the molecular role of IL-6 in dental hard tissue metabolism.

The Inhibition of the Inducible Nitric Oxide Synthase Enhances the DPSC Mineralization under LPS-Induced Inflammation

“…Expression-levels of CD90 ( Figure 4 B) are also decreased dose-dependently in the presence of CM544 and independently from the concentrations when the FAB1020 is present. It is therefore plausible to assume that the observations reported for LPS-stimulated DPSCs in the presence of several antioxidants [ 10 ], or rather the stimulation with a low LPS concentration, does not affect the mineralization capacity of pulp cells, are strongly validated. It has already been reported that low concentrations of NO stimulate odontogenic differentiation [ 24 ], and LPS is known to be an enhancer in NO production through NfκB activation [ 25 ].…”

“…Remarkable expression-levels of CD90, CD73, CD105 and CD29 represent the minimal criteria for defining a multipotent mesenchymal stromal cell [ 21 ]. It has been already reported that a DPSC exposure to compounds able to act on the antioxidant molecular machinery can modulate CD marker expression and can be crucial in the MSC fate decision in terms of cell stemness loss in favor of modulation of osteogenic gene expression and mineralization occurrence [ 10 ]. In particular, the decreased expression of the GPI-anchored cell surface protein CD90 has been linked to the enhancement of the MSC osteogenic differentiation in vitro [ 22 , 23 ].…”

“…In parallel, DPSCs were exposed to the iNOS inhibitors 1400W or CM544 (stock solutions 50 mM in deionized water) or FAB1020 (stock solution 50 mM in DMSO) at 12.5, 25 and 50 µM, with or without LPS. All the exposures were performed under odontogenic conditions by diluting the LPS and compounds in complete α-MEM supplemented with 10 nM dexamethasone, 10 mM β-glycerophosphate and 50 µg/mL ascorbic acid (all from Merck, Darmstadt, Germany) as described elsewhere [ 10 ]. Fresh exposure media were provided every 72 h.…”

“…Resident mesenchymal stem cells inside the dental pulp, i.e., dental pulp stem cells (DPSCs), are vulnerable to bacterial product-triggered infections and respond by secreting inflammatory mediators and with dysregulated mineralization [ 9 ]. It has been recently reported that both these processes might be prone to a disturbance of the redox homeostasis, and oxidative and nitrosative stress can influence vital functions of human dental pulp cells and their mineralization potential [ 10 ].…”

Molecular Biological Comparison of Dental Pulp- and Apical Papilla-Derived Stem Cells

“…IL-6, a pleiotropic cytokine, was secreted in high levels by both DPSC and SCAP under standard culture conditions. It is not only involved in regeneration, inflammation, and the activation of immune cells, but also an important factor to maintain homeostasis [ 41 ]. Studies showed that regenerative and anti-inflammatory properties are mediated by a classic signaling pathway where the IL-6 receptor is membrane-bound on target cells.…”