Growth Factor Liberation and DPSC Response Following Dentine Conditioning

Abstract

Liberation of the sequestrated bioactive molecules from dentine by the action of applied dental materials has been proposed as an important mechanism in inducing a dentinogenic response in teeth with viable pulps. Although adhesive restorations and dentinebonding procedures are routinely practiced, clinical protocols to improve pulp protection and dentine regeneration are not currently driven by biological knowledge. This study investigated the effect of dentine (powder and slice) conditioning by etchants/conditioners relevant to adhesive restorative systems on growth factor solubilization and odontoblast-like cell differentiation of human dental pulp progenitor cells (DPSCs). The agents included ethylenediaminetetraacetic acid (EDTA; 10%, pH 7.2), phosphoric acid (37%, pH <1), citric acid (10%, pH 1.5), and polyacrylic acid (25%, pH 3.9). Growth factors were detected in dentine matrix extracts drawn by EDTA, phosphoric acid, and citric acid from powdered dentine. The dentine matrix extracts were shown to be bioactive, capable of stimulating odontogenic/osteogenic differentiation as observed by gene expression and phenotypic changes in DPSCs cultured in monolayer on plastic. Polyacrylic acid failed to solubilize proteins from powdered dentine and was therefore considered ineffective in triggering a growth factor-mediated response in cells. The study went on to investigate the effect of conditioning dentine slices on growth factor liberation and DPSC behavior. Conditioning by EDTA, phosphoric acid, and citric acid exposed growth factors on dentine and triggered an upregulation in genes associated with mineralized differentiation, osteopontin, and alkaline phosphatase in DPSCs cultured on dentine. The cells demonstrated odontoblast-like appearances with elongated bodies and long extracellular processes extending on dentine surface. However, phosphoric acid-treated dentine appeared strikingly less populated with cells, suggesting a detrimental impact on cell attachment and growth when conditioning by this agent. These findings take crucial steps in informing clinical practice on dentineconditioning protocols as far as treatment of operatively exposed dentine in teeth with vital pulps is concerned.

Axin2-expressing cells differentiate into reparative odontoblasts via autocrine Wnt/β-catenin signaling in response to tooth damage

“…This suggests that Wnt/β-catenin signaling is not enhancing the secretory activity of odontoblasts. The ability of Wnt/β-catenin signaling to selectively enhance reparative dentinogenesis is intriguing and may suggest that Wnt/β-catenin signaling is working in synergy with other damage activated signaling pathways (such as signaling molecules sequestered in dentine tubules that are released in response to trauma and injury) to potentiate dentine production 32, 33 . Alternately, Wnt/β-catenin signaling may be increasing the number of odontoblast-like cells, whereas primary odontoblast are unaffected as they are post-mitotic.…”

Disclosing the physiology of pulp tissue for vital pulp therapy

“…EDTA (Sadaghiani et al 2016), calcium hydroxide (Graham et al 2006) and MTA (Tomson et al 2007). TGF-b1 can regulate bioactive molecules probably through p38 phosphorylation .…”

“…Findings have demonstrated the solubilization of these molecules by pulp capping agents such as calcium hydroxide cements, MTA (Graham et al 2006, Tomson et al 2007. Other potential ways to release bioactive molecules from the dentine matrix in a clinical situation may be using EDTA, phosphoric acid and citric acid (Sadaghiani et al 2016). MTA can also induce odontoblastic differentiation of human DPSCs via the MAPK (Rathinam et al 2015), BMP/Smad (Jung et al 2015), Wnt/b-catenin (Chen et al 2016) and NF-jb signalling pathways (Rathinam et al 2015) and was able to activate the p38 MAPK pathway , Rathinam et al 2015.…”

“…On the other hand, for direct pulp capping an overall success rate of 80.5% for MTA has been reported when compared with calcium hydroxide (59% success rate) up to 123 months (Mente et al 2014). For this reason, there are considerable efforts in the field of regenerative and molecular dentistry to use more biological approaches, as the use of biomaterials is not extensively developed considering our biological knowledge (Sadaghiani et al 2016). For this reason, there are considerable efforts in the field of regenerative and molecular dentistry to use more biological approaches, as the use of biomaterials is not extensively developed considering our biological knowledge (Sadaghiani et al 2016).…”

“…Hence, there is an ongoing quest to find pulp capping agents that have improved physico-mechanical properties, and potentiate the best biological response (Da Rosa et al 2017). For this reason, there are considerable efforts in the field of regenerative and molecular dentistry to use more biological approaches, as the use of biomaterials is not extensively developed considering our biological knowledge (Sadaghiani et al 2016).…”