ROS Dependent Wnt/β-Catenin Pathway and Its Regulation on Defined Micro-Pillars—A Combined In Vitro and In Silico Study

Abstract

The physico-chemical surface design of implants influences the surrounding cells. Osteoblasts on sharp-edged micro-topographies revealed an impaired cell phenotype, function and Ca2+ mobilization. The influence of edges and ridges on the Wnt/β-catenin pathway in combination with the cells’ stress response has not been clear. Therefore, MG-63 osteoblasts were studied on defined titanium-coated micro-pillars (5 × 5 × 5 µm) in vitro and in silico. MG-63s on micro-pillars indicated an activated state of the Wnt/β-catenin pathway. The β-catenin protein accumulated in the cytosol and translocated into the nucleus. Gene profiling indicated an antagonism mechanism of the transcriptional activity of β-catenin due to an increased expression of inhibitors like ICAT (inhibitor of β-catenin and transcription factor-4). Cells on pillars produced a significant reactive oxygen species (ROS) amount after 1 and 24 h. In silico analyses provided a detailed view on how transcriptional activity of Wnt signaling is coordinated in response to the oxidative stress induced by the micro-topography. Based on a coordinated expression of regulatory elements of the Wnt/β-catenin pathway, MG-63s are able to cope with an increased accumulation of β-catenin on micro-pillars and suppress an unintended target gene expression. Further, β-catenin may be diverted into other signaling pathways to support defense mechanisms against ROS.

The Anchorage of Bone Cells onto an Yttria-Stabilized Zirconia Surface with Mild Nano-Micro Curved Profiles

“…In earlier studies with corundum-blasted Ti surfaces or Ti pillar structures, we observed an attempted phagocytosis of the sharp-edged elevations, which unnecessarily costs the cells a great deal of energy, as seen by a reduced ATP level and increased ROS production [ 23 , 24 ]. Subsequently, the MG-63 cells were no longer able to function as osteoblasts, i.e., the extracellular matrix protein synthesis of collagen I, bone sialo protein 2, and fibronectin was inhibited [ 22 , 25 ].…”

“…We revealed earlier that topographies with sharp edges changed not only the overall cell morphology and intracellular actin cytoskeleton formation [ 22 ] but also hampered diverse cell functions. Edges, ridges, crevices, and points on titanium surfaces provoked an increase in reactive oxygen species (ROS) in cells [ 23 ], reduced the intracellular adenosine triphosphate (ATP)-content [ 24 ], and decelerated calcium ion mobilization from intracellular stores [ 25 ]. In addition, the wnt-signaling pathway was disturbed, i.e., we observed increased expression of inhibitors like ICAT (inhibitor of β-catenin and transcription factor-4) [ 23 ].…”

“…Edges, ridges, crevices, and points on titanium surfaces provoked an increase in reactive oxygen species (ROS) in cells [ 23 ], reduced the intracellular adenosine triphosphate (ATP)-content [ 24 ], and decelerated calcium ion mobilization from intracellular stores [ 25 ]. In addition, the wnt-signaling pathway was disturbed, i.e., we observed increased expression of inhibitors like ICAT (inhibitor of β-catenin and transcription factor-4) [ 23 ]. Not least, the cells attempted, unavailingly, to phagocytize these elevations, which led to cellular stress followed by impaired synthesis of extracellular matrix proteins [ 24 ].…”

Relating simulation studies by provenance—Developing a family of Wnt signaling models

“…There are two exceptions: the simulation model by Sick et al 2006 [31] [31,45,51,56], or cadherin-mediated cell adhesion [34, 39,49] are incorporated in (a). Submodels involving crosstalk with ERK/FGF/PI3K/Akt [32,36,53], Notch [33,36,48], and ROS/Dvl-mediated pathways [51,57] are shown in the lower panels of (b), respectively.…”

“…Lee et al (2003) [28], which was the first validated simulation model of the canonical Wnt signaling pathway. This shows that models are usually not built independently from one another, but are often [28] x [29] x [30] x [31] x [32] o x [33] x x [34] x [35] x x x [36] x x [39] o [41] x [45] x x [46] x x [48] o x [49] x x x [51] x [57] x The top row shows the origin of the cells used by the 19 studies. Not applicable means that the parameters values were obtained from theoretical calculations/considerations from a textbooks or without concrete reference to a wet-lab study.…”