Attempted Phagocytosis of Surface Features and the resulting Osteoblast SignalingTuesday (09.05.2017) 15:30 - 15:50 Part of:
Ingrowth of metallic implants into the bone is determined by the rapid adhesion and covering of the surface by osteoblasts. Osteoblasts are able to perceive the physico-chemical properties of their surroundings, especially changes in the surface topography. As a result, the cells pass these surface-triggered signals into the cell, which can modulate their adhesion structures, growth or production of their extracellular matrix. In case of the osteoblasts, these can influence their main function as bone matrix producers and consequently also the ingrowth of the implant. (Nebe et al.) Therefore, the knowledge of the dependence of cell behavior on topographical features are crucial for the design of implant surfaces. Human MG-63 osteoblastic cells growing on surface-fixed micro-pillar structures with the dimensions of 5 µm in length, width, height and spacing, altered their actin cytoskeleton organization and morphology. The changed cell architecture resulted in a decreased synthesis of extracellular matrix proteins collagen-I, (Matschegewski et al.) and fibronectin as well as impaired ATP induced mobilization of intracellular calcium. (Staehlke et al.) Recently, we revealed an attempted caveolae-mediated phagocytosis of the surface-fixed micro-pillars accompanied by increased energy demands, such as increased ATP-metabolism, resulting in higher cell stress, e.g. ROS generation. A similar cell behavior was found for rough corundum-blasted titanium surfaces, commercially used for bone-replacing implants. (Moerke et al.) Phagocytosis is known to be an energy-dependent process and therefore the topography-triggered phagocytosis may lead to the observed impaired osteoblastic cell signaling. But the complex interplay between the topography-induced cell morphology and functional changes is still not completely understood. Therefore, we investigated the signaling pathways downstream of the cellular adhesion-receptors, the integrins, to get a better insight into how the cells transduce the information about their underlying topography and which pathway may regulate the cellular responses. Preliminary results indicate a regulatory role of the Rho/ROCK pathway in the surface topography signal transduction.