title: Cell morphology and focal adhesion location alters internal cell stress.
abstract: Extracellular mechanical cues have been shown to have a profound effect on osteogenic cell behaviour. However, it is not known precisely how these cues alter intracellular mechanics to initiate changes in cell behaviour. In this study, a combination of in vitro culture of MC3T3-E1 cells and finite-element modelling was used to investigate the effects of passive differences in substrate stiffness on intracellular mechanics. Cells on collagen-based substrates were classified based on the presence of cell processes and the dimensions of various cellular features were quantified. Focal adhesion (FA) density was quantified from immunohistochemical staining, while cell and substrate stiffnesses were measured using a live-cell atomic force microscope. Computational models of cell morphologies were developed using an applied contraction of the cell body to simulate active cell contraction. The results showed that FA density is directly related to cell morphology, while the effect of substrate stiffness on internal cell tension was modulated by both cell morphology and FA density, as investigated by varying the number of adhesion sites present in each morphological model. We propose that the cells desire to achieve a homeostatic stress state may play a role in osteogenic cell differentiation in response to extracellular mechanical cues.
authors.affiliation: Centre for Biomechanics Research (BMEC), Department of Biomedical Engineering, NUI Galway, Galway, Republic of Ireland National Centre for Biomedical Engineering Science (NCBES), NUI Galway, Galway, Republic of Ireland.
authors.forename: C A
authors.initials: CA
authors.lastname: Mullen
authors.affiliation: Centre for Biomechanics Research (BMEC), Department of Biomedical Engineering, NUI Galway, Galway, Republic of Ireland.
authors.forename: T J
authors.initials: TJ
authors.lastname: Vaughan
authors.affiliation: Centre for Biomechanics Research (BMEC), Department of Biomedical Engineering, NUI Galway, Galway, Republic of Ireland National Centre for Biomedical Engineering Science (NCBES), NUI Galway, Galway, Republic of Ireland.
authors.forename: M C
authors.initials: MC
authors.lastname: Voisin
authors.affiliation: INSERM UMR957, Laboratory of the Pathophysiology of Bone Resorption, Faculty of Medicine, University of Nantes, Nantes, France.
authors.forename: M A
authors.initials: MA
authors.lastname: Brennan
authors.affiliation: INSERM UMR957, Laboratory of the Pathophysiology of Bone Resorption, Faculty of Medicine, University of Nantes, Nantes, France.
authors.forename: P
authors.initials: P
authors.lastname: Layrolle
authors.affiliation: Centre for Biomechanics Research (BMEC), Department of Biomedical Engineering, NUI Galway, Galway, Republic of Ireland National Centre for Biomedical Engineering Science (NCBES), NUI Galway, Galway, Republic of Ireland laoise.mcnamara@nuigalway.ie.
authors.forename: L M
authors.initials: LM
authors.lastname: McNamara
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002454:Cell Differentiation; D002460:Cell Line; D022001:Focal Adhesions / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D010012:Osteogenesis; D013312:Stress, Physiological
keywords: extracellular mechanical environment; finite-element; focal adhesion; osteoblast; osteocyte; single cell force microscopy