title: How linear tension converts to curvature: geometric control of bone tissue growth.
abstract: This study investigated how substrate geometry influences in-vitro tissue formation at length scales much larger than a single cell. Two-millimetre thick hydroxyapatite plates containing circular pores and semi-circular channels of 0.5 mm radius, mimicking osteons and hemi-osteons respectively, were incubated with MC3T3-E1 cells for 4 weeks. The amount and shape of the tissue formed in the pores, as measured using phase contrast microscopy, depended on the substrate geometry. It was further demonstrated, using a simple geometric model, that the observed curvature-controlled growth can be derived from the assembly of tensile elements on a curved substrate. These tensile elements are cells anchored on distant points of the curved surface, thus creating an actin "chord" by generating tension between the adhesion sites. Such a chord model was used to link the shape of the substrate to cell organisation and tissue patterning. In a pore with a circular cross-section, tissue growth increases the average curvature of the surface, whereas a semi-circular channel tends to be flattened out. Thereby, a single mechanism could describe new tissue growth in both cortical and trabecular bone after resorption due to remodelling. These similarities between in-vitro and in-vivo patterns suggest geometry as an important signal for bone remodelling.
authors.affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany. Cecile.Bidan@mpikg.mpg.de
authors.forename: Cécile M
authors.initials: CM
authors.lastname: Bidan
authors.forename: Krishna P
authors.initials: KP
authors.lastname: Kommareddy
authors.forename: Monika
authors.initials: M
authors.lastname: Rumpler
authors.forename: Philip
authors.initials: P
authors.lastname: Kollmannsberger
authors.forename: Yves J M
authors.initials: YJ
authors.lastname: Bréchet
authors.forename: Peter
authors.initials: P
authors.lastname: Fratzl
authors.forename: John W C
authors.initials: JW
authors.lastname: Dunlop
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001696:Biomechanical Phenomena; D016723:Bone Remodeling / Q000502:physiology*; D018786:Bone Substitutes; D017886:Durapatite; D051379:Mice; D008858:Microscopy, Phase-Contrast; D008954:Models, Biological; D010006:Osteoblasts / Q000166:cytology* / Q000502:physiology*; D010012:Osteogenesis / Q000502:physiology; D015398:Signal Transduction; D013718:Tensile Strength; D054457:Tissue Scaffolds
chemical_list: D018786:Bone Substitutes; D017886:Durapatite