title: From single cells to tissues: interactions between the matrix and human breast cells in real time.
abstract: BACKGROUND
  Mammary gland morphogenesis involves ductal elongation, branching, and budding. All of these processes are mediated by stroma--epithelium interactions. Biomechanical factors, such as matrix stiffness, have been established as important factors in these interactions. For example, epithelial cells fail to form normal acinar structures in vitro in 3D gels that exceed the stiffness of a normal mammary gland. Additionally, heterogeneity in the spatial distribution of acini and ducts within individual collagen gels suggests that local organization of the matrix may guide morphogenesis. Here, we quantified the effects of both bulk material stiffness and local collagen fiber arrangement on epithelial morphogenesis.
  
  
  RESULTS
  The formation of ducts and acini from single cells and the reorganization of the collagen fiber network were quantified using time-lapse confocal microscopy. MCF10A cells organized the surrounding collagen fibers during the first twelve hours after seeding. Collagen fiber density and alignment relative to the epithelial surface significantly increased within the first twelve hours and were a major influence in the shaping of the mammary epithelium. The addition of Matrigel to the collagen fiber network impaired cell-mediated reorganization of the matrix and increased the probability of spheroidal acini rather than branching ducts. The mechanical anisotropy created by regions of highly aligned collagen fibers facilitated elongation and branching, which was significantly correlated with fiber organization. In contrast, changes in bulk stiffness were not a strong predictor of this epithelial morphology.
  
  
  CONCLUSIONS
  Localized regions of collagen fiber alignment are required for ductal elongation and branching suggesting the importance of local mechanical anisotropy in mammary epithelial morphogenesis. Similar principles may govern the morphology of branching and budding in other tissues and organs.
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, County Londonderry, United Kingdom.
authors.forename: Clifford
authors.initials: C
authors.lastname: Barnes
authors.affiliation: Department of Integrative Physiology and Pathobiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Lucia
authors.initials: L
authors.lastname: Speroni
authors.affiliation: Department of Biomedical Engineering, Tufts University, Boston, Massachusetts, United States of America.
authors.forename: Kyle P
authors.initials: KP
authors.lastname: Quinn
authors.affiliation: Department of Integrative Physiology and Pathobiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Mael
authors.initials: M
authors.lastname: Montevil
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, County Londonderry, United Kingdom.
authors.forename: Kurt
authors.initials: K
authors.lastname: Saetzler
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, County Londonderry, United Kingdom.
authors.forename: Gbemisola
authors.initials: G
authors.lastname: Bode-Animashaun
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, County Londonderry, United Kingdom.
authors.forename: George
authors.initials: G
authors.lastname: McKerr
authors.affiliation: Department of Biomedical Engineering, Tufts University, Boston, Massachusetts, United States of America.
authors.forename: Irene
authors.initials: I
authors.lastname: Georgakoudi
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, County Londonderry, United Kingdom.
authors.forename: C Stephen
authors.initials: CS
authors.lastname: Downes
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, County Londonderry, United Kingdom; Department of Integrative Physiology and Pathobiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Carlos
authors.initials: C
authors.lastname: Sonnenschein
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, County Londonderry, United Kingdom.
authors.forename: C Vyvyan
authors.initials: CV
authors.lastname: Howard
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, County Londonderry, United Kingdom; Department of Integrative Physiology and Pathobiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Soto
mesh_terms: D000199:Actins / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D019610:Cytoprotection; D004847:Epithelial Cells / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D006801:Humans; D042361:Mammary Glands, Human / Q000166:cytology*; D009024:Morphogenesis; D038081:Organogenesis / Q000502:physiology*; D059008:Time-Lapse Imaging; D046509:Tissue Culture Techniques
chemical_list: D000199:Actins; D003094:Collagen