Hyunsu Lee1, Keith Bonin1, Martin Guthold2. 1. Department of Physics, Wake Forest University, Winston-Salem, NC 27109, USA. 2. Department of Physics, Wake Forest University, Winston-Salem, NC 27109, USA. Electronic address: gutholdm@wfu.edu.
Abstract
BACKGROUND: The epithelium forms a protective barrier against external biological, chemical and physical insults. So far, AFM-based, micro-mechanical measurements have only been performed on single cells and confluent cells, but not yet on cells in mature layers. METHODS: Using a combination of atomic force, fluorescence and confocal microscopy, we determined the changes in stiffness, morphology and actin distribution of human mammary epithelial cells (HMECs) as they transition from single cells to confluency to a mature layer. RESULTS: Single HMECs have a tall, round (planoconvex) morphology, have actin stress fibers at the base, have diffuse cortical actin, and have a stiffness of 1 kPa. Confluent HMECs start to become flatter, basal actin stress fibers start to disappear, and actin accumulates laterally where cells abut. Overall stiffness is still 1 kPa with two-fold higher stiffness in the abutting regions. As HMECs mature and form multilayered structures, cells on apical surfaces become flatter (apically more level), wider, and seven times stiffer (mean, 7 kPa) than single and confluent cells. The main drivers of these changes are actin filaments, as cells show strong actin accumulation in the regions where cells adjoin, and in the apical regions. CONCLUSIONS: HMECs stiffen, flatten and redistribute actin upon transiting from single cells to mature, confluent layers. GENERAL SIGNIFICANCE: Our findings advance the understanding of breast ductal morphogenesis and mechanical homeostasis.
BACKGROUND: The epithelium forms a protective barrier against external biological, chemical and physical insults. So far, AFM-based, micro-mechanical measurements have only been performed on single cells and confluent cells, but not yet on cells in mature layers. METHODS: Using a combination of atomic force, fluorescence and confocal microscopy, we determined the changes in stiffness, morphology and actin distribution of human mammary epithelial cells (HMECs) as they transition from single cells to confluency to a mature layer. RESULTS: Single HMECs have a tall, round (planoconvex) morphology, have actin stress fibers at the base, have diffuse cortical actin, and have a stiffness of 1 kPa. Confluent HMECs start to become flatter, basal actin stress fibers start to disappear, and actin accumulates laterally where cells abut. Overall stiffness is still 1 kPa with two-fold higher stiffness in the abutting regions. As HMECs mature and form multilayered structures, cells on apical surfaces become flatter (apically more level), wider, and seven times stiffer (mean, 7 kPa) than single and confluent cells. The main drivers of these changes are actin filaments, as cells show strong actin accumulation in the regions where cells adjoin, and in the apical regions. CONCLUSIONS: HMECs stiffen, flatten and redistribute actin upon transiting from single cells to mature, confluent layers. GENERAL SIGNIFICANCE: Our findings advance the understanding of breast ductal morphogenesis and mechanical homeostasis.
Authors: M L Gardel; F Nakamura; J H Hartwig; J C Crocker; T P Stossel; D A Weitz Journal: Proc Natl Acad Sci U S A Date: 2006-01-30 Impact factor: 11.205
Authors: Emad Moeendarbary; Léo Valon; Marco Fritzsche; Andrew R Harris; Dale A Moulding; Adrian J Thrasher; Eleanor Stride; L Mahadevan; Guillaume T Charras Journal: Nat Mater Date: 2013-01-06 Impact factor: 43.841