Mesenchymal stem cell mechanics from the attached to the suspended state.
Human mesenchymal stem cells (hMSCs) are therapeutically useful cells that are typically expanded in vitro on stiff substrata before reimplantation. Here we explore MSC mechanical and structural changes via atomic force microscopy and optical stretching during extended passaging, and we demonstrate that cytoskeletal organization and mechanical stiffness of attached MSC populations are strongly modulated over >15 population doublings in vitro. Cytoskeletal actin networks exhibit significant coarsening, attendant with decreasing average mechanical compliance and differentiation potential of these cells, although expression of molecular surface markers does not significantly decline. These mechanical changes are not observed in the suspended state, indicating that the changes manifest themselves as alterations in stress fiber arrangement rather than cortical cytoskeleton arrangement. Additionally, optical stretching is capable of investigating a previously unquantified structural transition: remodeling-induced stiffening over tens of minutes after adherent cells are suspended. Finally, we find that optically stretched hMSCs exhibit power-law rheology during both loading and recovery; this evidence appears to be the first to originate from a biophysical measurement technique not involving cell-probe or cell-substratum contact. Together, these quantitative assessments of attached and suspended MSCs define the extremes of the extracellular environment while probing intracellular mechanisms that contribute to cell mechanical response.
Maloney
John M
JM
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, USA.
Nikova
Dessy
D
Lautenschläger
Franziska
F
Clarke
Emer
E
Langer
Robert
R
Guck
Jochen
J
Van Vliet
Krystyn J
KJ
D001696:Biomechanical Phenomena; D002448:Cell Adhesion; D006801:Humans; D055595:Mechanical Phenomena; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D018625:Microscopy, Atomic Force; D012212:Rheology; D013535:Suspensions
D013535:Suspensions