Viscoelastic properties of the cell nucleus

Mechanical factors play an important role in the regulation of cell physiol ogy. One pathway by which mechanical stress may influence gene expression i s through a direct physical connection from the extracellular matrix across the plasma membrane and to the nucleus, However, little is known of the me chanical properties or deformation behavior of the nucleus. The goal of thi s study was to quantify the viscoelastic properties of mechanically and che mically isolated nuclei of articular chondrocytes using micropipet aspirati on in conjunction theoretical viscoelastic model. Isolated nuclei behaved a s viscoelastic solid materials similar to the cytoplasm, but were 3-4 times stiffer and nearly twice as viscous as the cytoplasm, Quantitative informa tion of the biophysical properties and deformation behavior of the nucleus may provide further insight on the relationships between the stress-strain state of the nucleus and that of the extracellular matrix, as well as poten tial mechanisms of mechanical signal transduction. (C) 2000 academic Press.