The mammalian cell is like such an opaque, fully-packed, and yet miniature bag, the physical nature of its content illusive. In a recent study (PNAS 2009 106:10632-10637) led by Enhua Zhou and Jeffrey Fredberg from Harvard University, in collaboration with Xavier Trepat from the University of Barcelona, the Institute for Bioengineering of Catalonia, and Ciber Enfermedades Respiratorias, the scientists indeed ‘pressed’ and ‘felt’ the cytoplasm.
By doing so and comparing to other known inert soft matter systems, the researchers found quite unexpectedly that the cell behaves as a collection of soft hydrogel particles, implying that the macromolecules are probably much less rigid than one would think. The authors tested cells in the airways, the lung, the kidney and even those in the brain. Surprisingly, the mechanical behavior was remarkably ‘universal.’ These findings highlight the rich mechanical behavior of the cell, but also provide a new mechanism by which the cell can regulate its mechanical behavior – by compressing or decompressing itself.