Comparison of nanomechanical properties of in vivo and in vitro keratin 8/18 networks

TL;DR

This study compares the mechanical properties of in vivo keratin cytoskeletons from pancreatic cancer cells with in vitro keratin 8/18 networks using microrheology, revealing significant differences in their viscoelastic behavior.

Contribution

It provides a direct comparison of in vivo and in vitro keratin network mechanics, highlighting differences in storage and loss moduli and insights into their network topology.

Findings

In vivo keratin cytoskeletons have higher storage moduli than in vitro networks.

In vitro keratin networks exhibit higher loss moduli compared to in vivo.

Mechanical properties vary with distance from the nucleus in in vivo networks.

Abstract

In our work we compare the mechanical properties of the extracted keratin cytoskeleton of pancreatic carcinoma cells with the mechanical properties of in vitro assembled keratin 8/18 networks. For this purpose we use microrheology measurements with embedded tracer beads. This method is a suitable tool, because the size of the beads compared to the meshsize of the network allows us to treat the network as a continuum. Observing the beads motion with a CCD-High-Speed-Camera then leads to the dynamic shear modulus. Our measurements show lower storage moduli with increasing distance between the rim of the nucleus and the bead, but no clear tendency for the loss modulus. The same measurement method applied to in vitro assembled keratin 8/18 networks shows different characteristics of storage and loss moduli. The storage modulus is one order of magnitude lower than that of the extracted cytoskeleton and the loss modulus is higher. We draw conclusions on the network topology of both keratin network types based on the mechanical behaviour.