Force spectroscopy of hepatocytic extracellular matrix components

Probing the unseen structure and function of liver cells through atomic force microscopy

With the arrival of atomic force microscopy (AFM) about thirty years ago, this new imaging tool opened up a new area for the exploration of biological samples, ranging from the tissue and cellular level down to the supramolecular scale. Commercial instruments of this new imaging technique began to appear in the five years following its discovery in 1986 by Binnig, Quate & Gerber. From that point onwards the AFM has attracted many liver biologists, and the number of publications describing structure-function relationships on the diverse set of liver cells has grown steadily ever since. It is therefore timely to reflect on the achievements of AFM in disclosing the cellular architecture of hepatocytes, liver sinusoidal endothelial cells, Kupffer cells, stellate cells and liver-associated natural killer cells. In this thematic paper, we present new data and provide an in-depth overview of the current AFM literature on liver cell biology. We furthermore include a future outlook on how this scanning probe imaging tool and its latest developments can contribute to clarify various structural and functional aspects of cells in liver health and disease.

Impact of alginate composition: from bead mechanical properties to encapsulated HepG2/C3A cell activities for in vivo implantation

Recently, interest has focused on hepatocytes' implantation to provide end stage liver failure patients with a temporary support until spontaneous recovery or a suitable donor becomes available. To avoid cell damage and use of an immunosuppressive treatment, hepatic cells could be implanted after encapsulation in a porous biomaterial of bead or capsule shape. The aim of this study was to compare the production and the physical properties of the beads, together with some hepatic cell functions, resulting from the use of different material combinations for cell microencapsulation: alginate alone or combined with type I collagen with or without poly-L-lysine and alginate coatings. Collagen and poly-L-lysine increased the bead mechanical resistance but lowered the mass transfer kinetics of vitamin B12. Proliferation of encapsulated HepG2/C3A cells was shown to be improved in alginate-collagen beads. Finally, when the beads were subcutaneously implanted in mice, the inflammatory response was reduced in the case of alginate mixed with collagen. This in vitro and in vivo study clearly outlines, based on a systematic comparison, the necessity of compromising between material physical properties (mechanical stability and porosity) and cell behavior (viability, proliferation, functionalities) to define optima hepatic cell microencapsulation conditions before implantation.