The role of liver sinusoidal cells in hepatocyte-directed gene transfer

Abstract

Hepatocytes are a key target for gene therapy of inborn errors of metabolism as well as of acquired diseases such as liver cancer and hepatitis. Gene transfer efficiency into hepatocytes is significantly determined by histological and functional aspects of liver sinusoidal cells. On the one hand, uptake of vectors by Kupffer cells and liver sinusoidal endothelial cells may limit hepatocyte transduction. On the other hand, the presence of fenestrae in liver sinusoidal endothelial cells provides direct access to the space of Disse and allows vectors to bind to receptors on the microvillous surface of hepatocytes. Nevertheless, the diameter of fenestrae may restrict the passage of vectors according to their size. On the basis of lege artis measurements of the diameter of fenestrae in different species, we show that the diameter of fenestrae affects the distribution of transgene DNA between sinusoidal and parenchymal liver cells after adenoviral transfer. The small diameter of fenestrae in humans may underlie low efficiency of adenoviral transfer into hepatocytes in men. The disappearance of the unique morphological features of liver sinusoidal endothelial cells in pathological conditions like liver cirrhosis and liver cancer may further affect gene transfer efficiency. Preclinical gene transfer studies should consider species differences in the structure and function of liver sinusoidal cells as important determinants of gene transfer efficiency into hepatocytes.

Figure 1

A: Scanning electron micrograph of the endothelial lining of a human liver sinusoid. Sinusoidal fenestrae, mostly grouped in sieve plates, appear as openings in the endothelial lining and are indicated by arrows. EC, endothelial cell. Scale bar represents 500 nm. B: Transmission electron micrograph of fenestrae in a human liver sinusoid. The endothelial lining is cut tangentially and shows the occurrence of fenestrae as complete holes in the endothelium. Fenestrae are indicated by arrows. EC, endothelial cell; MV, microvillous surface of hepatocytes. The right top corner of the picture shows the lumen of the sinusoid. Scale bar represents 250 nm. C: Distribution of sinusoidal liver fenestrae in humans, New Zealand White rabbits, and C57BL/6 mice. Data constitute an extrapolation to an infinite number of measurements of previously published frequency distribution histograms.

Figure 2

Schematic drawing of a liver sinusoid. The sinusoidal wall is formed by liver sinusoidal endothelial cells and juxtaposed Kupffer cells. Whereas endocytosis of gene transfer vectors by Kupffer cells and liver sinusoidal endothelial cells limits hepatocyte transduction, the presence of fenestrae in liver sinusoidal endothelial cells provides a direct access to the space of Disse and the microvillous surface of hepatocytes and may allow transcellular migration of vectors. As indicated in the bottom panel, the diameter of fenestrae may restrict the passage of gene transfer vectors according to their size.