3D hepatic cultures simultaneously maintain primary hepatocyte and liver sinusoidal endothelial cell phenotypes

Abstract

Developing in vitro engineered hepatic tissues that exhibit stable phenotype is a major challenge in the field of hepatic tissue engineering. However, the rapid dedifferentiation of hepatic parenchymal (hepatocytes) and non-parenchymal (liver sinusoidal endothelial, LSEC) cell types when removed from their natural environment in vivo remains a major obstacle. The primary goal of this study was to demonstrate that hepatic cells cultured in layered architectures could preserve or potentially enhance liver-specific behavior of both cell types. Primary rat hepatocytes and rat LSECs (rLSECs) were cultured in a layered three-dimensional (3D) configuration. The cell layers were separated by a chitosan-hyaluronic acid polyelectrolyte multilayer (PEM), which served to mimic the Space of Disse. Hepatocytes and rLSECs exhibited several key phenotypic characteristics over a twelve day culture period. Immunostaining for the sinusoidal endothelial 1 antibody (SE-1) demonstrated that rLSECs cultured in the 3D hepatic model maintained this unique feature over twelve days. In contrast, rLSECs cultured in monolayers lost their phenotype within three days. The unique stratified structure of the 3D culture resulted in enhanced heterotypic cell-cell interactions, which led to improvements in hepatocyte functions. Albumin production increased three to six fold in the rLSEC-PEM-Hepatocyte cultures. Only rLSEC-PEM-Hepatocyte cultures exhibited increasing CYP1A1/2 and CYP3A activity. Well-defined bile canaliculi were observed only in the rLSEC-PEM-Hepatocyte cultures. Together, these data suggest that rLSEC-PEM-Hepatocyte cultures are highly suitable models to monitor the transformation of toxins in the liver and their transport out of this organ. In summary, these results indicate that the layered rLSEC-PEM-hepatocyte model, which recapitulates key features of hepatic sinusoids, is a potentially powerful medium for obtaining comprehensive knowledge on liver metabolism, detoxification and signaling pathways in vitro.

Figure 1. Merged phase-contrast (hepatocytes) and fluorescent images of red-fluorescent rLSECs.

Images obtained on day 4 (A–F) and day 12 (G–L) after isolation of hepatocytes and rLSECs. A. 25K rLSEC-Hepatocyte, B. 50K rLSEC-Hepatocyte, C. 25K rLSEC-5L-Hepatocyte, D. 50K rLSEC-5L-Hepatocyte, E. 25K rLSEC-15L-Hepatocyte, F. 50K rLSEC-15L-Hepatocyte. Figures G–L represents the same conditions as in A–F. Hep = Hepatocytes. Scale bar = 50 microns.

Figure 2. SE-1 immunostaining to monitor rLSEC phenotype, images obtained on day 4 in culture.

A. rLSEC monolayer, B. 50K rLSEC-Hepatocyte, C. 50K rLSEC-5L-Hepatocyte, and D. 50K rLSEC-15L- Hepatocyte. Scale bar = 50 microns.

Figure 3. SE-1 immunostaining to monitor rLSEC phenotype, images obtained on day 12 in culture.

A. rLSEC monolayer, B. 50K rLSEC-Hepatocyte, C. 50K rLSEC-5L-Hepatocyte, and D. 50K rLSEC-15L- Hepatocyte. Scale bar = 50 microns.

Figure 4. Urea secretion and albumin production over a 12 day culture period.

A. Urea production B. Albumin secretion. An asterisk (*) indicates a statistically significant increase on day 12 in comparison to HMs. Hep = hepatocytes.

Figure 5. Fold change in CYP enzyme activity over a 12 day culture period.

A. CYP1A1/2 B. CYP3A. An asterisk (*) indicates a statistically significant increase on day 12 in comparison to HMs. Hep = hepatocytes.

Figure 6. Dipeptidyl peptidase IV (DPP IV) immunostaining for bile canaliculi obtained on day 12 in culture.

A. HM, B. 25K rLSEC-Hepatocyte, C. 50K rLSEC-Hepatocyte, D. 25K rLSEC-5L-Hepatocyte, E. 25K rLSEC-15L-Hepatocyte, F. 50K rLSEC-5L-Hepatocyte, G. 50K rLSEC-15L-Hepatocyte. Scale bar = 50 microns.