Spontaneous hepatocyte migration towards an endothelial cell tube network

A crucial part of the engineering liver tissue is contribution of nonparenchymal cells and maintenance of a complex three-dimensional (3D) structure in vitro for their normal physiology and function. We generated 3D hepatic tissue using primary isolated rat hepatocytes and an endothelial cell tube network from human endothelial vein epithelial cells (HUVECs). To create the 3D hepatic tissue, coculture of primary hepatocytes and tube-structured HUVECs was performed on a Matrigel®. After the HUVECs formed the tube structures, primary isolated rat hepatocytes were inoculated onto the HUVEC tube-structured layer and cultured for 24 hr. We investigated the cell migration, cellular interaction, and distributions of HUVEC tube structures and hepatocytes using multi cell-imaging incubator, confocal microscopy, and electron microscopy analyses. During the culture time, time-lapse imaging showed spontaneous migration of the hepatocytes in the gel, and after the 24-hr culture period, the vast majority of the hepatocytes had moved and adhered to the surface of the HUVEC tube structures. A confocal microscopy assay confirmed this unique 3D cellular interaction between hepatocytes and HUVEC tube structures. The hepatocytes were able to maintain their spherical shape, as well as HUVECs (tube-like form with tubular cavity). We speculate that coculturing of hepatocytes and endothelial cells replicates part of their normal physiology and may help induce migration in vitro and the growth of complex biological tissue structures.