Cell-cell Interactions Are Essential for Maintenance of Hepatocyte Function in Collagen Gel But Not on Matrigel

Prabhas V. Moghe, Robin N. Coger, Mehmet Toner, Martin L. Yarmush

Full text at: http://www3.interscience.wiley.com/cgi-bin/fulltext/71004078/PDFSTART?CRETRY=1&SRETRY=0

Given the potential pharmacological, toxicological, and therapeutic potential, hepatocytes are often cultured on collagen as a monolayer and or induced three-dimensional aggregates. The study compared the importance of cellular aggregation and seeding density in two different hepatocyte culture systems, the two-dimensional monolayer in a collagen sandwiches and three-dimensional aggregates induced by the mouse sarcoma derived Matrigels. In order to determine the effectiveness of each of these systems in retaining hepatocyte function, the culture medium was measured for rat serum albumin content by enzyme-linked immunosorbant assay (ELISA) with purified rat albumin and peroxide-conjugated antibody and DNA content analysis.

Upon culturing, the hepatocytes cultured in the collagen sandwich after 10 days appeared more flattened and exhibited bright cell-cell contacts compared to the hepatocytes cultured in the Matrigel, where they appeared round and formed comparatively large three-dimensional aggregates. Albumin secretion were obtained each day for five different seeding densities (1.75, 3.5, 7.0, 17.5, and 70.0 x103 cells/cm2) and normalized to the amount of DNA present within each culture as obtained by the DNA content analysis. With high cell seeding densities the, both cultures exhibit similar levels in elevated function. However, as the cell seeding densities decreases, the collagen sandwich cultures exhibited a rapid deterioration in albumin secretion while the Matrigel cultures maintained similar levels of albumin secretion.

The decreasing secretion levels in the collagen sandwich and the maintenance of secretion levels in the Matrigel may be associated with the differences between the cell-cell and cell-matrix contact levels in the two cultures. As a result of the different morphologies that the collagen sandwich and the Matrigel induce, cell-cell contact and cell-matrix contact varies differently between the two systems. In both systems, the cell-cell interaction parameter decreases with cell decreasing cell density. The cell-matrix interaction parameter, however, remain relatively unchanged in the collagen sandwich as cell density decreases whereas the cell-matrix interaction parameter increases in the Matrigel as the cell density decreases. Thus, the paper concludes that in collagen sandwich systems, the maintenance of hepatocyte function corresponds to the amount of cell-cell contact whereas hepatocyte function is maintained from matrix derived cues.

I chose this paper as, in the liver project, we are also testing the maintenance of hepatocyte function in a new matrix, agerose. However, we will be measuring albumin secretion rates using western blots and determining the number of viable cells after one week of culture using hemocytometer counts. This paper might provide insight into how cellular aggregation, seeding density, and the resulting cell morphology might affect rates of albumin secretion and hepatocyte functional maintenance in different culturing systems.