Proline-mediated enhancement of hepatocyte function in a collagen gel sandwich culture configuration

Isolated rat primary hepatocytes were cultured between two layers of gelled collagen in a sandwich configuration that reinstates the cellular polarity necessary for long-term function in vitro. Maintenance of hepatocyte function, as measured by the secretion of albumin, was shown to be dependent on both the sandwich gel configuration and the continued presence of L-proline in the culture media. Cis-hydroxyproline, an analog of proline known to prevent the proper folding of triple helical collagen molecules, inhibited the response of sandwiched hepatocytes to proline in a dose-dependent and reversible manner. The addition of cis-hydroxyproline to cultures established for 7 days also resulted in the inhibition of hepatocyte function. These data support the hypothesis that continued collagen synthesis by hepatocytes is critical for hepatocyte function in the sandwich gel configuration.