(9f) Cytochrome P450-Mediated Detoxification Studies On in Vitro Three-Dimensional (3D) Hepatic Architectures

The liver is the main site for the biotransformation and detoxification of drugs and toxins. It contains several phase I (hydroxylation and oxidation) and phase II (conjugation) enzymes which catalyze the metabolism of xenobiotics and drugs, and excretion. Cytochrome P450 (CYP) enzymes are a class of enzymes that are primarily responsible for the metabolism of drugs, toxins, and xenobitics. Due to these reasons, the kinetic of these enzymes is widely studied.

The testing of drugs and pharmaceuticals is commonly conducted on hepatocyte monolayers and on animals. Hepatocyte monolayes do not present a physiologically relevant model and animal testing is time-consuming, costly and of limited predictability. We report the assembly of in vitro 3D hepatic architectures that capture key spatial, geometric, and physiological characteristics of the liver. The 3D hepatic constructs are comprised of primary rat hepatocytes, liver sinusoidal endothelial cells (LSECs) and an intermediate polyelectrolyte multilayer (PEM). Hepatocyte-PEM-LSECs cellular constructs exhibited enhanced albumin secretion and stable urea production over a culture period in comparison to hepatocyte-LSEC constructs in absence of PEM and hepatocyte monolayers. CYP1A1/2 enzyme activity was shown to be enhanced up to 16-fold over a seven-day culture period in comparison to hepatocyte monolayers or collagen sandwich cultures. Well defined bile canaliculi and LSEC phenotype were maintained in the 3D hepatic systems. The detoxification kinetics of several CYP enzymes such as CYP2B, CYP2C, and CYP3A are being measured in the 3D hepatic architectures.