Clinical versatility of porcine hepatocytes in the light of interspecies differences in cytochrome P450 regulation and expression
Background and aims: In fulminant hepatic failure, the clinical use of bioartifical liver support with porcine hepatocytes is the subject of a controversial debate. Cytochrome P450 (CYP) metabolic functions have relevant implications for drug metabolism and detoxification. In this study, we investigate interspecies differences in CYP gene expression between human and porcine primary hepatocytes and the impact of interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) exposition mimicking cytokine release in fulminant hepatic failure. Methods: Primary hepatocyte Cultures were isolated From human resection specimens and from German landrace pigs. Cell cultures (single and co-cultures) were exposed to porcine vs. human IL-6 and TNF-alpha, respectively. Changes in quantitative CYP gene expression were investigated by semi-quantitative RT-PCR. Results: Significant differences in species-specific CYP gene expression by human and porcine hepatocytes were found after exposure to species-identical IL-6 (10 ng/ml) for CYP 1A1, CYP 2C, CYP 3A (P = 0.002, 0.022, 0.017, respectively) or species-identical TNF-alpha (30ng/ml) for CYP 1A2 and CYP 2A (P = 0.037, 0.023, respectively). In single vs. co-culture, human hepatocytes demonstrated stronger repression of CYP 1A1, 2C8 and 3A4 expression after dosage with human IL-6 (10ng/ml) (P = 0.022, 0.031, 0.014, respectively). Conclusion: Our findings demonstrate significant species-specific differences in CYP gene expression and regulation when high doses of IL-6 and TNF-alpha are used (10 and 30 ng/ml, respectively). These findings may point to species-specific physiological incompatibilities of porcine hepatocytes and thus limit their clinical versatility.