Addition of dexamethasone alters the bile acid composition by inducing CYP8B1 in primary cultures of human hepatocytes

Abstract Background Primary human hepatocytes offer the best human in vitro model for studies on human liver cell metabolism. Investigators use a variety of different media supplements and matrix bio-coatings and the type of culture system used may influence the outcome. Objectives To optimize in vitro conditions for primary human hepatocytes with regard to bile acid synthesis. Methods Human hepatocytes were isolated and cultured on collagen type I or EHS matrigel in cell media with or without dexamethasone. The glucocorticoid receptor (GR) antagonist RU486 was used to elucidate the involvement of GR. Results Hepatocytes cultured on EHS matrigel produced more bile acids and expressed higher levels of CYP7A1 than cells cultured on rat tail collagen. Supplementation with dexamethasone increased the formation of cholic acid (CA) and decreased chenodeoxycholic acid (CDCA) formation. In line with these results, the mRNA expression of CYP8B1 increased following dexamethasone treatment. Surprisingly, the mRNA expression of CYP7A1 and CYP27A1 was not increased to the same extent. By using the GR antagonist RU486 we concluded that CYP8B1 induction is mediated via a GR independent pathway. An altered expression of retinoid-related orphan receptor (ROR) α and ROR α target gene Glucose-6-phosphatase (G6Pase) suggests that ROR α signaling may regulate CYP8B1 expression. Conclusion Primary human hepatocytes have an increased bile acid synthesis rate when cultured on matrigel as compared to collagen. Exposure to glucocorticoid hormones stimulates the expression of CYP8B1, leading to an increased formation of CA and alteration of the bile acid composition. The effect is most likely mediated through a GR independent pathway, possibly through ROR α.