The human constitutive androstane receptor promotes the differentiation and maturation of hepatic-like cells

Abstract

Expression of the constitutive androstane receptor (CAR, NR1I3) is enriched in the mature mammalian liver and increasingly recognized for its prominent role in regulating a myriad of processes including biotransformation, chemical transport, energy metabolism and lipid homeostasis. Previously, we demonstrated that CAR levels were markedly enhanced during the differentiation of hepatic-like cells derived from hESCs, prompting the hypothesis that CAR contributes a key functional role in directing human hepatogenesis. Here we demonstrate that over-expression of CAR in human embryonic stem cells (ESCs), transduced by a lentiviral vector, accelerates the maturation of hepatic-like cells, with CAR over-expressing cells exhibiting a 2.5-fold increase in albumin secretion by day 20 in culture differentiation, and significantly enhanced levels of mRNA expression of several liver-selective markers, including hepatic transcription factors, plasma proteins, biotransformation enzymes, and metabolic enzymes. CAR over-expressing cells also exhibited enhanced CITCO-inducible CYP3A7 enzymatic activity. Knockdown of CAR via siRNA attenuated the differentiation-dependent expression programs. In contrast, expression levels of the pregnane X receptor (PXR), a nuclear receptor most similar to CAR in primary sequence, were negligible in human fetal liver tissues or in the differentiating hESCs, and stable over-expression of PXR in hepatic-induced hESCs failed to enhance expression of hepatic phenotype markers. Together, these results define a novel role for human CAR in hepatic lineage commitment.

Genome-wide analysis of human constitutive androstane receptor (CAR) transcriptome in wild-type and CAR-knockout HepaRG cells

“…Considering that activation of hCAR by both CITCO and PB also repressed the expression of cell growth promoting genes such as TEK and RGCC, hCAR could have a role in suppressing cell proliferation and potential tumor development in human liver. Indeed, activation of hCAR by CITCO was reported to cause cell cycle arrest and enhanced apoptosis in human brain tumor stem cells [54], whereas overexpression of hCAR in human embryonic stem cells increased albumin secretion and promoted the differentiation and maturation of hepatic-like cells [55]. Nonetheless, these findings in human are in contrast to what has been reported previously in animal models, in which the tumor promotion effects of TCPOBOP and PB rely predominantly on a functional mCAR [17, 56].…”

Small-molecule modulators of the constitutive androstane receptor

“…In other studies, CAR activation in the rodent liver increased cell proliferation and inhibited apoptosis, resulting in an increased incidence of hepatocellular carcinomas and liver injury from chronic exposure to CAR activators. In addition, CAR levels were markedly enhanced during the differentiation of hepatic-like cells derived from human embryonic stem cells, suggesting that CAR has a key functional role in directing human hepatogenesis [127]. …”

Molecular interactions of dioxins and DLCs with the xenosensors (PXR and CAR): An in silico risk assessment approach

“…Similarly, nuclear receptor, constitutive androstane receptor (CAR, NR1I3) is involved in the regulation of transcription of genes encoding xenobiotic and steroid metabolizing enzymes . It can be predominantly traced in liver . Similar to PXR, CAR is also known to exhibit its role in endobiotic functions such as glucose and lipid metabolism, hence making it an attractive target of metabolic disorders such as obesity and type 2 diabetes .…”

“…6 It can be predominantly traced in liver. 7 Similar to PXR, CAR is also known to exhibit its role in endobiotic functions such as glucose and lipid metabolism, hence making it an attractive target of metabolic disorders such as obesity and type 2 diabetes. 8 It is also involved in the modulation of genes responsible for cell growth and differentiation.…”