Unveiling dynamic hepatocyte plasticity in HepaRG cells with a dual CYP reporter system

Primary hepatocytes are widely utilized for investigating drug efficacy and toxicity, yet variations between batches and limited proliferation capacity present significant challenges. HepaRG cells are versatile cells, capable of maintaining an undifferentiated state and differentiating through dimethyl sulfoxide treatment, allowing for molecular analysis of hepatocyte plasticity. To elucidate the underlying molecular mechanisms of HepaRG cell plasticity, we used CYP3A4G/7R HepaRG cells engineered to express DsRed under the control of the fetus-specific CYP3A7 gene and EGFP under the adult-specific CYP3A4 gene promoter. In time-lapse imaging of CYP3A4G/7R HepaRG cells, we observed CYP3A7-DsRed expression transitioning from negative to positive during proliferation period and CYP3A4-GFP expression activating during differentiation. The de-differentiation potency of differentiated CYP3A4G/7R HepaRG cells was assessed using inhibitors and cytokines. It was found that Y-27632 (Y), A-83-01 (A), and CHIR99021 (C) (collectively referred to as YAC), which are known to promote liver regeneration in mice, did not induce CYP3A7-DsRed expression. Instead, these inhibitors increased CYP3A4-GFP expressing population. Furthermore, CHIR99021 alone increased CYP3A4-GFP-positive cells, while Wnt3a treatment increased CYP3A7-DsRed-positive cells, suggesting that Wnt signaling plays distinct roles in HepaRG cells. It was apparent that de-differentiated cells had increased CYP3A4 activity after a second round of differentiation, compared to differentiated cells after the first round. Transcriptomic analysis of HepaRG cells revealed distinct profiles between proliferative, differentiated, and de-differentiated states, highlighting their robust plasticity. Notably, hepatoblastic cells de-differentiated by YAC or C displayed transcriptome patterns similar to undifferentiated cells, whereas CYP3A7-DsRed and CYP3A4-GFP exhibited expression patterns different from those of undifferentiated cells. These findings underscore the dynamic nature of HepaRG cells while cautioning against solely relying on CYP3 family gene expression as a marker of differentiation.