Hepatocyte Nuclear Factor 4 Alpha Activation Is Essential for Termination of Liver Regeneration in Mice

Abstract

Hepatocyte nuclear factor 4 alpha (HNF4α) is critical for hepatic differentiation. Recent studies have highlighted its role in inhibition of hepatocyte proliferation and tumor suppression. However, the role of HNF4α in liver regeneration (LR) is not known. We hypothesized that hepatocytes modulate HNF4α activity when navigating between differentiated and proliferative states during LR. Western blotting analysis revealed a rapid decline in nuclear and cytoplasmic HNF4α protein levels, accompanied with decreased target gene expression, within 1 hour after two‐thirds partial hepatectomy (post‐PH) in C57BL/6J mice. HNF4α protein expression did not recover to pre‐PH levels until day 3. Hepatocyte‐specific deletion of HNF4α (HNF4α‐KO [knockout]) in mice resulted in 100% mortality post‐PH, despite increased proliferative marker expression throughout regeneration. Sustained loss of HNF4α target gene expression throughout regeneration indicated that HNF4α‐KO mice were unable to compensate for loss of HNF4α transcriptional activity. Deletion of HNF4α resulted in sustained proliferation accompanied by c‐Myc and cyclin D1 overexpression and a complete deficiency of hepatocyte function after PH. Interestingly, overexpression of degradation‐resistant HNF4α in hepatocytes delayed, but did not prevent, initiation of regeneration after PH. Finally, adeno‐associated virus serotype 8 (AAV8)‐mediated reexpression of HNF4α in hepatocytes of HNF4α‐KO mice post‐PH restored HNF4α protein levels, induced target gene expression, and improved survival of HNF4α‐KO mice post‐PH. Conclusion: In conclusion, these data indicate that HNF4α reexpression following initial decrease is critical for hepatocytes to exit from cell cycle and resume function during the termination phase of LR. These results indicate the role of HNF4α in LR and have implications for therapy of liver failure.

Control of Cell Identity by the Nuclear Receptor HNF4 in Organ Pathophysiology

“…Indeed, HNF4A was recently shown to support epithelial regeneration in the intestine in response to irradiation in a mouse genetic model [ 66 ]. Moreover, HNF4A is required for termination of liver regeneration, which requires inhibition of hepatocyte proliferation and reacquisition of their fully differentiated phenotype [ 67 , 68 , 69 ]. Accordingly, HNF4A is necessary to maintain hepatocyte identity in adult mice through regulation of liver-specific genes involved in lipid, glucose, and xenobiotic metabolism, as well as blood coagulation [ 67 , 70 , 71 ].…”

“…Modulation of HNF4 signaling through changes in expression or chromatin binding is not restricted to fluctuating physiological circumstances such as those linked to feeding but also occurs in pathophysiological situations. For instance, partial hepatectomy (PHx) of the mouse liver is accompanied by reduced chromatin accessibility as well as H3K27ac levels at HNF4A binding sites, decreased HNF4A genome occupancy, and diminished expression of HNF4A itself [ 68 , 69 ]. In line, reduced HNF4A expression and binding were identified as major contributors to the suppression of hepatocyte-specific genes and downregulation of liver biosynthetic functions during the liver repopulation process after acute injury in the Fumarylacetoacetate hydrolase ( Fah ) null mouse model [ 125 ].…”

“…Additionally, endoplasmic reticulum stress (ERS) leads to reduced HNF4 recruitment to the Cebpa and Pparg coactivator 1 alpha ( Ppargc1a / Pgc1a ) promoters [ 130 ], in line with ERS repressing genes involved in hepatic metabolic functions including genes regulating lipid homeostasis [ 131 , 132 ]. This is linked to SRC kinase-induced HNF4A proteasomal degradation upon acute ERS and subsequent loss of HNF4A mRNA expression [ 68 , 69 , 133 ]. Importantly, in line with HNF4 controlling hepatic cell identity, our group has redefined the paradigm related to acute ERS-induced changes in the liver by pointing to profound transcriptomic alterations linked to a global loss of hepatic molecular identity [ 69 ].…”

Emergent properties of HNF4α-PPARγ network may drive consequent phenotypic plasticity in NAFLD

“…Hepatocyte Nuclear Factor 1α (HNF1α) [16][17][18]. HNF4α is an established master regulator of induction and maintenance of the hepatic cell state [19,20]. HNF4α knockout mice exhibit severe hepatomegaly (enlarged liver) and steatosis [16,19].…”

Co-encapsulation of HNF4α Overexpressing UMSCs and Human Primary Hepatocytes Ameliorates Mouse Acute Liver Failure

“…(10) Hepatocyte nuclear factor-4 alpha (HNF4α) is an important transcription factor of the nuclear hormone receptor family, and is essential for maintaining a normal liver architecture. (11) Moreover, it also plays a crucial role in hepatic differentiation, metabolic function and formation of a polarized hepatic epithelium and cell-cell contact. (12) Moreover, as supported by similar research, (13,14) our previous study showed that HNF4α-overexpressing UMSCs (HNF4α-UMSCs) has signi cantly improved the differential status of hepatocyte-like cells by activating the expression of genes related to hepatocyte function.…”