TGF-β1 signaling regulates mouse hepatic stellate cell differentiation via the Jagged1/Notch pathway.

AIMS

We tested whether transforming growth factor β1 (TGF-β1) signaling plays an important role in hepatic stellate cell differentiation fate and investigated the role of Jagged1/Notch in this process.

MATERIALS AND METHODS

TGF-β1 was overexpressed and transforming growth factor receptor 1 (TGF-β-R1) was knocked down by a lentiviral vector in mouse hepatic stellate cells (mHSCs). Transfection efficiency was assessed with immunofluorescence, quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) and western blotting. The downstream genes alpha-smooth muscle actin (α-SMA), Jagged1 and the differentiation markers alpha-fetoprotein (AFP), albumin (ALB), cytokeratin19 (CK19), SRY (sex determining region Y)-box 9 (SOX9), and hairy and enhancer of split-1 (Hes1) were measured with qRT-PCR and western blotting.

KEY FINDINGS

SpHBLV-CMVIE-TGF-β1, pHBLV-CMVIE-GFP, pHBLV-U6-TGF-β-R1 shRNA, and pHBLV-U6-RFP were successfully transfected. Over-expression of the TGF-β1 gene caused mHSCs to transform into myofibroblasts (MFs) and expression of Jagged1 and cholangiocyte markers (CK19, SOX9, Hes1) were significantly upregulated (P<0.01). Importantly, after blocking TGF-β1 signaling via gene silencing, expression of Jagged1 was much reduced, but the mature hepatocyte marker (ALB) was obviously increased. In addition, AFP, a hepatic stem cell marker, was expressed at the highest level in the control groups.

SIGNIFICANCE

Our findings emphasize that the TGF-β1 signaling pathway regulates expression of Jagged1 in mHSCs which is associated with transformation of mHSCs into MFs, thus demonstrating a novel mechanism via which TGF-β1 signaling controls the differentiation fate of mHSCs through regulation of the Jagged1/Notch pathway.