Wang Tao, Chen Tao, Liang Hong-Yin, Yan Hong-Tao, Lin Ning, Liu Li-Ye, Luo Hao, Huang Zhu, Li Nan-Lin, Liu Wei-Hui, Tang Li-Jun
General Surgery Center, Chengdu Military General Hospital, Chengdu, Sichuan Province, 610083, China.
Cell Tissue Res. 2014 Jul;357(1):173-84. doi: 10.1007/s00441-014-1825-9. Epub 2014 Apr 17.
In a previous study, the Notch pathway inhibited with N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (also called DAPT) was shown to promote the differentiation of fetal liver stem/progenitor cells (FLSPCs) into hepatocytes and to impair cholangiocyte differentiation. The precise mechanism for this, however, was not elucidated. Two mechanisms are possible: Notch inhibition might directly up-regulate hepatocyte differentiation via HGF (hepatocyte growth factor) and HNF (hepatocyte nuclear factor)-4α or might impair cholangiocyte differentiation thereby indirectly rendering hepatocyte differentiation as the dominant state. In this study, HGF and HNF expression was detected after the Notch pathway was inhibited. Although our initial investigation indicated that the inhibition of Notch induced hepatocyte differentiation with an efficiency similar to the induction via HGF, the results of this study demonstrate that Notch inhibition does not induce significant up-regulation of HGF or HNF-4α in FLSPCs. This suggests that Notch inhibition induces hepatocyte differentiation without the influence of HGF or HNF-4α. Moreover, significant down-regulation of HNF-1β was observed, presumably dependent on an impairment of cholangiocyte differentiation. To confirm this presumption, HNF-1β was blocked in FLSPCs and was followed by hepatocyte differentiation. The expression of markers of mature cholangiocyte was impaired and hepatocyte markers were elevated significantly. The data thus demonstrate that the inhibition of cholangiocyte differentiation spontaneously induces hepatocyte differentiation and further suggest that hepatocyte differentiation from FLSPCs occurs at the expense of the impairment of cholangiocyte differentiation, probably being enhanced partially via HNF-1β down-regulation or Notch inhibition.
在先前的一项研究中，用N-[N-(3,5-二氟苯乙酰基)-L-丙氨酰基]-S-苯甘氨酸叔丁酯（也称为DAPT）抑制Notch信号通路，可促进胎肝干细胞/祖细胞（FLSPCs）向肝细胞分化，并损害胆管细胞分化。然而，其确切机制尚未阐明。可能有两种机制：Notch抑制可能通过肝细胞生长因子（HGF）和肝细胞核因子（HNF）-4α直接上调肝细胞分化，或者可能损害胆管细胞分化，从而间接使肝细胞分化成为主导状态。在本研究中，检测了Notch信号通路被抑制后HGF和HNF的表达。虽然我们最初的研究表明，抑制Notch诱导肝细胞分化的效率与通过HGF诱导的相似，但本研究结果表明，Notch抑制并不会导致FLSPCs中HGF或HNF-4α的显著上调。这表明Notch抑制在没有HGF或HNF-4α影响的情况下诱导肝细胞分化。此外，观察到HNF-1β显著下调，推测这依赖于胆管细胞分化的受损。为了证实这一推测，在FLSPCs中阻断HNF-1β，随后观察肝细胞分化情况。成熟胆管细胞标志物的表达受损，肝细胞标志物显著升高。因此，数据表明胆管细胞分化的抑制会自发诱导肝细胞分化，并进一步表明FLSPCs向肝细胞的分化是以胆管细胞分化受损为代价发生的，可能部分通过HNF-1β下调或Notch抑制而增强。
