To the Editor:
We thank Dr. Huang and colleagues for their interest and comments on our recent study, “Small molecule-mediated reprogramming of human hepatocytes into bipotent progenitor cells” published in the Journal of Hepatology.
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We learnt with great interest from the Dr. Huang’s letter that the YAC cocktail (Y27632, A83-01, and CHIR99021) originally developed by Katsuda et al.
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for reprogramming of rodent hepatocytes was also effective in human hepatocytes. The process of conversion of human hepatocytes into stemness state using the YAC system took a long time and was independent of HGF supplementation. Based on these data, Huang et al. propose an indirect role of HGF in the reprogramming of human hepatocytes.In our work, we found that a combination of 2 small molecules (A83-01 and CHIR99021) with HGF (termed HAC system) was very effective in reprogramming human hepatocytes, whereas treatment with either HGF or AC alone induced neither expansion of small epithelial cells nor expression of hepatic progenitor marker genes.
Furthermore, pharmacologically selective inhibition of MET receptor and ERK1/2 signaling caused a complete suppression of hepatic progenitor cell generation. Therefore, we believe that combined HAC treatment played an essential role in reprogramming human hepatocytes into chemically derived hepatic progenitors (hCdHs).
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It is worth noting that Y27632, one of the components used by Huang and colleagues for reprogramming human hepatocytes, is an inhibitor of a Rho-associated protein kinase (ROCK) known to affect various cellular functions by modulating diverse signaling pathways.
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More specifically, it was reported that ROCK inhibition promoted cancer stem cell characteristics by activating the phosphorylation of the MET receptor.[5]
It seems possible that the YAC system utilizing ROCK inhibition could be associated with activation of MET receptor-dependent signaling. Further studies are needed to systematically address this issue.In response to their question regarding the presence of fibroblast-like cells, we would like to point out that the process of reprogramming human hepatocytes in the HAC system was considerably more rapid (2 weeks compared to 4 weeks in the YAC system). We did not observe proliferation of fibroblast-like cells when hepatocytes were isolated from either healthy livers or non-tumorous healthy parts of diseased liver. However, when we applied the HAC method to hepatocytes isolated from donors with liver fibrosis or end-stage liver diseases, we found proliferation of fibroblast-like cells. Our current efforts are directed towards understanding the mechanisms underlying the molecular differences driving chemical reprogramming in healthy versus diseased hepatocytes.
Finally, in response to the concern regarding the type of cells used for chemical reprogramming in our published manuscript, we would like to clarify that hepatocytes were isolated either from donor liver samples of the patients suffering from non-cancerous diseases (gallbladder polyp and intrahepatic duct stone) or from non-tumorous parts of livers taken at least 3 cm apart from hepatocellular carcinoma (3 cases) and metastatic tumor of colon cancer (1 case) to minimize the possibility of contamination with tumor cells.
Financial support
This research was supported by Grants from the Medical Research Center (2017R1A5A2015395), Basic Science Research Program (2017R1D1A1B03030508), and the Bio & Medical Technology Development Program (2018M3A9H1023910) funded by the National Research Foundation (NRF) of the Ministry of Education, Science and Technology (MEST).
Conflict of interest
The authors declare no conflicts of interest that pertain to this work.
Please refer to the accompanying ICMJE disclosure forms for further details.
Authors’ contributions
SBL and JJ wrote the letter. YK, KK and DS discussed the experiments. JHY, DC and VF revised the letter.
Supplementary data
The following are the Supplementary data to this article:
- Supplementary Data 1
References
Author names in bold designate shared co-first authorship
- Small molecule-mediated reprogramming of human hepatocytes into bipotent progenitor cells.J Hepatol. 2019; 70: 97-107
- Conversion of terminally committed hepatocytes to culturable bipotent progenitor cells with regenerative capacity.Cell Stem Cell. 2017; 20: 41-55
- Direct Rho-associated kinase inhibition [correction of inhibiton] induces cofilin dephosphorylation and neurite outgrowth in PC-12 cells.Cell Mol Biol Lett. 2006; 11: 12-29
- Genetic and pharmacological inhibition of Rho-associated kinase II enhances adipogenesis.J Biol Chem. 2007; 282: 29574-29583
- Induction of the stem-like cell regulator CD44 by Rho kinase inhibition contributes to the maintenance of colon cancer-initiating cells.Cancer Res. 2012; 72: 5101-5110
Article info
Publication history
Published online: May 13, 2019
Identification
Copyright
© 2019 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.
