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Liver Regeneration using Blood-derived Hepatocytes

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Review of “Expansion and Hepatic Differentiation of Adult Blood-Derived CD34+ Progenitor Cells and Promotion of Liver Regeneration after Acute Injury” from Stem Cells Translational Medicine by Stuart P. Atkinson

The potential applications of functional liver cells, or hepatocytes, range from basic research to new drug development and cell-based regenerative therapies. However, hepatocytes are difficult to expand in vitro [1], and so researchers have been searching for alternative strategies in liver regeneration. Previous preclinical/clinical trials found CD34-positive hematopoietic stem cells (HSCs) to be effective in the treatment of liver diseases [2-4], although the generation of sufficient numbers of CD34-positive cells and their efficient differentiation into hepatocytes are current problems.

However, these problems may now have been solved in the form of a new study in Stem Cells Translational Medicine study [5]? The study, from tenacious researchers from the laboratory of H. Peter Lorenz (Stanford University, USA), describes the efficient expansion of mouse blood-derived CD34+ progenitor cells (BDPCs) and their conversion into hepatocytes cells with high regenerative potential using a simple a coculture system [6].

The coculture system described uses a transwell system, in which mitotically inactivated AML12 hepatocytes layer the wells, and the total nucleated cell fraction of mouse peripheral blood is cultured in the transwell insert. Over a three-week period, the presence of the hepatocytes mediated a large increase in CD34+ BDPC number (See Figure – GFP marks nucleated blood cells at day 15) and following reselection and reseeding into the co-culture plates, expansion accelerated even further.

Further co-culture enhanced differentiation of BDPCs into hepatocytes with the appropriate morphology (elongated, flat, and polygonal, with a decreased ratio of nucleus to cytoplasm ratio), a hepatocytic marker expression profile (e.g. CK8, CK18, CK19, α-fetoprotein, integrin-β1, and A6), and a range of liver-specific functional activities (e.g. glycogen storage, urea production, and albumin secretion)

But do these blood-derived hepatocytes have regenerative activity? Following intravenous injection of differentiated BDPCs into the liver of a mouse model of acute liver injury mouse, the cells homed to the injured liver where they mediated an increase in survival, a reduction in both liver inflammation and liver cell damage, and the recovery of body weight as compared to untreated control mice. Furthermore, the application of differentiated BDPCs completely reversed carbon tetrachloride (CCl4) toxicity-associated liver necrosis with no associated inflammatory cell infiltration, suggesting that transplanted differentiation BDPCs represent a safe an effective means to boost liver regeneration.

Could this strategy solve our hepatocyte drought? The authors note that the starting material (peripheral blood) is plentiful and easy to collect and that the differentiated BDPCs are highly proliferative (doubling time of 48 hours), can be robustly expanded in vitro for over two years without the loss of CD34 expression, and do not appear to be tumorigenic in vivo. Furthermore, they also hope to identify the hepatocyte-secreted factors which mediate BDPC differentiation and to pinpoint if transplanted differentiated BDPCs directly repopulate the liver or whether they promote and endogenous regenerative response. Hopefully, these further studies will propel this blood-derived hepatocytes treatment modality towards the clinic as a much-needed tool for liver regeneration in human patients.

References

  1. Sokal EM From hepatocytes to stem and progenitor cells for liver regenerative medicine: advances and clinical perspectives. Cell Prolif 2011;44 Suppl 1:39-43.
  2. Garg V, Garg H, Khan A, et al. Granulocyte colony-stimulating factor mobilizes CD34(+) cells and improves survival of patients with acute-on-chronic liver failure. Gastroenterology 2012;142:505-512 e501.
  3. Sharma M, Rao PN, Sasikala M, et al. Autologous mobilized peripheral blood CD34(+) cell infusion in non-viral decompensated liver cirrhosis. World J Gastroenterol 2015;21:7264-7271.
  4. Nakamura T, Torimura T, Iwamoto H, et al. CD34(+) cell therapy is safe and effective in slowing the decline of hepatic reserve function in patients with decompensated liver cirrhosis. J Gastroenterol Hepatol 2014;29:1830-1838.
  5. Hu M, Li S, Menon S, et al. Expansion and Hepatic Differentiation of Adult Blood-Derived CD34+ Progenitor Cells and Promotion of Liver Regeneration After Acute Injury. Stem Cells Translational Medicine 2016;5:723-732.
  6. Li S, Huang KJ, Wu JC, et al. Peripheral blood-derived mesenchymal stem cells: candidate cells responsible for healing critical-sized calvarial bone defects. Stem Cells Transl Med 2015;4:359-368.