Background: The availability of well-characterized human liver cell populations that can be frozen and thawed will be critical for cell therapy. We addressed whether human hepatocytes can recover after cryopreservation and engraft in immunodeficient mice. Methods: We isolated cells from discarded human livers and studied the properties of cryopreserved cells. The viability of thawed cells was established with multiple in vitro assays, including analysis of liver gene expression, ureagenesis, cytochrome P450 activity, and growth factor-induced cell proliferation. The fate of transplanted cells was analysed in immunodeficient NOD-SCID mice. Results: After thawing, the viability of human hepatocytes exceeded 60%. Cells attached to culture dishes, proliferated following growth factor stimulation and-exhibited liver-specific functions. After transplantation in NOD-SCID mice, cells engrafted in the peritoneal cavity, a heterologous site, as well as the liver itself, retained hepatic function and proliferated in response to liver injury. Transplanted hepatocytes were integrated in the liver parenchyma. Occasionally, transplanted cells were integrated in bile ducts. Conclusions: Cryopreserved human liver cell showed the ability to retain functional integrity and to reconstitute both hepatic and biliary lineages in mice. These studies offer suitable paradigms aimed at characterizing liver cells prior to trainsplantation in people.
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