Objective: The hepatic integration of human adipose tissue derived mesenchymal stem cells (hAT-MSCs) in vivo with or without prior differentiation to hepatocyte-like cells in vitro was investigated. Methods and results: Cells, isolated either from peritoneal or subcutaneous adipose tissue, expressed mesenchymal stem cell surface markers and featured multiple lineage differentiation. Under conditions favouring hepatocyte differentiation, hAT-MSCs gained hepatocytic functions in vitro including urea formation, glycogen synthesis, cytochrome P450 enzyme activity, and expression of hepatocyte-specific transcripts of carbamoylphosphate synthetase, albumin and cytochrome P450 type 3A4 (CYP3A4). Transgenic expression of green fluorescent protein emerged upon hepatocyte differentiation when driven by the hepatocyte-specific promoter of the cytosolic phosphoenolpyruvate carboxykinase gene but was constitutive from the ubiquitin gene promoter. Human AT-MSCs were transplanted into livers of immunodeficient Pfp/Rag2−/− mice with or without prior hepatocyte differentiation in vitro. Donor-derived human cells engrafted in the mouse host liver predominantly in the periportal region of the liver lobule. They expressed HepPar1 and albumin, typical features of differentiated human hepatocytes, in the otherwise negative mouse liver background. Engraftment was significantly more efficient using hAT-MSCs pre-differentiated to hepatocyte-like cells in vitro as compared with undifferentiated cells. Conclusions: Pre-differentiation of human MSCs from adipose tissue into hepatocyte-like cells in vitro facilitates long term functional hepatic integration in vivo.

Aims: At present, clinical success of hepatocyte transplantation as an alternative to whole liver transplantation is hampered by the limited availability of suitable donor organs for the isolation of transplantable hepatocytes. Hence, novel cell sources are required to deliver hepatocytes of adequate quality for clinical use. Mesenchymal stem cells (MSCs) from human bone marrow may have the potential to differentiate into hepatocytes in vitro and in vivo. Methods: Isolated MSCs were selected by density gradient centrifugation and plastic adherence, differentiated in the presence of human hepatocyte growth medium and transplanted in immunodeficient Pfp/Rag2 mice. Results: Here, we demonstrate that human MSCs gain in vitro the characteristic morphology and function of hepatocytes in response to specified growth factors. Specifically, preconditioned MSCs store glycogen, synthesise urea and feature the active hepatocyte-specific gene promoter of phosphoenolpyruvate carboxykinase (PCK1). After transplantation into livers of immunodeficient mice, preconditioned MSCs engraft predominantly in the periportal portion of the liver lobule. In situ, the cells continue to store glycogen and express PCK1, connexin32, albumin and the human hepatocyte-specific antigen HepPar1, indicating that the transplanted cells retain prominent qualities of hepatocytes after their regional integration. Conclusion: MSCs derived from human bone marrow may serve as a novel source for the propagation of hepatocyte-like cells suitable for cell therapy in liver diseases.

The acute-phase reaction comprises a variety of systemic changes in response to tissue injury and infection. Synthesis of several plasma proteins in the liver undergoes dramatic changes during the acute-phase reaction. These changes are mediated by the action of cytokines, mainly interleukin 6-(IL6-) and interleukin 1-(IL1-) type cytokines. The role of these cytokines is reviewed in detail. Attention is payed to the differences recently detected between the locally and systemically induced acute-phase response-in particular, the newest findings concerning the meaning of single cytokines. Also, changes in liver metabolic enzyme expression under acute-phase conditions are discussed. The impact ofcytokine and cytokine-receptor knockout or transgenic mouse models on current knowledge is provided. The role of cytokines together with that of soluble cytokine receptors in the resolution of the acute-phase response is discussed.