No abstract

The liver has an enormous potential to restore the parenchymal tissue loss due to injury. This is accomplished by the proliferation of either the hepatocytes or liver progenitor cells in cases where massive damage prohibits hepatocytes from entering the proliferative response. Under debate is still whether hepatic stem cells are involved in liver tissue maintenance and regeneration or even whether they exist at all. The definition of an adult tissue‐resident stem cell comprises basic functional stem cell criteria like the potential of self‐renewal, multipotent, i.e. at least bipotent differentiation capacity and serial transplantability featuring the ability of functional tissue repopulation. The relationship between a progenitor and its progeny should exemplify the lineage commitment from the putative stem cell to the differentiated cell. This is mainly assessed by lineage tracing and immunohistochemical identification of markers specific to progenitors and their descendants. Flow cytometry approaches revealed that the liver stem cell population in animals is likely to be heterogeneous giving rise to progeny with different molecular signatures, depending on the stimulus to activate the putative stem cell compartment. The stem cell criteria are met by a variety of cells identified in the fetal and adult liver both under normal and injury conditions. It is the purpose of this review to verify hepatic stem cell candidates in the light of the stem cell definition criteria mentioned. Also from this point of view adult stem cells from non‐hepatic tissues such as bone marrow, umbilical cord blood or adipose tissue, have the potential to differentiate into cells featuring functional hepatocyte characteristics. This has great impact because it opens the possibility of generating hepatocyte‐like cells from adult stem cells in a sufficient amount and quality for their therapeutical application to treat end‐stage liver diseases by stem cell‐based hepatocytes in place of whole organ transplantation. © 2012 International Society for Advancement of Cytometry

NASH is a benign disease and will progress, if untreated, into fibrosis/cirrhosis and potentially into HCC. Human cell therapy approaches for the treatment of NASH have not been addressed yet. The present work aimed at establishing an animal model to evaluate the feasibility of stem cell‐derived hepatocytes.Immunodeficient Pfp/Rag2−/− mice were fed a methionin‐cholin‐deficient diet (MCD diet) up to 5 weeks. Alanine aminotransferase (ALT) and triglycerides were determined in the serum. Histological analyses of liver sections were performed to detect structural abnormalities by HE, the collagen distribution by sirius‐red and fat depositions by sudan III staining. Expression of the acute phase protein SAA, the proinflammatory cytokine TNFα, the marker for activated stellate cells αSMA as well as collagen1 in liver tissue were specified by RT‐PCR.Already 3 weeks after feeding the MCD diet, microsections displayed a deteriorated architecture of the liver tissue, which worsened with continued feeding. By HE‐staining massive steatosis and hepatocellular injury were observed and confirmed by sudan III staining in livers of animals fed the MCD diet as compared to animals fed the control diet. Fibrosis in livers of animals on MCD diet was obvious by collagen staining. The marker of hepatocyte fade ALT was significantly higher (2‐fold) in the serum of mice on MCD diet. Serum triglycerides were significantly lower in MCD diet‐fed animals. RT‐PCR analysis revealed elevated mRNA levels of SAA and TNFα as well as of αSMA and collagen1 in the livers of mice fed the MCD diet.Thus, immunodeficient Pfp/Rag2 mice fed with the MCD diet displayed typical features of NASH, which makes this animal model suitable to evaluate pre‐clinically human cell therapy approaches of liver diseases.

MSC increasingly gain attention for clinical cell therapy of liver diseases. Before translation into the clinics feasibility must be proven preferably in large animal models.The aim of the study was to demonstrate in the large animal model of the pig whether MSC from bone marrow (pBM‐MSC) of the Crista iliaca and from BM of the femur/shank display differences in regard to their hepatogenic differentiation potential.MSC were isolated either from BM of the Crista iliaca or Os femoris. Mesenchymal features were analysed by flow cytometry. Functional properties like the synthesis of urea and glycogen were compared during hepatogenic differentiation.pBM‐MSC from both sources were negative for hematopoietic markers CD14, CD45 but positive for mesenchymal markers CD44, CD29, CD90, CD105. pBM‐MSC from both sources could be differentiated along the adipocyte, osteocyte and hepatocyte lineage. With differentiation progressing glycogen and urea synthesis increased featuring typical hepatocyte functions. After 21 days of differentiation urea synthesis amounted to 3 nmol/10.000 cells × 24h comparable to the rate in primary pig hepatocytes after 8 days of culture.pBM‐MSC from various sources are not different in respect to their mesenchymal features and their hepatogenic differentiation potential. Hence, hollow bones might be particularly useful to isolate allogeneic bone marrow cell transplants.

No abstract