Background/Aims: The hematopoietic and hepatic systems are intertwined in the liver during fetal life. Cells expressing the hematopoietic stem cell marker CD34 and cytokeratin 7/8 (CK7/8) are hypothesized to be common stem cells for the hematopoietic and hepatic systems. Our aim was to determine if human fetal liver cells expressing CD34 and CK7/8 represent a common stem cell for both the hernatopoietic and hepatic systems. Methods: CD34(+)CK7/8(+) cells from midgestation livers were analyzed for the expression of various markers by flow cytometry and isolated based on their expression of CD34, nerve growth factor receptor (NGFR) and lack of CD45 expression. CD34(+)CD38(-) hematopoietic stem cells were also isolated and cultured in the presence of various hepatopoietins. Results: CD34(+)CK7/8(+) cells comprised 3.4-8.5% of the erythrocyte-depleted liver. CD34(+)CK7/8(+) cells had unique light-scatter properties compared to hematopoietic precursors and did not express most markers associated with hernatopoietic cells. They did stain with CD13, CD59, NGFR, desmin and alpha-smooth muscle actin. In culture, these cells had a stellate appearance. Cultured hernatopoietic stem cells failed to generate hepatocytes. Conclusions: CD34(+)CK7/8(+) cells are not common stem cells but rather appear to be hepatic stellate cells. A link between the hematopoietic and hepatic systems during fetal life requires further investigation. (C) 2003 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Megakaryocyte growth and development factor (MGDF), or thrombopoietin, has received considerable attention as a therapeutic agent for treating thrombocytopenia or for its use in the ex vivo culture of hematopoietic stein cells. MGDF is known to support the growth of a broad spectrum of hematopoietic precursors obtained from adult or neonatal tissues, but its effects on the growth of fetal progenitors and stem cells has not been studied. Human CD38(+)CD34(2+) progenitors and CD38(-)CD34(2+) cells, a population that contains stem cells, were isolated from midgestation liver and grown under defined conditions with MGDF and various cytokines known to support the growth of primitive hematopoietic precursors. In clonal assays of colony-forming cells (CFCs), MGDF supported the growth of 15-25% of candidate stem cells when combined with granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor (GM-CSF), flk-2/flt3 ligand, or stem cell factor. MGDF was observed to strongly support the early stages of hematopoiesis and expansion of high proliferative potential CFCs. More mature progenitors were expanded nearly 78-fold in 1 wk of culture with MGDF+SCF+GM-CSF. MGDF alone was also found to support the short-term (2 d) survival of CD38(-)CD34(2+) high proliferative potential CFCs. The effects of MGDF were more modest on CD38(+)CD34(2+) progenitors with only additive increases in colony formation being observed. These findings suggest that MGDF administration in fetuses and neonates may strongly affect the growth and mobilization of primitive hematopoietic progenitors and that MGDF may find use in the ex vivo growth and expansion of fetal stem cells.

Background: Biliary atresia ( BA) is a neonatal cholestatic disease of unknown etiology. It is the leading cause of liver transplantation in children. Many similarities exist between BA and graft versus host disease suggesting engraftment of maternal cells during gestation could result in immune responses that lead to BA. The aim of this study was to determine the presence and extent of maternal microchimerism ( MM) in the livers of infants with BA. Methods: Using fluorescent in situ hybridization ( FISH), 11 male BA & 4 male neonatal hepatitis ( NH) livers, which served as controls, were analyzed for X and Y-chromosomes. To further investigate MM in BA, 3 patients with BA, and their mothers, were HLA typed. Using immunohistochemical stains, the BA livers were examined for MM. Four additional BA livers underwent analysis by polymerase chain reaction (PCR) for evidence of MM. Results: By FISH, 8 BA and 2 NH livers were interpretable. Seven of eight BA specimens showed evidence of MM. The number of maternal cells ranged from 2 - 4 maternal cells per biopsy slide. Neither NH specimen showed evidence of MM. In addition, immunohistochemical stains confirmed evidence of MM. Using PCR, a range of 1 - 142 copies of maternal DNA per 25,000 copies of patients DNA was found. Conclusions: Maternal microchimerism is present in the livers of patients with BA and may contribute to the pathogenesis of BA.