Searching for common stem cells of the hepatic and hematopoietic systems in the human fetal liver: CD34+ cytokeratin 7/8+ cells express markers for stellate cells.

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 hematopoietic 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 hematopoietic cells. They did stain with CD13, CD59, NGFR, desmin and alpha-smooth muscle actin. In culture, these cells had a stellate appearance. Cultured hematopoietic 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.