Bone marrow-derived hepatocytes.

Several independent reports have demonstrated that bone marrow cells can give rise to different hepatic epithelial cells types, including oval cells, hepatocytes and duct epithelium. These observations have resulted in the hypothesis that bone marrow resident stem cells, specifically haematopoietic stem cells, are an important source for liver epithelial cell replacement, particularly during chronic injury. However, the bulk of published data on the role of bone marrow stem cells in liver damage suggest that they do not play a significant physiological role in replacement of epithelial cells in any known form of hepatic injury. Fully functional bone marrow-derived hepatocytes indeed exist, but are extremely rare and are generated by cell fusion, not stem cell differentiation.