Involvement of hematopoietic stem cells in liver fibrosis : clarification of origin of hepatic stellate cells using single cell transplantation method

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We have known that non-blood cells, which are derived from hematopoietic stem cells, exist in the CCl_4-injured liver ; however, we have never evaluated the characteristics of the cells. Single Lin-c-kit^+Sca-l^+CD34^- cells from EGFP mice (EGFP^+ KSL-CD34^- cells) were deposited into round-bottomed 96-well plates and cultured in the presence of IL-11 and SCF for 7 days. The contents of the wells containing 20 or fewer viable clusters of cells derived from single EGFP^+KSL-CD34^- cells were injected into the tail veins of irradiated C57BL/6J mice. We induced liver injury by CCl_4 treatment in transplanted mice, which showed high levels of long-term, multilineage hematopoietic engraftment at 2 months after BM transplantation. After 12 weeks of CCl_4 treatment, we detected EGFP^+ hepatic stellate cells, which contained intracytoplasmic lipid droplets(Oil-red-O positive) and expressed vimentin, glial fibrillary acidic protein, and ADAMTS 13. Moreover, EGFP^+ cells isolated from the liver … More synthesized collagen I in culture. The hematopoietic stem cell-derived hepatic stellate cells seen in male-to-male transplants revealed only one Y chromosome. We presented our research results in 2006 ASH annual meeting (at Orlando) and published them in Blood Journal(2008 ; 111 : 2427-2435).Although we proved that hematopoietic stem cells can transdifferentiate into hepatic stellate cells in liver injury, pathways and mechanisms that regulate the transdifferentiation are remained unknown. We have found that myeloid lineage cells, especially monocytes and macrophages, can transdifferentiate into glomerular mesangial cells in our previous study. Then, we tried to examine the relationship between myeloid lineage cells and hepatic stellate cells. Monocytes and macrophages were prepared by the culture of EGFP^+ KSL cells in the presence of SCF and M-CSF, and injected into liver-injured mice. We detected that the number of EGFP^+ cells in these mice were similar to those in bone marrow total nucleated cells-transplanted mice. Now, we are evaluating whether the EGFP^+ cells are Kupffer cells or hepatic stellate cells. Less