title: Influence of hematopoietic stem cell-derived hepatocytes on liver regeneration after sex-mismatched liver transplantation in humans.
abstract: BACKGROUND
  Presence of hematopoietic stem-cell-derived hepatocytes after clinical liver transplantation was demonstrated repeatedly. The relevance of this controversial mechanism of regeneration was discussed. Regarding frequency, the demonstrated results were divergent. In the present study, we propose to investigate the influence of growth and regeneration on the frequency of hematopoietic stem-cell-derived hepatocytes in transplanted organs.
  
  
  METHODS
  Paraffin-embedded liver specimens, obtained as clinically indicated, from female grafts transplanted into male recipients were investigated. The presence of Y-chromosome in hepatocytes, detected by fluorescence in situ hybridization (FISH), was the indicator for recipient origin. Slides were evaluated by assessing the relative number of Y-chromosome containing hepatocytes within 50 images representing an average of 775 hepatocytes.
  
  
  RESULTS
  In only 9 out of 81 specimens, single Y-chromosome positive hepatocytes were detected, resulting in a maximal frequency of 0.64%. Six positive specimens were obtained from full-size liver grafts and one from a partial liver graft. In the pediatric group, two positive samples were found. By staining additional sections from the nine positive specimens, no additional positive hepatocytes were detected suggesting an even lower frequency within the whole sample. We did not find any accumulation of Y-chromosome positive cells in any of the individually analyzed patient groups.
  
  
  CONCLUSIONS
  Transdifferentiation of hematopoietic stem cells is an extremely rare event in liver growth and regeneration after transplantation. Due to the low number of positive events, the biological relevance seems questionable.
authors.affiliation: Department of General, Visceral and Transplantation Surgery, University Hospital Essen,   Essen,   Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Schwerfeld-Bohr
authors.forename: Haidong
authors.initials: H
authors.lastname: Chi
authors.forename: Karl
authors.initials: K
authors.lastname: Worm
authors.forename: Uta
authors.initials: U
authors.lastname: Dahmen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D054338:Cell Transdifferentiation; D002648:Child; D002675:Child, Preschool; D041322:Chromosomes, Human, Y; D005260:Female; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D022781:Hepatocytes / Q000502:physiology*; D006801:Humans; D008115:Liver Regeneration; D016031:Liver Transplantation; D008297:Male; D008875:Middle Aged