title: Programmed cell death is an intrinsic feature of MDS progenitors, predominantly found in the cluster-forming cells.
abstract: OBJECTIVE
  Bone marrows (BM) of myelodysplastic syndrome (MDS) patients show increased proliferation and premature programmed cell death (PCD) in vivo as well as in vitro. We explored the proliferative capacity and apoptotic propensity of CD34+ progenitor cells of MDS patients excluding accessory cell interference.
  
  
  METHODS
  CD34+/CD3-/CD19- cells of 5 MDS patients and 5 normal BM were sorted as single cells into single wells and were cultured in liquid medium. Wells were evaluated on days 4, 7, 10, and 14. PCD was determined by staining with annexin V-FITC. Growth rate and cell doubling time (Td) were calculated for each colony-forming cell.
  
  
  RESULTS
  Normal BM CD34+ cells formed clusters and colonies and both showed increasing PCD in time, although within colonies the degree of apoptosis was twice as high (about 25%) as compared with clusters at all time points. In MDS increased cluster formation was observed at all evaluation points when compared to normal BM, whereas the number of colonies was markedly reduced (1/7 of normal). These colonies were also smaller, usually smaller than 100 cells. Significantly enhanced levels of PCD of clusters (53-79%) in combination with longer cell doubling times explain this slower formation of smaller colonies. Surprisingly, these colonies showed considerably lower levels of PCD (7-32%) as compared to normal (1-48%, median values).
  
  
  CONCLUSIONS
  In the absence of stromal influences and accessory cells, this study in MDS patients showed intrinsically enhanced proliferation and apoptosis of cluster-forming cells, as the opposite was true for colony-forming cells.
authors.affiliation: Department of Hematology, University Medical Center, Nijmegen, The Netherlands. lfrspan@gmail.com
authors.forename: Lambert F R
authors.initials: LF
authors.lastname: Span
authors.forename: Gertie
authors.initials: G
authors.lastname: Vierwinden
authors.forename: Arie H
authors.initials: AH
authors.lastname: Pennings
authors.forename: Jan B M
authors.initials: JB
authors.lastname: Boezeman
authors.forename: Reinier A P
authors.initials: RA
authors.lastname: Raymakers
authors.forename: Theo
authors.initials: T
authors.lastname: de Witte
mesh_terms: D018952:Antigens, CD34; D017209:Apoptosis; D001854:Bone Marrow Cells; D016022:Case-Control Studies; D049109:Cell Proliferation; D002469:Cell Separation; D002898:Chromosomes, Human, Pair 8; D003114:Colony-Forming Units Assay; D006412:Hematopoietic Stem Cells / Q000473:pathology*; D006801:Humans; D009190:Myelodysplastic Syndromes / Q000473:pathology*; D014314:Trisomy
chemical_list: D018952:Antigens, CD34