Proliferation and differentiation of myelodysplastic CD34+ cells: phenotypic subpopulations of marrow CD34+ cells

In a search for a mechanism to explain the impaired growth of progenitor cells in patients with myelodysplastic syndromes (MDS), marrow CD34+ cells were purified up to 94.9% +/- 4.2% for normal individuals and 88.1% +/- 17.6% for MDS patients, using monoclonal antibodies and immunomagnetic microspheres (MDS CD34+ cells). Phenotypic subpopulations of these CD34+ cells were analyzed for CD38, HLA-DR, CD33, CD13, CD14, CD41 and CD3 plus CD19, in association with proliferative and differentiative capacities. The 15 studies performed included 12 MDS patients. Coexpression rate of CD13 significantly increased in the MDS CD34+ cell population with a value of 91.4% +/- 11.6% and ranging from 60.3% to 100%, and exceeded 99% in four studies, whereas that of normal CD34+ cells was 49.9% +/- 15.8%, ranging from 28.2% to 70.1% (P < .001). Coexpression rate of CD38, HLA-DR, CD33, CD14, and CD3 plus CD19 in MDS CD34+ cells did not significantly differ from that of normal CD34+ cells. The total number of colonies and clusters grown from 100 normal marrow CD34+ cells was 40.4 +/- 8.6, the range being from 27.2 to 50.3; this varied in MDS marrow CD34+ cells with a value of 34.0 +/- 28.7, the range being 0 to 95.9. The lineage of colonies and clusters promoted by MDS marrow CD34+ cells was predominantly committed to nonerythroid with impaired differentiation in 13 of 15 studies (87%). CD13 is first expressed during hematopoiesis by colony-forming unit granulocyte-macrophage and is absent in erythroid progenitors. Therefore, this study provides direct evidence for the lineage commitment of MDS CD34+ cells to nonerythroid with impaired differentiation and explains the mechanism of nil or low colony expression of MDS progenitor cells to erythroid lineage.