Identification of primitive hematopoietic progenitor cells in the rhesus macaque

The close phylogenetic relationship of macaques to humans has resulted in t heir widespread use as a preclinical model for bone marrow transplantation and stem cell gene therapy. To facilitate fur ther use of this model. we un dertook analysis of hematopoietic cells using multiparametric flow cytometr ic analysis. Rhesus CD34(+) CD38(-) cells displayed a number of characteris tics of primitive hematopoietic cells, including low forward and orthogonal scatter and the lack of expression of lineage-specific markers or human ly mphocyte antigen-DR. Four-color flow cytometric analysis demonstrated that rhesus CD34(+) CD38(-) cells were heterogenous with respect to Thy-1 expres sion and were CD59(dim), Quantitative limiting dilution long-term culture-i nitiating cell (LTC-IC) analysis demonstrated that CD34(+) CD38(-) cells we re approximately 150-fold enriched for LTC-IC as compared with unfractionat ed bone marrow, and occurred at a frequency similar to that previously repo rted in humans. Thus, as in humans, the CD34(+)38(-) population of rhesus m acaque bone marrow is enriched for primitive, multipotent hematopoietic pro genitor cells.