Expansion of rhesus monkey hematopoietic stem cells in response to administration of chimeric leridistim or progenipoietin (Pro-gp)

Abstract

The phenotype of Rhesus monkey hematopoietic stem cells (HSC) has not bee well defined. We developed a monoclonal antibody (mAb) cocktail derived from known anti human mAbs that enabled us to enrich monkey HSC. Approximately 98% of the peripheral blood (PB) and 89% to 93% of bone marrow (BM) lineage positive (Lin+) cells were subtracted using anti CD2, CD4, CD8, CD11b, CD14, CD20 and CD44 mAbs and magnetic immunobead depletion. The Lin− cells were then stained with anti CD34 and CD38 mAbs and subdivided by FACS into Lin− CD34+ CD38+ and Lin− CD34+ CD38− cells. In a series of 9 control BM samples, FACS analysis indicated 1.6% ± 1.4% of the Lin− cells were CD34+ CD38−. After 5 daily SC injections of leridistim or PRO-GP, chimeric agonists for IL-3 and G-CSF or Flt-3 and G-CSF receptors, respectively, the % of Lin− CD34+ Cd38− cells was expanded 4-fold in mobilized PB and BM compared with the % in control BM. To test the hypothesis that monkey HSC are in the Lin− CD34+ CD38− fraction, we injected NOD/SCID mice with approximately equal numbers of Lin− CD34+ CD38+ and Lin− CD34+ CD38− cells from control and mobilized PB and BM. The Lin− CD34+ CD38− candidate HSC gave rise to a greater number of CD45+ CD3+ (T-cells) and CD45+ CD13+ (monocytes) monkey derived cells in NOD/SCID BM compared with Lin− CD34+ CD38− cells revealed a relatively high level of mRNA encoding the transcription factor GATA-2, a known product of mouse and human HSC. We conclude that monkey HSC, like human HSC, have a Lin− CD34+ CD38− phenotype and that they can be expanded and mobilized by cytokine treatment.