Inverse Tendency between Ex Vivo Expansion Potential of Hematopoietic Progenitors and Time to Engraftment after Hematopoietic Stem Cell Transplantation.
BACKGROUND
The CD34(+) cell dose and infused number of committed progenitor cells in transplantation are important factors in hematologic engraftment. However, the relationship between expansion potential of progenitor cells and hematologic engraftment remains controversial. We evaluated whether expansion potential of progenitor cells is a predictive factor of post-transplantation hematologic engraftment.


METHODS
Mononuclear cells isolated from mobilized peripheral blood and bone marrow were cultured with cytokine cocktail for 7 days. Progenitor cells and committed progenitors were analyzed using stem cell markers (CD34 and CD133) and lineage specific markers. Hematologic engraftment was defined as neutrophil counts over 500/microL and platelet counts over 20,000/microL without transfusion. Acute and chronic graft-versus-host disease (GVHD) were investigated.


RESULTS
There was inverse tendency between the number and fold expansion of progenitor cells or committed (granulocytic or megakaryocytic) progenitors and time to engraftment. Especially, fold expansion of CD34(+)/CD33(+) cells was significantly correlated with time to neutrophil engraftment in bone marrow transplantation (r=-0.56, P=0.04). The infused number and fold expansion of lymphoid progenitors were not related to the occurrence of acute or chronic GVHD.


CONCLUSIONS
We could not prove that expansion potential of progenitor cells and committed progenitor cells is correlated to hematologic engraftment although there is a correlation between CD34(+)/ CD33(+) cells and time to neutrophil engraftment. But, a further study on the value of expansion potential is required because there is an inverse tendency.