Role of the microenvironment on hematopoiesis. I. Stem cell differentiation into granulocytic and megakaryocytic cell...

Lineage commitment and differentiation of stem cells derived from bone marrow was investigated by using specific histochemistry for identification of spleen colonies. The number of colonies formed by injection of 1 x 10(5) bone marrow cells into irradiated murine syngeneic recipients was similar to the previously reported results with 1 x 10(6) spleen cells. The results of this study with bone marrow-derived cells have been compared with those from studies done with spleen-derived cells. A significant increase (p less than 0.01) was observed in the number of granulocytic colonies formed by bone marrow cells versus spleen-derived cells. This suggests that bone marrow-derived cells promote granulopoiesis in the recipient spleen. A 50% increase of megakaryocyte colonies was observed within the splenic pulp in the midzone region when compared with that on the surface (p less than 0.01). This indicates that the splenic microenvironment in this area was conducive for megakaryocytopoiesis. These results provide further evidence of the influence of the microenvironment on hematopoiesis.