Enhanced hematopoiesis in vivo and in vitro by splenic stromal cells derived from the mouse with recombinant granulocyte colony-stimulating factor

Splenic stromal cells (CF-1 cells) were established from a mouse administered recombinant human granulocyte colony-stimulating factor (rG-CSF) to clarify the mechanism of splenic extramedullary hematopoiesis induced by the factor. The cells were negative for alkaline phosphatase, factor VIII-related antigen, mac I, and phagocytosis. They were positive for acid phosphatase, collagen type I, collagen type III, and fibronectin. CF-1 cells were not converted to adipocytes in a confluent culture with 10(-6) mol/L hydrocortisone. [35S]rG-CSF bound to CF-1 cells specifically in the growth phase but not in the resting phase. The CF-1 cells had greater colony-stimulating activities than the normal splenic stromal cells. When CF-1 cells were added to bone marrow cells in the spleen colony-forming cells (CFU-S) assay, the number of colonies in the spleen increased between 1.4 and 1.8 times the control without these stromal cells. On the other hand, the normal splenic stromal cells had no effect on increasing the number of CFU-S colonies. Therefore, these data suggest that a factor- dependent hematopoietic microenvironment is generated in the spleen by rG-CSF, and the stromal cells that have the hematopoietic potency become dominant in splenic extramedullary hematopoiesis induced by rG- CSF.