Haematopoiesis Measured by Spleen Colony and Diffusion Chamber Techniques in Mice Treated with One or Two Injections of Cyclophosphamide

Abstract

Summary. The effect of cyclophosphamide (CY) on haematopoiesis in mice was observed by the techniques of the spleen colony and the diffusion chamber. Two hours after injection of CY, the number of spleen colony‐forming units (CFU) was reduced to 11% of control, whereas diffusion‐chamber progenitor cells (DCPC) were less affected and 30% survived initially. Histological examination showed that erythroid CFU were significantly more reduced than granuloid CFU, most likely because CY selectively impairs the ability of surviving multipotent stem cells to erythroid differentiation. This defect was repaired within a few days.A second injection of CY 4 days after the first had similar effects, indicating that the selective effect on erythroid CFU was independent of proliferative rate. DCPC were less affected by the second CY injection than by the first, possibly because a higher proliferative rate increased their resistance towards CY.The pattern of depletion and regeneration after one or two injections of CY indicates that the two techniques do not assay identical cell populations. Whereas the spleen colony technique predominantly measures multipotent stem cells, the diffusion chamber technique most probably to a larger extent measures unipotent (committed) stem cells.