Murine recovery from busulfan‐induced hematopoietic toxicity as assessed by three assays for colony‐forming cells

Abstract

These studies were designed to explore further the interrelationships between various stem cell and other hematopoietic compartments of the mouse. Busulfan (BU) has been shown by others to have a profound effect on the transplantable pluripotent stem cells capable of forming colonies on spleens (CFU) of lethally irradiated recipients -more so than on cells of differentiated compartments. Another presumed assay of pluripotent stem cells consists of counting colonies on spleens of nontransplanted sublethally irradiated mice as a quantitation of endogenous colony-forming units (E-CFU). We examined and compared BU-induced damage and recovery as measured by E-CFU, CFU, CFU-C, total cellularity of marrow, peroxidase-positive cells per marrow, spleen weight, radioactive iron uptake into spleen and marrow, and hematocrit. E-CFU were severely damaged by BU, but recovery was significantly more rapid than that measured for CFU. These results were compatible with other data suggesting that cycling stem cells are more likely to survive radiation and less likely to survive removal and transplantation. Thus, the actual number of pluripotent stem cells lies between the CFU and E-CFU values, Damage t o more mature granulocytic and erythrocytic compartments lagged behind damage to E-CFU and CFU. Abortive rises in these more mature compartments were observed, which suggested limited but distinct self-replication activity of "stem cells" more differentiated than the CFU, E-CFU systems. Time of final recovery of the damaged hematopoietic system was compatible with a concept of recovery of pluripotent stem cell system(s) preceding recovery of more mature compartments.

Assessment of myelotoxicity caused by environmental chemicals.

“…This residual marrow damage would not be predicted by parameters such as bone marrow cellularity, peripheral blood counts or even in some cases by CFU-S numbers (20,36). However "stressors" such as serial transfer of marrow (20), anemia (21) or irradiation (19) have.revealed that these mice have a more limited hemopoietic response than controls.…”

“…Marrow CFU-E numbers follow a predictive pattern, increased following bleeding (34) and decreased during plethora induced by red cell transfusions (35). Erythroid progenitors as measured by clonal assays are sensitive to cytostatic agents (30,36,37) and known marrow toxicicants such as benzene (38,39). Use of these assays has revealed that some patients with aplastic anemia possess a population of lymphocytes capable of suppressing in vitro erythroidcolony formation by normal human bone marrow (40), whereas in congenital hypoplastic (DiamondBlackfan) anemia, lymphocytes are normal, and the defect appears to reside in the erythroid progenitors (41).…”

“…Thus these assays allow not only study of erythroid progenitor cell numbers but can also contribute to our understanding of hormonal factors and cell to cell interaction as may occur in disease states. Another technique used to study erythropoiesis is 59Fe uptake in spleen and marrow which provides a specific marker for hemoglobin synthesis (15,36). In this assay, mice are killed 18 hr after injection of the isotope and tissues collected for counting.…”

Reduction of Busulfan-Induced Granulocytopoietic Toxicity in Mice by Postbusulfan Injection of Endotoxin

“…A single dose of busulfan (Myleran) causes a severe and prolonged depression of all hematopoietic cell lines (1,2). Cells forming spleen colonies, either by transplantation (CFU-S) o r studied endogenously (E-CFU), are reduced to very low levels almost immediately following busulfan.…”

“…Mice were given busulfan, followed by endotoxin, and total nucleated cells per humerus, peroxidase positive cells per humerus, and CFU-C were monitored during the succeeding 2 weeks. For a detailed consideration of the effect of busulfan alone on these measures of hematopoiesis and also on transplanted and endogenous spleen colonies, hematocrit, spleen weight, and iron uptake per spleen and humerus, please see Boggs et al (1).…”