Chemotherapy prior to autologous bone marrow transplantation impairs long-term engraftment in mice

Objective. Autologous bone marrow transplantation in cancer patients is often preceded by multiple cycles of chemotherapy. In this study, we assessed in a mouse model whether stem cells were affected by prior chemotherapy. Methods. Donor mice were treated with three consecutive injections of 150 mg/kg 5-fluorouracil (5-FU). Peripheral blood counts were allowed to recover before the subsequent dose of 5-FU was given. Mice recovered from three doses of 5-FU and showed normal steady-state hematopoiesis. Bone marrow cells from these mice were mixed with congenic competitor cells and transplanted into lethally irradiated recipients. Results. Although in vivo homing of cells from these mice was not impaired, donor leukocyte contribution steadily decreased posttransplantation. In contrast to in vivo homing, both in vitro migration toward stromal-derived factor (SDF)-1 and the average CXC chemokine receptor-4 (CXCR4) expression were lower in 5-FU-treated cells. Moderate reductions in L-selectin and CD11a expression were observed on stem cells of 5-FU-treated mice. CD43, CD44, CD49d, and CD49e were normally expressed and could thus not explain the reduced engraftment of these cells. Conclusion. We therefore conclude that 5-FU either directly damages stem cells or that the replicative stress induced by 5-FU causes a decline in stem cell reconstitution potential resulting in lower chimerism levels posttransplantation, that declines in time. (C) 2003 International Society for Experimental Hematology. Published by Elsevier Inc

Achieving temperature-size changes in a unicellular organism.

The temperature-size rule (TSR) is an intraspecific phenomenon describing the phenotypic plastic response of an organism size to the temperature: individuals reared at cooler temperatures mature to be larger adults than those reared at warmer temperatures. The TSR is ubiquitous, affecting >80% species including uni- and multicellular groups. How the TSR is established has received attention in multicellular organisms, but not in unicells. Further, conceptual models suggest the mechanism of size change to be different in these two groups. Here, we test these theories using the protist Cyclidium glaucoma. We measure cell sizes, along with population growth during temperature acclimation, to determine how and when the temperature-size changes are achieved. We show that mother and daughter sizes become temporarily decoupled from the ratio 2:1 during acclimation, but these return to their coupled state (where daughter cells are half the size of the mother cell) once acclimated. Thermal acclimation is rapid, being completed within approximately a single generation. Further, we examine the impact of increased temperatures on carrying capacity and total biomass, to investigate potential adaptive strategies of size change. We demonstrate no temperature effect on carrying capacity, but maximum supported biomass to decrease with increasing temperature

Locomotor activity in Drosophila melanogaster selected for different wing lengths

Locomotor activity and its plasticity were investigated in Drosophila melanogaster lines selected for Long and for Short wings at two different temperatures. Flies were tested in a locometer at two different Activity temperatures. Locomotor activity, a physiological character, showed phenotypic plasticity: locomotor activity scores (l.a.s.) were higher at 25 degrees C than at 20 degrees C in all lines. Although at each selection temperature the lines differed significantly in the morphological character wing length, l.a.s.'s were similar in lines with Long and with Short wings per selection temperature. However, a significant difference between selected and unselected control - lines was found. At each selection temperature, plasticity of l.a.s.'s in all lines was similar, except for the Short line selected at 20 degrees C, which showed a higher plasticity. In contrast to earlier experiments no significant correlations between l.a.s. and fresh body weight, and between l.a.s. and wing length were found within each line

Identification of quantitative trait loci regulating haematopoietic parameters in B6AKRF2 mice

The haematopoietic system is a complex organised tissue with a hierarchical structure. Identification of organisational pathways within the haematopoietic system is relevant for a better understanding of haematopoiesis in health and disease. We have analysed numerous haematopoicticm parameters in two panels of a total of 157 genetically distinct B6AKRF2 mice, derived from an intercross between AKR and C57B1/6 mice, strains known to differ in various stem cell traits. The major objective of our study was to assess the extent to which various haematopoietic parameters, such as stem cell numbers, progenitor cell cycling, progenitor cell mobilisation and neutrophil numbers in blood and bone marrow are coregulated. The genotypes of these mice were used to search for genetic loci that regulate these parameters. We found significant quantitative trait loci (QTL) associated with the number of stem cells (CAFC-35) in the bone marrow and the number of neutrophils in the blood. However, most haematopoietic parameters appeared to be controlled by non-heritable (epigenetic) factors, or by multiple QTLs. Our study reveals striking differences in structure of the haematopoietic hierarchy between individual mice. Surprisingly, stem and progenitor cell pool size and proliferation rate, as well as peripheral blood cell counts are all independently regulated

Growth factor treatment prior to low-dose total body irradiation increases donor cell engraftment after bone marrow transplantation in mice

Low-toxicity conditioning regimens prior to bone marrow transplantation (BMT) are widely explored. We developed a new protocol using hematopoietic growth factors prior to low-dose total body irradiation (TBI) in recipients of autologous transplants to establish high levels of long-term donor cell engraftment. We hypothesized that treatment of recipient mice with growth factors would selectively deplete stem cells, resulting in successful long-term donor cell engraftment after transplantation. Recipient mice were treated for 1 or 7 days with growth factors (stem cell factor [SCF] plus interleukin 11 [IL-11], SCF plus Flt-3 ligand [FL], or granulocyte colony-stimulating factor [G-CSF]) prior to low-dose TBI (4 Gy). Donor cell chimerism was measured after transplantation of congenic bone marrow cells. High levels of donor cell engraftment were observed in recipients pretreated for 7 days with SCF plus IL-11 or SCF plus FL. Although 1-day pretreatments with these cytokines initially resulted in reduced donor cell engraftment, a continuous increase in time was observed, finally resulting in highly significantly increased levels of donor cell contribution. In contrast, G-CSF treatment showed no beneficial effects on long-term engraftment. In vitro stem cell assays demonstrated the effect of cytokine treatment on stem cell numbers. Donor cell engraftment and number of remaining recipient stem cells after TBI were strongly inversely correlated, except for groups treated for 1 day with SCIF plus IL-11 or SCF plus FL. We conclude that long-term donor cell engraftment can be strongly augmented by treatment of recipient mice prior to low-dose TBI with hematopoietic growth factors that act on primitive cells

Impaired hematopoietic stem cell functioning after serial transplantation and during normal aging

Adult somatic stem cells possess extensive self-renewal capacity, as their primary role is to replenish aged and functionally impaired tissues. We have previously shown that the stem cell pool in short-lived DBA/2 (D2) mice is reduced during aging, in contrast to long-lived C57BL/6 (136) mice. This suggests the existence of a genetically determined mitotic clock operating in stem cells, which possibly limits organismal aging. In the study reported here, unfractionated bone marrow (BM) cells or highly purified Lin(-)Sca-1(+)c-kit(+) (LSK) cells were serially transplanted in lethally irradiated D2 and B6 mice. In both strains, serial transplantation resulted in a substantial loss of stem cell activity. However, as we estimate that in B6 mice, the maximum number of population doublings of primitive cells is approximately 30, in D2 mice this is only approximately 20, resulting in a 1,000-fold difference in expansion potential, irrespective of whether whole bone marrow or purified hematopoietic stem cells (HSCs) were transplanted. Interestingly, recipients reconstituted with serially transplanted BM cells were able to accept a freshly isolated graft without any further conditioning. Finally, we show that whereas transplantation of BM cells into healthy, nonconditioned, young B6 recipients does not lead to engraftment, young BM cells do engraft and provide multilineage reconstitution in nonirradiated aged mice. Our data clearly establish the relevance of an intrinsic, genetically controlled program associated with impaired stem cell functioning during aging