Differential effects of recombinant human colony stimulating factor (rh G-CSF) on stem cells in marrow, spleen and peripheral blood in mice

A combined model of human erythropoiesis and granulopoiesis under growth factor and chemotherapy treatment

BACKGROUND

Haematotoxicity of conventional chemotherapies often results in delays of treatment or reduction of chemotherapy dose. To ameliorate these side-effects, patients are routinely treated with blood transfusions or haematopoietic growth factors such as erythropoietin (EPO) or granulocyte colony-stimulating factor (G-CSF). For the latter ones, pharmaceutical derivatives are available, which differ in absorption kinetics, pharmacokinetic and -dynamic properties. Due to the complex interaction of cytotoxic effects of chemotherapy and the stimulating effects of different growth factor derivatives, optimal treatment is a non-trivial task. In the past, we developed mathematical models of thrombopoiesis, granulopoiesis and erythropoiesis under chemotherapy and growth-factor applications which can be used to perform clinically relevant predictions regarding the feasibility of chemotherapy schedules and cytopenia prophylaxis with haematopoietic growth factors. However, interactions of lineages and growth-factors were ignored so far.

RESULTS

To close this gap, we constructed a hybrid model of human granulopoiesis and erythropoiesis under conventional chemotherapy, G-CSF and EPO applications. This was achieved by combining our single lineage models of human erythropoiesis and granulopoiesis with a common stem cell model. G-CSF effects on erythropoiesis were also implemented. Pharmacodynamic models are based on ordinary differential equations describing proliferation and maturation of haematopoietic cells. The system is regulated by feedback loops partly mediated by endogenous and exogenous EPO and G-CSF. Chemotherapy is modelled by depletion of cells. Unknown model parameters were determined by fitting the model predictions to time series data of blood counts and cytokine profiles. Data were extracted from literature or received from cooperating clinical study groups. Our model explains dynamics of mature blood cells and cytokines after growth-factor applications in healthy volunteers. Moreover, we modelled 15 different chemotherapeutic drugs by estimating their bone marrow toxicity. Taking into account different growth-factor schedules, this adds up to 33 different chemotherapy regimens explained by the model.

CONCLUSIONS

We conclude that we established a comprehensive biomathematical model to explain the dynamics of granulopoiesis and erythropoiesis under combined chemotherapy, G-CSF, and EPO applications. We demonstrate how it can be used to make predictions regarding haematotoxicity of yet untested chemotherapy and growth-factor schedules.

Therapeutic potential of growth factors in pulmonary emphysematous condition

Pulmonary emphysema is a major manifestation of chronic obstructive pulmonary disease (COPD), which is characterized by progressive destruction of alveolar parenchyma with persistent inflammation of the small airways. Such destruction in the distal respiratory tract is irreversible and irreparable. All-trans-retinoic acid was suggested as a novel therapy for regeneration of lost alveoli in emphysema. However, profound discrepancies were evident between studies. At present, no effective therapeutic options are available that allow for the regeneration of lost alveoli in emphysematous human lungs. Recently, some reports on rodent's models have suggested the beneficial effects of various growth factors toward alveolar maintenance and repair processes.

The role of plasma granulocyte colony stimulating factor and bone marrow dysfunction after severe trauma

BACKGROUND

Bone marrow dysfunction is common in severely injured trauma patients, with release of hematopoietic progenitor cells (HPC) into the peripheral blood. Granulocyte colony stimulating factor (G-CSF) is a potent stimulator of HPC mobilization. We hypothesized that plasma G-CSF levels are elevated after trauma and correlate with postinjury anemia and infection.

STUDY DESIGN

Blood from 83 severely injured patients was collected at several time points for determination of G-CSF levels and HPC mobilization and compared with that from healthy volunteers. Data were categorized by age, sex, Injury Severity Score (ISS), and whether the patient was in shock. Hemoglobin and transfusion requirements and hospital-acquired infection data were recorded. Data are expressed as mean ± SEM.

RESULTS

After trauma, there is a 50-fold increase in plasma levels of G-CSF in trauma patients compared with controls (1,640.4 ± 304.3 pg/mL vs 33.0 ± 6.8 pg/mL, p < 0.001). Patients who presented in shock had 5-times higher G-CSF levels than nonshock trauma patients and a 75-fold increase compared with controls (2,528.7 ± 536.4 pg/mL vs 728.0 ± 191.0 pg/mL vs 33.0 ± 6.8 pg/mL, p < 0.001). Age, sex, and ISS had no effect on G-CSF levels. Mobilization of HPC was sustained for up to 10 days after injury and involved multiple cells types. Higher G-CSF levels were also associated with lower hemoglobin levels and greater transfusion requirements 3 weeks after injury and a higher incidence of hospital-acquired pneumonia and bacteremia.

CONCLUSIONS

Plasma G-CSF is markedly elevated after injury and is greater in patients who present in shock. The rise in G-CSF was also associated with prolonged mobilization of HPC. Elevation of G-CSF in humans after severe trauma may play a significant role in the development of post-traumatic bone marrow dysfunction, anemia, and infection.

Effects of granulocyte-colony-stimulating factor on progenitor cell mobilization and heart perfusion and function in normal mice

BACKGROUND AIMS

Mobilization of stem cells and progenitor cells from the bone marrow (BM) into the peripheral blood (PB) by granulocyte-colony-stimulating factor (G-CSF) is being investigated for cardiac regeneration in ischemic heart disease. However, hematopoietic (HPC), mesenchymal (MPC) and endothelial (EPC) progenitor mobilization have not been optimized and the effect of G-CSF on myocardial perfusion and cardiac function in a normal heart has never been studied.

METHODS

Normal mice were injected daily for 1-10 days with subcutaneous recombinant human G-CSF. PB and BM were evaluated for HPC and EPC by flow cytometry and HPC and MPC by hematopoietic (CFU-GM) and mesenchymal (CFU-F) colony assays. Echocardiography, microSPECT imaging, cardiac catheterization and immunohistochemistry were performed in mice treated for 10 days.

RESULTS

HPC and CFU-GM in PB peaked after 2 days, CFU-F after 4 days and EPC after 3 days. Thereafter, while HPC temporally decreased before showing a second peak, EPC remained detectable only at low levels. In BM, hematopoietic stem cells (HSC) and CFU-GM did not increase much overall but peaked twice on days 2 and 7. EPC (peak on day 7) production increased in the BM, but CFU-F formation declined considerably after day 2. G-CSF enhanced myocardial perfusion and vascularization but impaired hemodynamic performance of the heart through apparently increased ventricular wall rigidity.

CONCLUSIONS

G-CSF induces the mobilization of HPC, EPC and CFU-F progenitors in PB according to very different patterns, and has a significant impact on perfusion and function of the normal heart.

Combined effect of IL-17 and blockade of nitric oxide biosynthesis on haematopoiesis in mice

AIM

The study was undertaken to extend our investigation concerning both the in vivo activity of interleukin (IL)-17 and the specific role of nitric oxide (NO) in IL-17-induced effects in the process of haematopoiesis.

METHODS

CBA mice were simultaneously treated with IL-17 and/or nitric oxide synthase (NOS) inhibitor, l-NAME, for 5 days and changes within various haematopoietic cell lineages in bone marrow, spleen and peripheral blood were analysed.

RESULTS

Findings showed that administration of both IL-17 and l-NAME stimulated increase in net haematopoiesis in normal mice. IL-17-enhanced myelopoiesis was characterized by stimulation of both femoral and splenic haematopoietic progenitor cells and morphologically recognizable granulocytes. Additionally, IL-17 induced alterations in the frequency of erythroid progenitor cells in both bone marrow and spleen, accompanied with their mobilization to the peripheral blood. As a consequence of these changes in the erythroid cell compartments, significant reticulocytosis was observed, which evidenced that in IL-17-treated mice effective erythropoiesis occurred. Exposure of mice to NOS inhibitor also increased the number of both granulocyte-macrophage and erythroid progenitors in bone marrow and spleens, and these alterations were followed by the mobilization of erythroid progenitors and elevated content of reticulocytes in peripheral blood. The specific role of NO in IL-17-induced haematopoiesis was demonstrated only in the IL-17-reducing effect on bone marrow late stage erythroid progenitors, CFU-E.

CONCLUSION

The results demonstrated the involvement of both IL-17 and NO in the regulation of haematopoietic cell activity in various haematopoietic compartments. They further suggest that IL-17 effects are differentially mediated depending on the haematopoietic microenvironments.

Identification of CD13+CD36+ cells as a common progenitor for erythroid and myeloid lineages in human bone marrow

OBJECTIVE

To identify bipotential precursor cells of erythroid and myeloid development in human bone marrow.

MATERIALS AND METHODS

Cells coexpressing CD13 and CD36 (CD13+CD36+) were investigated by analyzing cell-surface marker expression during erythroid development (induced with a combination of cytokines plus erythropoietin), or myeloid development (induced with the same cocktail of cytokines plus granulocyte colony-stimulating factor of bone marrow-derived CD133 cells in liquid cultures. CD13+CD36+ subsets were also isolated on the 14(th) day of cultures and further evaluated for their hematopoietic clonogenic capacity in methylcellulose.

RESULTS

Colony-forming analysis of sorted CD13+CD36+ cells of committed erythroid and myeloid lineages demonstrated that these cells were able to generate erythroid, granulocyte, and mixed erythroid-granulocyte colonies. In contrast, CD13+CD36- or CD13-CD36+ cells exclusively committed to granulocyte/monocyte or erythroid colonies, respectively, but failed to form mixed erythroid-granulocyte colonies; no colonies were detected in CD13-CD36- cells with lineage-supporting cytokines. In addition, our data confirmed that erythropoietin induced both erythroid and myeloid commitment, while granulocyte colony-stimulating factor only supported the differentiation of the myeloid lineage.

CONCLUSIONS

The present data identify some CD13+CD36+ cells as bipotential precursors of erythroid and myeloid commitment in normal hematopoiesis. They provide a physiological explanation for the cell identification of myeloid and erythroid lineages observed in hematopoietic diseases. This unique fraction of CD13+CD36+ cells may be useful for further studies on regulating erythroid and myeloid differentiation during normal and malignant hematopoiesis.

Repeated hematopoietic stem and progenitor cell mobilization without depletion of the bone marrow stem and progenitor cell pool in mice after repeated administration of recombinant murine G-CSF

Administration of recombinant-human G-CSF (rhG-CSF) is highly efficient in mobilizing hematopoietic stem and progenitor cells (HSC/HPC) from the bone marrow (BM) toward the peripheral blood. This study was designed to investigate whether repeated G-CSF-induced HSC/HPC mobilization in mice could lead to a depletion of the bone marrow HSC/HPC pool with subsequent loss of mobilizing capacity. To test this hypothesis Balb/c mice were treated with a maximum of 12 repeated 5-day cycles of either 10 microg rhG-CSF/day or 0.25 microg rmG-CSF/day. Repeated administration of rhG-CSF lead to strong inhibition of HSC/HPC mobilization toward the peripheral blood and spleen after >4 cycles because of the induction of anti-rhG-CSF antibodies. In contrast, after repeated administration of rmG-CSF, HSC/HPC mobilizing capacity remained intact for up to 12 cycles. The number of CFU-GM per femur did not significantly change for up to 12 cycles. We conclude that repeated administration of G-CSF does not lead to depletion of the bone marrow HSC/HPC pool.

Does Granulocyte Colony-Stimulating Factor Worsen Anemia in Early Breast Cancer Patients Treated With Epirubicin and Cyclophosphamide?

Purpose

We report on the effects of granulocyte colony-stimulating factor (G-CSF) on hemoglobin (Hb) value in early breast cancer patients receiving high-dose epirubicin and cyclophosphamide (EC) adjuvant treatment.

Methods

Five hundred and six stage I or stage II female breast cancer patients were treated with E 120 mg/m2 and C 600 mg/m2 with or without G-CSF and randomly assigned to receive in a factorial 2 × 2 design: EC; EC + lonidamine; EC + G-CSF; EC + lonidamine + G-CSF. Five consecutive G-CSF schedules tested 100 randomly assigned patients each: (1) 480 μg subcutaneously on days 8 to 14; (2) 480 μg on days 8, 10, 12, 14; (3) 300 μg on days 8 to 14; (4) 300 μg on days 8, 10, 12, and 14; and (5) 300 μg on days 8 and 12. The mean Hb level of 246 patients receiving EC plus G-CSF was compared with that of 240 patients receiving EC alone. The data presented are derived from an exploratory hypothesis-generating analysis.

Results

The EC dose intensity did not statistically differ between the G-CSF and the control arm. From the third cycle onward, the mean Hb value resulted significantly lower in G-CSF arm compared with control at each time point of each cycle (P < .0001). No statistically significant difference in the mean Hb level was observed between schedule 5 and control. Of interest, from the second course onward, the mean Hb level tended to be lower in patients receiving seven or four G-CSF injections compared with those patients who received only two injections.

Conclusion

Our data suggest that a G-CSF dose-related effect may play a role in worsening anemia in patients receiving adjuvant EC.

Renal Cell Carcinoma Producing Granulocyte Colony-stimulating Factor

Severe neutrophilia caused by renal cell carcinoma secreting granulocyte colony-stimulating factor (G-CSF) is a rare manifestation of renal cancer. A 70-year-old woman presented with a 2-year history of severe anemia, severe neutrophilia and elevated serum G-CSF, which completely resolved after radical nephrectomy. Histologic study revealed a histologically high-grade, stage pT1N0M0 renal cell carcinoma. Serum G-CSF level was elevated preoperatively and returned to normal postoperatively. Immunohistochemical study of the tumor tissue using anti-G-CSF monoclonal antibody revealed positive staining in the cancer cells. Careful follow-up of white blood cell count and physical examination for neck lymph node enlargement led to the timely identification of tumor recurrence 17 months after surgery, which resulted in prompt and successful salvage immunotherapy. In this case, G-CSF appeared to contribute to the leukocytosis, as both serum G-CSF level and white blood cell count closely correlated with the clinical tumor growth. White blood cell count should be closely monitored as an indicator of disease activity in patients with G-CSF-producing renal cell carcinoma.

Functional analysis of human hematopoietic repopulating cells mobilized with granulocyte colony-stimulating factor alone versus granulocyte colony-stimulating factor in combination with stem cell factor

Using in vitro progenitor assays, serum-free in vitro cultures, and the nonobese diabetic/severe combined immune-deficient (NOD/SCID) ecotropic murine virus knockout xenotransplantation model to detect human SCID repopulating cells (SRCs) with multilineage reconstituting function, we have characterized and compared purified subpopulations harvested from the peripheral blood (PB) of patients receiving granulocyte colony-stimulating factor (G-CSF) alone or in combination with stem cell factor (SCF). Mobilized G-CSF plus SCF PB showed a 2-fold increase in total mononuclear cell content and a 5-fold increase in CD34-expressing cells depleted for lineage-marker expression (CD34(+)Lin(-)) as compared with patients treated with G-CSF alone. Functionally, G-CSF plus SCF-mobilized CD34(+)CD38(-)Lin(-) cells contained a 2-fold enhancement in progenitor frequency as compared with G-CSF-mobilized subsets. Despite enhanced cellularity and progenitor capacity, G-CSF plus SCF mobilization did not increase the frequency of SRCs as determined by limiting dilution analysis by means of unfractionated PB cells. Purification of SRCs from these sources demonstrated that as few as 1000 CD34(+)CD38(-)Lin(-) cells from G-CSF-mobilized PB contained SRC capacity while G-CSF plus SCF-mobilized CD34(+)CD38(-)Lin(-) cells failed to repopulate at doses up to 500 000 cells. In addition, primitive CD34(-)CD38(-)AC133(+)Lin(-) cells derived from G-CSF plus SCF-mobilized PB were capable of differentiation into CD34-expressing cells, while the identical subfractions from G-CSF PB were unable to produce CD34(+) cells in serum-free cultures. Our study defines qualitative and quantitative distinctions among subsets of primitive cells mobilized by means of G-CSF plus SCF versus G-CSF alone, and therefore has implications for the utility of purified repopulating cells from these sources.

Effect of PYCNOGENOL on the toxicity of heart, bone marrow and immune organs as induced by antitumor drugs

PYCNOGENOL is a mixture of water-soluble bioflavonoids extracted from the bark of pine trees growing in the southwest coastal region of France. In the present paper the effects of PYCNOGENOL (Pyc) on the toxicity of bone marrow, heart and immune organs induced by anticancer drugs were investigated, in mice. The following results were obtained: 1. Pyc at the orally-administered dose of 200 and 150 mg/kg body wt. markedly prevented the elevation of serum creatine phosphokinase (CPK) activity and the decrease of heart rate in mice treated with doxorubicin (Dox); 2. Pyc at 100 and 150 mg/kg body wt. significantly antagonized the inhibition of DNA synthesis in thymus induced by subcutaneous injection of cyclophosphamide (Cyc); 3. Pyc at 150 and 200 mg/kg body wt. markedly induced increase of erythrocytes and hemoglobin, but had no effect on leukopenia, in Cyc-treated mice; and 4. Pyc has no antagonizing effect on the anticancer activity of Dox and Cyc. All the results suggest that Pyc possesses a protective effect on the cardiotoxicity of Dox and the inhibition of thymus DNA synthesis induced by Cyc in mice.

Enhancement of G-CSF-induced stem cell mobilization by antibodies against the beta 2 integrins LFA-1 and Mac-1

The beta 2 integrins leukocyte function antigen-1 (LFA-1, CD11a) and macrophage antigen-1 (Mac-1, CD11b) have been reported to play a role in the attachment of CD34(+) cells to stromal cells in the bone marrow. When administered prior to interleukin-8 (IL-8), anti-LFA-1 antibodies completely prevent the IL-8-induced mobilization of hematopoietic stem cells in mice. Here, we studied the role of anti-beta 2 integrin antibodies in granulocyte colony-stimulating factor (G-CSF)-induced mobilization of hematopoietic progenitor cells. Administration of antibodies against the alpha chain of LFA-1 or against the alpha chain of Mac-1 followed by daily injections of G-CSF for more than 1 day resulted in a significant enhancement of mobilization of hematopoietic progenitor cells when compared with mobilization induced by G-CSF alone. Also, the number of late (day 28) cobblestone area-forming cells in vitro was significantly higher after mobilization with anti-LFA-1 antibodies followed by 5 microg G-CSF for 5 days than with G-CSF alone (119 +/- 34 days vs 17 +/- 14 days), indicating mobilization of repopulating stem cells. Pretreatment with blocking antibodies to intercellular adhesion molecule-1 (ICAM-1; CD54), a ligand of LFA-1 and Mac-1, did not result in an effect on G-CSF-induced mobilization, suggesting that the enhancing effect required an interaction of the beta 2 integrins and one of their other ligands. Enhancement of mobilization was not observed in LFA-1-deficient (CD11a) mice, indicating that activated cells expressing LFA-1 mediate the synergistic effect, rather than LFA-1-mediated adhesion.

Limitations of a mouse model of sickle cell anemia

We aimed to use an established murine model of sickle cell anemia to develop an unambiguous method for testing new therapies, with survival as an end point. Survival rates following various challenges were compared for three different groups of mice: (a) sickle cell mice expressing human hemoglobin-S exclusively ((h)beta(s)); (b) littermates that expressed both human hemoglobin S and murine beta major globin ((h)beta(s)(m)beta); and (c) wild-type C57BL/6 mice (wt). Two types of challenge were tested. The first set of studies was based upon recent observations indicating that granulocyte-colony stimulating factor (G-CSF) can precipitate severe complications in patients with sickle cell disease. While (h)beta(s) mice had higher neutrophil counts than (h)beta(s)(m)beta mice at baseline, (h)beta(s) mice tolerated several different doses and schedules of either human or murine G-CSF without adverse effects. A second type of challenge tested whether sickle cell mice exhibit an enhanced susceptibility to hemoglobin deoxygenation. Acute hemoglobin deoxygenation was accomplished either by a single intraperitoneal injection of sodium bisulfite or by a 1-h exposure to hypoxia. Neither intervention resulted in a significantly different survival rate for (h)beta(s) mice compared to either (h)beta(s)(m)beta or wt mice. Chronic twice-weekly exposures to hypoxia (1 h per exposure) also failed to produce significant differences in survival rates between (h)beta(s) mice, (h)beta(s)(m)beta, and wt mice over a period of 12 weeks. Our results demonstrate that neither G-CSF administration nor hypoxia accentuates survival differences between this model of sickle cell mouse and normal controls.

Drugs elevating extracellular adenosine promote regeneration of haematopoietic progenitor cells in severely myelosuppressed mice: their comparison and joint effects with the granulocyte colony-stimulating factor

We tested capabilities of drugs elevating extracellular adenosine and of granulocyte colony-stimulating factor (G-CSF) given alone or in combination to modulate regeneration from severe myelosuppression resulting from combined exposure of mice to ionizing radiation and carboplatin. Elevation of extracellular adenosine was induced by joint administration of dipyridamole (DP), a drug inhibiting the cellular uptake of adenosine, and adenosine monophosphate (AMP), serving as an adenosine prodrug. DP+AMP, G-CSF or all these drugs in combination were administered in a 4-d treatment regimen starting on day 3 after induction of myelosuppression. Comparable enhancements of haematopoietic regeneration due to elevation of extracellular adenosine or to action of G-CSF were demonstrated as shown by elevated numbers of haematopoietic progenitor cells for granulocytes/macrophages (GM-CFC) and erythrocytes (BFU-E) in the bone marrow and spleen in early time intervals after termination of the drug treatment, i.e. on days 7 and 10 after induction of myelosuppression. Coadministration of all the drugs further potentiated the restoration of progenitor cell pools in the haematopoietic organs. The effects of the drug treatments on progenitor cells were reflected in the peripheral blood in later time intervals of days 15 and 20 after induction of myelosuppression, especially as significantly elevated numbers of granulocytes and less pronounced elevation of lymphocytes and erythrocytes. The results substantiate the potential of drugs elevating extracellular adenosine for clinical utilization in myelosuppressive states, e.g. those accompanying oncological radio- and chemotherapy.

Bone and bone-marrow interactions: haematological activity of osteoblastic growth peptide (OGP)-derived carboxy-terminal pentapeptide. Mobilizing properties on white blood cells and peripheral blood stem cells in mice

Osteogenic growth peptide (OGP) increases blood and bone marrow cellularity in mice, and enhances engraftment of bone marrow transplant. Carboxy-terminal pentapeptide (OGP10-14) holds several properties of full-length polypeptide. We evaluated whether synthetic OGP-derived pentapeptide (sOGP10-14) has some activity on peripheral blood cell recovery after cyclophosphamide-induced aplasia, and on stem cell mobilization. Peripheral blood stem cell (PBSC) mobilization was evaluated by administering granulocyte-colony stimulating factor (G-CSF) or sOGP10-14 after cyclophosphamide (CTX) injection. Haematological parameters and CD34/Sca-1 positive cells were sequentially evaluated. Colony-forming tests were performed in bone marrow cells from CTX-, G-CSF- and sOGP10-14-treated mice. sOGP10-14 was able to enhance band cells and monocyte recovery after cyclophosphamide administration. White blood cell (WBC) counts reached the maximum peak by day +10 but, on day +7, a significant recovery was already detected in sOGP10-14 treated mice. On day +10 the WBC increase in sOGP10-14-treated mice was comparable to that found in G-CSF treated ones. Moreover, CD34/Sca-1 positive early precursors were significantly mobilized by sOGP10-14 compared to the control group. In sOGP10-14-treated mice, the colony-forming unit-granulocyte-macrophage-megakaryocyte (GEMM-CFU) and burst-forming unit-erythroid (BFU-E) were significantly increased in bone marrow cells in comparison to mice treated with CTX only. These results suggest a central role of sOGP10-14 in bone and bone marrow interaction, and a possible role of sOGP10-14 as a mobilizing agent.

Progenipoietin-1: a multifunctional agonist of the granulocyte colony-stimulating factor receptor and fetal liver tyrosine kinase-3 is a potent mobilizer of hematopoietic stem cells

OBJECTIVE

Progenipoietin-1 is an agonist of both the granulocyte colony-stimulating factor and fetal liver tyrosine kinase-3 receptors capable of inducing the proliferation of multiple hematopoietic cell lineages. The potential of progenipoietin-1 to mobilize transplantable hematopoietic stem cells into the peripheral blood was evaluated.

METHODS

Cohorts of donor mice were treated with either progenipoietin-1, fetal liver tyrosine kinase-3 ligand, granulocyte colony-stimulating factor, or a vehicle control. Hematopoietic progenitor/stem-cell activity in donor blood was assayed by radioprotection, multilineage reconstitution, secondary transplantation, and competitive repopulation.

RESULTS

Only 1 microL of peripheral blood from progenipoietin-1-treated donors was required to protect 80% of lethally irradiated mice, while in contrast 1 microL of peripheral blood from granulocyte colony-stimulating factor-treated donors failed to protect any recipients. The radioprotected recipients of progenipoietin-1-treated donor cells showed donor-derived (Ly5.2) multilineage hematopoietic reconstitution for up to 6 months. Serial transplantation studies using bone marrow from radioprotected, chimeric recipients demonstrated long-term donor-derived hematopoiesis, indicating the successful transplantation of multipotent hematopoietic stem cells. The engraftment potential of progenipoietin-1 donor-derived cells was directly compared with donors treated with granulocyte colony-stimulating factor or fetal liver tyrosine kinase-3 ligand alone or in combination. Both spleen colony-forming activity and competitive repopulating activity was highest in the blood from progenipoietin-1-treated donors.

CONCLUSIONS

These studies demonstrate that progenipoietin-1 is a potent mobilizer of transplantable hematopoietic stem cells and indicate that this dual-receptor agonist has greater biologic activity than its constituent molecules.

Comparison of the hematopoietic activity of flt-3 ligand and granulocyte-macrophage colony-stimulating factor acting alone or in combination

The hematopoietic sequelae of intramuscular administration of flt-3 ligand (FL) and granulocyte-macrophage colony-stimulating factor (GM-CSF) alone, or in combination, were compared in BALB/c mice. Changes in hematopoiesis were measured in the marrow, spleen and blood using an in vitro colony-forming unit (CFU) assay and flow cytometrically (expression of CD34 and stem cell antigen (Sca)-1). FL administration was associated with a significant increase in the absolute number of CFU and CD34+ cells in the marrow and CFU, CD34+, Sca-1+, and CD34+ Sca-1+ cells in the spleen and blood. These data demonstrate that FL expands and mobilizes a range of hematopoietic progenitors. By comparison, GM-CSF administration was associated with a significant increase in the number of CFU in the spleen and a significant reduction in marrow CD34+, Sca-1+, and CD34+Sca-1+ cells. These data suggest that GM-CSF-driven expansion of CFU may be at the expense of more primitive cells. The pattern of progenitor cell expansion associated with FL + GM-CSF administration was similar to that of FL alone with the following exceptions. The numbers of spleen and blood CFU were significantly greater and the number of marrow CD34+Sca-1+ cells were significantly less, than with FL alone. These data suggest that co-administration of these cytokines may combine the expansion of the more primitive cell populations (associated with FL) with the expansion of the more mature CFU population (associated with GM-CSF) to yield a greater overall CFU expansion and elevation of CFU in the blood. However, increasing the expansion and mobilization of the relatively mature, rather than the more primitive, hematopoietic progenitors, may be of limited value as a mobilization strategy, if the goal is the expansion and isolation of increased numbers of "high-quality," primitive cells for transplantation.

Identification of a genetic locus modulating splenomegaly induced by granulocyte colony-stimulating factor in mice

Clinically detectable splenomegaly and splenic rupture are uncommon but potentially life-threatening consequences of G-CSF administration. Increased spleen size in mice injected with G-CSF is a complex genetic trait amenable to investigation in experimental inter-strain crosses by quantitative trait analysis. A quantitative trait locus (QTL) with highly significant linkage (LOD 7.9) for splenomegaly was identified within a 22 centimorgan (cM) region on chromosome 1. Inheritance of a C57BL/6 haplotype in this region was associated with a greater spleen weight. The relevance of this locus was confirmed by analysing the responses of mice congenic for the distal 12 cM of this region (C57BL/6 and C57BL/6.SJL-Ptprc(a) Pep3(b)). Consistent with the QTL effect, mice lacking C57BL/6 alleles in this region had reduced splenomegaly induced by G-CSF. Intriguingly, peripheral blood neutrophilia and progenitor cell mobilisation responses to G-CSF were also significantly influenced.

Recombinant human granulocyte colony-stimulating factor after kidney transplantation: a retrospective analysis to evaluate the benefit or risk of immunostimulation

BACKGROUND

Leukopenia due to immunosuppressive drugs represents a well-known complication in graft recipients, which might put patients at an increased risk for infections. In this study, recombinant human granulocyte colony-stimulating factor (rhG-CSF), a hematopoietic growth factor that selectively stimulates neutrophil colony formation and neutrophil cell differentiation, was tested for safety and efficacy.

METHODS

We evaluated 30 episodes of leukopenia (<2000/mm3) in 19 kidney graft recipients treated with rhG-CSF. This cohort was compared with an age- and sex-matched historical control group without therapy. Peripheral and differential blood cell counts were analyzed, and the duration of leukopenia was estimated. Furthermore, the occurrence of infections associated with leukopenia was investigated.

RESULTS

All patients responded to rhG-CSF therapy. Peripheral leukocyte counts increased from 1756+/-582 to a peak of 8723+/-3038/mm3 (P<0.0001). On the average, the peak was reached after 2.7 days (range 1 to 8). Furthermore, the effect was fairly persistent, because in 22 of 30 episodes leukocyte counts were within the normal range after 7 days. The elevation of total leukocytes was mainly due to a specific increase in neutrophil granulocytes from 1143+/-514 to 6895+/-1950/mm3 on the peak day (P<0.0001). Patients in the G-CSF group were leukopenic for a mean of 1.29+/-0.59 days, whereas in the control group leukopenia persisted for at least 7 days. Consequently, the rate of infections was significantly higher (P<0.045) in nontreated patients.

CONCLUSION

rhG-CSF was safe and effective in leukopenic kidney graft recipients. Leukopenic episodes in treated patients were significantly shorter, and infections occurred at a significantly lower rate. No evidence was found that rhG-CSF therapy might trigger rejection episodes, and no side effects were observed.

Maturation rate of mouse neutrophilic granulocytes: acceleration by retardation of proliferation, but no detectable influence from G-CSF or stromal cells

Our purpose was to examine the possible influence of stromal and humoral mediators on granulocytic maturation rates. Sorted immature murine progenitor (Lin-Sca-1+) cells were cultured in peritoneal diffusion chambers (DCs) with or without a confluent layer of irradiated bone marrow stromal cells on one of the micropore membrane walls. In other experiments, 10 microg/kg/d recombinant G-CSF (rhG-CSF) was administered continuously into DC host mice through s.c. implanted osmotic minipumps. Operationally, maturation rate was assessed as the ratio between the number of polymorphonuclear cells (PMN) and proliferative granulocytes (PG) in short-term cultures, based on the differential cell counts, and supported by flow cytometric measurement of a granulocytic differentiation marker; and by the emergence time of PMN in the DCs, obtained by extrapolation. Also, increased maturation is associated with increased cell density, as reflected by the positioning of the granulocytes during centrifugation in a discontinuous Percoll gradient. This method, as well as the conversion rate of 3H-thymidine labeled PG into the heavier non-PG maturational stages, were also used as indicators of maturation rate. After five, six, and seven days of culture in the peritoneal cavity, DC cells were harvested. Their proliferative status, based on measurement of incorporated bromodeoxyuridine, was determined, and their maturation rates were evaluated. Proliferation of immature granulocytic progenitor cells was apparently inhibited by direct contact with bone marrow stromal cells, and stimulated by G-CSF during the early stage of culturing. However, the subsequent maturation rate, which could be accelerated by increasing culture cellularity, thus decreasing PG proliferation rate, was not detectably influenced by either stromal cells or G-CSF.

Granulocyte-colony stimulating factor (G-CSF)-primed, delayed marrow harvests as a source of hematopoietic stem and progenitor cells for allogeneic transplantation

We evaluated the ability of G-CSF to increase the number of hematopoietic stem cells obtained by "delayed" BM harvest for allogeneic transplantation. Five normal donors received G-CSF @ 10 mcg/kg/day x 5 followed by repeat PB and BM assays at day 6 and 16, and BM harvest at day 16. Stem cells were not increased in the BM at day 16. Five patients underwent BMT and engrafted at +10 to +19 days. While the tested strategy offers no intrinsic advantages, its potential cannot be evaluated fully without alternative timing and/or additional, "early acting" growth factors.

The effect of G-CSF on the composition of human bone marrow

The effects on bone marrow cellularity and morphology of 6 days' treatment with granulocyte colony-stimulating factor (G-CSF) in 35 patients were studied. Examination of trephine biopsies showed a highly significant increase in cellularity (P < 10-13). Assessment of aspirates revealed an increase in the myeloid to erythroid (M : E) ratio (P = 0.00006), the proportion of myeloid cells (P < 10-8), myelocytes (P = 0.00007), metamyelocytes (P = 0.04), band forms (P = 0.0005) and neutrophils (P = 0.02). This study presents a comprehensive analysis of the effects of six days' administration of G-CSF on human bone marrow.

Granulocyte Colony-Stimulating Factor–Mobilized Allogeneic Stem Cell Transplantation Maintains Graft-Versus-Leukemia Effects Through a Perforin-Dependent Pathway While Preventing Graft-Versus-Host Disease

Minimization of graft-versus-host disease (GVHD) with preservation of the graft-versus-leukemia (GVL) effect is a crucial step to improve the overall survival of allogeneic bone marrow transplantation (BMT) for patients with hematological malignancies. We and other investigators have shown that granulocyte colony-stimulating factor (G-CSF)–mobilized allogeneic peripheral stem cell transplantation (PBSCT) reduces the severity of acute GVHD in murine models. In this study, we investigated whether G-CSF–mobilized PBSC maintain their GVL effect in a murine allogeneic transplant model (B6 → B6D2F1). B6 mice (H-2b) were injected subcutaneously with human G-CSF (100 μg/kg/d) for 6 days and their splenocytes were harvested on day 7 as a source of PBSC. G-CSF mobilization dramatically improved transplant survival compared with nonmobilized controls (95% v0%, P &lt; .001). Systemic levels of lipopolysaccharide and tumor necrosis factor- were markedly reduced in recipients of allogeneic G-CSF–mobilized donors, but cytolytic T lymphocyte (CTL) activity against host tumor target cells p815 was retained in those recipients. When leukemia was induced in recipients by coinjection of p815 tumor cells (H-2d) at the time of transplantation, all surviving recipients of G-CSF–mobilized B6 donors were leukemia-free at day 70 after transplant, whereas all mice who received T-cell–depleted (TCD) splenocytes from G-CSF–mobilized B6 donors died of leukemia. When splenocytes from G-CSF–mobilized perforin-deficient (pfp−/−) mice were used for transplantation, 90% of recipients died of leukemia, demonstrating that perforin is a crucial pathway mediating GVL effects after G-CSF–mobilized PBSCT. These data illustrate that G-CSF–mobilized allogeneic PBSCT separate GVL from GVHD by preserving perforin-dependent donor CTL activity while reducing systemic inflammation.

Granulocyte Colony-Stimulating Factor–Mobilized Allogeneic Stem Cell Transplantation Maintains Graft-Versus-Leukemia Effects Through a Perforin-Dependent Pathway While Preventing Graft-Versus-Host Disease

Minimization of graft-versus-host disease (GVHD) with preservation of the graft-versus-leukemia (GVL) effect is a crucial step to improve the overall survival of allogeneic bone marrow transplantation (BMT) for patients with hematological malignancies. We and other investigators have shown that granulocyte colony-stimulating factor (G-CSF)–mobilized allogeneic peripheral stem cell transplantation (PBSCT) reduces the severity of acute GVHD in murine models. In this study, we investigated whether G-CSF–mobilized PBSC maintain their GVL effect in a murine allogeneic transplant model (B6 → B6D2F1). B6 mice (H-2b) were injected subcutaneously with human G-CSF (100 μg/kg/d) for 6 days and their splenocytes were harvested on day 7 as a source of PBSC. G-CSF mobilization dramatically improved transplant survival compared with nonmobilized controls (95% v0%, P < .001). Systemic levels of lipopolysaccharide and tumor necrosis factor- were markedly reduced in recipients of allogeneic G-CSF–mobilized donors, but cytolytic T lymphocyte (CTL) activity against host tumor target cells p815 was retained in those recipients. When leukemia was induced in recipients by coinjection of p815 tumor cells (H-2d) at the time of transplantation, all surviving recipients of G-CSF–mobilized B6 donors were leukemia-free at day 70 after transplant, whereas all mice who received T-cell–depleted (TCD) splenocytes from G-CSF–mobilized B6 donors died of leukemia. When splenocytes from G-CSF–mobilized perforin-deficient (pfp−/−) mice were used for transplantation, 90% of recipients died of leukemia, demonstrating that perforin is a crucial pathway mediating GVL effects after G-CSF–mobilized PBSCT. These data illustrate that G-CSF–mobilized allogeneic PBSCT separate GVL from GVHD by preserving perforin-dependent donor CTL activity while reducing systemic inflammation.

Fluorine-18 fluorodeoxyglucose splenic uptake from extramedullary hematopoiesis after granulocyte colony-stimulating factor stimulation

Two patients with sarcoma, one with recurrent osteosarcoma of the spine and the other with metastatic synovial cell sarcoma, were treated with high-dose chemotherapy that produced severe leukopenia. The patients received granulocyte colony-stimulating factor (G-CSF) to stimulate the bone marrow (480 mg given subcutaneously twice daily for 5 to 7 days); their responses were seen as a marked increase in peripheral leukocyte count with no change in the erythrocyte or platelet counts. The patients had fluorine-18 fluorodeoxyglucose (F-18 FDG) imaging 24 hours after the end of G-CSF treatment. Diffusely increased uptake of F-18 FDG was seen in the bone marrow in both patients. In addition, markedly increased uptake in the spleen was noted in both, indicating that the spleen was the site of extramedullary hematopoiesis. The patients had no evidence of splenic metastases. The first patient had a history of irradiation to the dorsal spine, which was less responsive to G-CSF administration than was the nonirradiated lumbar spine.

Effect of FLT3 Ligand and Granulocyte Colony-Stimulating Factor on Expansion and Mobilization of Facilitating Cells and Hematopoietic Stem Cells in Mice: Kinetics and Repopulating Potential

We have previously identified a cellular population in murine bone marrow that facilitates engraftment of highly purified hematopoietic stem cells (HSC) across major histocompatibility complex (MHC) barriers without causing graft-versus-host disease. Here we investigated the effect of flt3 ligand (FL) and granulocyte colony-stimulating factor (G-CSF) on the mobilization of facilitating cells (FC) and HSC into peripheral blood (PB). Mice were injected with FL alone (day 1 to 10), G-CSF alone (day 4 to 10), or both in combination. The number of FC (CD8+/βTCR−/γδTCR−) and HSC (lineage−/Sca-1+/c-kit+) was assessed daily by flow cytometry. Lethally irradiated allogeneic mice were reconstituted with PB mononuclear cells (PBMC). FL and G-CSF showed a highly significant synergy on the mobilization of FC and HSC. The peak efficiency for mobilization of FC (21-fold increase) and HSC (200-fold increase) was reached on day 10. Our data further suggest that the proliferation of FC and HSC induced by FL in addition to the mobilizing effect mediated by G-CSF might be responsible for the observed synergy of both growth factors. Finally, the engraftment potential of PBMC mobilized with FL and G-CSF or FL alone was superior to PBMC obtained from animals treated with G-CSF alone. Experiments comparing the engraftment potential of day 7 and day 10 mobilized PBMC indicate that day 10, during which both FC and HSC reached their maximum, might be the ideal time point for the collection of both populations. © 1998 by The American Society of Hematology.

Effect of FLT3 Ligand and Granulocyte Colony-Stimulating Factor on Expansion and Mobilization of Facilitating Cells and Hematopoietic Stem Cells in Mice: Kinetics and Repopulating Potential

We have previously identified a cellular population in murine bone marrow that facilitates engraftment of highly purified hematopoietic stem cells (HSC) across major histocompatibility complex (MHC) barriers without causing graft-versus-host disease. Here we investigated the effect of flt3 ligand (FL) and granulocyte colony-stimulating factor (G-CSF) on the mobilization of facilitating cells (FC) and HSC into peripheral blood (PB). Mice were injected with FL alone (day 1 to 10), G-CSF alone (day 4 to 10), or both in combination. The number of FC (CD8+/βTCR−/γδTCR−) and HSC (lineage−/Sca-1+/c-kit+) was assessed daily by flow cytometry. Lethally irradiated allogeneic mice were reconstituted with PB mononuclear cells (PBMC). FL and G-CSF showed a highly significant synergy on the mobilization of FC and HSC. The peak efficiency for mobilization of FC (21-fold increase) and HSC (200-fold increase) was reached on day 10. Our data further suggest that the proliferation of FC and HSC induced by FL in addition to the mobilizing effect mediated by G-CSF might be responsible for the observed synergy of both growth factors. Finally, the engraftment potential of PBMC mobilized with FL and G-CSF or FL alone was superior to PBMC obtained from animals treated with G-CSF alone. Experiments comparing the engraftment potential of day 7 and day 10 mobilized PBMC indicate that day 10, during which both FC and HSC reached their maximum, might be the ideal time point for the collection of both populations. © 1998 by The American Society of Hematology.

Influence of rhG-CSF scheduling on megakaryocytopoietic recovery following 5-fluorouracil-induced hematotoxicity in splenectomized B6D2F1 mice

Recombinant human granulocyte colony-stimulating factor, rhG-CSF, is widely applied to ameliorate neutropenia following chemotherapy. However, rhG-CSF can exert negative effects on megakaryocytopoiesis that might cause a delay of megakaryocyte recovery. Therefore, the present study was designed to test different rhG-CSF administration protocols with regard to their megakaryocytic inhibitory potential in a 5-fluorouracil (5-FU)-induced experimental model system. Splenectomized B6D2F1 mice received a single injection of 5-FU (150 mg/kg) on day 0 followed by 50 micrograms/kg/day rhG-CSF given daily for either zero, four, or eight days. Five days after 5-FU, bone marrow and blood hematopoiesis were reduced significantly when compared with controls, independent of whether or not animals received rhG-CSF. However, nine days after 5-FU, granulopoietic recovery from 5-FU-induced toxicity was faster for rhG-CSF-treated versus untreated mice as demonstrated by higher values for colony forming unit-granulocyte macrophage (CFU-GM) and granulocytes (CFU-GM: 7.2 +/- 0.4 versus 5 +/- 0.6 x 10(4)/femur, granulocytes: 4.3 +/- 2 versus 1.4 +/- 0.4 x 10(5)/ml, respectively). Furthermore, significant mobilization of CFU-megakaryocyte (CFU-Meg) and CFU-GM into the peripheral blood was induced by the eight-day administration of rhG-CSF following 5-FU (day 9: 911 +/- 102 CFU-Meg/ml, 2330 +/- 152 CFU-GM/ml). However, megakaryocytic cells in these same mice were considerably lower when compared with those of animals receiving no rhG-CSF (CFU-Meg: 2.7 +/- 0.2 x 10(3) versus 4.2 +/- 0.2 x 10(3)/femur; small acetylcholinesterase positive (SAChE+) cells: 4.9 +/- 0.3 x 10(3) versus 7.3 +/- 0.9 x 10(3)/femur; megakaryocytes: 2.5 +/- 0.2 x 10(3) versus 4.1 +/- 0.7 x 10(3)/femur; platelets: 2.67 +/- 0.5 x 10(9) versus 3.1 +/- 0.5 x 10(9)/ml, respectively). On the other hand, the shortening of the rhG-CSF treatment from eight to four days caused a rapid granulopoietic recovery comparable to animals receiving eight days of G-CSF with no significant delay in megakaryocytic recovery when compared with mice treated with 5-FU alone; however, with four days of rhG-CSF, the mobilization of CFU into the peripheral blood was significantly less effective. Taken together, the results showed that a shortening of rhG-CSF treatment after chemotherapy is capable of ameliorating neutropenia without negatively affecting megakaryocytopoietic recovery. If, however, maximum recruitment of CFU into the peripheral blood circulation by rhG-CSF for subsequent harvest and transplantation is needed, any shortening of rhG-CSF administration is not advisable.

Alternative testing systems for evaluating noncarcinogenic, hematologic toxicity

Hematopoietic tissues are the targets of numerous xenobiotics. Clinical hematotoxicity is either a decrease or an increase in peripheral blood cell counts in one or more cell lineages--a cytopenia or a cytosis, respectively--that carries a risk of an adverse clinical event. The purpose of in vitro hematotoxicology is the prediction of these adverse hematologic effects from the effects of the toxicants on human hematopoietic targets under controlled experimental conditions in the laboratory. Building on its important foundations in experimental hematology and the wealth of hematotoxicology data found in experimental oncology, this field of alternative toxicology has developed rapidly during the past decade. Although the colony-forming unit-granulocyte/monocyte neutrophil progenitor is most frequently evaluated, other defined progenitors and stem cells as well as cell types found in the marrow stroma can be evaluated in vitro. End points have been proposed for predicting toxicant exposure levels at the maximum tolerated dose and the no observable adverse effect level for the neutrophil lineage, and several clinical prediction models for neutropenia have developed to the point that they are ready for prospective evaluation and validation in both preclinical species and humans. Known predictive end points are the key to successful comparisons across species or across chemical structures when in vitro dose-response curves are nonparallel. Analytical chemistry support is critical for accurate interpretation of in vitro data and for relating the in vitro pharmacodynamics to the in vivo pharmacokinetics. In contrast to acute neutropenia, anemia and acute thrombocytopenia, as well as adverse effects from chronic toxicant exposure, are much more difficult to predict from in vitro data. Pharmacologic principles critical for clinical predictions from in vitro data very likely will apply to toxicities to other proliferative tissues, such as mucositis.

Photofrin increases murine spleen cell transferrin receptor expression and responsiveness to recombinant myeloid and erythroid growth factors

When given to normal male mice, the photochemotherapeutic agent Photofrin (porfimer sodium), a complex mixture of monomeric and oligomeric non-metallic porphyrins, significantly increased relative spleen weight, spleen cell numbers, DNA replication, levels of granulocyte-macrophage and erythroid progenitors and cellular responsiveness to different recombinant (r) myeloid growth factors. In contrast, monomeric hematoporphyrin had no effect on spleen weight, cellularity, erythroid progenitor levels or spleen cell cycle status. Photofrin significantly increased spleen cell expression of the receptor (CD71) for the iron transport protein transferrin by 72 h post-injection but did not affect levels of a receptor (CD25) for the T-cell growth factor interleukin-2 (IL-2) or spleen cell responsiveness to rIL-2. Further evidence of increased splenic erythropoietic activity in Photofrin-treated mice was provided by double color flow cytometric studies which indicated that the treatment elevated the number of nucleated spleen cells recognized by the erythroid lineage-specific monoclonal antibody TER-119. A majority of TER-119+ cells also expressed CD71 and the heat stable antigen, a marker of developing hematopoietic cells as well as mature erythrocytes. The capacity of Photofrin to stimulate murine hematopoietic activity appears to be a property not shared by other porphyrin photosensitizers.

Flt3 Ligand Synergizes With Granulocyte-Macrophage Colony-Stimulating Factor or Granulocyte Colony-Stimulating Factor to Mobilize Hematopoietic Progenitor Cells Into the Peripheral Blood of Mice

Peripheral blood progenitor cells (PBPC) are increasingly being used in the clinic as a replacement for bone marrow (BM) in the transplantation setting. We investigated the capacity of several different growth factors, including human flt3 ligand (FL), alone and in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF ) or granulocyte colony-stimulating factor (G-CSF ), to mobilize colony forming cells (CFU) into the peripheral blood (PB) of mice. Mice were injected subcutaneously (SC) with growth factors daily for up to 10 days. Comparing the single agents, we found that FL alone was superior to GM-CSF or G-CSF in mobilizing CFU into the PB. FL synergized with both GM-CSF or G-CSF to mobilize more CFU, and in a shorter period of time, than did any single agent. Administration of FL plus G-CSF for 6 days resulted in a 1,423-fold and 2,717-fold increase of colony-forming unit–granulocyte-macrophage (CFU-GM) and colony-forming unit granulocyte, erythroid, monocyte, megakaryocyte (CFU-GEMM) in PB, respectively, when compared with control mice. We also followed the kinetics of CFU numerical changes in the BM of mice treated with growth factors. While GM-CSF and G-CSF alone had little effect on BM CFU over time, FL alone increased CFU-GM and CFU-GEMM threefold and fivefold, respectively. Addition of GM-CSF or G-CSF to FL did not increase CFU in BM over levels seen with FL alone. However, after the initial increase in BM CFU after FL plus G-CSF treatment for 3 days, BM CFU returned to control levels after 5 days treatment, and CFU-GM were significantly reduced (65%) after 7 days treatment, when compared with control mice. Finally, we found that transplantation of FL or FL plus G-CSF–mobilized PB cells protected lethally irradiated mice and resulted in long-term multilineage hematopoietic reconstitution.

Genetic Influences Determining Progenitor Cell Mobilization and Leukocytosis Induced by Granulocyte Colony-Stimulating Factor

The mechanisms involved in the mobilization of progenitor cells into the blood by granulocyte colony-stimulating factor (G-CSF ) and other cytokines are poorly understood. To identify important influences on this complex process, in vivo murine models were used. Granulocyte-macrophage colony-stimulating factor (GM-CSF ) transgenic, Max41 transgenic, W/WV, Mpl-null, GM-CSF receptor (β chain)-null mice, wild-type littermate controls, and six inbred strains of mice were injected with 200 μg/kg/d G-CSF for 5 days. Three parameters of response were monitored: white blood cell count (WCC), peripheral blood progenitor cell (PBPC) numbers, and spleen weight. In all genotypes studied, G-CSF induced increases in these three parameters. However, PBPC mobilization in W/WV and Mpl-null mice was only 30% and 9%, respectively, of that observed in wild-type mice. In contrast, perturbations of GM-CSF signalling had no demonstrable effect on in vivo responses to G-CSF. Broad variability was evident between inbred strains for each parameter of the response to G-CSF. A 10-fold range in response was observed for circulating progenitor cell numbers, similar to that observed for normal human subjects receiving G-CSF. The interstrain differences were in the distribution of mature and progenitor cells between peripheral blood, bone marrow, and spleen rather than in the total numbers of these cells in the body. Results of an F2 intercross of low-responding C57BL/6 and intermediate-responding SJL mice indicated that regulation of progenitor cell mobilization is a complex genetic trait, that there is a correlation between this trait and WCC response (r2 = .5), and that this approach may serve as a useful model for the identification of genes involved in the mobilization process.

Host F1 Mice Pretreated With Granulocyte Colony-Stimulating Factor Accept Parental Bone Marrow Grafts in Hybrid Resistance System

In the setting of hybrid resistance, parental C57BL/6 bone marrow (BM) grafts are vigorously rejected by lethally irradiated (C57BL/6xDBA/2) F1 mice. However, F1 mice pretreated by continuous administration of granulocyte colony-stimulating factor (G-CSF ) with a miniosmotic pump before BM grafting developed day-8 splenic colonies of donor origin. This inhibitory effect on rejection was reversible because F1 mice regained the capacity to reject parental BM when the pump ceased functioning. The appearance of only a small number of colonies with the administration of G-CSF soon after BM grafting suggested the importance in producing this inhibitory effect of pre-exposure of host mice to G-CSF. Because G-CSF administration with a syngeneic combination did not influence the number of colonies, an altered distribution of grafted precursors was unlikely. The absence of a reduction in the number of NK1.1-positive cells in G-CSF–treated mice suggested functional impairment of natural killer cells, major effectors in hybrid resistance, but further study is necessary to elucidate the mechanism underlying this phenomenon. However, our results indicate the importance of G-CSF as a regulator in a certain type of immune response and raise the possibility of clinical application in transplantation medicine.

Impaired production and increased apoptosis of neutrophils in granulocyte colony-stimulating factor receptor-deficient mice

We have generated mice carrying a homozygous null mutation in the granulocyte colony-stimulating factor receptor (G-CSFR) gene. G-CSFR-deficient mice have decreased numbers of phenotypically normal circulating neutrophils. Hematopoietic progenitors are decreased in the bone marrow, and the expansion and terminal differentiation of these progenitors into granulocytes is impaired. Neutrophils isolated from G-CSFR-deficient mice have an increased susceptibility to apoptosis, suggesting that the G-CSFR may also regulate neutrophil survival. These data confirm a role for the G-CSFR as a major regulator of granulopoiesis in vivo and provide evidence that the G-CSFR may regulate granulopoiesis by several mechanisms. However, the data also suggest that G-CSFR-independent mechanisms of granulopoiesis must exist.

Mobilization and collection of PBSC in healthy donors: comparison between two schemes of rhG-CSF administration

Procurement of a high number of progenitor cells is of primary interest in allogeneic PBSC transplantation. We have retrospectively compared toxicity, mobilization effect and progenitor cell yields of two different rhG-CSF schedules in 11 consecutive healthy individuals donating their PBSC. Five of them received rhG-CSF 16 micrograms/kg/d for 4 subsequent d in 2 divided subcutaneous injections (group A); similarly, 6 donors received rhG-CSF 10 micrograms/kg/d for 5 d (group B). The aphereses were started the last day of rhG-CSF treatment; 9 donors underwent 2 aphereses, one underwent 1 and another 3 procedures, always on subsequent days. Toxicity was mild, but moderate thrombocytopenia developed following apheretic collections, irrespective of rhG-CSF schedule. In all the donors WBC, as well as circulating CD34+ cells, CFU-GM, CFU-GEMM and BFU-E dramatically increased over the baseline values, peaking on d 5 or 6, with no statistical difference between the 2 groups for the height of the cell peaks. Also the peripheral lymphoid cell populations (CD3+, CD19+ and CD56+/CD3-) increased following the rhG-CSF administration. The number of MNC, CFU-GM, BFU-E, CFU-GEMM, as well as CD34+, CD3+, CD19+ and CD56+/CD3- cells collected by apheresis showed no statistical difference in the 2 groups. Overall, 8 of the 11 donors collected the target number of CD34+ cells > 4 x 10(6)/kg ideal recipient body weight with the first apheresis, with no difference between the 2 groups. Mobilization with rhG-CSF in healthy donors enables the collection of large number of progenitor cells with modest side effects. A schedule of 10 micrograms/kg for 5 d is as effective as 16 micrograms/kg for 4 d. A single apheresis would be enough in 80% of cases.

Transplantation of allogeneic peripheral blood stem cells mobilized by recombinant human granulocyte colony stimulating factor

Recombinant G-CSF has been given to over 150 normal donors for the collection of allogeneic or syngeneic peripheral blood stem cells (PBSC). G-CSF was found to be well-tolerated with mild-moderate bone pain, edema and mild thrombocytopenia being the observed side effects. To date, approximately 90 unmodified primary PBSC transplants from HLA-identical related donors have been performed with engraftment that is, in general, considerably more rapid than marrow. Acute graft-versus-host-disease (GVHD), grades II-IV occurred in 47% of patients and grades III-IV in 17%. Despite the infusion of one to two logs more T cells, these results are not remarkably different than would be expected with marrow transplantation. There have also been successful reports of using G-CSF mobilized allogeneic PBSC following second transplants for graft rejection or relapse. Allogeneic PBSC have been infused without reconditioning for correction of graft failure and unmodified or CD34 selected PBSC have also been given with marrow to augment the dose of hematopoietic cells. Further studies are needed to define the role of allogeneic PBSC for transplantation, refine PBSC mobilization and collection techniques and to evaluate the long-term effects of cytokines in normal donors.

Effects of rhG-CSF, 5-fluorouracil and extramedullary irradiation on murine megakaryocytopoiesis in vivo

The aim of this study was to systematically characterize possible rhG-CSF effects on the murine megakaryocyte-platelet system (untreated and recovering from chemotherapy or extramedullary irradiation). In untreated, splenectomized male B6D2F1 mice, rhG-CSF treatment (50 micrograms/kg/d for up to 8 d) markedly decreased femoral megakaryocytopoiesis. CFU-Meg, small acetylcholinesterase-positive (SAChE) cells, and megakaryocytes were significantly reduced to 35-70%; platelets, however, were not affected. Peripheral CFU-Meg and CFU-GM increased up to 200-fold. Following a single injection of 5-FU (150 mg/kg) on day 0, rhG-CSF (50 micrograms/kg/d) on days 1-8 suppressed the megakaryocytopoietic recovery as indicated by significantly lower platelet numbers on day 9. Granulopoietic recovery was accelerated by rhG-CSF. When rhG-CSF treatment was started on day 5, no beneficial effect on granulopoietic recovery was observed, but again platelet levels were significantly lower on day 9, indicating that within the first 4 d of rhG-CSF application, recruitment or lineage competition was not a critical event. To test for the effects of extramedullary irradiation on circulating progenitors, mice pretreated with 50 micrograms/kg/d of rhG-CSF for 8 d received irradiation to the chest with 500 cGy resulting in a substantial kill of circulating CFU-Meg and CFU-GM of up to 99%. However, this striking decrease of blood progenitors did not significantly affect their total body contents. This study indicates that rhG-CSF treatment can impair bone marrow megakaryocytopoiesis, which might be an important consideration for those clinical situations that carry a high potential for treatment-induced thrombocytopenia.

Hemopoietic stem cells: analysis of some parameters critical for engraftment

In this review four parameters relevant to the grafting of hemopoietic stem cells (HSC) are analyzed: the nature and amounts of grafted HSC, the sources of HSC and the "in vivo" fate of the grafted cells. One may oppose cells with short-term repopulating ability to cells with long-term reconstitutive capacity. The former comprise progenitors, while the latter consist of primitive stem cells, corresponding to murine pre-colony forming units-spleen (pre-CFU-S) (and to some murine CFU-S) or to human pre-colony forming units (pre-CFU). In the mouse, the number of progenitors involved in short-term reconstitution is large, while that of primitive cells operating months after the transplantation is reduced. These results may be extrapolated to humans, suggesting that it is possible to engraft a limited number of genetically modified HSC. However, the administration of large numbers of reconstituting cells appears to be a cautionary procedure, since it should insure polyclonal hemopoiesis, which is the physiological situation in mammals. Besides marrow, peripheral blood from adult patients treated with chemotherapy and growth factors, and cord blood from newborns, are promising sources of HSC. Successful engraftment depends not only on the quality and quantity of HSC, but also on the integrity of the marrow microenvironment. This microenvironment may be impaired by chemo- and radiotherapy, which provides a theoretical basis for the transplantation of stromal cells along with that of HSC.

Transplantation of allogeneic peripheral blood stem cells after myeloablative treatment of a patient in blastic crisis of chronic myelocytic leukemia

A 48-year-old man in blastic crisis of chronic myelocytic leukemia received a transplant of allogeneic peripheral blood stem cells. The donor was his HLA-identical sister, who refused to donate bone marrow cells, but agreed to donate peripheral blood stem cells. The patient received standard transplant conditioning with cyclophosphamide (120 mg/kg) and busulfan (16 mg/kg). Peripheral blood stem cells were mobilized with granulocyte colony stimulating factor and collected by apheresis. After transplantation, the white blood cell count and the result of microscopic analysis of the bone marrow became normal, and the leukocyte karyotype became 46XX. DNA fingerprinting showed complete chimerism. Graft-versus-host disease was suppressed with cyclosporine and methyl-prednisolone. The patient died of recurrence of leukemia on day 102+.

Bone marrow regeneration under cytotoxic drug regimens: behaviour ranging from homeostasis to unpredictability in a model for hemopoietic differentiation

In the process of hemopoiesis, bone marrow stem cells differentiate into the various types of mature blood cells. We present a model for bone marrow dynamics, which retrieves its ability to continuously modulate the balance between self-renewal and differentiation, even under periodic cytodestructive perturbations. Yet, a temporally stochastic perturbation results in chaotic-like behaviour which has no deterministic source.