Effects of Hemopoietic Growth Factors on Stem Cells in Vitro

Probiotic Consumption Boosts Thymus in Obesity and Senescence Mouse Models

The ability of the immune system to respond to different pathogens throughout life requires the constant production and selection of T cells in the thymus. This immune organ is very sensitive to age, infectious processes and nutrition disorders (obesity and malnutrition). Several studies have shown that the incorporation of some probiotic bacteria or probiotic fermented milk in the diet has beneficial effects, not only at the intestinal level but also on distant mucosal tissues, improving the architecture of the thymus in a malnutrition model. The aim of the present study was to determine whether supplementation with the probiotic strain Lactobacillus casei CRL 431 and/or its cell wall could improve body weight, intestinal microbiota and thymus structure and function in both obese and aging mice. We evaluated probiotic administration to BALB/c mice in 2 experimental mouse models: obesity and senescence, including mice of different ages (21, 28, 45, 90 and 180 days). Changes in thymus size and histology were recorded. T-lymphocyte population and cytokine production were also determined. The consumption of probiotics improved the cortical/medullary ratio, the production and regulation of cytokines and the recovery of mature T-lymphocyte populations of the thymus in obese and old mice. Probiotic incorporation into the diet could not only modulate the immune system but also lead to thymus function recovery, thus improving quality of life.

Cell-based interventions for therapeutic angiogenesis: review of potential cell sources

Alternative therapies are currently being developed to treat patients with chronic limb ischemia who are unable to be revascularized in order to avoid amputation. Cell-based therapy using mononuclear cells is gaining attention as many clinical trials are currently underway. We review cell differentiation along with the different potential cell sources for use in therapeutic angiogenesis.

Distinguishing mast cell and granulocyte differentiation at the single-cell level

The lineage restriction of prospectively isolated hematopoietic progenitors has been traditionally assessed by bulk in vitro culture and transplantation of large number of cells in vivo. These methods, however, cannot distinguish between homogenous multipotent or heterogeneous lineage-restricted populations. Using clonal assays of 1 or 5 cells in vitro, single-cell quantitative gene expression analyses, and transplantation of mice with low numbers of cells, we show that a common myeloid progenitor (CMP) is Sca-1(lo)lin(-)c-Kit(+)CD27(+)Flk-2(-) (SL-CMP; Sca-1(lo) CMP) and a granulocyte/macrophage progenitor (GMP) is Sca-1(lo)lin(-)c-Kit(+)CD27(+)Flk-2(+)CD150(-/lo) (SL-GMP; Sca-1(lo) GMP). We found that mast cell progenitor potential is present in the SL-CMP fraction, but not in the more differentiated SL-GMP population, and is more closely related to megakaryocyte/erythrocyte specification. Our data provide criteria for the prospective isolation of SL-CMP and SL-GMP and support the conclusion that mast cells are specified during hematopoiesis earlier than and independently from granulocytes.

Thrombocytopenia in Patients With Chronic Hepatitis C: A Possible Role of HCV on Platelet Progenitor Cell Maturation

A total of 30 patients with chronic hepatitis C (HCV) thrombocytopenia (TP) and 20 healthy controls were studied. Both groups were subjected to complete medical history, clinical examination in addition to assessment of hepatitis markers: level of thrombopoietin (Tpo), Geimsa-stained bone marrow smears, and in vitro short-term megakaryocytic progenitors culture (CFU-MK). Serum Tpo level was significantly elevated in patients with TP HCV. Short-term CFU-MK showed an evident depression in the colony-forming unit—megakaryocyte (CFU-meg). There is a positive correlation between the number of CFU-meg and the platelet count and between serum Tpo level and prothrombin time, transaminase, albumin, and the Child Pugh score of liver disease; a negative correlation between serum Tpo level and the number of CFU-meg and between serum Tpo level and the platelet count. Thus, the level of Tpo could be an indicator of intact functional response of the hepatocytes.

The effect of bleeding on hematopoietic stem cell cycling and self-renewal

Hematopoietic stem cells (HSCs) divide and give rise to more committed progenitors, which ultimately produce all lineages of blood cells. HSCs can be induced to enter the cell cycle in vitro and in vivo by stimulatory cytokines and in vivo by ablation of bone marrow (BM) cells with irradiation or chemotherapeutic agents. Although it has been postulated that rates of HSC proliferation increase with normal hematopoietic stresses, such as infection or hemorrhage, this hypothesis has never been directly tested. The ability to analyze HSCs prospectively by cell-surface phenotype c-kit(+), Thy1.1(lo), Sca-1(+), Linage(neg/lo) has allowed us to perform a detailed examination of the effects of bleeding on the cell cycle kinetics of HSCs. Our results demonstrate for the first time that HSCs in both the BM and the spleen proliferate and self-renew in response to tail-vein bleeding in mice. This response was suppressed when red blood cells, but not when white blood cells, were transferred after bleeding. Thus, regulators of HSC proliferation can sense and respond to red blood cell levels.

NF-E2-mediated enhancement of megakaryocytic differentiation and platelet production in vitro and in vivo

OBJECTIVE

NF-E2 is a prime regulator of megakaryocyte (MK) terminal differentiation and platelet release. By overexpressing the p45 subunit of NF-E2, we aim to increase the proportion of mature MKs and the potential for platelet production in vitro and in vivo.

METHODS

Retroviral vectors expressing p45-NF-E2 together with the enhanced green fluorescent protein (eGFP) were used to transduce murine bone marrow cells (BMCs). Aspects of MK differentiation, proliferation, proplatelet, and platelet production were evaluated.

RESULTS

Compared to controls, a higher proportion of BMCs overexpressing p45-NF-E2 were found to express the MK markers CD41, CD42a, and CD42b, with some effect on cell proliferation. Early MK differentiation, characterized by colony-forming unit (CFU)-MK formation, was enhanced by p45-NF-E2 overexpression at the expense of CFU-granulocyte macrophage development. An increased number of acetylcholinesterase(+) MKs was also observed in NF-E2(++) cultures. Although endomitosis was found not to be affected, the resultant upregulation of NF-E2 target genes was also followed by significant increases in proplatelet and functional platelet production. Transplantation of enriched MK progenitor cells overexpressing p45-NF-E2 into lethally irradiated mice resulted in a threefold increase in eGFP(+)/NF-E2(++) platelet production in vivo over 10 days, although no appreciable expansion in their number was observed over 32 days.

CONCLUSION

These results suggest that enforced expression of p45-NF-E2 selectively enhances many aspects of MK differentiation, including MK maturation, proplatelet formation, and platelet release. In addition, p45 overexpression increases MK commitment during early megakaryopoiesis, while inhibiting white blood cell differentiation.

Neutrophils secrete MIP-1 beta after adhesion to laminin contained in basement membrane of blood vessels

We have recently demonstrated that granulocyte colony-stimulating factor (G-CSF) stimulated the production of epithelial-cell-derived-neutrophil attractant-78 (ENA-78) by neutrophils and that ENA-78 might promote the accumulation of neutrophils that had migrated from the intravascular space into inflammatory tissues. In this study, we examined whether other chemokines could be secreted by neutrophils that had accumulated after migrating from the intravascular space into the inflammatory tissues. We demonstrated that adhesion to laminin contained in the basement membrane and Matrigel, which is an artificial basement membrane model, induced macrophage inflammatory protein-1 beta (MIP-1 beta) in neutrophils and that MIP-1 beta secreted by neutrophils induced the chemotaxis of dendritic cells. These findings suggest that neutrophils transmigrating through the basement membrane are stimulated to secrete MIP-1 beta by the basement membrane, inducing the transmigration of dendritic cells from the intravascular space into inflammatory tissues. We propose that neutrophils intervene between innate immune response and specific immune response by secreting MIP-1 beta during the transmigration through the basement membrane.

Autocrine production of epithelial cell–derived neutrophil attractant-78 induced by granulocyte colony-stimulating factor in neutrophils

Whereas mobilization to inflammatory sites is an important function of neutrophils, it remains to be determined whether granulocyte colony-stimulating factor (G-CSF) stimulates the mobilization of neutrophils to the inflammatory sites. This study compared the expression of more than 9000 genes in neutrophils treated with and without G-CSF with the use of a DNA microarray system to determine the effects of G-CSF on the function of neutrophils. It was found that messenger RNA expression of epithelial cell–derived neutrophil attractant-78 (ENA-78), which has been reported to be a chemotactic factor for neutrophils, was induced by G-CSF in neutrophils. The study demonstrated that the supernatant of G-CSF–treated neutrophils induced the chemotaxis of neutrophils and that anti–ENA-78 antibody and anti–CXCR-2 antibody inhibited the chemotaxis. These data suggest that G-CSF may enhance the mobilization of neutrophils and consequently augment the accumulation of neutrophils in the inflammatory sites through the secretion of ENA-78.

Timing of the appearance of multipotential and committed haemopoietic progenitors in peripheral blood after mobilization in patients with lymphoma

The pattern of emergence of multipotential (CFU-A) and committed (CFU-GM and BFU-E) progenitor cells in peripheral blood has been examined in patients with Hodgkin's disease and non-Hodgkin's lymphoma. Mobilization protocols used chemotherapy with or without granulocyte colony-stimulating factor (n=8 and n=5, respectively). In all patients, the numbers of CFU-A, CFU-GM and BFU-E peaked simultaneously, rather than sequentially, suggesting that marrow regeneration after these mobilization protocols occurred from progenitors at all stages of differentiation. We conclude that peripheral blood stem cell harvest strategies based on peak values for total progenitor numbers will also capture maximum numbers of multipotential progenitors. However, the variable relationship between CFU-A and CFU-GM numbers suggests that overall progenitor cell numbers can give only a broad estimate of the absolute numbers of multipotential progenitors in an individual harvest.

Effect of granulocyte and granulocyte macrophage colony stimulating factors (G-CSF and GM-CSF) on neonatal neutrophil functions

Although there are many studies on the effect of granulocyte and granulocyte-macrophage colony stimulating factors (G/GM-CSF) on adult neutrophil functions, there is little information regarding their influence on neonatal cells. We studied the in vitro effect of G/GM-CSF on neutrophil chemotaxis, polarization, and superoxide anion generation in 47 neonates compared with 35 adults. We found that G-CSF and GM-CSF significantly enhanced the chemotaxis of newborn infants' neutrophils, normalizing their chemotactic defect [from 35 +/- 7 cells/field (mean +/- SE) to 49 +/- 5 cells/field with G-CSF, p < 0.05 and to 55 +/- 4 cells/field with GM-CSF, p < 0.001]. It is notable that the maximal neutrophil response to the cytokines was observed particularly in the newborn infants with severe impairment in their chemotactic activity. Statistical analysis of the data showed a significant inverse correlation, which supported this observation (r = -0.6, p < 0.02 for G-CSF; r = -0.76, p < 0.001 for GM-CSF). The reduced polarization of neonatal compared with adult cells [71 +/- 5% versus 86 +/- 2% (mean +/- SE), p < 0.05], was corrected by CSF-priming (to 87 +/- 4% with G-CSF and to 92 +/- 2% with GM-CSF, p < 0.05). In addition, the neutrophil superoxide generation was significantly improved in both groups following the CSF-priming. GM-CSF and G-CSF gave comparable results in all functions studied except that GM-CSF improved superoxide release to a greater extent. This study shows a significant improvement of the neonatal neutrophil functions following in vitro CSF-priming and contributes to a better understanding of the neonatal neutrophil behavior when treated with G/GM-CSF.

Immunobiology of allogeneic peripheral blood mononuclear cells mobilized with granulocyte-colony stimulating factor

The use of mobilized peripheral blood (PB) stem cells for autologous transplantation initially generated much enthusiasm because of enhanced engraftment in comparison to marrow stem cells and avoidance of general anesthesia for the donor. Its application to the allogeneic setting seemed inevitable. For obvious ethical reasons, allogeneic donors are mobilized with cytokines only, mainly granulocyte colony-stimulating factor (G-CSF). Results from preliminary studies suggest that in comparison to standard bone marrow transplants, outcomes such as engraftment, host-versus-graft reaction, graft-versus-host disease, graft-versus-leukemia and immunological reconstitution may be different. Surprisingly, G-CSF, previously recognized as a late acting lineage-specific factor for neutrophil production, not only disrupts homeostasis between stem cells and their microenvironment, but also induces significant quantitative and qualitative changes in the accessory cell compartment, affecting lymphocytes, monocytes, natural killer, dendritic, and stromal cells. Furthermore, mobilization of huge numbers of non-professional antigen presenting cells (CD34+ stem cells) amplifies the tolerizing potential of PB stem cell grafts. Thus, G-CSF mobilization provides PB transplants with different immunobiologic properties in comparison to standard bone marrow grafts. Whether these immunobiologic differences will lead to better transplant outcomes remains to be shown through much awaited results of large randomized clinical trials.

Combination of stem cell factor and granulocyte colony-stimulating factor mobilizes the highest number of primitive haemopoietic progenitors as shown by pre-colony-forming unit (pre-CFU) assay

Fifty-two patients with poor prognosis carcinoma of the breast underwent peripheral blood stem cell (PBSC) mobilization using five different regimens. The yields of primitive haemopoietic progenitors were quantified by a recently described pre-colony-forming unit (pre-CFU) assay using limiting dilution analysis (LDA). Results of days 14 and 35 pre-CFU were also correlated with conventional CD34+ cell enumeration, CFU-GM (granulocyte-macrophage) and long-term culture-initiating cell (LTCIC) assays. The yield of pre-CFUs with the combination of granulocyte colony-stimulating factor (G-CSF) and stem cell factor (SCF) was significantly higher than with G-CSF alone, cyclophosphamide (Cyclo) and granulocyte-monocyte colony-stimulating factor (GM-CSF), interleukin (IL)-3 and GM-CSF, or Cyclo alone. No significant correlation between neutrophil engraftment and pre-CFU could be demonstrated. Furthermore, CFU-GM was shown to bear a stronger correlation with pre-CFU and LTCIC than CD34+ cell measurement; thus, CFU-GM remains a useful biological tool for haemopoietic stem cell assay. We conclude that the combination of G-CSF and SCF mobilizes the highest number of pre-CFUs as measured by functional pre-CFU assay, which provides an alternative measurement of primitive haemopoietic progenitors to the LTCIC assay.

Effects of pentoxifylline on the haematologic status in anaemic patients with advanced renal failure

OBJECTIVE

Erythropoietin (EPO) deficiency is the main cause of renal anaemia. However, inhibition of erythropoiesis by cytokines such as tumour necrosis factor alpha (TNF-a) may play an important role. The aim of this work was to study the effects of pentoxifylline, an agent with anti-TNF-a properties, on the haematologic status in anaemic patients with advanced renal failure.

MATERIAL AND METHODS

In a prospective study, 7 anaemic patients with advanced renal disease (creatinine clearance <30 ml/min) were treated with pentoxifylline (400 mg orally daily) for 6 months. The evolution of haemoglobin, haematocrit, creatinine clearance and serum EPO and TNF-a a concentrations were compared with those obtained from an untreated control group.

RESULTS

Haemoglobin and haematocrit significantly increased in the pentoxifylline-treated patients (9.9+/-0.5 g/dl and 27.9+/-1.6% at baseline; 10.6+/-0.6 g/dl and 31.3+/-1.9% at the 6th month, respectively, p < 0.01), whereas no variation was seen in the control group. Serum EPO levels remained stable in all patients. However, the serum TNF-a concentration decreased significantly in patients receiving pentoxifylline (basal 623+/-366 pg/ml; 6th month 562+/-358 pg/ml, p < 0.01), but not in the control group.

CONCLUSIONS

Our findings suggest that the inhibition of erythropoiesis by cytokines may play a significant role in renal anaemia. The administration of agents with anti-cytokine properties, such as pentoxifylline, can improve the haematologic status in anaemic patients with advanced renal failure.

Assay systems for hematopoietic stem and progenitor cells

Progress in our understanding of the hematopoietic system as well as novel cellular and molecular biology techniques are increasingly promoting the ex vivo manipulation and therapeutic use of hematopoietic stem and progenitor cells. For both, development of stem cell therapies and basic hematopoietic research, test systems for hematopoietic stem cells are required to monitor the intrinsic and ex vivo-induced properties of these cells. In vitro assays for primitive hematopoietic cells (colony-forming units-blast, cobblestone area-forming cells, long-term culture-initiating cells [LTC-IC]) have been established which demonstrate the proliferative and differentiation capacities of these populations. The potentials of these assays have been recently enhanced by the extended LTC and the switch LTC modifications. Although some hematopoietic cells characterized in vitro have the multipotential and proliferative properties of pluripotent hematopoietic stem cells (PHSC), their capacity to long-term repopulate hematopoiesis in vivo, a hallmark of PHSC, has not been established. Without this confirmation, populations defined in vitro should not be considered the equivalent of PHSC. In animals, the properties of primitive hematopoietic cells can be systematically analyzed by multiple in vivo assays. Therefore, various strategies have been pursued to develop an animal model for human hematopoiesis. In fetal sheep and immunodeficient mice, the functions of human PHSC are reproduced, and long-term multilineage repopulation capacity and extensive proliferative potential have been demonstrated for xenografted human cells. Thus, both models can be considered stem cell assays and may significantly enhance the study of early hematopoiesis and the development of therapeutic strategies.

Neonatal sepsis: pathogenesis and supportive therapy

Bacterial infections remain an important cause of neonatal mortality and morbidity. Pathogenesis of the neonate's predilection to infection are multifactorial. Factors directly attributable to the infant include humoral, phagocytic, and cellular deficiencies. Septic neonates may have reduced neutrophil storage pools that cause profound neutropenia. Both correlate with poor prognosis. Antibiotic administration is mandatory in neonatal sepsis. Supplementary treatments may be useful. Granulocyte transfusions, when available, provide neutrophils, improving the neonate's neutrophil count and neutrophil function. The efficacy of intravenous immunoglobulin (i.v.IG) is questionable because the prophylactic and therapeutic administration of i.v.IG fails to reduce the incidence of bacterial infections or affect the overall survival rate. Hyperimmune preparations seem to be more effective. The administration of granulocyte colony-stimulating factor induces myeloid progenitor proliferation, enhances the neutrophil storage pool, produces neutrophilia, and improves neutrophil function. More extensive, well-designed, and carefully control trials are needed to determine the benefit of supportive therapies for neonatal sepsis.

Myeloid and megakaryocytic hypoplasia in related standardbreds

Myeloid and megakaryocytic bone marrow hypoplasia in association with moderate to profound neutropenia was observed in 8 young Standardbred horses sired by the same stallion; 7 horses were intermittently thrombocytopenic. Evaluation of serial neutrophil counts in 2 horses suggested that a cyclic variation in neutrophil numbers was present, that lymphocyte numbers increased when neutrophil counts decreased, and that platelet counts decreased when neutrophil counts decreased. Preliminary bone marrow cultures indicated that myeloid progenitor cells were present and that these cells were able to respond to exogenous growth factors by differentiating. A bone marrow microenvironment or growth factor defect is suspected. Seven of 8 horses died or were euthanized. One horse with moderate neutropenia and a normal platelet count has been racing for 3 years. Necropsies in 4 horses did not reveal a cause for the myeloid hypoplasia. A familial basis for the disease is suspected.

Transcription factor NF-E2 is required for platelet formation independent of the actions of thrombopoietin/MGDF in megakaryocyte development

Despite the importance of blood platelets in health and disease, the mechanisms regulating their formation within megakaryocytes are unknown. We generated mice lacking the hematopoietic subunit (p45) of the heterodimeric erythroid transcription factor NF-E2. Unexpectedly, NF-E2-/- mice lack circulating platelets and die of hemorrhage; their megakaryocytes show no cytoplasmic platelet formation. Though platelets are absent, serum levels of the growth factor thrombopoietin/MGDF are not elevated above controls. Nonetheless, NF-E2-/- megakaryocytes proliferate in vivo in response to thrombopoietin administration. Thus, as an essential factor for megakaryocyte maturation and platelet production, NF-E2 must regulate critical target genes independent of the action of thrombopoietin. These findings provide insight into the genetic analysis of megakaryocyte maturation and thrombopoiesis.

Selection and characterization of an erythroeosinophilic subclone (LAMA-87) and an eosinophilic subclone (LAMA-88) from the multipotential cell line LAMA-84

The human leukemic cell line LAMA-84 was established and characterized as an erythromegakaryocytic cell line. In the present study we show that these cells can differentiate in estrone-treated athymic mice and give rise to an erythroeosinophilic cell line (LAMA-87). This new cell line expressed glycoporin A, alpha beta and gamma globin chain mRNA but also eosinophilic peroxidase. Hemin slightly increased the total hemoglobin production of the cells and phorbol diester (TPA), dimethyl sulfoxide (DMSO) and sodium butyrate (SB) increased the expression of megakaryocytic markers (gpIIb/IIIa complex). When inoculated into non-treated athymic mice, LAMA-87 cells can differentiate to give rise to eosinomonocytic cells (LAMA-88). This new cell line expresses eosinophilic peroxidase, Luxol fast blue stain and synthesizes lysozyme. Depending on the inducer used, LAMA-88 can differentiate along a monocytic lineage (TPA, DMSO, SB and vitamin D3). These three LAMA cell lines should be useful in further studies of the molecular regulation of the pluripotent cell commitment and may provide a model for the understanding of human hematopoiesis.

Cellular signalling events stimulated by myeloid haemopoietic growth factors

In haemopoietic cells, proliferation, commitment to development, lineage restriction and survival via suppression of apoptosis can all be controlled by haemopoietic growth factors. The mechanisms underlying the regulation of these events can now be studied since recombinant forms of most of these haemopoietic growth factors are now available. Recent advances in cell purification techniques and the development of multipotent cell lines (see Spangrude et al, 1988; Whetton, 1990; Heyworth et al, 1988, 1990a; Jones et al, 1990) have provided suitable cell populations on which to study the cellular signalling events associated with differentiation and lineage restriction. This process has started with the elucidation of the structure and expression of many of the myeloid growth factor receptors, which should now facilitate progress in the study of the signal transduction mechanisms these growth factors employ. Another important facet of these studies will be to determine whether a single growth factor with multiple target cell types, ranging from multipotent cells to postmitotic cells (e.g. neutrophils), employs distinct signalling mechanisms depending on the target cell in question. The cellular signalling events elicited by each of these growth factors and the ways in which they can regulate the transcriptional activation of genes associated with specific developmental events are going to be key areas of haemopoietic research in the next few years.

Assessment of an EIA for measuring human serum erythropoietin as compared with RIA and an in-vitro bioassay

A recently developed enzyme-linked immunosorbent assay (EIAZ, ELISA) using two murine monoclonal anti-erythropoietin antibodies was compared with a radioimmunoassay (RIA) and a commercial in-vitro bioassay, EPOS, for measuring serum erythropoietin (Epo) in humans. Specificity and validity for Epo-EIA and the other two assays were examined. The serum Epo in normal subjects was 18 +/- 12 mU/ml (mean +/- SD, n = 80) for EIA compared with 22.5 +/- 18.5 mU/ml (n = 20) for RIA and 136 +/- 132 mU/ml (n = 14) for the bioassay. The serum Epo concentrations in normals and patients were highly comparable between EIA and RIA for Epo (P less than 0.01, r = 0.95). Epo concentrations by the EIA for normal female and male subjects were 20.5 +/- 13 and 16.5 +/- 10 mU/ml, respectively. Epo levels in patients with secondary polycythaemia or autoimmune haemolytic anaemia were significantly higher than normal subjects by the three methods. Epo levels in patients with chronic renal failure were within the normal range. By the EPOS bioassay, the Epo concentrations of normals and patients with renal failure were significantly higher than expected (136 +/- 132 and 447 +/- 273, respectively). Due to its inherent design, the EPOS bioassay possibly measures bone marrow proliferative activity in response to other serum growth regulators besides erythropoietin and was found to be unsuitable for clinical assessment of Epo. We concluded that the new EIA and RIA were similarly sensitive, reliable and accurate for measurement of serum Epo. The EIA method has the advantage of being less time consuming, more convenient and avoids the use of a radioisotope.

Use of Recombinant Canine Granulocyte Colony-Stimulating Factor to Decrease Myelosuppression Associated with the Administration of Mitoxantrone in the Dog

Ten dogs were given mitoxantrone at a dose of 5 mg/m2 body surface area intravenously. Recombinant canine granulocyte colony-stimulating factor (rcG-CSF) was administered subcutaneously daily for 20 days after an infusion of mitoxantrone in five of these dogs to determine the effect of the hematopoietic growth factor on the duration and severity of myelosuppression. The median neutrophil counts dropped below normal (less than 3,000/uL) for 2 days in the dogs that received rcG-CSF, and for 5 days in the dogs that received only mitoxantrone. Four of five dogs not treated with rcG-CSF and none of those receiving rcG-CSF developed serious neutropenia (less than 1,500/uL). The neutrophil counts were significantly (P less than 0.05) higher in the rcG-CSF treated dogs at all time points except before the administration of the colony-stimulating factor, and the sixth day after the mitoxantrone was administered. These findings demonstrate that rcG-CSF is capable of reducing the duration and severity of mitoxantrone-induced myelosuppression.

Evaluation of recombinant canine granulocyte colony-stimulating factor as an inducer of granulopoiesis. A pilot study

Five healthy young adult dogs were given recombinant canine granulocyte colony-stimulating factor (rcG-CSF) at a dosage of 5 micrograms/kg/day subcutaneously for 4 weeks to evaluate the effect on complete blood cell counts. The mean neutrophil counts +/- standard deviation (SD) increased significantly (P less than 0.01) from 6,537/microliters +/- 1,726 (range, 4,950-9,512/microliters) to 26,330/microliters +/- 7,066 (range, 15,368-35,785/microliters) within 24 hours after the first injection of rcG-CSF. Mean monocyte counts +/- SD were significantly increased (P less than 0.05) from baseline values of 751/microliters +/- 168 (range, 444-891/microliters) to 2,514/microliters +/- 878 (range, 1,740-3,752/microliters) on day 5 of rcG-CSF administration. Mean neutrophil and monocyte counts (+/- SD) continued to increase reaching a maximum of 72,125/microliters +/- 15,073 (range, 50,915-96,278/microliters) and 3,972/microliters +/- 2,621 (range, 685-8,030/microliters), respectively by day 19. These increased neutrophil and monocyte counts were maintained until the administration of rcG-CSF was stopped. Blood counts returned to normal within 5 days after discontinuing the rcG-CSF. One week after discontinuing treatment, rcG-CSF was started again at 5 micrograms/kg/day subcutaneously. Within 48 hours following administration of rcG-CSF, mean neutrophil counts +/- SD increased from 5,860/microliters +/- 1,819 (range, 3,720-8,650/microliters) to 57,444/microliters +/- 8,173 (range, 43,983-68,278/microliters). Myeloid:erythroid ratios increased from a mean of 1.63:1 on day 1 prior to administration of rcG-CSF to 3.3:1 on day 10 in three dogs for which bone marrow samples were evaluated. Recombinant canine G-CSF did not cause clinically significant toxicosis in any of the dogs.

Expression of an erythroid transcription factor in megakaryocytic and mast cell lineages

The nuclear factor GF-1 (also known as NF-E1, Eryf-1; refs 1-3 respectively) is important in regulation of the transcription of globin and other genes that are specifically expressed in erythroid cells. We have previously shown that GF-1 of both mouse and human origin is a 413-amino-acid polypeptide with two novel zinc-finger domains whose expression is restricted to erythroid cells. Using in situ hybridization of mouse bone marrow cells and northern blot analysis of purified cell populations and permanent cell lines, we show here that GF-1 is expressed in two other hematopoietic lineages, megakaryocytes and bone marrow-derived mast cells. Our findings are consistent with results from hematopoietic progenitor culture which suggest a relationship between erythroid, megakaryocytic and mast cell lineages, and imply that GF-1 is expressed in committed multipotential cells and their progeny. Hence, the mere presence of this transcription factor is unlikely to be sufficient to programme differentiation of a single haematopoietic lineage. GF-1 may regulate the transcription of not only erythroid genes, but also many genes characteristic of megakaryocytes and mast cells, or genes shared among these lineages.