Effects of recombinant canine stem cell factor, a c-kit ligand, and recombinant granulocyte colony-stimulating factor on hematopoietic recovery after otherwise lethal total body irradiation

The effects of recombinant canine stem cell factor (rcSCF) on hematopoiesis were studied in normal dogs and in dogs given otherwise lethal total body irradiation (TBI) without marrow transplant. Results were compared with previous and concurrent data with recombinant granulocyte colony-stimulating factor (rG-CSF). Four normal dogs received 200 micrograms rcSCF per kilogram body weight daily either by continuous intravenous infusion for 28 days (n = 2) or by subcutaneous (SC) injection in two divided doses for 20 days (n = 2). All dogs showed at least a twofold increase in peripheral blood neutrophil counts starting approximately 7 days after the initiation of treatment. Hematocrit level and monocyte, lymphocyte, eosinophil, reticulocyte, and platelet counts were not elevated. Marrow sections after rcSCF treatment showed panhyperplasia. The only toxicity was facial edema during the first few days of rcSCF administration, presumably caused by mast cell stimulation. Ten dogs were given 400 cGy TBI at 10 cGy/min from two opposing 60Co sources. They were given no marrow infusion and received 200 micrograms/kg/d rcSCF SC in two divided doses for 21 days starting within 2 hours of TBI. Five of the 10 dogs showed complete and sustained hematopoietic recovery and survived as compared with 1 of 28 control dogs not receiving growth factor (P < .005). RcSCF treatment allowed for hematopoietic recovery in two of seven dogs administered 500 cGy of TBI but in none of five dogs given 600 cGy of TBI. Results with rcSCF are similar to those obtained with rG-CSF. The rate of neutrophil recovery in rcSCF-treated dogs after 400 cGy TBI was not different from that of rG-CSF-treated dogs (P = .65), but the rate of platelet recovery was faster (P = .06) in the rcSCF-treated animals. Combined treatment with rcSCF and rcG-CSF after 500 cGy TBI did not result in strongly improved survival as compared with results obtained with either factor alone.     

Effect of recombinant human granulocyte colony-stimulating factor on hematopoiesis of normal dogs and on hematopoietic recovery after otherwise lethal total body irradiation

This study was designed to test whether recombinant human G-CSF (rh G-CSF) affects hematopoiesis in normal dogs and, if so, to test the effects of G-CSF in dogs given otherwise lethal total body irradiation (TBI). Rh G-CSF given subcutaneously at 10 or 100 micrograms/kg/d for 14 days to two normal dogs increased peripheral blood neutrophils eight to tenfold and monocytes four to sixfold above controls. Lymphocyte counts remained unchanged at the lower dose and increased threefold at the higher dose of rh G-CSF. No significant changes were observed in eosinophil, platelet, reticulocyte, or hematocrit levels. After 2 weeks of treatment with rh G-CSF, bone marrow displayed myeloid hyperplasia and left-shifted granulocytopoiesis. After discontinuation of rh G-CSF, peripheral leukocyte counts returned to control levels within three days. Five dogs administered 400 cGy TBI at 10 cGy/min from two opposing 60Co sources and no marrow infusion or growth factor, all developed profound pancytopenia and died between 17 and 23 days after TBI with infections secondary to marrow aplasia. Four of five dogs treated within two hours after 400 cGy TBI with 100 micrograms rh G-CSF/kg/d subcutaneously twice a day for 21 days showed complete and sustained endogenous hematopoietic recovery. In contrast, five dogs irradiated with 400 cGy TBI and treated with 100 micrograms rh G-CSF/kg/d starting on day 7 after TBI, all died between days 17 and 20 after TBI with infections secondary to marrow aplasia. Rh G-CSF, if administered shortly after irradiation, can reverse the otherwise lethal myelosuppressive effect of radiation exposure.     

Stimulation of canine hematopoiesis by recombinant human granulocyte-macrophage colony-stimulating factor

The effect of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) on canine hematopoiesis was evaluated. rhGM-CSF stimulated granulocyte-macrophage colony formation of canine marrow depleted of accessory cells up to tenfold. Stimulation of colony formation was abrogated by anti-rhGM-CSF antiserum or heat inactivation. rhGM-CSF also stimulated in vivo canine hematopoiesis both when given as continuous i.v. infusion and as intermittent s.c. injections. Neutrophil, monocyte, and lymphocyte counts were increased three- to eightfold above controls, whereas values for eosinophils, reticulocytes, and hematocrits were not changed. Bone marrow histology after 2 weeks of treatment with rhGM-CSF showed hypercellularity with myeloid hyperplasia and left-shifted granulocytopoiesis. After discontinuation of rhGM-CSF, peripheral leukocyte counts returned to control level within 3-7 days. Platelet counts decreased rapidly after starting rhGM-CSF, to 5000-15,000 platelets/mm3, and increased within 24 h after stopping rhGM-CSF treatment, whereas marrow histology after 2 weeks of rhGM-CSF application showed the normal number and morphology of megakaryocytes.     

Recovery from severe hematopoietic suppression using recombinant human granulocyte-macrophage colony-stimulating factor

The ability of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) to enhance recovery of a radiation-suppressed hematopoietic system was evaluated in a nonuniform radiation exposure model using the rhesus monkey. Recombinant human GM-CSF treatment for 7 days after a lethal, nonuniform radiation exposure of 800 cGy was sufficient to enhance hematopoietic reconstitution, leading to an earlier recovery. Monkeys were treated with 72,000 U/kg/day of rhGM-CSF delivered continuously through an Alzet miniosmotic pump implanted subcutaneously on day 3. Treated monkeys demonstrated effective granulocyte and platelet levels in the peripheral blood, 4 and 7 days earlier, respectively, than control monkeys. Granulocyte-macrophage colony-forming unit (CFU-GM) activity in the bone marrow was monitored to evaluate the effect of rhGM-CSF on marrow recovery. Treatment with rhGM-CSF led to an early recovery of CFU-GM activity suggesting that rhGM-CSF acted on an earlier stem cell population to generate CFU-GM. Thus, the effect of rhGM-CSF on hematopoietic regeneration, granulocyte recovery, and platelet recovery are evaluated in this paper.     

DLA-identical bone marrow grafts after low-dose total body irradiation: the effect of canine recombinant hematopoietic growth factors

Previous studies found that bone marrow (BM) allografts from DLA- identical littermates resulted in survival of two thirds of recipient dogs after otherwise lethal doses of 450 to 600 cGy of total body irradiation (TBI) because of successful allografts or autologous recovery after rejection of the allografts. The current study asked whether survival could be further improved by treating allograft recipients with recombinant canine granulocyte colony-stimulating factor (G-CSF), stem cell factor (SCF), or G-CSF/SCF. Of 21 dogs, 14 (67%) receiving allografts but no growth factors survived, 10 with successful allografts (including 5 mixed chimeras) and 4 with autologous recovery; whereas 7 animals died, 5 from infections during BM aplasia and 2 from acute graft-versus-host disease. By comparison, 30 of 34 dogs (88%) receiving hematopoietic growth factors in addition to the BM graft survived, 17 with successful allografts (including 10 mixed chimeras) and 13 with autologous recovery; whereas 4 died, all with infection related to BM aplasia after rejection of the allograft. Survival was similar for recipients of G-CSF, SCF, or the combination of G-CSF and SCF. Logistic regression analyses, which accounted for possible effects of TBI dose, showed a trend for improved survival in dogs receiving growth factors (P = .09), no change in allogeneic engraftment (P = .74), and a slight increase in autologous recovery (P = .22). In agreement with previous data, we found that grafts of BM from DLA-identical littermates improved survival of recipient dogs exposed to low but otherwise lethal doses of TBI. A further improvement in survival could be achieved by additional treatment with G-CSF, SCF, or G-CSF/SCF. Results suggest that treatment by hematopoietic growth factors along with BM grafts should be considered for victims of radiation accidents.     

Lack of efficacy of thrombopoietin and granulocyte-macrophage colony-stimulating factor after total body irradiation and autologous bone marrow transplantation in Rhesus monkeys

OBJECTIVE: If administered in a sufficiently high dose to overcome receptor-mediated clearance and in a well-scheduled manner, thrombopoietin (TPO) prominently stimulates hematopoietic reconstitution following myelosuppressive treatment and potentiates the efficacy of both granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF). However, TPO alone is not effective after bone marrow transplantation. Based on results of GM-CSF and TPO treatment after myelosuppression that resulted in augmented thrombocyte, reticulocyte, and leukocyte regeneration, we evaluated TPO/GM-CSF treatment after lethal irradiation followed by autologous bone marrow transplantation. MATERIALS AND METHODS: Young adult Rhesus monkeys were subjected to 8-Gy total body irradiation (TBI) (x-rays) followed by transplantation of 10(7)/kg unfractionated bone marrow cells. TPO 5 microg/kg was administered intravenously at day 0 to obtain rapidly high levels. Animals then were treated with 5 microg/kg Rhesus TPO and 25 microg/kg GM-CSF given SC on days 1 to 14 after TBI. RESULTS: The grafts shortened the profound pancytopenia induced by 8-Gy TBI from 5-6 weeks to 3 weeks. The combination of TPO and GM-CSF did not significantly influence the recovery patterns of thrombocytes (p = 0.39), reticulocytes (p = 0.08), white blood cells (p = 0.08), or bone marrow progenitors compared to TPO alone. CONCLUSIONS: The present study demonstrates that, after high-dose TBI and transplantation of a limited number of unfractionated bone marrow cells, simultaneous administration of TPO and GM-CSF after TBI is ineffective in preventing pancytopenia. This result contrasts sharply with the prominent stimulation observed in a 5-Gy TBI myelosuppression model, despite a similar level of pancytopenia in the 8-Gy model of the present study. The discordant results of this growth factor combination in these two models may imply codependence of the hematopoietic response to TPO and/or GM-CSF on other factors or cytokines.     

Effects of recombinant granulocyte colony-stimulating factor (rG-CSF) and recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) on acute radiation hematopoietic injury in mice

We have attempted to evaluate in vivo effects of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) on acute radiation hematopoietic injury in mice. BDF1 mice, irradiated with 7.5-Gy x-rays, were injected i.p. twice daily for 10 days with 10(5) U recombinant human G-CSF, 3.75 x 10(5) U recombinant murine GM-CSF, or a combination of both. G-CSF significantly enhanced the recovery of not only peripheral leukocytes but also platelets and hematocrit on days 14 and 21 after irradiation. GM-CSF significantly enhanced the recovery of platelets on day 14 and peripheral leukocytes on day 21. G-CSF markedly enhanced the recovery of spleen colony-forming units (CFU-S), colony-forming units in culture (CFU-C), erythroid burst-forming units (BFU-E), and megakaryocyte colony-forming units (CFU-Meg) both in bone marrow and in the spleen. GM-CSF significantly enhanced the recovery of CFU-Meg in bone marrow on day 14. We found synergistic effects between G-CSF and GM-CSF on CFU-S, CFU-C, and CFU-Meg in the spleen on day 14, although we found antagonistic effects between G-CSF and GM-CSF on CFU-S and CFU-C in bone marrow on day 7, and on platelet counts on day 7. These results indicate that the administration of recombinant G-CSF and GM-CSF may be useful in accelerating hematopoietic recovery in patients with acute radiation hematopoietic injuries.     

A controlled trial of recombinant human granulocyte-macrophage colony-stimulating factor after total body irradiation, high-dose chemotherapy, and autologous bone marrow transplantation for acute lymphoblastic leukemia or malignant lymphoma.

Infections during granulocytopenia are major complications of autologous bone marrow transplantation (ABMT). Since recombinant human granulocyte-macrophage colony-stimulating factor (rhuGM-CSF) has proved to accelerate bone marrow recovery after cytostatic chemotherapy, we studied its effects on hematopoietic regeneration and on infectious complications after total body irradiation (TBI) and high-dose chemotherapy followed by ABMT. Eighty-one patients with acute lymphoblastic leukemia (ALL) in complete remission (CR) or with non-Hodgkin's lymphoma (NHL) in CR or partial remission were randomized in a double-blind, placebo-controlled trial. They received either rhuGM-CSF 250 micrograms/m2 (Escherichia coli-derived) daily by continuous infusion after ABMT, or placebo. Treatment was continued until the neutrophil counts reached greater than 500/microL for 1 week. The maximum treatment duration was 30 days. Thirty-nine patients in the rhuGM-CSF group and 40 patients in the placebo group were evaluable. The median time needed to reach a neutrophil count of 500/microL was 15 days with rhuGM-CSF and 28 days with placebo (P = .0001). Bacterial infections occurred in 14 (35.9%) of the patients with rhuGM-CSF and in 25 (62.5%) of the patients given the placebo (P = .024). Nine of the 14 bacterial infections in the rhuGM-CSF group and 20 of the 25 infections in the placebo group were diagnosed within the first 10 days after ABMT. Capillary leakage and a reversible fluid retention were seen in five of the rhuGM-CSF-treated patients. Patients treated with rhuGM-CSF had lower serum protein and albumin levels than patients in the placebo group. There was no statistically relevant difference in overall survival between the two groups (P = .47). Relapse occurred in 14 (34%) patients with rhuGM-CSF and in 18 (45%) patients with placebo. We conclude that continuous infusion of rhuGM-CSF after ABMT accelerates the regeneration of granulocytes and reduces the number of bacterial infections.     

Effect of recombinant granulocyte-macrophage colony-stimulating factor on murine thrombocytopoiesis in vitro and in vivo

To investigate the effect of recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) on murine megakaryocytopoiesis in vitro, the factor was added to both serum-free colony assays and liquid marrow cultures. GM-CSF had a significant megakaryocytic colony-stimulating activity. After 2 hours of preincubation with and without 10 ng/mL rGM-CSF, the percentage of megakaryocyte colony-forming cell (CFU-MK) in DNA synthesis was determined by tritiated-thymidine suicide using colony growth. The reduction of CFU-MK colony numbers in marrow culture was 47.5% +/- 9.9%, 20.9% +/- 5.2% (control), respectively, indicating that the factor affected cell cycle at CFU-MK levels. When acetylcholinesterase (AchE) production was measured fluorometrically after 4 days of liquid culture, rGM-CSF elicited an increase in AchE activity in a dose-dependent fashion. To determine if the hematopoietin acts directly on megakaryocytic differentiation, 2 ng/mL rGM-CSF was added to serum-free cultures of 295 single megakaryocytes isolated from CFU-MK colonies. An increase in size was observed in 65% of cells initially 10 to 20 microns in diameter, 71% of cells 20 to 30 microns, and 40% of cells greater than 30 microns. Conversely, in absence of GM-CSF, 17%, 31%, and 10% of cells in each group increased in diameter. These data suggest that rGM-CSF promotes murine megakaryocytopoiesis in vitro and that the response to the factor is direct. To determine if the factor influences megakaryocytic/thrombocytic lineage in vivo, 1 and 5 micrograms of rGM-CSF were administered intraperitoneally every 12 hours for 6 consecutive days. Although a two- to three-fold increase in peripheral granulocytes was observed, neither megakaryocytic progenitor cells or platelets changed. Histologic analysis of bone marrow megakaryocytes showed no increase in size and number. The in vivo studies demonstrated no effect of GM-CSF on thrombocytopoiesis. The discrepancies between the in vitro and in vivo effects of GM-CSF require additional investigations.     

Influence of mobilized peripheral blood cells on the hematopoietic recovery by autologous marrow and recombinant human granulocyte-macrophage colony-stimulating factor after high-dose cyclophosphamide, etoposide, and cisplatin.

Peripheral blood cells (PBC) can hasten hematopoietic recovery after high-dose chemotherapy. To determine if PBC apheresed after mobilization further enhance hematopoietic recovery over that achieved with autologous bone marrow (ABM) and recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF), 14 patients with metastatic solid tumors were supported by ABM and rhGM-CSF during the first course of high doses of cyclophosphamide, etoposide, and cisplatin (CVP) and 11 of these 14 patients by mobilized PBC with ABM and rhGM-CSF during the second CVP. Each patient served as his or her own control. Identical doses of CVP were administered in both courses: cyclophosphamide 5.25 g/m2, etoposide 1,200 mg/m2, and cisplatin 165 to 180 mg/m2. PBC were collected on day 10 after mobilization with cyclophosphamide (3 g/m2) intravenously (IV) on day 1, doxorubicin (50 mg/m2) as a continuous IV infusion over 48 hours starting day 2, and rhGM-CSF as a daily 4-hour IV infusion starting day 4 at 0.6 mg/m2 for 14 days. Comparing recovery in the 11 patients to receive two cycles of therapy, the median days to an absolute neutrophil count of 0.1 x 10(9)/L and 0.5 x 10(9)/L were not statistically significant between the two courses; neither was there a difference in the incidence of fever and bacteremia. The median number of days to platelet count of 0.02 x 10(12)/L unmaintained by platelet transfusion was 20 from marrow infusion for course 1 and 16 for course 2 (P = .059). The median number of days to a platelet count of 0.05 x 10(12)/L was significantly shortened: 24 and 19 days for courses 1 and 2, respectively (P = .045). Patients who received PBC required fewer number of platelet transfusions. Extramedullary toxicities were not different between the groups. Our finding of enhanced early recovery of platelets and reduced platelet transfusion requirement is in concordance with other studies.     

Effect of recombinant human granulocyte-macrophage colony-stimulating factor on myelopoiesis in patients with refractory metastatic carcinoma

The effect of human recombinant GM-colony-stimulating factor (CSF) was evaluated in ten patients with refractory metastatic carcinoma. Initially they received an intravenous (IV) bolus injection of 5 or 25 micrograms/m2 for assessment of acute responses. Six days later, continuous IV infusions of 100 or 500 micrograms/m2 were initiated for a 14-day treatment course. All patients developed profound leukopenia within five to 30 minutes of the bolus injection. This appeared to result from increased expression of an adhesion-promoting glycoprotein (GP) on neutrophils and monocytes as judged by increased reactivity to the Mo1 monoclonal antibody (MoAb). Leukocyte counts returned to normal levels within two hours as cells were released from marrow stores. With the continuous infusion, leukocyte counts increased by 24 hours; peak values of 22,960 and 75.900/microL were achieved after ten to 14 days of treatment with the two dose levels of GM-CSF. This leukocytosis was due to an increase in virtually all cell types. At the high dose level, there was a striking increase in neutrophils (49,400/microL) and eosinophils (20,905/microL) with a sixfold increase in monocytes and two- to threefold increase in lymphocytes. Leukocyte counts declined promptly after cessation of the infusion but remained above baseline for as long as 2 weeks in some patients. These results suggest that GM- CSF may be useful as an adjuvant therapy by stimulating myelopoiesis in cancer patients.     

Use of recombinant human granulocyte-macrophage colony-stimulating factor in graft failure after bone marrow transplantation

The effect of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) was evaluated in 37 patients with marrow graft failure after allogeneic (n = 15), autologous (n = 21), or syngeneic (n = 1) bone marrow transplantation. rhGM-CSF was administered by 2-hour infusion at doses between 60 and 1,000 micrograms/m2/d for 14 or 21 days. At doses of less than 500 micrograms/m2, rhGM-CSF was well-tolerated and did not exacerbate graft-versus-host disease in allogeneic transplant recipients. No patient with myelogenous leukemia relapsed while receiving rhGM-CSF. Twenty-one patients reached an absolute neutrophil count (ANC) greater than or equal to 0.5 x 10(9)/L within 2 weeks of starting therapy while 16 did not. None of seven patients who received chemically purged autologous marrow grafts responded to rhGM-CSF. The survival rates of GM-CSF-treated patients were significantly better than those of a historical control group.     

Immunization with recombinant human granulocyte-macrophage colony-stimulating factor as a vaccine adjuvant elicits both a cellular and humoral response to recombinant human granulocyte-macrophage colony-stimulating factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is an important cytokine for the generation and propagation of antigen-presenting cells and for priming a cellular immune response. We report here that use of recombinant human GM-CSF (rhGM-CSF), administered as an adjuvant in a peptide-based vaccine trial given monthly by intradermal injection, led to the development of a T-cell and antibody response to rhGM-CSF. An antibody response occurred in the majority of patients (72%). This antibody response was not found to be neutralizing. In addition, by 48-hour delayed type hypersensitivity (DTH) skin testing, 17% of patients were shown to have a cellular immune response to the adjuvant rhGM-CSF alone. Thymidine incorporation assays also showed a peripheral blood T-cell response to rhGM-CSF in at least 17% of the patients. The generation of rhGM-CSF-specific T-cell immune responses, elicited in this fashion, is an important observation because rhGM-CSF is being used as a vaccine adjuvant in various vaccine strategies. rhGM-CSF-specific immune responses may be incorrectly interpreted as antigen-specific immunity, particularly when local DTH responses to vaccination are the primary means of immunologic evaluation. We found no evidence of hematologic or infectious complications as a result of the development of rhGM-CSF-specific immune responses.     

Molecular cloning and in vivo evaluation of canine granulocyte-macrophage colony-stimulating factor

Canine granulocyte-macrophage colony-stimulating factor (caGM-CSF) was cloned and expressed to allow further investigation of GM-CSF in a large animal model. The cDNA is 850 base pairs (bp) long and encodes a peptide of 144 amino acids. The nucleotide and amino acid sequence homology between caGM-CSF and human GM-CSF (hGM-CSF) is 80% and 70%, respectively. A mammalian expression vector pCMV/CAGM was constructed and used to transfect COS cells for expression of caGM-CSF. Supernatant from transfected COS cells enriched with caGM-CSF was shown to have significant stimulating activity in granulocyte-macrophage colony forming unit (CFU-GM) assays of canine marrow. caGM-CSF, expressed from bacteria, was used to treat seven dogs at varying doses twice daily subcutaneously (sc) for 14 to 16 days. Circulating blood neutrophils and monocytes increased significantly. The increase in circulating eosinophils was variable. Thrombocytopenia developed during administration of caGM-CSF but corrected rapidly after cessation of treatment. Evaluation of survival times of 51Cr-labeled autologous platelets suggested increased consumption as the primary reason for thrombocytopenia. A species-specific GM-CSF will be a useful tool for hematologic or immunologic studies in dogs.     

Primitive human hematopoietic progenitor cells express receptors for granulocyte-macrophage colony-stimulating factor

Most cytokines act only synergistically in assays of primitive progenitor cell proliferation, and effects have usually been observed first after prolonged cell culture. Studies reporting that primitive progenitors lack receptors for a number of cytokines, including granulocyte-macrophage colony stimulating factor (GM-CSF), could indicate that several "synergistic" cytokines primarily affect cells that have differentiated in vitro. Here, however, we show that freshly isolated primitive progenitor cells (CD34hi CD38-) express receptors for GM-CSF at levels 20%-30% of granulo-monocytic progenitors. Although GM-CSF had minimal effects on the survival or proliferation of primitive progenitors when added alone, the cytokine enhanced stem cell factor (SCF) induced cell cycle entry in the first generation. The effect was not observed when cells were incubated sequentially with SCF and GM-CSF. The results suggest that the synergistic effects of GM-CSF are mediated directly on primitive progenitor cells and that the cytokine may be useful to enhance cell cycle entry of hematopoietic stem cells.     

Treatment of active Crohn's disease with recombinant human granulocyte-macrophage colony-stimulating factor

Treatment for Crohn's disease is aimed at immunosuppression. Yet inherited disorders associated with defective innate immunity often lead to development of a Crohn's-like disease. We performed an open-label dose-escalation trial (4-8 microg/kg per day) to investigate the safety and possible benefit of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the treatment of 15 patients with moderate to severe Crohn's disease. No patients had worsening of their disease. Adverse events were negligible and included minor injection site reactions and bone pain. Patients had a significant decrease in mean Crohn's disease activity index (CDAI) score during treatment (p<0.0001). After 8 weeks of treatment, mean CDAI had fallen by 190 points. Overall, 12 patients had a decrease in CDAI of more than 100 points, and eight achieved clinical remission. Retreatment was effective, and treatment was associated with increased quality-of-life measures. GM-CSF may offer an alternative to traditional immunosuppression in treatment of Crohn's disease.     

In vivo stimulation of megakaryocytopoiesis by recombinant murine granulocyte-macrophage colony-stimulating factor

Murine recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) was injected in mice, and the effects on bone marrow, splenic megakaryocytes, megakaryocyte precursors (megakaryocyte colony-forming units [CFU-Meg]) were evaluated. In mice injected three times a day for 6 days with 12,000 to 120,000 U rGM-CSF, no significant modification of both platelet levels and mean platelet volume was observed, while there was a twofold increase in blood neutrophils. However, the rate of platelet production, as assessed by the measurement of 75selenomethionine incorporation into blood platelets, was On the contrary, administration of up to 384,000 U rGM-CSF two times a day for 2 days, as for a typical "thrombopoietin assay," failed to modify platelet production. A significant dose-related increase in the number of splenic megakaryocytes occurred in mice receiving 60,000 to 120,000 U rGM-CSF, while a slight increase in the number of bone marrow megakaryocytes was observed in mice injected with 120,000 U rGM-CSF. The proportion of bone marrow megakaryocytes with a size less than 18 microns and greater than 35 microns resulted significantly higher in mice receiving rGM-CSF in comparison with controls; an increase in the percentage of splenic megakaryocytes greater than 35 microns was also observed. A statistically significant increase in the total spleen content of CFU-Meg was observed after administration of 90,000 and 120,000 U rGM-CSF three times a day for 6 days, while no effect on bone marrow CFU-Meg was recorded, irrespective of the dose delivered. Finally, 24 hours after a single intravenous injection of rGM-CSF, there was a significant increase in the proportion of CFU-Meg in S-phase, with the splenic progenitors being more sensitive than bone marrow-derived CFU-Meg. These data indicate that rGM-CSF has in vivo megakaryocyte stimulatory activity, and are consistent with previous in vitro observations. However, an effective stimulation of megakaryocytopoiesis in vivo, bringing about an increase in the levels of blood platelets, may require interaction of rGM-CSF with other cytokines.     

Effect of granulocyte-macrophage colony-stimulating factor on lymphokine-activated killer cell induction

The treatment of cancer with lymphokine-activated killer (LAK) cells in conjunction with high-dose interleukin-2 (IL-2) has been limited by the toxicity of IL-2 and the narrow range of tumors that respond to therapy. Cytokines that are capable of augmenting lower doses of IL-2 are, therefore, a major focus of research. We report here that granulocyte-macrophage colony-stimulating factor (GM-CSF) can augment low-dose IL-2 LAK induction from murine splenocytes. Anti-tumor necrosis factor alpha (anti-TNF alpha) or anti-interferon gamma (anti- IFN gamma) monoclonal antibodies did not inhibit (IL-2 + GM-CSF)- induced LAK generation, indicating that GM-CSF augmentation does not require TNF alpha or IFN gamma activity. Depletion of natural killer cells before culture did not inhibit low-dose IL-2-induced LAK generation or the ability of GM-CSF to augment LAK generation. In contrast, depletion of both CD4+ and CD8+ T cells before culture inhibited the generation of LAK activity. However, depletion of only CD4+ T cells, or only CD8+ T cells, did not inhibit the generation of IL-2 or (IL-2 + GM-CSF) LAK activity. These results suggest that LAK precursors are present in both the CD4+ and CD8+ T-cell populations and suggest that the addition of GM-CSF to low-dose IL-2 may result in the generation of T-derived LAK cells.     

Effect of granulocyte-macrophage colony-stimulating factor inducer on left ventricular remodeling after acute myocardial infarction

OBJECTIVES: We sought to determine the influence of granulocyte-macrophage colony-stimulating factor (GM-CSF) induction on post-myocardial infarction (MI) remodeling, especially in relation to the inflammatory response and myocardial fibrosis. BACKGROUND: Granulocyte-macrophage colony-stimulating factor modifies wound healing by promoting monocytopoiesis and infiltration of monocytes and macrophages into injured tissue; however, the effect of GM-CSF induction on the infarct healing process and myocardial fibrosis is unclear. METHODS: A model of MI was produced in Wistar rats by ligation of the left coronary artery. The MI animals were randomized to receive GM-CSF inducer (romurtide 200 microg/kg/day for 7 consecutive days) (MI/Ro) or saline (MI/C). RESULTS: Echocardiographic and hemodynamic studies on day 14 revealed increased left ventricular (LV) end-diastolic dimension, decreased fractional shortening, elevated LV end-diastolic pressure, and decreased LV maximum rate of isovolumic pressure development in MI/Ro compared with MI/C. Immunoblotting showed that expression of transforming growth factor (TGF)-beta1 in the infarcted site on day 3 after MI was decreased in MI/Ro compared with MI/C. In the infarcted site, TGF-beta1, collagen type I and type III messenger ribonucleic acid (mRNA) expression on day 3, and collagen content on day 7 were reduced in MI/Ro compared with MI/C, in association with marked infarct expansion. In MI/Ro, monocyte chemoattractant protein-1 mRNA level and the degree of infiltration of monocyte-derived macrophages (ED-1-positive)were greater in the infarcted site on day 7 than those in MI/C. CONCLUSIONS: The GM-CSF induction by romurtide facilitated infarct expansion in association with the promotion of monocyte recruitment and inappropriate collagen synthesis in the infarcted region during the early phase of MI.