Tissue sources of bone marrow colony stimulating factor

Possible tissue sources in C57BL mice of the serum factor stimulating colony formation in vitro by mouse bone marrow cells have been investigated. A reproducible technique employing batch chromatography on calcium phosphate gel was developed for the extraction and assay of material with colony stimulating activity from mouse tissues. Sixteen hematopoietic and non-hematopoietic tissues from C57BL mice were found to vary widely in their content of extractable activity. Characterisation of the colony stimulating factors (CSF's) from these tissues by assay of stepped concentrations of eluate showed that CSF's from most tissues were similar in chromatographic behavior, but all differed significantly from those of serum in being both more disperse and more firmly bound to calcium phosphate gel. Male submaxillary salivary gland gave the richest yield of CSF. CSF from this source displayed a greater dispersity on and affinity to calcium phosphate, a lower electrophoretic mobility and a smaller average sedimentation coefficient than that from any other source investigated. Colony morphology appeared to be identical for all tissue sources investigated.     

Colony stimulating activity of serum from germfree normal and leukemic mice

Serum from germfree Swiss/HaM mice exhibited a reduced capacity to stimulate granulocytic and mononuclear cell colony formation by DBA/1 bone marrow cells in vitro when compared with serum from conventional Swiss/HaM mice. Sera from germfree preleukemic and leukemic AKR mice exhibited strong colony stimulating activity, indicating that the increased colony stimulating activity previously observed in the serum of conventional leukemic mice is not the consequence of bacterial or fungal infections supervening in leukemic animals with deficient immune responses.     

EFFECTS OF HUMAN LEUKOCYTE CONDITIONED MEDIUM ON MOUSE HAEMOPOIETIC PROGENITOR CELLS

Medium conditioned by human peripheral blood leukocytes (HLCM) was studied for its in vitro effects on haemopoietic progenitor cells (CFU-s and CFU-c) present in mouse bone marrow. HLCM has poor colony stimulating activity in semi-solid cultures of mouse bone marrow cells. but invariably increases the number of colonies obtained in the presence of plateau levels of semi-purified colony stimulating factor (CSF). In liquid cultures, HLCM appears to contain a potent initiator of DNA synthesis in CFU-s. an activity which coincides with an increased CFU-s maintenance and causes a three- to four-fold increase in CFU-c number. It is apparent from this study that HLCM, in addition to stimulating colony formation in cultures of human bone marrow cells, has a profound in vitro effect on primitive haemopoietic progenitor cells of the mouse, which cannot be attributed to CSF.     

Proliferative effects of purified granulocyte colony-stimulating factor (G-CSF) on normal mouse hemopoietic cells

When granulocyte colony-stimulating factor (G-CSF), purified to homogeneity from mouse lung-conditioned medium, was added to agar cultures of mouse bone marrcw cells, it stimulated the formation of small numbers of granulocytic colonies. At high concentrations of G-CSF, a small proportion of macrophage and granulocyte-macrophage colonies also developed. G-CSF stimulated colony formation by highly enriched progenitor cell populations obtained by fractionation of mouse fetal liver cells using a fluorescence-activated cell sorter, indicating that G-CSF probably acts directly on target progenitor cells. Granulocytic colonies stimulated by G-CSF were small and uniform in size, and at 7 days of culture were composed of highly differentiated cells. Studies using clonal transfer and the delayed addition of other regulators showed that G-CSF could directly stimulate the initial proliferation of a large proportion of the granulocvte-macrophage progenitors in adult marrow and also the survival and/or proliferation of some multipotential, erythroid, and eosinophil progenitors in fetal liver. However, G-CSF was unable to sustain continued proliferation of these cells to result in colony formation. When G-CSF was mixed with purified granulocyte-macrophage colony-stimulating factor (GM-CSF) or macrophage colony-stimulating factor (M-CSF), the combination stimulated the formation by adult marrow cells of more granulocyte-macrophage colonies than either stimulus alone and an overall size increase in all colonies. G-CSF behaves as a predominantly granulopoietic stimulating factor but has some capacity to stimulate the initial proliferation of the same wide range of progenitor cells as that stimulated by GM-CSF.     

Haemopoietic growth factors: their role in cell development and their clinical use

Mature blood cells are derived from haemopoietic stem cells which grow and proliferate to give rise to progenitor cells more restricted in their proliferation and differentiation capacity. These in turn give rise to cells belonging to any of the haemopoietic lineages. The haemopoietic growth factors interleukin 3, granulocyte-macrophage colony-stimulating factor, granulocyte colony stimulating factor, macrophage colony-stimulating factor and erythropoietin act on haemopoietic cells to promote cell survival, proliferation, differentiation and maturation, as well as many functions of the mature cells. These factors, now purified to homogeneity and molecularly cloned have recently become available. This has facilitated studies of their roles in cell production, and the range of target cells sensitive to them in vitro and in vivo in several species. The latter experimental data led to the first clinical trials where these factors have been used successfully in several clinical settings: erythropoietin to correct the anaemia of renal disease; granulocyte and granulocyte-macrophage colony-stimulating factors to accelerate haemopoietic regeneration after chemotherapy and bone marrow transplantation, and in other situations where increase in the numbers of white cells and stimulation of their function were required. The results to date allow optimism; the clinical use of growth factors not only in haematology and oncology, but in wider fields of medicine may well constitute a major breakthrough in the near future.     

THE PRESENCE OF A CSF ENHANCING ACTIVITY IN THE SERUM OF ENDOTOXIN-TREATED MICE

Serum taken from mice a few hours after injection of endotoxin is a potent source of a stimulator of in vitro myelopoiesis. By means of dose-response studies, the biological activity of this material was compared to that of a colony stimulating factor (CSF) from pregnant mouse uteri. Postendotoxin serum appears to contain two different activities: a stimulating activity which may be identical to CSF and an activity which augments the action of CSF. The separate nature of the two activities is demonstrated by differences in the rate at which they are diluted out and by differences in the time at which they are maximally present after endotoxin administration. It is therefore concluded that the colony-stimulating properties of postendotoxin serum are not due solely to CSF present in the serum.     

Therapeutic implications of serum factors inhibiting proliferation and inducing differentiation of myeloid leukemic cells

Murine post-endotoxin sera contain high levels of myeloid colony-stimulating factor(s) (GM-CSF) and factors capable of inducing terminal granulocyte and macrophage differentiation of the murine myelomonocytic leukemic cell line WEHI-3. The combination of C. parvum and endotoxin induced a serum activity capable of inducing tumor necrosis and inhibiting leukemic colony formation in vitro. This factor (TNF) could be separated from the differentiation-inducing factor (GM-DF) and from CSF. In conjunction with a Phase I trial of highly purified endotoxin in patients with advanced malignancy, we monitored human post-endotoxin sera for CSF and GM-DF. Induction of GM-DF occurred maximally at 2-6 h and was associated with increased serum levels of CSF active against the patient's own bone marrow. Following repeated injections of escalating doses of endotoxin, persistent levels of GM-DF were detected both pre-endotoxin and 24 h post-endotoxin treatment. The ability to induce repeatedly a serum protein with potent capacity to promote terminal differentiation of myelomonocytic leukemic cells suggests a possible therapeutic role in human myeloid leukemias.     

THE IN VITRO DIFFERENTIATION OF DENSITY SUB-POPULATIONS OF COLONY-FORMING CELLS UNDER THE INFLUENCE OF DIFFERENT TYPES OF COLONY-STIMULATING FACTOR

The in vitro proliferation and differentiation of myeloid progenitor cells (CFU-c) in agar culture from CBA/Ca mouse bone marrow cells was studied. Density sub-populations of marrow cells were obtained by equilibrium centrifugation in continuous albumin density gradients. The formation of colonies of granulocytes and/or macrophages was studied under the influence of three types of colony-stimulating factor (CSF) from mouse lung conditioned medium CSF_MLCM), post-endotoxin mouse serum (CSF_ES) and from human urine (CSF_Hu). The effect of the sulphydryl reagent mercaptoethanol on colony development was also examined. The density distribution of CFU-c was dependent on the type of CSF. Functional heterogeneity was found among CFU-c with partial discrimination between progenitor cells forming pure granulocytic colonies and those forming pure macro-phage colonies. Mercaptoethanol increased colony incidence but had no apparent effect on colony morphology or the density distribution of CFU-c.     

Stimulation by normal and leukemic mouse sera of colony formation in vitro by mouse bone marrow cells

Using a modification of the agar gel method for bone marrow culture, serum from various strains of mice has been tested for colony stimulating activity. Ninety percent of sera from AKR mice with spontaneous or transplanted lymphoid leukemia and 40–50% of sera from normal or preleukemic AKR mice stimulated colony formation by C57B1 bone marrow cells. Sera from 6% of C3H and 30% of C57B1 mice stimulated similar colony formation. The incidence of sera with colony stimulating activity rose with increasing age. All colonies were initially mainly granulocytic in nature but later became pure populations of mononuclear cells. Bone marrow cells exhibited considerable variation in their responsiveness to stimulation by mouse serum. Increasing the serum dose increased the number and size of bone marrow cell colonies and with optimal serum doses, 1 in 1000 bone marrow cells formed a cell colony. Preincubation of cells with active serum did not stimulate colony formation by washed bone marrow cells. The active factor in serum was filterable, non-dialysable and heat and ether labile.     

Bone Marrow Colony-stimulating Activity of Sera in Infectious Mononucleosis

From 44 to 100% of sera from patients with infectious mononucleosis exhibited the capacity to stimulate colony formation in vitro by mouse bone marrow cells. The proportion of sera with colony-stimulating activity was highest in patients with a short fever period and developing low Paul-Bunnell titres. Patients with a more severe course of the disease generally displayed no, or only weak, colony-stimulating activity in their sera, and also had higher Paul-Bunnell titres. The level of serum colony-stimulating activity tended to fall in the convalescent stages of the disease.     

Physical separation of colony stimulating cells from in vitro colony forming cells in hemopoietic tissue

Hemopoietic colony formation in agar occurred spontaneously in mass cultures of marrow cells obtained from a number of species (guinea pig, rat, lamb, rabbit, pig, calf, human and Rhesus monkey). This contrasted with the observation that colony formation by mouse bone marrow exhibited an absolute requirement for an exogenous source of a colony stimulating factor. Analysis of spontaneous colony formation in Rhesus monkey marrow cultures revealed the presence of a cell type in hemopoietic tissue, capable of elaborating colony stimulating factor when used to condition media or as feeder layers. Equilibrium density gradient centrifugation separated colony stimulating cells from in vitro colony forming cells in monkey bone marrow. Separation studies on spleen, blood and marrow characterized the stimulating cells as of intermediate density, depleted or absent in fractions enriched for cells of the granulocytic series and localized in regions containing lymphocytes and monocytes. Adherence column separation of peripheral blood leukocytes showed the stimulating cells to be actively adherent, unlike the majority of lymphocytes, and combined adherence column and density separation indicated that stimulating cells were present in hemopoietic tissue within the population of adherent lymphocytes or monocytes.     

SERUM LEVELS OF COLONY STIMULATING FACTOR(S) AND THE GROWTH OF BONE MARROW CELLS IN DIFFUSION CHAMBERS

Fluctuations in the body fluids of long-ranged humoral substance(s) capable of stimulating the growth of bone marrow granulocytic and macrophage-like cells in diffusion chamber cultures in vivo, was observed after whole body irradiation of mice. The fluctuation pattern was similar to that of the in vitro colony stimulating factor(s) of the sera of irradiated mice which indicates a relation between in vivo and in vitro active factor(s).     

Differentiation of Mouse Bone Marrow Precursor Cells into Neutrophil Granulocytes by an Activity Separation from WEHI-3 Cell-Conditioned Medium

Colonies comprised exclusively of neutrophil granulocytes have been obtained by growing mouse bone marrow cells in nutrient semisolid agar cultures. A stimulator of predominantly granulocyte colony formation was present in the breakthrough fraction of preparations of colony-stimulating activity separated on DEAE-Sephadex A. The source of colony-stimulating activity was concentrated conditioned medium of a murine myelomonocytic cell line (WEHI-3), which unfractionated stimulated the growth of colonies of granulocytes, macrophages, megakaryocytes, as well as mixed colony types. After stepwise column chromatography of the conditioned medium, the breakthrough fraction was shown to stimulate predominantly granulocyte colony formation, and the fraction eluted with 1 M NaCl was found to induce primarily macrophage colony growth. Colony morphology was independent of the concentration of eluate used. The morphology of colonies varied with increasing concentrations of the breakthrough fraction. At low concentrations, granulocyte colony formation was almost exclusively observed. With increasing concentrations of this fraction, an increasing proportion of the colonies were found to contain macrophages. The effect of concentration of this activity was in marked contrast to previous findings where the incidence of granulocyte colony formation was inversely related to the concentration of colony-stimulating activity. This differential responsiveness of cell to stimulus has previously been interpreted as low concentrations of a growth and differentiation factor being required for macrophage production and high concentrations of the same factor required for granulocyte formation. Separation of these activities by DEAE Sephadex chromatography, and alteration of the dose-response curve, such that granulocyte colony formation varies directly with the amount of stimulator, indicates that the differentiation of these two cell blood lineages may be controlled by separate entities.     

CD45+/CD133+ positive cells expanded from umbilical cord blood expressing PDX‐1 and markers of pluripotency

UCB (human umbilical cord blood) contains cells able to differentiate into non‐haematopoietic cell lineages. It also contains cells similar to primitive ESCs (embryonic stem cells) that can differentiate into pancreatic‐like cells. However, few data have been reported regarding the possibility of expanding these cells or the differential gene expression occurring in vitro. In this study, we expanded formerly frozen UCB cells by treatment with SCF (stem cell factor) and GM‐CSF (granulocyte–macrophage colony stimulating factor) in the presence of VPA (valproic acid). Gene expression profiles for beta cell differentiation and pluripotency (embryo stem cell phenotype) were analysed by RT‐PCR and immunocytochemistry. The results show a dramatic expansion (>150‐fold) of haematopoietic progenitors (CD45⁺/CD133⁺) which also expressed embryo markers of pluripotency (nanog, kfl‐4, sox‐2, oct‐3/4 andc‐myc), nestin, and pancreatic markers such as pax‐4, ngn‐3, pdx‐1 and syt‐1 (that is regulated by pdx‐1 and provides the cells with a Ca⁺⁺ regulation mechanism essential for insulin exocytosis). Our results show that UCB cells can be expanded to produce large numbers of cells of haematopoietic lineage that naturally (without the need of retroviral vectors or transposons) express a gene pattern compatible with endocrine pancreatic precursors and markers of pluripotency. Further investigations are necessary to clarify, first, whether in this context, the embryogenes expressed are functional or not, and secondly, since these cells are safer than cells transfected with retroviral vectors or transposons, whether they would represent a potential tool for clinical application.     

Potentiation of bone marrow colony growth in vitro by the addition of lymphoid or bone marrow cells

Colony formation and growth in vitro by C57B1 mouse bone marrow cells were analysed following stimulation by a standard dose of serum colony stimulating factor. Under restricted conditions, colony crowding was observed to potentiate colony growth rates. The addition of thymic or lymph node lymphoid cells or nonviable bone marrow cells also potentiated colony growth. Extensive reutilisation of nuclear material by bone marrow colony cells was observed when labeled lymphoid and bone marrow cells were added to the culture system. The results provide evidence that lymphocytes can exert trephocytic effects on proliferating hematopoietic cells.     

Synergism of leukemic blast growth factors in medium conditioned by human bladder carcinoma cell line 5637

Leukemic blast growth factors (LBGFs) are necessary for in vitro growth of clonogenic cells from patients with acute myeloblastic leukemia. As the human bladder carcinoma cell line 5637 had previously been reported to secrete abundant LBGFs into the culture supernatant, the LBGFs in 5637-conditioned medium (5637-CM) were characterized. Measurement of LBGFs was done using an in vitro leukemic blast colony assay in methylcellulose culture. LBGFs in 5637-CM were fractionated by anion exchange chromatography, and two peaks of activity were recovered. Pool B (high-salt eluent) and/or purified granulocyte colony-stimulating factor (G-CSF) were added to the clonogenic leukemic blast cell assays. It was found that pool B was more active than G-CSF in the majority of cases examined and that the two types of activity were synergistic in some cases.     

Enhancement by transforming growth factor-beta 1 (TGF-beta 1) of the proliferation of leukemic blast progenitors stimulated with IL-3.

We studied the effect of transforming growth factor-beta 1 (TGF-beta 1) on colony formation of leukemic blast progenitors from ten acute myeloblastic leukemia (AML) patients stimulated with granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), interleukin-6 (IL-6), or interleukin-1 beta (IL-1 beta). These CSFs and interleukins by themselves stimulated the proliferation of leukemic blast progenitors without adding TGF-beta 1. G-CSF, GM-CSF, and IL-3 stimulated blast colony formation in nine patients, IL-6 stimulated it in five, and IL-1 beta stimulated in four. TGF-beta 1 significantly reduced blast colony formation stimulated by G-CSF, GM-CSF, or IL-6 in all patients. In contrast, TGF-beta 1 enhanced the stimulatory effect of IL-3 on blast progenitors from three cases, while in the other seven patients TGF-beta 1 reduced blast colony formation in the presence of IL-3. To study the mechanism by which TGF-beta 1 enhanced the stimulatory effect of IL-3 on blast progenitors, we carried out the following experiments in the three patients in which it occurred. First, the media conditioned by leukemic cells in the presence of TGF-beta 1 stimulated the growth of leukemic blast progenitors, but such effect was completely abolished by anti-IL-1 beta antibody. Second, the addition of IL-1 beta in the culture significantly enhanced the growth of blast progenitors stimulated with IL-3. Third, leukemic cells of the two patients studied were revealed to secrete IL-1 beta and tumor necrosis factor-alpha (TNF-alpha) constitutively; the production by leukemic cells of IL-1 beta and TNF-alpha was significantly promoted by TGF-beta 1. Furthermore, the growth enhancing effect of TGF-beta 1 in the presence of IL-3 was fully neutralized by anti-IL-1 beta antibody. These findings suggest that TGF-beta 1 stimulated the growth of blast progenitors through the production and secretion of IL-1 beta by leukemic cells.     

Haemopoietic stem cells during development of mouse embryo.

Haemopoiesis in mammals takes place in yolk-sac and in mouse it can be detected on the 7th day of gestation. Erythropoietin (EPO) responsive cells can be detected from 7th day onwards. However, the cells committed to the myeloid lineage which can respond to the haemopoietic growth factor (viz. granulocyte macrophage colony stimulating factor; GM-CSF) can be demonstrated only on 10th day of gestation. At the same time, the 12-day spleen colony forming cells i.e. the late colony forming unit spleen (CFU-s) which are multipotent stem cells can also be detected. Data suggest that the stem cells seen in the embryo from 7-10 days of gestation may be a primitive population confined only to the yolk-sac. Liver haemopoiesis which begins in the liver of 13-day embryos is due to primitive haemopoietic pluripotent stem cells, arising de novo in the embryo and not in the yolk-sac, since no primitive pluripotent stem cells capable of repopulating lethally irradiated bone-marrow can be detected in the yolk-sac.     

Induction by recombinant human granulocyte colony-stimulating factor of differentiation of mouse myeloid leukemic M1 cells

The effect of recombinant human granulocyte colony-stimulating factor (G-CSF) on induction of differentiation of mouse myeloid leukemic M1 cells was examined. Purified G-CSF caused dose-dependent induction of phagocytic activity and lysozyme activity in M1 cells. Its half-maximally effective concentration was 10 ng/ml. On treatment of M1 cells with G-CSF (100 ng/ml) for 4 days, 30-50% of the cells differentiated morphologically into macrophage cells; 30-40% of the cells were blast cells and 20-30% of the cells were forms intermediate between blastic cells and mature macrophages.     

Stimulation of macrophage plasminogen activator activity by colony-stimulating factors

Colony-stimulating factors (CSFs) stimulate granulocyte-macrophage production from single hemopoietic progenitor cells. Various preparations of purified CSFs of two different subclasses have been shown here to stimulate a plasminogen-dependent fibrinolytic (plasminogen activator) activity from resident and starch-induced mouse peritoneal macrophages. Lymphocyte supernatants also stimulate macrophage plasminogen activator (PA) activitty. Since they contain colony stimulating activity, it is possible that one or more sublcasses of CSF in these supernatants is responsible for this effect. Since both colony-stimulating and macrophage growth activities have been detected at inflammatory sites, these findings could reflect a role for CSF in inflammatory processes.