Inhibition of agar colony formation by partially purified granulocyte extracts (chalone)

Human granulopoiesis in vitro--medium-dependent growth regulation by a granulocyte-derived inhibitor

A number of reports have indicated that mature blood granulocytes produce regulators that inhibit proliferation of progenitor cells in the bone marrow. However, this concept of negative feedback of granulopoiesis is still controversial. To examine whether conflicting results may depend upon the experimental set-up, we have compared colony formation by human bone marrow cells in different growth media. Unmodified McCoy's medium, which in feeder layer cultures supports the formation of large numbers of colonies, was a poor growth medium in cultures supplied with crude or recombinant colony stimulating factor (CSF). The colony formation improved when the medium was supplemented with defined additives. In CMRL 1066 cultures, granulocyte extract (GRE) consistently caused a strong inhibition of colony formation. In contrast, with unmodified McCoy's medium, granulocyte extract enhanced colony formation in a dose-dependent manner. The enhancing effect of granulocyte extract coincided with low colony numbers in the control cultures. The stimulatory effect of granulocyte extract in McCoy's medium, switched to strong inhibition when thymidine, a component of CMRL 1066 medium, was added. The inhibitory and stimulatory activities were found in the same molecular weight fractions (30-60 kD) after gel filtration. Both modulators in granulocyte extract appeared to be independent of monocytes and T lymphocytes in the bone marrow, as shown by removal of these cells with magnetic microspheres coated with specific monoclonal antibodies. The present work shows that regulation of cell proliferation in vitro depends strongly on culture conditions, such as choice of medium. It appears that thymidine acts as co-factor for the inhibitor in granulocyte extract.

Colony inhibiting factor in mature granulocytes from normal individuals and patients with chronic myeloid leukemia

Inhibitory activity in extract from human blood granulocytes was tested on granulocyte-macrophage colony formation in vitro. The inhibition depended on the type of serum used. With mouse BMC and FCS in the cultures, extract corresponding to 2.5 X 10(4) granulocytes/ml reduced the colony number by 35%, and extract from 2 X 10(5) cells caused maximal inhibition (80-90%). With HS and mouse BMC the colony number was reduced by only 11-12%, but stronger inhibition (55%) was observed when the serum concentration was reduced. With both types of sera the total cell number per culture plate was reduced relatively more than the colony number. Human GM-CFC were as sensitive as mouse GM-CFC, and extract from CML granulocytes inhibited less (p less than 0.01) than extract from normal cells. Biochemical studies indicated that the inhibitor is a protein with a molecular weight of 30-60,000. Lactoferrin, a putative inhibitor of CSF production, did not inhibit spontaneous or CSF-induced colony formation in these studies.

Effects of a hemoregulatory peptide (HP5b) on erythroid and myelopoietic colony formation in vitro

A hemoregulatory peptide (HP5b) associated with mature human granulocytes has been investigated for inhibitory effects on murine hemopoietic stem cells in vitro. Both highly purified peptide from natural sources and a synthetic analog peptide have been investigated in parallel. Strong inhibitory effects were found on myelopoietic colony formation in the dose range 10(-13)-10(-5) mol/l. On exceeding this dose, the inhibitory effect disappeared. Moderate to slight inhibitory effects on erythroid colony formation (BFU-E and CFU-E) from adult animals were only seen in 1,000 X the optimal doses for myelopoiesis. No effect was found on CFU-E from fetal liver. The peptide thus has a selective effect on myelopoiesis in a certain dose range. A regulatory mechanism for the peptide on hemopoiesis is proposed.

In vivo stimulation of murine granulopoiesis by human urinary extract from patients with aplastic anemia

Significant in vivo stimulation of granulopoiesis was induced in mice by the administration of an extract from the urine of patients with aplastic anemia (AA). Sialic acid has been identified as an important molecular component for the in vivo biological activity of this granulopoietic factor, "granulopoietin," which is distinct and different from endotoxin. Urine from patients with AA was successively fractionated by Sephadex G-50 and DEAE-cellulose chromatography. The resultant extract, which we refer to as AA urinary extract, contained approximately equal to 44 international units of erythropoietin per A unit of protein and induced 15,000 colonies of granulocyte/macrophage precursor cells (granulocyte/macrophage colony-forming units, CFU-gm) per A unit of protein with mouse bone marrow. Eight daily intraperitoneal injections of this extract in mice induced a 6.2-fold increase in peripheral blood granulocytes and a 14.6-fold increase of splenic CFU-gm, with concomitant increases in the proliferation rates of CFU-gm in both bone marrow and spleen. Pretreatment of the AA urinary extract with sialidase significantly diminished these granulopoietic effects in vivo (P less than 0.001). In contrast, both extracts (i.e., native AA and sialidase-treated AA urinary extracts) revealed high granulocyte/macrophage colony-stimulating factor activity in vitro when clonal assays were performed with mouse bone marrow. Increased in vivo and in vitro granulopoietic activities were found in the concanavalin A "break-through" fraction, indicating that these activities were due to protein(s) that did not bind to the lectin. These results reveal that this urinary extract from patients with AA is capable of inducing significant granulopoiesis in mice and that sialic acid is an important component in the maintenance of this granulopoietic effect in vivo but not in vitro.

Circadian variations in the committed stem cell responsiveness to granulopoiesis inhibitory factor (chalone) in vitro

The effect of inhibitory extracts of human granulocytes (chalone) on the circadian rhythm of myelopoietic colony formation in soft agar (CFUc) was studied over one year. Normally, the number of bone marrow CFUc shows a strong circadian rhythm. Preincubation of the cells with the extracts before plating modulated this rhythm with phase shifts and modifications of amplitude. The effects of the extracts oscillated between significant inhibition and stimulation over a 24 h period. No significant seasonal variations in the inhibitory effects were found.

Effect of granulocytic chalone on the growth rate of continuous cell lines propagated in vitro: a new assay system

The progress of research on granulocytic chalone has been hampered by a lack of reliable assay systems. This paper reports the use of continuous cell lines growing in liquid suspension culture as a new method for assessing the effect of granulocytic chalone on cell proliferation. Partially purified granulocytic chalone (PPGC) was added to cultures of a rat myeloid cell line (W25), a human myeloid cell line (HL60), a human B lymphocytic cell line (8392), and a human T lymphocytic cell line (8402). The growth rate of the target cell populations was directly assessed by serial cell counts. PPGC pretreatment resulted in a significant inhibition of cell proliferation of the 2 myeloid permanent cell lines, while the growth rate of the lymphocytic cell lines was not affected. Moreover, inhibition of cell proliferation was spontaneously reversed when PPGC treatment was discontinued. Since PPGC from ox leucocytes displayed an inhibitory effect on cell proliferation which was specific to the myeloid cells, spontaneously reversible and not species-specific, it appears to have all the essential properties of a granulocytic chalone.

Biological properties of partially purified granulocyte extract (chalone) assayed in soft agar culture

The inhibitory effects of partly purified low molecular weight granulocyte extracts (GE) from human peripheral blood were investigated on mouse myelopoietic cells in agar cultures. By repeated freezing and thawing the inhibitory effect of the extract was lost, and instead a stimulatory effect was seen. The stimulation was seen mainly as an increase of colonies and clusters from the sixth day of culture. The degree of inhibition depended on the length of the preincubation time. After half an hour a stable and lasting inhibition was found. The biological effects of the extracts were temperature dependent. Inhibition or stimulation was seen when the target cells were exposed to GE at 37 degrees C and not at 4 degrees C. Colony formation in agar showed circannual variation with maxima in spring and autumn and minima in summer and winter. The data indicated that the inhibitory effect of GE did not show circannual variations.

Control of CFUc proliferation by selective endogenous inhibitors

The susceptibility of mouse bone marrow colony forming cells (CFUc) to three different types of proliferation inhibitors in capillary semisolid agar gel was studied. GI-3, a target specific peptide containing granulocyte fraction, T4-1, an oligospecific thymic factor of proteid nature, and the alkylating cytostatics dianhydrogalactitol (DAD) inhibit myeloid colony formation as a function of concentration. The respective MED values amount to 8, 10, and 0.002 microgram/ml. When compared with this same parameter 3H-TdR incorporation into DNA of liquid bone marrow cultures showed a single fold charge for the endogenous inhibitors (GI-3, T4-1) for the cytostatic (DAD) a 3 to 4 fold lower difference. It was demonstrated, that in competitive antagonism of GI-3 and colony stimulating factor the inhibitor prevails over CSF.

Chalone inhibition of granulocyte colony growth in agar: kinetic quantitation by capillary tube scanning

Mouse bone marrow cells were seeded into capillary tubes containing agar with colony stimulating factor. The development of myelomonocytic clusters and colonies was followed by daily tube scanning using their light scattering properties. Three kinetic scanning parameters were determined and the significance of different threshold settings was evaluated; viz. the number of signals, the mean signal height and the signal integrals. The inhibitory effect of two extracts with known granulocyte chalone activity which had been prepared from human peripheral leukocytes and rat bone marrow cells, was followed with the scanning method. A continuous reduction of clusters and colony formation and their growth throughout the incubation period was observed which suggested a sustained retardation of proliferation of both the stem cells committed for myelomonopoiesis and their progeny.