Effect of recombinant human granulocyte macrophage‐colony stimulating factor in long‐term marrow cultures from patients with aplastic anemia

Abstract

The hematopoietic system in patients with aplastic anemia (AA) shows both quantitative and qualitative deficiencies, i.e., reduced numbers of hematopoietic progenitor cells (HPC) and impaired HPC proliferation in long-term marrow cultures (LTMC). Since re-combinant human granulocyte macrophage-colony stimulating factor (rhGM-CSF) has been shown to be a potent stimulator of normal hematopoiesis, both in vivo and in vitro, in the present study we wanted to assess the possibility of stimulating hematopoiesis in LTMC from 17 patients with AA, by weekly addition of rhGM-CSF (10 ng/ml). In LTMC from 11 patients (group of responders), rhGM-CSF induced a significant increase (4.8-fold, compared with untreated cultures) in the levels of myeloid progenitor cells; in contrast, in six patients (group of nonresponders), myeloid progenitors were refractory to this cytokine. In the group of responders, rhGM-CSF also induced a pronounced increment in the levels of nonadherent and adherent cells (5.99-and 5.18-fold, respectively, compared with untreated cultures). Among the different myelopoietic lineages, rhGM-CSF preferentially stimulated the macrophagic lineage; this was evident both at the progenitor and mature cell levels. Interestingly, the effect of rhGM-CSF in LTMC from AA patients was only transient. Indeed, the effects mentioned above were observed only during the first three weeks of culture; afterwards, myeloid progenitor and nonadherent cell levels in treated cultures declined, practically reaching the levels observed in untreated cultures. At the moment, we do not know whether this transient stimulatory effect is due to the production of inhibitory cytokines, by macrophages generated in response to rhGM-CSF, or to the exhaustion of the HPC pool in AA cultures. In all 17 patients, rhGM-CSF had no effect on the kinetics of erythroid or multipotent progenitor cells. These results are in keeping with clinical studies in which it has been observed that most AA patients treated with rhGM-CSF show increments in circulating monocytes and granulocytes, as well as in bone marrow cellularity. However, little or no effect is observed on erythropoiesis. The actual mechanisms involved in the in vitro effects of rhGM-CSF on myeloid progenitor cells from AA bone marrow are still not completely understood. Future studies on this issue should be encouraged, since they may help to understand the in vivo (clinical) effects of this cytokine. Am.

Tumor necrosis factor‐α levels in long‐term marrow cultures from patients with aplastic anemia: modulation by granulocyte‐macrophage colony‐stimulating factor

“…In keeping with our previous report [10], addition of rhGM-CSF to LTMC from AA patients resulted in a signi®cant increase in CFC levels, as compared to untreated cultures, during the ®rst two weeks of culture ( Figure 2). The median increase observed was 4.8-fold, on week 1, and 3.9-fold on week 2.…”

“…The levels of myeloid, erythroid and multipotent progenitor cells in LTMC were followed throughout a 7-week culture period. The growth patterns observed were similar to those reported previously by us [7,10]. At all time points analyzed, CFC levels were signi®cantly higher (P < 0.05) in cultures from normal BM than in cultures from AA patients and by week 6 no CFC were detected in AA LTMC (Figure 1).…”

“…However, such an increase was only transient. Indeed, after 5 weeks, rhGM-CSF-treated cultures showed reduced CFC levels which were even lower than those observed in untreated cultures [10].…”

“…Recently, we tried to improve the in vitro growth of hematopoietic progenitor cells from AA patients in LTMC by adding recombinant human Granulocyte-Macrophage Colony-Stimulating Factor (rhGM-CSF), a hematopoietic stimulatory cytokine [10]. Our results showed that rhGM-CSF induced a signi®cant increase in the levels of CFC during the ®rst two weeks of culture.…”

Granulocyte-macrophage colony stimulating factor and immunosuppression in the treatment of pediatric acquired severe aplastic anemia

“…Infections continue to be a major cause of morbidity and mortality in patients with SAA 3. Because the addition of a hematopoietic cytokine may allow for an enhanced myeloid response and a decreased risk of infection 4, cytokine therapy in combination with IS has been studied.…”