Blast colony-forming cells in myelodysplastic syndrome: decreased potential to generate erythroid precursors.

In vitro colony-forming abilities of highly purified primitive hematopoietic cells in eight cases of myelodysplastic syndrome (MDS) were studied using the blast cell colony assay. Blast cell colony formation from seven normal bone marrow (NBM) samples was studied in parallel. Blast cell colonies were formed in 7/8 cases of MDS, the numbers not significantly differing from those generated by NBM. In contrast the more mature hematopoietic progenitors (granulocyte-erythroid-macrophage-megakaryocyte colony-forming unit, CFU-GEMM; erythroid burst-forming units, BFU-E; granulocyte colony-forming units, CFU-G; eosinophilic colony-forming units, CFU-Eo) were severely depressed in numbers in MDS marrow. After replating of blast cell colonies in secondary cultures, colonies were obtained in 5/8 MDS cases. A marked difference was evident in the composition of the secondary colonies between MDS and normal marrow. Whereas secondary colonies derived from normal blast cell colonies consisted of about 45% of erythroid cells, MDS blast colonies generated mainly colonies of the granulocytic-monocytic lineage and no erythroid colonies. The normal quantitative level of CFU-blast progenitors in MDS in the context of their impaired ability to generate lineage specific progeny upon secondary plating suggests that the incompetence of maturation of MDS may reside in the CFU-blast progenitor cell being incapable of properly responding to growth factor stimulation.

Positive and negative effects of tumor necrosis factor on colony growth from highly purified normal marrow progenitors.

The effects of recombinant human tumor necrosis factor alpha (TNF alpha) on colony growth were studied using highly enriched progenitor cells from normal human bone marrow. Supplementation of TNF to culture resulted in a dose-dependent suppression of granulocyte colony-stimulating factor (G-CSF) induced granulocytic colony formation and also erythropoietin (Epo) induced erythroid burst formation. However, the number of erythroid bursts, stimulated by interleukin-3 (IL-3) plus Epo, increased when TNF was added at comparable concentrations. Further, TNF enhanced eosinophilic colony growth induced by IL-3 or granulocytic-macrophage colony-stimulating factor (GM-CSF). In GM-CSF cultures TNF (100-1000 U/ml) also induced granulocytic and macrophage colonies. The addition of neutralizing antibodies against G-CSF, GM-CSF, or interleukin-6 (IL-6) to culture did not abrogate the observed effects of TNF, so that stimulation of myeloid colony growth was unlikely to result from the secondary induction of G-CSF or GM-CSF. TNF therefore exerts favourable effects on hematopoietic progenitors responsive to the more primitive colony-stimulating factors (IL-3, GM-CSF) and potent negative effects on precursors reactive to the single lineage G-CSF and Epo. These contrasting effects of TNF suggest that TNF, when available to marrow progenitors at similar tissue concentrations, may drive hematopoiesis within the progenitor cell compartment into selected directions.

Erythropoiesis in myelodysplastic syndrome: expression of receptors for erythropoietin and kit ligand.

Ineffective erythropoiesis due to an impaired response to erythropoietin (EPO) is a prominent abnormality in myelodysplastic syndromes (MDS). The growth factor kit ligand (KL) may restore the in vitro erythroid colony-forming response to EPO in a subset of patients. The inability of MDS erythroid progenitors to react properly to EPO and/or KL has not been resolved. We have investigated erythropoietin receptor (EPO-R) and KL receptor (c-kit) expression in 15 cases of MDS by FACS analysis. The percentage of bone marrow cells expressing the EPO-R from patients with MDS were comparable to normal marrow. No apparent correlation was found between the number of MDS cells coexpressing the EPO-R and CD34 and impaired erythroid response. C-kit was expressed in most MDS patients, including those not responding to KL in EPO-induced cultures. In nine MDS cases the different splice variants of the EPO-R were analyzed. MDS cells, like normal marrow, expressed the full length EPO-R. These results show that impaired erythroid response in MDS cannot be explained by a quantitative lack of receptors for EPO or KL and that most likely suppression of erythroid response is caused by defective receptor signalling following ligand binding, representing a functional defect within the receptor itself or at a level downstream of the receptor.

Synergistic effects between GM-CSF and G-CSF or M-CSF on highly enriched human marrow progenitor cells.

The human multilineage hematopoietic growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF) induces multipotent, erythroid, and eosinophil colony formation from highly enriched normal bone marrow cells. We have examined the effects of GM-CSF combined with granulocyte-CSF (G-CSF) or macrophage-CSF (M-CSF) on the monolineage granulocytic, eosinophilic, and macrophage progenitor cells (CFU-G, CFU-Eo, and CFU-M) in accessory cell depleted marrow fractions. GM-CSF effects were assessed in direct comparison with those of interleukin-3 (IL-3) plus G-CSF or M-CSF. GM-CSF strongly synergized with G-CSF in the formation of granulocytic colonies with respect to number and size and enhanced the in vitro survival of CFU-G. More immature cells were present in colonies induced by the mixture of GM-CSF and G-CSF than by G-CSF alone. GM-CSF also synergized with M-CSF in the formation of macrophage colonies (number and size). The addition of G-CSF and M-CSF did not influence eosinophil colony formation induced by GM-CSF or IL-3. Experiments directly comparing GM-CSF and IL-3 revealed that the effects of GM-CSF on G and M colony-forming cells were significantly greater than those of IL-3. The potent positive effects between GM-CSF and G-CSF as well as between GM-CSF and M-CSF provide a powerful mechanism of amplification of granulopoiesis and monocytopoiesis.

Peri-procedural use of rivaroxaban in elective percutaneous coronary intervention to treat stable coronary artery disease. The X-PLORER trial.

Patients on rivaroxaban requiring percutaneous coronary intervention (PCI) represent a clinical conundrum. We aimed to investigate whether rivaroxaban, with or without an additional bolus of unfractionated heparin (UFH), effectively inhibits coagulation activation during PCI. Stable patients (n=108) undergoing elective PCI and on stable dual antiplatelet therapy were randomised (2:2:2:1) to a short treatment course of rivaroxaban 10 mg (n=30), rivaroxaban 20 mg (n=32), rivaroxaban 10 mg plus UFH (n=30) or standard peri-procedural UFH (n=16). Blood samples for markers of thrombin generation and coagulation activation were drawn prior to and at 0, 0.5, 2, 6-8 and 48 hours (h) after start of PCI. In patients treated with rivaroxaban (10 or 20 mg) and patients treated with rivaroxaban plus heparin, the levels of prothrombin fragment 1 + 2 at 2 h post-PCI were 0.16 [0.1] nmol/l (median) [interquartile range, IQR] and 0.17 [0.2] nmol/l, respectively. Thrombin-antithrombin complex values at 2 h post-PCI were 3.90 [6.8]µg/l and 3.90 [10.1] µg/l, respectively, remaining below the upper reference limit (URL) after PCI and stenting. This was comparable to the control group of UFH treatment alone. However, median values for thrombin-antithrombin complex passed above the URL with increasing tendency, starting at 2 h post-PCI in the UFH-alone arm but not in rivaroxaban-treated patients. In this exploratory trial, rivaroxaban effectively suppressed coagulation activation after elective PCI and stenting.

Somatostatin and its cyclic octapeptide analog SMS 201-995 as inhibitors of proliferation of human acute lymphoblastic and acute myeloid leukemia.

Somatostatin (SS) is a 14 amino acid peptide which is secreted by the hypothalamus and the pancreatic islets. It expresses antiproliferative activity in various organ systems, experiments have suggested effects of SS on hematopoietic cells. Here we present investigations regarding the effect of SS and its analog SMS 201-995 (SMS) on the in vitro proliferation of acute lymphoblastic leukemia (ALL; n = 7 cases), acute myeloid leukemia (AML; n = 21 cases) and chronic lymphocytic leukemia (CLL; n = 2 cases). Both SS and SMS inhibited spontaneous leukemic cell growth in approximately 1/3 of cases (i.e. 7/19). G-CSF stimulated AML cells were inhibited by SMS in 11/21 cases. AML cell proliferation induced by IL-3 or GM-CSF was suppressed in only 3/21 and 6/21 cases, respectively. In ALL cells, IL-7-induced proliferation was suppressed by SMS in 3/7 cases. The effect of SMS seemed to depend on the type of the hematopoietic growth factor, and on their concentrations. In fact, high concentrations of G-CSF could override SMS blocking completely. Colony formation by normal marrow progenitors and DNA synthesis by HL-60 and T11/65 leukemic cell lines were not affected by SMS. In conclusion, somatostatin may act as a negative regulator of the proliferative activity of human leukemia.

Kit ligand improves in vitro erythropoiesis in myelodysplastic syndrome.

Erythropoiesis in response to erythropoietin (Epo) in myelodysplastic syndrome (MDS) in vitro and in vivo is severely impaired. We investigated the stimulative effect of c-kit ligand (KL) on the erythroid colony-forming abilities of bone marrow cells from 17 patients with MDS. The effects of normal donor-derived marrow were examined in comparison. Suppression of erythroid colony formation in MDS in response to Epo could not be restored by the addition of interleukin-3 (IL-3) to culture. In cultures dishes supplemented with KL, erythroid colony formation was dramatically enhanced, regarding both colony number and size. Colony-forming abilities by MDS progenitors were improved following costimulation with KL, particularly in refractory anemia (RA) and refractory anemia with ring sideroblasts (RARS); however, little enhancement was apparent following KL stimulation of marrow from patients with refractory anemia with excess of blasts (RAEB), refractory anemia with excess of blasts in transformation (RAEB-t), and chronic myelomonocytic leukemia (CMML). These results suggest that KL responsiveness of patients with low-risk MDS may still be intact, and that with progression to high-risk MDS, erythroid progenitors lose proliferative reactivity to both KL and Epo stimulation. KL may have a therapeutic role in restoring erythropoiesis in a subset of patients with MDS.

Relative contributions of human types 1 and 2 T-helper cell-derived eosinophilotrophic cytokines to development of eosinophilia.

The relative contributions of type 1 and 2 T-helper (Th1 and Th2) cell-derived interleukin (IL-5), granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-3 were studied in the regulation of sequential events in the development of eosinophilia. Using eosinophils from normal donors and neutralizing antibodies that selectively block cytokine activities, we analyzed the effects of these cytokines in supernatants (SN) of well-characterized allergen-specific Th2 and Th1 T-lymphocyte clones (TLC) generated from atopic and nonatopic individuals, respectively. Eosinophil colony formation from CD34+ bone marrow progenitor cells in semisolid cultures could be induced both by Th1 and Th2 SN, mainly mediated by the synergistic effects of GM-CSF and IL-3, whereas IL-5 had only a minor additive effect. High production of mature eosinophils in liquid cultures of unseparated mononuclear bone marrow cells could only be induced by Th2 SN, which could be more than 90% blocked by anti-IL-5, but not by anti-IL-3 or anti-GM-CSF. Chemotaxis of mature peripheral blood eosinophils could equally well be induced by Th1 and Th2 SN, although the relative contribution of the individual cytokines was clearly different in the two sets of SN. Priming of platelet-activating factor (PAF) release by peripheral blood eosinophils was regulated by additive effects of the three cytokines and was stronger induced by the Th2 SN than by the Th1 SN. The present results indicate that IL-5, GM-CSF, and IL-3 control eosinophils throughout the course of development of eosinophilia, having different individual contributions in different compartments. The apparent strong and selective IL-5-dependence of certain yet undefined steps in eosinophil production in the bone marrow supports the concept of the generally assumed causal relation between predominant activation of IL-5-producing Th2 cells in response to allergens and development of eosinophilia in atopic disease.

R-h-erythropoietin counteracts the inhibition of in vitro erythropoiesis by tumour necrosis factor alpha in patients with rheumatoid arthritis.

Anaemia of chronic disease (ACD) is a common extra-articular manifestation of rheumatoid arthritis (RA). Tumour necrosis factor alpha (TNF alpha) plays an important role in the development of ACD. The objective of the present study was to assess inhibition of in vitro colony-forming unit erythrocyte (CFUe) and blast-forming unit erythrocyte (BFUe) growth by TNF alpha and to examine whether this suppression could be counteracted by adding increasing concentrations of recombinant human erythropoietin (EPO) (r-h-EPO) to bone marrow cultures of RA patients with ACD and without anaemia (controls). Bone marrow cells of RA patients with ACD and control patients were cultured. The cultures were incubated with increasing concentrations of r-h-EPO (0.25; 0.5; 1; 2 U/ml), each in combination with increasing quantities of TFN alpha (0; 50; 100; 200; 400 U/ml). CFUe and BFUe were assessed after 7 and 14 days, respectively. Dose-dependent inhibition of BFUe and CFUe by increasing concentrations of TNF alpha was observed in ACD and controls. Regarding CFUe (ACD patients) incubated with 0.25 U/ml EPO, 50 U/ml TNF alpha caused 28% suppression compared to cultures without TNF alpha. Increasing the concentration of r-h-EPO from 0.25 U/ml to 2 U/ml completely restored the number of CFUe. A similar pattern was observed in BFUe growth in both groups. These data demonstrated the suppressive effects of TNF alpha on erythropoiesis in vitro and that the suppressed erythropoiesis could be partly corrected by the addition of excess r-h-EPO to the cultures. No significant differences were observed between ACD and control RA patients.(ABSTRACT TRUNCATED AT 250 WORDS)