Erythropoiesis after kidney transplantation: the role of erythropoietin, burst promoting activity and early erythroid progenitor cells.

Successful kidney transplantation is followed by the anemia correction due to re-establishment of normal erythropoietin secretion. The possible role of growth factors and cytokines regulating hematopoiesis in this anemia correction are not completely understood. The aim of this study was to investigate the role of erythropoietin and other stimulators in the regulation of erythropoiesis after kidney transplantation. Thirty-six kidney graft recipients with stable graft function for more than 12 months were studied. According to the hemoglobin levels they were divided into: group 1 (12 patients) with normal graft function (sCr = 145.2 +/- 15.8 micromol/l) and normal hemoglobin (12.7+/-0.3 g/dl), group 2 (11 patients) with normal graft function (sCr = 135 +/- 6.5 miromol/l) and posttransplant erythrocytosis (Hb = 18.1 +/- 0.2 g/dl) and group 3 (13 patients) with chronic graft failure (sCr = 223.7 +/- 28.9 micromol/l, range 181-294) and anemia (Hb = 9.0 +/- 0.8 g/dl). Early erythroid progenitors (BFU-E) from peripheral blood, serum immunoreactive Epo and burst promoting activity (BPA) in PHA-LCM prepared from patients' peripheral blood mononuclear cells were measured in all studied patients. The expected Epo for Hb was found normal in patients with normal graft function, 10 times higher in patients with PTE and low in patients with anemia. BPA in PHA-LCM prepared from PTE was increased in 4/6 patients, normal in 4/6 anemic patients, but it was decreased in 5 patients with normal Hb. The mean values were 20.8 +/- 6.3 in PTE group and 16.2 +/- 6.8 in anemic group, and 4.1 +/- 1.8 (at the level of normal controls) in group 1. The number of BFU-E derived colonies was low in most patients with normal hemoglobin and anemia, and increased in most patients with PTE. Spontaneous BFU-E colonies i.e. without Epo added to the cultures were found in 7 of 12 patients with PTE. The mean values of BFU-E showed significant differences between patients with PTE (17.43 +/- 7.3), and patients with normal hemoglobin and anemia (4.39 +/- 1.2 vs. 6.5 +/- 1.1). The results presented suggest that inappropriate Epo secretion depends on the graft function and is the primarily important regulator that caused PTE or anemia after kidney transplantation. Synergistic action of BPA with Epo as well as increased sensitivity of early erythroid precursors to these stimulators could explained sustained erythropoiesis in PTE patients. The high BPA levels in anemic transplant patients with moderate chronic graft failure could be beneficial if rHuEpo treatment is applied in this patient group.

The influence of acute sterile inflammation on erythropoiesis in rats.

Many different cell types, coordinated by proinflammatory mediators, take part in the acute inflammatory reaction, but there is a lack of evidence regarding the role of erythroid cells in such conditions. In this study, changes in bone marrow, splenic, and peripheral blood erythroid cells and in erythropoietin (Epo) blood levels were investigated up to 72 hours after polyvinylpyrrolidone (PVP)-induced sterile inflammation in male Wistar rats (two intraperitoneal injections of 15 mL 3.5% PVP at 18-hour intervals). Transient changes within progenitor erythroid cells were observed in the bone marrow. Significant increases in the number of splenic immature erythroid progenitors (BFU-E) 6 hours and mature erythroid progenitors (CFU-E), erythroblasts, and orthochromatic erythroblasts 48 and 72 hours after the induction of inflammation pointed to stimulated splenic erythropoiesis. This was confirmed by semiquantitative assessment of splenic smears, which demonstrated expansion of erythroid cells at hours 48 and 72. The changes observed in the bone marrow and spleen indicated that during acute inflammation erythropoiesis was stimulated and that the spleens of PVP-treated rats were favorable to erythroid development. The significant increase in the percentage of peripheral blood reticulocytes 48 and 72 hours after PVP-induced inflammation provided evidence that effective erythropoiesis occurred. In spite of the stimulated erythropoiesis, serum levels of Epo remained unchanged, implying that other non-Epo regulatory molecules may be responsible for erythroid cellular changes.

In vivo effects of recombinant human erythropoietin on bone marrow hematopoiesis in patients with chronic renal failure.

Studies of hemopoietic progenitors and precursors in bone marrow before and after two months of recombinant human erythropoietin (rhEpo) therapy in 12 patients with uremic anemia are the subject of this investigation caried out in order to have a better insight into the effect of Epo in vivo. Eight patients were on hemodialysis and four others were predialysis patients with chronic renal failure. The starting dose of rhEpo was 30-50 U/kg bw and was increased by 50 percent every four weeks. The mean hemoglobin values rose from 6.08 +/- 1.03 to 9.8 +/- 1.98 g/dl at the time of study. The number of bone marrow derived erythroid colonies, both early (BFU-E) and late (CFU-E) were found to be higher than subnormal values, found before the therapy. The percentage of erythroid progenitors in cell cycle increased to higher than normal values for BFU-E and to normal values for CFU-E. At the same time granulocytic progenitors (CFU-GM) decreased to the range of normal values (67.3 per 10 superset5 cells). Slightly increased Epo levels (approx. 30mU/ml) during the replacement therapy were optimal for correction of anemia. The rhEpo therapy induced an increase of percentage of erythroblasts and the decrease of myeloid to erythroid ratio (M/E) in the bone marrow. Only in predialysis patients in whom the target hemoglobin values were achieved by rhEpo therapy at the time of the study the percentage of erythroblasts in the bone marrow increased to normal values. Increase of erythroblasts in bone marrow in patients under two months of substitutive therapy with rhEpo with the increase of both, early and late erythroid progenitors we have observed, is significant indicating the stimulative effect of rhEpo on all subsets of erythropoiesis leading to normalization of erythropoiesis at all levels. No stimulative effect of rhEpo replacement therapy on granulopoiesis was observed.

Factors inducing posttransplant erythrocytosis.

In this study factors possibly contributing to the development of erythrocytosis after renal transplantation (PTE) were analyzed. Out of 131 transplanted patients nine developed PTE (mean hemoglobin 17. 9 +/- 0.3 g/dl) 2 to 27 months after transplantation (group 1) and were compared to the nine with normal hemoglobin concentration (mean hemoglobin 12.4 +/- 0.2 g/dl, control group 2). The study was performed about two years after transplantation (25 +/- 3.9 months group 1 and 23.7 +/- 2.6 months group 2). Immunosuppressive therapy given in standard doses consisted of cyclosporine, azathioprine and prednisone. At the onset of the study no difference in renal graft function was noted between the groups (for group 1 sCr = 111.7 +/- 10.4 micromol/l and for group 2 sCr = 154.6 +/- 27.6 micromol/l). The mean serum immunoreactive erythropoietin (Epo) levels were significantly higher in PTE patients compared to control group of patients (33.9 +/- 4.6 mU/ml vs 21.6 +/- 2.5 mU/ml, p = 0.03). In addition, the ratio between observed to expected (O/E) Epo, a useful index in assessing Epo secretion in renal transplant patients, was ten times higher for group 1 than for group 2 (Median value 10.0 vs. 1.05). Spontaneous growth of Burst-forming unit- erythroid (BFU-E) in peripheral blood was detected in 5 out of 9 patients from group 1 and none in patients from group 2 (p = 0.04). Burst Promoting Activity (BPA) in Phytohemagglutinine Stimulated Leukocytes Condition Medium (PHA-LCM) from patients blood were higher in the PTE patients than in controls. Whole blood cyclosporine levels were higher in group 1 than in group 2 throughout the first 30 weeks after transplantation. It was concluded that sustained erythropoiesis after correction of renal anemia by kidney transplantation, leading to PTE could be explained as a consequence of increased levels of Epo and BPA and increased sensitivity of early erythroid progenitors to these stimulators induced by high cyclosporine levels.

Erythropoietin & erythroid progenitors in rats exposed to chronic hypoxia.

In order to better understand the mechanisms affecting erythropoietin (Epo) synthesis and red cell mass increase under chronic hypoxia, we examined Epo production and erythroid progenitors (CFU-E) in rats exposed to normobaric hypoxia for four weeks. Hypoxia induced the rise of hematocrit (Htc), hemoglobin (Hb) concentration and the red blood cell (RBC) number with a plateau in hematocrit values after two weeks. After 24 h of hypoxia, Epo levels were increased 20 fold, followed by a significant decrease. After the first week of hypoxia, the values were still higher than in the controls, but after two weeks Epo levels did not differ significantly from the normal values. The fall of Epo levels coincided with the plateau values of hematocrit. The changes in the CFU-E number followed the changes in Epo concentration: a two fold increase after 24 h of hypoxia; a further increase during the next two weeks reaching a peak on day 14, and then a progressive decrease at the time when Epo concentration was at a normal level. Although decreased, but still higher than normal, the CFU-E number during the last two weeks of hypoxia could be necessary for the maintenance of an achieved steady state under persistent hypoxic conditions with normal Epo concentration sufficient to maintain the existing rate of erythropoiesis.

The effect of IL-1 receptor antagonist on the proliferation of hematopoietic progenitor cells in regenerating bone marrow.

To evaluate the involvement of IL-1 on bone marrow granulocyte-macrophage (CFU-GM) and erythroid (BFU-E and CFU-E) progenitor cell regeneration during the recovery of hematopoiesis after sublethal irradiation of CBA mice, we examined the effects of IL-1 receptor blockade by recombinant human IL-1 receptor antagonist (rhIL-1ra). The actual number of progenitors and proportion of these cells in S phase of the cell cycle were determined in regenerating bone marrow cells obtained 3 days after 2 Gy irradiation both following the in vivo administration of rhIL-1ra, as well as after the in vitro preincubation with increasing amounts of rhIL-1ra. The results revealed that rhIL-1ra decreased the number and the proportion of CFU-GM in the S phase in regenerating bone marrow. As concerning erythroid progenitors, rhIL-1ra treatment suppressed BFU-E and enhanced CFU-E-derived colony growth, indicating that the biological effects of IL-1 might be different depending on the stage of differentiation. The observed effects pointed to the importance of the basal levels of IL-1, as well as IL-1 receptor expression during the recovery of hematopoiesis.

In vivo effects of interleukin-1 receptor antagonist on hematopoietic bone marrow progenitor cells in normal mice.

The multiple effects of interleukin-1 (IL-1) on hematopoietic cells are mainly documented in disturbed hematopoiesis, but its production and participation during constitutive hematopoiesis are still unproven. To assess the involvement of IL-1 in the regulation of steady-state hematopoiesis in vivo, we have investigated the consequences of IL-1 receptor blockade by recombinant human IL-1 receptor antagonist (rhIL-1Ra) in normal CBA/H mice treated with two i.p. injections of rhIL-1Ra (2 x 50 micrograms/mouse) seventeen and two hours before sacrifice. The cellularity, the number of granulocyte-macrophage (CFU-GM), the number of erythroid (BFU-E) progenitor cells and the percentage of these cells in S phase of the cell cycle, as well as the morphologically recognizable cells in bone marrow were estimated. In peripheral blood, hematocrit, the number and differential count of nucleated cells, the number erythrocytes and the percentage of reticulocytes were determined. IL-1Ra treatment significantly reduced the number of femoral CFU-GM and BFU-E, while all the other analyzed parameters were not different from the level obtained in control, non-treated animals. These findings show that a number of bone marrow IL-1-responsive cells were affected by the IL-1 receptor blockade, indicating that the expression of IL-1 receptors and endogenous IL-1 secretion occur as part of constitutive hematopoiesis.

[Causes of anemia after kidney transplantation]. / Uzroci anemije posle transplantacije bubrega.

In this paper possible causes of anemia in patients after kidney transplantation were investigated. Anemia developed in 29 patients 14 to 22 months after kidney transplantation. At the time when these patients became anemic fourteen had normal graft function while the others 15 suffered chronic graft failure due to chronic rejection in 11 patients combined with cyclosporine nephrotoxicity in other four patients. Anemia in patients with normal graft function was caused by iron (in 8), folic acid deficiency (in 16) and vitamin B12 deficiency (in 2 patients). In this patients group anemia improved after substitution therapy. Therapy with rHuEpo was necessary in patients with chronic graft failure, indicating that erythropoietin deficiency was the main cause of their anemia. However, chronic graft failure progression, expressed by 1/sCr/time was not accelerated by anemia improvement. It could be concluded that examination of etiologic factors of posttransplant anemia is prerequisite for the most adequate treatment whose effects depend on graft function.

Effects of gluconodeltalactone and Lactobacillus plantarum on the production of histamine and tyramine in fermented sausages.

Fermented sausages were made experimentally with addition of 0.3% (w/w) gluconodeltalactone (GDL) or a starter culture of Lactobacillus plantarum, unable to produce histamine or tyramine. Controls were produced without GDL and starter culture. During 15 days preparation and storage periods, number of bacteria and lactobacilli, pH, and levels of histamine, tyrosine and tyramine were monitored, and organoleptic evaluations were carried out. Maximal histamine levels were 19.41 micrograms/g of dry matter in the GDL-added sausages, 18.64 micrograms/g in the control, and 17.20 micrograms/g in the starter sausages. Maximal tyramine levels were 1249.16 micrograms/g in the GDL sausages, 1101.16 micrograms/g in the control, and 906.35 micrograms/g in the starter sausages. Sausages produced with GDL proved less acceptable in organoleptic evaluation due to an unpleasant sour flavour.

Hematopoietic growth factors in anemia of Belgrade laboratory (b/b) rats.

In this study, the extent to which growth factor production and microenvironment might be responsible for defective erythropoiesis and granulopoiesis in anemic b/b rats is investigated. Radioimmunoassay-determined serum erythropoietin (Epo) levels are high in b/b rats and closely related to degree of anemia. The low number of erythroid progenitors in b/b rats despite a high Epo level suggested that the defective erythropoiesis could be due to a low level of burst-promoting activity (BPA). A pokeweed mitogen-stimulated medium (PWM-SCM) was prepared with b/b rat spleen cells and used in normal and anemic rat bone marrow and spleen cultures to determine BPA and other growth factor levels. No erythroid burst-forming unit-derived colonies were found but granulocyte-macrophage colony-forming units were counted in significant number, suggesting that the production of growth factors that supports the growth of granulopoietic progenitors is not significantly disturbed. Because BPA is produced mainly by T-lymphocytes, the low BPA level in b/b rat PWM-SCM raised the question of the functional capacity of T-lymphocytes. Investigations showed a decrease in the proliferative activity of b/b rat spleen mitogen-activated T-lymphocytes to about 20% of controls as well as a decrease in interleukin-2 activity in b/b rat spleen cell supernatants. These results point to defective T-lymphocytes. A study of bone marrow fibroblastoid cell colonies (CFU-F) revealed significantly lower CFU-F counts in the b/b rats. This finding is indicative of a disturbed microenvironment, which could also to some extent be responsible for decreased growth factor production and depressed hematopoiesis in the b/b rat.

Serum erythropoietin levels in hemodialysed patients after administration of recombinant human erythropoietin.

In anemic patients on regular hemodialysis (HD), correction of anemia with recombinant human erythropoietin (rHuEpo) administered intravenously (iv) or subcutaneously (sc) was followed over a 2-month period. Monitoring serum Epo post-dose concentrations after the first iv rHuEpo injection and following another regular injection after 2 months of therapy with rHuEpo iv in 9 patients showed that the Epo elimination half-life was reduced from 7.48 h to 4.68 h. In the same patients the initially low percentage of erythroblasts and mature erythroid progenitors increased during 2 months of rHuEpo therapy. Because Epo molecules bound to Epo receptors are internalized in target cells we suggest that the expansion of the Epo responsive cell pool could explain the shorted Epo elimination time after 2 months of rHuEpo treatment. By monitoring serum Epo concentration following sc rHuEpo injection in 7 HD patients it was found that the modest increase in serum Epo levels (30-60 mU/ml) was sufficient to correct anemia.

Erythropoietin and improvement of anemia in long-term hemodialysis patients.

Two groups, with 4 patients each were selected for study out of 155 patients on regular hemodialysis (HD): Group I, with hematocrit (PCV) less than 20% and group II, with PCV greater than 30%. The patients in both groups had been anemic at the start of HD treatment, but a significant improvement in their anemia had occurred only among the patients in the Group II. The main difference between the two patient groups, other than the degree of anemia, was found to be in serum erythropoietin (Ep) levels. No significant differences were observed between the two groups in serum urea, creatinine, parathyroid hormone or CFU-E growth inhibition. Acquired cystic disease of the kidney was found in five patients from group I, and in 11 patients from group II. The correlation between the number of cysts in the kidneys and the patient's PCV and serum Ep levels proved significantly positive. The results presented could be regarded as another proof that diseased kidney is capable of functioning as an Ep producing organ despite the loss of excretory function.

Endogenous BFU-E in peripheral blood in diagnosis of polycythemia vera.

Erythroid progenitors (CFU-E and BFU-E) growth in vitro from bone marrow and peripheral blood of patients with polycythemia vera (PV) was studied using a methylcellulose culture technique. The aim of the study was to find out whether the in vitro colony formation of peripheral blood could be used in the differential diagnosis of PV. In all 25 patients studied, endogenous colonies were found in the bone marrow and peripheral blood. The parallel study of both bone marrow and peripheral blood erythroid progenitors indicates that the presence of endogenous BFU-E in peripheral blood is a dependable test for PV. The results presented here showed that the abnormalities in PV erythroid progenitors are expressed at the level of both CFU-E and BFU-E, suggesting multiple changes in the erythroid progenitors. Our finding indicate that peripheral blood BFU-E differ from bone marrow BFU-E with regard to their dependence for further differentiation on BPA, the activity present in PHA-LCM.

Megakaryocytopoiesis in experimentally induced chronic normobaric hypoxia.

It was recently proposed that prolonged hypoxia produces hypomegakaryocytic thrombocytopenia by reducing the pool of committed megakaryocyte progenitor cells at the expense of a greatly expanded erythroid progenitor pool. In order to test this hypothesis we have studied the relationship between megakaryocytopoiesis, erythropoiesis, and granulopoiesis at the level of progenitor cells (megakaryocyte colony-forming unit, CFU-Mk; erythroid CFU, CFU-E; erythroid burst-forming units; BFU-E; and granulocyte-macrophage CFU, CFU-GM) in the marrow of rats exposed for 4 weeks to normobaric hypoxia. We have found that hypomegakaryocytic thrombocytopenia was accompanied by decreased CFU-Mk, increased CFU-E, and a normal number of BFU-E and CFU-GM. These results support the hypothesis that prolonged hypoxia reduces the precursor cell commitment to differentiate into the megakaryocyte series by enhancing demand for differentiation into the erythroid cell line. However, the underlying mechanism needs further investigation.

Erythropoiesis in paroxysmal nocturnal hemoglobinuria.

Ten patients with paroxysmal nocturnal hemoglobinuria were studied. The diagnosis was made on the basis of hemolytic anemia, a positive Ham test and hemosiderinuria. Six patients had primary paroxysmal nocturnal hemoglobinuria evolved from aplastic anemia. These four patients also had a milder form of the disease, Over long periods of the follow-up, large variations of hemoglobin values and red blood cell counts were observed. Both absolute and percent reticulocyte counts were increased. Erythroblast counts in the bone marrow were 3-5 times higher than normal. Reticulocyte counts in the bone marrow were 3-5 times higher than normal. Reticulocyte counts showed wide variations but substantially smaller than those in autoimmune hemolytic anemias. Serum iron was either normal or increased, while the bone marrow iron store was high or low. However, the finding of urinary hemosiderin in all cases spoke against depletion of iron stores. The red blood cell life span was moderately shortened. Kinetic studies with 59Fe showed a high red blood cell iron incorporation, while the curves frequently had irregular shapes (broken curve) or an early, abrupt fall. Studies of late erythroid progenitors (CFU-E) indicated that this compartment was preserved. Even after long observation periods was no stem cell pool depletion due to an increased red blood cell demand observed.

Erythroid progenitors in anemic Belgrade laboratory (b/b) rats.

The anemia of Belgrade b/b rats has been shown to be due to intracellular iron deficiency. The aim of this study of erythropoiesis at the progenitor cell level in these rats was to determine if a defect is present in the early phase of red cell production. Both erythroid colony-forming unit (CFU-E)- and erythroid burst-forming unit (BFU-E)-derived colonies were found to be few in untreated b/b rats and made up of a small number of poorly hemoglobinized erythroblasts of different size and irregular cell shape. Following treatment with iron, the anemia of the rats improved, and the number of CFU-E-derived colonies and the number of cells per colony increased, but the peculiar erythroblast morphology persisted. The high serum level of biologically active erythropoietin (Ep) in b/b rats rules out inadequate Ep production as a cause of their anemia. The results presented indicate, in addition to the earlier described defective transmembrane iron transport, a defect in erythroid progenitor cells. The effect of iron treatment in these rats detected in vitro on erythroid progenitors confirms the importance of iron for cellular proliferation.

Chronic myeloid leukemia associated with pure red cell aplasia and terminating in promyelocytic transformation.

After intermittent treatment with busulphan over a 7-year period for chronic myeloid leukemia (CML) in chronic phase, a 39-year-old female developed leukocytosis in association with pure red cell aplasia (PRCA). Bone marrow examination confirmed erythroid aplasia, and culture revealed a total absence of erythroid progenitor cells. The patient then was treated with azathioprine, corticosteroids, cyclophosphamide, plasma exchange, and cyclosporin A, but she remained erythroblastopenic and transfusion dependent for more than a year, at which time a promyelocytic transformation supervened. The authors propose that this sequence of events, hitherto unreported, is a manifestation of the multistep progression of CML.

Polycythemic mice--an appropriate model for investigation of granulopoiesis.

In posthypoxic polycythemic mice (P) expanded granulopoiesis was found. After aplasia induced by a sublethal dose of cyclophosphamide (Cy), more granulocytic cells both in the bone marrow and spleen were found in P than in normal (N) mice treated in the same way. Spontaneous regeneration of granulocytic precursors during the first three days after Cy was more intensive in P mice, and a significant role of the spleen in CFU-GM regeneration was observed. It is suggested that P animals could be used as an appropriate model for investigation of the cell specificity of humoral regulators of granulopoiesis and their action, as well as in studies on the competition of granulocytic and erythroid cells.