The impact of a hypercatecholamine state on erythropoiesis following severe injury and the role of IL-6

BACKGROUND: Severe traumatic injury can lead to hemorrhagic shock-induced bone marrow (BM) dysfunction resulting in persistent anemia. The hypercatacholamine state that accompanies severe injury has been shown to impact the growth of erythroid progenitors. IL-6 has a role both in the acute phase response of trauma and has been implicated in the development of anemia. The aim of this study was to investigate the severity of a hyper-adrenergic stimulus on pluripotent progenitors (GEMM-CFU) as well as erythroid progenitors (BFU-E and CFU-E) and the potential regulatory role of IL-6. METHODS: Normal human BM mononuclear cells were isolated and erythropoiesis was assessed by the growth of GEMM-CFU, BFU-E and CFU-E in the presence of adrenergic agonists, norepinephrine (NE) and epinephrine (EPI), at increasing concentrations. Similarly, normal BM stroma cells were grown to confluence then incubated with NE and EPI. Supernatant was harvested and IL-6 levels were determined using ELISA. RESULTS: Under physiologic conditions (10(-7) M), NE and EPI increase BFU-E and CFU-E growth (374% and 177% versus 100% control). At severe stress levels (10(-3) M), NE and EPI completely inhibited BFU-E and CFU-E growth (5% and 4% versus 100% control). GEMM-CFU growth was increased by NE and not EPI at 10(-7) M. The presence of NE and EPI increased IL-6 levels in a dose-dependent fashion. CONCLUSIONS: The proliferative effect of adrenergic agonists at physiologic levels on normal erythropoiesis begins early during erythroid differentiation. At severe stress levels, BFU-E and CFU-E growth is inhibited. The erythropoietic dysfunction and resultant anemia seen following severe injury may be due to the presence of a severe hypercatecholamine state and may be mediated by IL-6.     

Responsiveness to recombinant erythropoietin therapy in end-stage renal disease. An analysis of the predictive value of several biological measurements, including circulating erythroid progenitors.

In end-stage renal disease (ESRD), the human recombinant erythropoietin doses required to keep haemoglobin in the target range may vary considerably between patients. Previous studies have failed to find any predictive factor of the response. We thus performed the present investigation in 30 ESRD patients to discover if the haematological response to human recombinant erythropoietin (rHuEpo) was related to the results of circulating erythroid progenitor cultures. Peripheral erythroid burst forming units (BFU-E) were cultured in a plasma clot system in the absence or in the presence of autologous serum just before starting rHuEpo therapy. The results showed a higher BFU-E number in ESRD patients than in controls and a stimulatory effect of autologous serum in both patients and controls. Comparison between culture results and haematological response yielded positive correlation between the BFU-E number and the haemoglobin increase during the first month of treatment, and negative correlation between the increase of BFU-E numbers during the first week of therapy and the rHuEpo doses required for a long-term response. We thus conclude that in ESRD patients the individual response to rHuEpo is linked to the numbers of circulating BFU-E.     

Desferrioxamine improves burst-forming unit-erythroid (BFU-E) proliferation in haemodialysis patients

Background: In chronic renal failure, desferrioxamine (DFO) may improve erythropoiesis independent from its aluminium (Al) chelating effect. The mechanism of this action is still unknown. Methods: To verify whether DFO influences proliferation of erythropoietic precursors, we studied 10 patients on chronic haemodialysis, free from malignancies or other haematological diseases, iron deficiency, bone marrow fibrosis, and Al toxicity. Al accumulation was excluded by the DFO test. Peripheral blood samples were drawn for basal burst-forming unit-erythroid (BFU-E) assay. Mononuclear cells were isolated by density gradient centrifugation with Ficoll-Hypaque, and incubated for 15 days with three different experimental conditions: (a) low-dose recombinant human erythropoietin (rHuEpo) (3 U/ml); (b) high dose rHuEpo, (30 U/ml); (c) both DFO (167 &mgr;g/ml) and rHuEpo (3 U/ml). We determined TIBC, transferrin, ferritin, reticulocytes, hypochromic erythrocytes, soluble transferrin receptor (sTR), haemoglobin (Hb), and haematocrit (Hct) at baseline and then every 14 days. Patients received 5 mg/kg DFO infused during the last hour of each dialysis session for 6 weeks; six patients remained in the study for an additional 6 more weeks. BFU-E assays were set up after 6 and 12 weeks of DFO therapy. Results: At baseline DFO had small effect on BFU-E proliferation (33.9±25 vs 30.4±25.9) and high-dose rHuEpo had a significant effect (45.15±27 vs 30.4±25.9, P<0.01). After 6 weeks of DFO therapy a significant increase in BFU-E proliferation was observed in all culture conditions (78.25±32 vs 30.45±25.9 standard culture, P<0.01; 110.9±30 vs45.15±27 high dose rHuEpo, P<0.01; 98.75±32 vs 45.15±27 DFO culture, P<0.01). Moreover, the increase in BFU-E proliferation was significant greater with DFO culture than standard culture (P<0.01). The same trend was found at the third BFU-E assay, performed in only six patients, when all culture conditions showed a further increase of erythroid precursor proliferation. However, the DFO culture was not significantly greater than the standard culture, while the high-dose rHuEpo was significantly greater than the DFO culture. Patients in group 1 (n=10), had a significant increase in reticulocytes (1.5±0.6 vs 1.72±0.3, P<0.01) and of hypochromic erythrocytes (HE) (5.6±5.1 vs 14.4±12.7, P<0.01), while sTR, Epo, Hb, and Hct were only minimally increased. Ferritin decreased significantly (448±224 vs 196±215, P<0.01) and TIBC and transferrin were unchanged. Conclusions: Thus DFO increases erythroid activity by BFU-E proliferation and increases reticulocytes in haemodialysis patients. Such an effect may be related to increased iron utilization. DFO may be a useful tool for anaemic patients with good iron stores and without Al overload. Key words: desferrioxamine; erythroid progenitors; erythropoiesis; haemodialysis      

Lipid and apolipoprotein patterns during erythropoietin therapy: roles of erythropoietin, route of administration, and diet

Background. Long term effects of rHuEpo on the blood lipid profile have not been well documented. The aim of this paper is to prospectively evaluate whether rHuEpo therapy affects lipid metabolism, and whether these effects are influenced by changes in dietary habits and by route of rHuEpo administration. Methods. The study was performed in 33 maintenance haemodialysis patients (MHP) treated for one year with rHuEpo either intravenously (n = 15) or subcutaneously (n = 18), three times per week at the end of each dialysis session. The doses were 50 IU/kg intravenously or 35 IU/kg subcutaneously during the first 6 months and 20 IU/kg during the following months. The control group consisted of 17 MHP not treated with rHuEpo. Total cholesterol, LDL-cholesterol and HDL-cholesterol, triglycerides, apolipoproteins A1 and B, haemoglobin, serum albumin, blood urea nitrogen, serum creatinine, Kt/V, protein catabolic rate, and plasma erythropoietin were assessed at months 0, 2, 4, 6, 9, 12 and 2 weeks after rHuEpo discontinuation. Changes in food intake were evaluated on the basis of weekly dietary diaries before, and 3 and 9 months after treatment. Patients were divided into two groups: group A consisted of 19 patients who showed an increase in their energy intake (10% or more of basal value), and group B was formed by 14 patients without or with slight changes in their food intake. After the 6th month, dialysis schedules were adapted to new protein catabolic rate values in patients who increased their food intake. Results. During follow-up, there were no significant changes in any of the parameters in the control group. In group A, blood urea nitrogen, serum creatinine, protein catabolic rate, cholesterol, LDL cholesterol, triglycerides and apolipoprotein B increased significantly since the first months of rHuEpo treatment, and changes in cholesterol and apolipoprotein B correlated significantly with changes in protein catabolic rate. In group B, cholesterol, LDL cholesterol, and apolipoprotein B decreased significantly after the 6th month of treatment, without changes in blood urea nitrogen, serum creatinine and protein catabolic rate values. In both groups A and B, HDL cholesterol decreased significantly until the 6th month and returned to basal values in the following months and apolipoprotein A1 decreased until the 4th month and rose to levels higher than basal values in the following months. First rHuEpo administration and rHuEpo suspension at end of follow-up did not show any acute effect on lipid profile, despite significant changes in plasma erythropoietin values. Changes in lipid profile were similar with intravenous and subcutaneous administration of rHuEpo. Conclusions: We infer that long-term rHuEpo treatment positively affects the lipid profile, but in some patients who show exaggerated increase in their food intake these effects may be balanced and overcome by increment in some atherogenic blood lipid fractions. The changes in lipid and apolipoprotein patterns during rHuEpo therapy are not influenced by route of rHuEpo administration.     

The anemia of end-stage renal disease: hematopoietic progenitor cell response

Patients with the anemia of end-stage renal disease (ESRD) fail to display an appropriate compensatory increase in red cell production. In order to investigate the extent to which the impaired erythropoietic response is determined at the progenitor cell level, we determined the frequencies of marrow colony-forming cells in 11 anemic and 3 non-anemic, dialysis-dependent ESRD patients and 10 healthy individuals. In addition, we measured serum levels of erythropoietin (Epo) by radioimmunoassay. There were no significant differences (P greater than 0.1) between normal and ESRD groups in the frequencies of primitive or late erythroid (BFU-E and CFU-E, respectively), granulocyte-macrophage, and megakaryocyte progenitors, CFU-E/BFU-E ratios, or serum Epo levels. In contrast, 5 non-uremic patients with chronic anemia comparable in severity to the anemic ESRD patients had serum Epo levels and CFU-E/BFU-E ratios that were significantly increased (P less than 0.05 and P less than 0.001, respectively) in comparison to the normal controls and ESRD patients. Pre-dialysis serum and plasma from both ESRD groups were as supportive of autologous erythroid and non-erythroid colony growth in vitro as normal serum and plasma; inhibition was not observed. We conclude that the relative numbers of erythroid and non-erythroid progenitors and the majority of serum Epo levels are unchanged from normal in patients with the anemia of ESRD. However, their normal CFU-E/BFU-E ratio reflects an inadequate compensatory erythropoietic response due to their inability to appropriately increase Epo production in response to anemia. Inhibitors of autologous erythroid colony formation were not detected in ESRD serum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Recombinant human erythropoietin activates a broad spectrum of progenitor cells

Twenty uremic patients on regular hemodialysis received recombinant human Erythropoietin (rhEPO) in a dosage of 50 U/kg body wt (N = 9) and 80 U/kg body wt (N = 11), respectively, three times weekly. The number of circulating hemopoietic progenitor cells colony-forming unit-granulocyte-erythrocyte-macrophage (CFU-mix), burst-forming unit-erythroid (BFU-E) and colony-forming-granulocyte-macrophage (CFU-GM) in peripheral blood were assayed weekly by means of a commonly applied in vitro clonal assay. A significant increase of peripheral CFU-mix, BFU-E and CFU-GM could be observed within one week of supplementation therapy in both groups. The increase of BFU-E was followed by a rise of hematocrit within four and three weeks, respectively. These results suggest that the stimulatory in vivo effect of rhEPO administered in therapeutical doses is not restricted to the erythroid lineage but also includes progenitor cells committed to the myeloid lineage (CFU-GM) as well as the multipotent progenitors CFU-mix. The increment of circulating progenitor cells was seen with a dosage of 80 U/kg body wt and 50 U/kg body wt as well.     

Bone marrow failure following severe injury in humans

BACKGROUND: Hematopoietic failure has been observed in experimental animals following shock and injury. In humans, bone marrow dysfunction has been observed in the red cell component and characterized by a persistent anemia, low reticulocyte counts, and the need for repeated transfusions despite adequate iron stores. While a quantitative defect in white blood cell count has not been noted, an alteration in white blood cell function manifesting as an increased susceptibility to infection is well established. Since the etiology of this anemia remains unknown and the bone marrow has been rarely studied following injury, we measured various parameters of hematopoiesis directly using bone marrow from trauma patients and tested the hypothesis that trauma results in profound bone marrow dysfunction, which could explain both the persistent anemia and the alteration in white blood cell function. METHODS: Bone marrow aspirates and peripheral blood were obtained between day 1 and 7 following injury from 45 multiple trauma patients. Normal volunteers served as controls. Peripheral blood was assayed for hemoglobin concentration, reticulocyte count, erythropoietin levels, white blood cell count, and differential. Peripheral blood and bone marrow were cultured for hematopoietic progenitors (CFU-GM, BFU-E, and CFU-E colonies). RESULTS: Bone marrow CFU-GM, BFU-E, and CFU-E colony formation was significantly reduced while peripheral blood CFU-GM, BFU-E, and CFU-E was increased in the trauma patients compared with normal volunteers. Bone marrow stroma failed to grow to confluence by day 14 in >90% of trauma patients. In contrast, bone marrow stroma from volunteers always reached confluence between days 10 and 14 in culture. The mean hemoglobin concentration and reticulocyte counts of the trauma patients were 8.6 +/- 1.0 g/dL and 2.75 +/- 0.7% respectively, while their plasma erythropoietin levels were 2 to 10 times greater than control values. CONCLUSIONS: Release of immature white blood cells into the circulation may also contribute to a failure to clear infection and an increased propensity to organ failure. Concomitantly, profound changes occur within the bone marrow, which include the increased release of erythroid and myeloid progenitors into the circulation, a decrease in progenitor cell growth within the bone marrow, and an impaired growth of the bone marrow stroma. Erythropoietin levels are preserved following trauma, implying that the persistent anemia of injury is related to the failure of the bone marrow to respond to erythropoietin.     

Haematopoietic progenitor cells in an infant who developed pancytopenia following an extensive burn

We observed a 24-month-old infant who developed anaemia, thrombocytopenia and neutropenia while recuperating from an extensive burn. In order to determine the mechanism(s) responsible for the pancytopenia, we quantified marrow-derived haematopoietic progenitor cells, assessed the relative proliferative rate of haematopoietic progenitor cells, and sought the presence of progenitor cell inhibitors. The concentration and relative proliferative rate of pluripotent progenitors (CFU-GEMM) were elevated. No inhibitors of progenitor cells were observed; in fact, the patient's serum contained very high levels of stimulatory activity for CFU-GEMM as well as for granulocyte-macrophage progenitors (CFU-GM). However, the marrow concentration of erythroid progenitors (BFU-E and CFU-E) was diminished. We conclude that the anaemia in this patient was the result of either hypoproduction of differentiated erythroid progenitors or intramyeloid destruction of early erythroid cells. In contrast, the neutropenia was likely to be due to accelerated neutrophil consumption at a rate that exceeded the capacity for increasing neutrophil production.     

Kinetics of erythropoiesis in dialysis patients receiving recombinant erythropoietin treatment

In eleven patients with uraemia on intermittent haemodialysis treatment, recombinant human erythropoietin (rHuEpo) was used at a dosage schedule of 100 IU/kg bodyweight thrice weekly. Erythrokinetic studies (blood volume, RBC survival and iron kinetics) were performed in nine cases before and after 6 months of treatment. The remaining two patients had only RBC and plasma volume determinations before and after treatment. Although total blood volume remained unchanged, RBC volume was increased in all cases. Red cell loss was not modified, and quantitative improvement of RBC production was noted in all cases. No qualitative defect of erythroid maturation or release was observed in the treated patients. In conclusion, rHuEpo treatment improves the anaemia of haemodialysis patients by normalising circulating RBC volume only through an increase in red cell production.     

Polyamines in the anemia of end-stage renal disease

The improvement in the anemia in patients with end-stage renal disease (ESRD) on continuous ambulatory peritoneal dialysis (CAPD) suggests that dialyzable substances present in the sera of uremic patients either inhibit erythropoiesis directly or inactivate erythropoietin (EPO). In the present study predialysis sera from patients with ESRD inhibited erythroid colony (CFU-E) (N = 10) formation to a significantly (P less than 0.01) greater degree than granulocyte-macrophage (CFU-GM) (N = 7) colony formation in mouse bone marrow (MBM) cultures. The polyamines spermine (SP) (18 to 560 nm/ml) and spermidine (SD) (4 to 648 nm/ml) exerted a more significant (P less than 0.05) inhibition of CFU-E (N greater than or equal to 5) than that of CFU-GM (N greater than or equal to 5) growth. Concentrations of 0.80, 1.0, and 1.5 nm/ml of putrescine (PU) were 92%, 85%, and 77% of erythroid colony (CFU-E) controls (N = 4) and 104%, 130%, and 127% of CFU-GM controls (N = 4). Putrescine (PU) at 1.5 nm/ml also produced a significant (P less than 0.05) inhibition of CFU-E, whereas CFU-GM were stimulated by PU. These data suggest that predialysis sera from uremic patients, as well as SP, SD, and PU, are selectively more inhibitory to CFU-E than CFU-GM growth. The immunoreactivity of EPO was not significantly changed when it was coincubated with SP, SD and PU and measured by radioimmunoassay. PU was found to inhibit noncompetitively the bioactivity of EPO in a CFU-E assay. These data support the hypothesis that polyamines may be important uremic toxins in the anemia of ESRD.     

Haemodynamic changes induced by the correction of anaemia by erythropoietin: role of antiplatelet therapy

BACKGROUND.: In a restrospective study, antiplatelet therapy has been shownto be associated with a decreased incidence of erythropoietin-inducedhypertension. In order to ascertain the role of antiplateletdrugs in the haemodynamic response to the correction of anaemiaby rHuEpo, 18 patients on chronic haemodialysis who startedrHuEpo therapy were prospectively studied. METHODS.: The subjects were randomly assigned to receive or not, one ofthe following antiplatelet drugs: ditazole (3 patients), ticlopidine(3 patients) or aspirin plus dipyridamole (3 patients). Cardiacindex (CI) by echo-Doppler, total peripheral resistance (TPR)and mean arterial pressure (MAP) were determined at baseline10 and 20 weeks following the initiation of rHuEpo therapy.rHuEpo therapy was administered subcutaneously at the same dose(40 U/kg thrice weekly) during the first 10 weeks. Ten uraemicpatients on haemodialysis who had never received rHuEpo therapyserved as the control group. RESULTS.: One patient in the group without antiplatelet drugs discontinuedthe study due to the development of severe hypertension after12 weeks on rHuEpo therapy. There were no significant differencesin the haemodynamic parameters at baseline. At 10 weeks, MAPwas higher in patients without than with antiplatelet drugsor controls untreated with rHuEpo (128.5 ± 28 versus100.6 ± 13.5 versus 98.7 ± 14 mmHg respectively,P = 0.0047), TPR was also higher in patients without antiplateletdrugs than in the 2 other groups (1919 ± 433 versus 1576± 359 versus 1418 ± 324 din.seg.cm^–5 m²respectively, P = 0.0231), but CI did not differ among the threegroups. At 20 weeks, MAP was still higher in patients withoutantiplatelet drugs than in patients with antiplatelet drugsor controls not on rHuEpo therapy respectively (112.9 ±24.6 versus 91.0 ± 9.0 versus 101.7 ± 14.1 mmHgrespectively, P = 0.075), but at this stage TPR and Cl did notdiffer among the three groups. CONCLUSIONS.: These data reinforce the previous observation that antiplatelettherapy may prevent the development of rHuEpo-induced hypertension.     

Hematopoietic inhibitors in chronic renal failure: lack of in vitro specificity

To assess the potential role of retained inhibitors in the pathogenesis of the anemia of chronic renal failure, we have studied simultaneously the effects of increasing concentrations of normal or uremic sera on the growth of erythroid colonies (from CFU-E), granulocyte-macrophage colonies (from CFU-GM), and megakaryocytic colonies (from CFU-Meg) in mouse marrow cell cultures. As compared to normal human serum, increasing concentrations of uremic sera induced a dose-dependent inhibition in the growth of all colony types. Significant correlations (P less than 0.001) were found between the ability of any individual uremic serum to support CFU-E, CFU-GM, and CFU-Meg growth, and, whenever significant inhibition was seen, all three progenitor types were affected. The inhibitory effect on CFU-E growth was significantly greater (P less than 0.01) in patients with serum creatinine concentrations greater than or equal to 7 mg/dl, but no correlation was found between CFU-E inhibition and hematocrit. Likewise, inhibition of CFU-GM and CFU-Meg growth was not associated with leukopenia or thrombocytopenia, respectively. Sera from patients undergoing chronic intermittent hemodialysis were assayed before and after one hemodialysis session. In each case, the degree of inhibition of CFU-E and CFU-GM growth decreased after hemodialysis, but improvement in CFU-Meg growth was more variable. These data indicate that uremic sera contain dialyzable inhibitors of in vitro hematopoiesis which increase with the severity of renal dysfunction, but these inhibitors lack specificity. If uremic inhibitors of erythropoiesis are of pathophysiologic significance in vivo, there must be unrecognized repair mechanisms for granulopoiesis and thrombopoiesis.     

Safety and efficacy of recombinant human erythropoietin treatment of anaemia associated with multiple myeloma in haemodialysed patients

Recombinant human erythropoietin (rHuEpo) was used to treatthe anaemia of four haemodialysed patients (3 males, 1 female)with advanced multiple myeloma; the type of serum M componentwas IgG kappa in all cases. During the 6-month period precedingrHuEpo therapy the patients received multiple blood transfusions(range 4–22 units of packed red cells per patient). Afterthe first month of treatment haematocrit increased from 23±3(SD) to 32±4% and during the last 3 months the maintenancedose of rHuEpo was 143±37 U/kg per week to achieve amean haematocrit of 35±1%. After introduction of rHuEpo,blood transfusions were no longer required and the patientsreported an improvement in wellbeing. No apparent worseningof multiple myeloma has been observed over the treatment periodranging from 5 to 34 months (cumulative duration of treatment55 months). Anti-hypertensive therapy was started in one caseand increased in two patients. We conclude that rHuEpo appearsto be effective and safe in treating anaemia associated withmultiple myeloma in patients requiring haemodialysis.     

In-vitro growth patterns of bone marrow erythroid progenitors from patients with post-renal transplant erythrocytosis

Background: Erythrocytosis is relatively common after renal transplantation and is associated with a higher risk of thromboembolism. Its aetiology is unclear and there is still debate about the most frequently suggested causes. The culture in vitro of erythroid progenitors is regarded as a useful tool for the differential diagnosis of patients with unclear erythrocytosis. We studied the growth in vitro of bone marrow erythroid progenitor from renal transplant patients with erythrocytosis and controls without erythrocytosis. Subjects and methods: Thirteen renal transplant patients with erythrocytosis and 12 normocythaemic renal transplant controls were studied. The clinical characteristics of these patients were evaluated and serum erythropoietin (Epo) and ferritin levels were determined. Bone marrow erythroid progenitors were cultured both with and without the addition of Epo to the medium. Results: Samples from six polycythaemic patients and seven controls did not grow spontaneously in the absence of exogenous Epo. Three cases of post-transplant erythrocytosis and five controls produced CFU-E, but not BFU-3. A few CFU-E and BFU-E grew spontaneously in samples from four polycythaemic patients but not in samples from the controls. Addition of 1 unit per millilitre Epo caused similar increases in the number of colonies in both polycythaemic patients and controls. Of the nine patients eligible for follow-up, all four with spontaneous growth of BFU-E had transient erythrocytosis and four of the five patients with no spontaneous growth or spontaneous growth of CFU-E only had persistent erythrocytosis requiring treatment with ACE inhibitors. Conclusions: Pathophysiology of post-transplant erythrocytes is heterogenous. In one-third of the patients, there was unexpected, spontaneous and transient growth of BFU-E which was not predictive of permanent erythrocytosis. The results of stem-cell studies suggest that in these cases erythrocytosis may be caused by defective regulation of erythroid progenitor proliferation, possibly due to particular cellular interactions or the effect of cyclosporin on erythropoiesis.     

Effectiveness of low-dose erythropoietin in predialysis chronic renal failure patients

Recombinant human erythropoietin (rHuEpo) has been shown tobe both effective and usually safe in patients with chronicrenal failure who have not yet reached the stage requiring dialysis.There are, however, disturbing reports on the possibility ofdeterioration of the reserve renal function in association withrHuEpo therapy. Most of the published studies have used rHuEpoin doses of 50–150 U/kg three times weekly subcutaneously.An open-label trial of rHuEpo therapy was conducted on 21 patientswith chronic renal failure treated sequentially at a referralhospital, rHuEpo was used in doses of 50 U/kg twice weekly for4 weeks followed by 25 U/kg twice weekly for 8 weeks subcutaneously,a regimen substantially lower than current recommendations.This was associated with a gentle but significant increase inhaematocrit (P<0.05) and haemoglobin (P<0.05), while theserum creatinine and the reciprocal of the creatinine remainedstable, with a tendency to improve rather than worsen (P=0.06).We conclude that there is no need to aim at a rapid increasein haematocrit and haemoglobin by rHuEpo therapy; rather a gentleincrease using modest doses is both effective and safe.     

Plasma endothelin in haemodialysis patients treated with recombinant human erythropoietin

Predialysis plasma endothelin (ET) values were followed duringthe first 8 weeks of rHuEpo treatment in 12 patients on routinehaemodialysis. Mean plasma ET was significantly increased inuraemic patients before rHuEpo (27.911.4 pmol/1), as comparedto 40 healthy controls (16.55.7 pmol/1) (p<0.0001). UnderrHuEpo treatment, predialysis values remained unchanged althoughdiastolic blood pressure increased after 2 and 6 weeks. We foundno correlation between ET and haemoglobin or blood pressurebefore or under rHuEpo treatment. These results confirmed thehigh levels of plasma ET in haemodialysis patients, but no increasewas observed during rHuEpo treatment.     

Prostaglandin-mediated suppression of in vitro growth of erythroid progenitor cells

In vitro hematopoiesis was evaluated in 37 patients with chronic renal failure (CRF) who developed moderate to severe anemia in order to clarify the relationship between the growth of erythroid progenitor cells and CRF-associated anemia. Bone marrow cells from these patients were cultured in the presence of recombinant erythropoietin. Both early and late erythroid progenitor cells (BFU-E and CFU-E) were significantly suppressed in patients with CRF compared to those in normal controls, while myeloid progenitor cells (GM-CFC) remained normal. Suppression of CFU-E was shown to be mediated by prostaglandin(s) secreted from bone marrow adherent cells. Furthermore, the suppression of CFU-E was inversely correlated with concentrations of uremic serum or parathyroid hormone added to the assay system. These observations suggest a possibility that late erythroid progenitor cells may be preferentially suppressed by the network consisting of parathyroid hormone, bone marrow adherent cells and prostaglandin(s).     

Enhanced platelet reactivity with erythropoietin but not following transfusion in dialysis patients

Although the haemostatic defects that occur in uraemia are complex,a major factor is the anaemia of renal failure. This may nowbe corrected by recombinant human erythropoietin (rHuEpo) therapyrather than by repeated blood transfusion. Platelet reactivityto shear stress and collagen was measured using non-anticoagulatedblood to study the effect of erythropoietin or blood transfusionon platelet function. Twenty dialysis patients were commencedon 25–50 U/kg rHuEpo twice weekly. The dose was adjustedafter 3 months to maintain target Hb 10–10.5 g/dl. A further15 patients were studied before and 10–12 days after receivingblood transfusion. Baseline platelet reactivity was subnormalin both groups versus control (P<0.0001). In the rHuEpo group,a significant increase in platelet reactivity was observed at2 months (P<0.005) which disappeared at 3 months. This wasnot related to the increase in Hb (7.3±0.3 to 10.2±0.3g/dl, P<0.0001). There was no change in platelet reactivityafter transfusion, despite an increase in Hb (6.2±0.2to 8.8±0.2 g/dl, P<0.0001) similar to that occurringin the rHuEpo group. We conclude that after rHuEpo therapy butnot after transfusion a transient increase in platelet reactivityoccurs which is dissociated from changes in platelet and redcell numbers.     

Anemia of chronic renal failure: inhibition of erythropoiesis by uremic serum

The pathogenesis of anemia in patients with end-stage renal disease was studied by assessing the effect of uremic serum on the proliferation and maturation of erythroid progenitor cells, BFU-E and CFU-E, into colonies in vitro. Nucleated peripheral blood cells from 10 anemic patients produced normal or increased numbers of BFU-E colonies in response to added erythropoietin when cultured in control serum, but declined a mean of 63% when autologous uremic serum was substituted. Uremic sera from 90 patients cultured with normal human marrow produced a mean decrease in BFU-E colony growth of 72%, and of CFU-E colony growth of 82%, compared to control serum. Neither hemodialysis nor peritoneal dialysis was effective in removing the inhibitor. We conclude that patients with uremia have adequate circulating erythroid progenitors that respond to erythropoietin normally when removed from the uremic environment, and that uremic serum is toxic and inhibitory to erythropoiesis. This may be an important mechanism in the anemia of chronic renal failure.