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)     

Insulin-like growth factor I plays a role in regulating erythropoiesis in patients with end-stage renal disease and erythrocytosis

Erythroid progenitor growth, the serum hormones that regulate erythropoiesis, and the effect of patient's serum on the growth of normal erythroid progenitors were assessed in eight patients with end-stage renal disease (ESRD) and erythrocytosis. All patients were male and had been on maintenance dialysis, they had a hematocrit >50% and/or a red blood cell count >6 x 10(12)/L and an arterial oxygen saturation >95%. Four had acquired cystic disease of the kidney (ACDK), and four other non-ACDK patients did not have known causes of secondary erythrocytosis after appropriate investigations and long-term follow-up. The methylcellulose culture technique was used to assay the erythroid progenitor (BFU-E/CFU-E) growth. Serum erythropoietin (EPO) and insulin-like growth factor I (IGF-I) levels were measured by RIA. Paired experiments were performed to determine the effects of 10% sera from ESRD patients and control subjects on normal marrow CFU-E growth. The numbers of EPO-dependent BFU-E in marrow and/or blood of patients with ESRD and erythrocytosis were higher than those of normal controls. No EPO-independent erythroid colonies were found. Serum EPO levels were constantly normal in one patient and elevated in three patients with ACDK; for non-ACDK patients, EPO levels were normal or low in two patients and persistently increased in one, but fluctuated in the remaining one on serial assays. There was no correlation between serum EPO levels and hematocrit values. The serum IGF-I levels in patients with ESRD and erythrocytosis were significantly increased compared with normal subjects or ESRD patients with anemia. We found an inverse correlation between serum EPO and IGF-I levels. Sera from patients with ESRD and erythrocytosis exhibited a stimulating effect on normal marrow CFU-E growth. The stimulating effect of sera from patients who had a normal serum EPO level and an elevated IGF-I level could be partially blocked by anti-IGF-I. The present study suggests that IGF-I plays an important role in the regulation of erythropoiesis in patients with ESRD and erythrocytosis who did not have an increased EPO production.     

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.     

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).     

Effects of erythropoietin, angiotensin II, and angiotensin-converting enzyme inhibitor on erythroid precursors in patients with posttransplantation erythrocytosis.

BACKGROUND: Angiotensin-converting enzyme inhibitors (ACEI) have become the treatment of choice for posttransplantation erythrocytosis (PTE). Yet the pathogenesis of PTE and the mechanisms of action of ACEI remain unclear. Therefore, we studied the dose response to erythropoietin (Ep), angiotensin II (AII), and the ACEI enalaprilat on the in vitro proliferation of erythroid progenitors in patients with PTE and in controls. We also evaluated ACE polymorphism in the two groups. METHODS: Twelve patients with PTE and 12 renal transplant patients without PTE were studied. Erythroid burst-forming units (BFU-E) were isolated from peripheral blood using standard methods. Ep sensitivity was determined for four patients with PTE and three control patients, using 0-3 U/ml Ep. AII dose response was studied in four patients with PTE and five control patients, using AII concentrations of 0-1000 nM. The effect of enalaprilat was studied in eight patients with PTE and eight control patients, using drug concentrations of 0-10 ng/ml. ACE gene insertion/deletion polymorphism was determined by polymerase chain reaction. RESULTS: PTE patients showed a significant shift of the Ep response curve to the left compared with controls, with 50% maximal growth occurring at a lower Ep concentration (0.3 U/ml vs. 0.95 U/ml, P<0.025.) However, there was no difference in the number of BFU-E colonies between PTE patients and controls. AII added to the growth medium produced only minor stimulation in both groups. PTE patients showed significant inhibition of BFU-E growth with 10 ng/ml enalaprilat, but controls showed no inhibition of BFU-E growth with ACEI. There was no difference in ACE polymorphism between PTE and controls. CONCLUSIONS: Our data suggest that PTE is associated with increased erythroid progenitor sensitivity to Ep. The effect of ACEI to decrease hematocrit in patients with PTE may be due to inhibition of red cell precursor growth.     

Expression of angiotensin II type I receptor on erythroid progenitors of patients with post transplant erythrocytosis

BACKGROUND: The pathogenesis of posttransplant erythrocytosis (PTE) has been elusive. Angiotensin converting enzyme inhibitors (ACEI) are efficacious in lowering the hematocrit of patients with PTE and angiotensin II (AII) type I receptors (AT1R) were recently detected on red blood cell precursors, burst-forming unit-erythroid- (BFU-E) derived cells. The purpose of this study was to determine whether there is increased expression of the AT1R on BFU-E-derived cells of patients with PTE, which might contribute to the pathogenesis of PTE. METHODS: Twelve healthy volunteers and 25 transplant recipients (13 patients with and 12 without PTE) were studied. BFU-E from peripheral blood were cultured in methylcellulose and BFU-E-derived colonies were harvested on day 10. Western blotting was used to detect AT1R and erythropoietin receptor (EpoR) expression. Intracellular free calcium in response to AII and erythropoietin (Epo) was measured with digital video imaging. RESULTS: There were no differences between transplant patients, with and without PTE, with respect to weight, age, sex, blood pressure, serum creatinine, circulating renin, angiotensin II, and Epo levels. Hematocrit, red blood cell number, BFU-E-derived colony number,and size were significantly increased in PTE compared with other two groups. AT1R expression was increased by 44% on the erythroid progenitors of PTE versus non posttransplant erythrocytosis patients and by 32% in PTE patients versus normal volunteers. AT1R expression correlated significantly with the hematocrit in PTE (Spearman r=0.68, P=0.01). In contrast, EpoR expression was equivalent in all groups. The AT1R was functional since a significant increase in [Ca(i)] was observed in Fura-2 loaded day 10 cells when stimulated with AII (182%, P<0.0001). CONCLUSION: An increase in AT1R density was observed in erythroid precursors of transplant patients with PTE compared to those without PTE and normal volunteers, and the level of AT1R expression in PTE correlated significantly with the hematocrit. In contrast, EpoR expression was not different in PTE compared with non posttransplant erythrocytosis or normal controls. This study supports a role for the AT1 receptor signaling pathway in the pathogenesis of PTE.     

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.     

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.     

Long-term effects of recombinant human erythropoietin on bone marrow progenitor cells

Eleven uraemic patients were treated with recombinant humanerythropoietin (rHuEpo). Seven haemodialysis patients and fourperitoneal dialysis patients received a starting dose of 80IU/kg i.v. and 40 IU/kg s.c. respectively, thrice weekly. Thenumber of burst-forming-unit erythroid (BFU-E), colony-forming-uniterythroid (CFU-E), granulocyte-monocyte (CFU-GM) and megakaryocyte(CFU-Mk) were assayed 2 weeks before (DO), and 1 (M1) and 6months (M6) after the initiation of rHuEpo treatment by meansof a commonly applied in-vitro clonal assay. All the patientsshowed the same haematopoietic response. A significant increaseof CFU-E and CFU-Mk could be observed within 1 month of treatment.At this time, no significant modification was observed in BFU-Eand CFU-GM number. At the 6th month the increase of CFU-E wasmaintained, whereas a significant fall of BFU-E, CFU-GM andCFU-Mk was observed. These results suggest that in-vivo effects of rHuEpo are notrestricted to the erythroid lineage but that erythropoietinmight also act as a co-factor of megakar-yopoiesis. In the longterm erythropoietin might induce erythroid differentiation inmultipotent progenitor cells at the expense of the non-erythroidprogenitors.     

Increased erythropoietin response to venesection in erythrocytosic renal transplant patients

Anaemia of end-stage chronic renal failure improves following successful kidney transplantation. However, erythrocytosis occurs in 6.8–17.3% of transplanted patients. Mechanism of post-transplant erythrocytosis (PTE) and its erythropoietin (Epo) dependence are still controversial. Firstly, we compared basal serum Epo levels of 10 PTE patients, 14 non-erythrocytosic renal transplant (non-PTE) patients and 12 healthy blood donors. Then we performed venesection in PTE patients and healthy blood donors and compared their Epo response to venesection 5 hours later. The mean basal serum Epo of 24.3 mU/ml was significantly higher in the PTE group than the 10.8 mU/ml in the non-PTE and 8.6 mU/ml in the healthy blood donor group (p<0.01). Epo levels in the non-PTE group did not differ significantly from those of healthy blood donors (p>0.05). Following venesection the mean serum Epo levels increased significantly in both groups, from 24.3 mU/ml to 67.7 mU/ml (p<0.001) in the PTE group and from 8.6 to 12.1 mU/ml (p<0.01) in the healthy blood donor group, but the increment in the PTE group was more marked. We conclude that PTE patients have elevated basal serum Epo levels and there is a feedback regulation of Epo secretion in these patients like in healthy blood donors, but in an exaggerated way.     

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.     

Captopril induces correction of postrenal transplant erythremia

Kidney transplant patients may develop post-transplant erythremia (PTE), and in order to avoid thromboembolism venesection, anticoagulation and native kidney removal have been suggested. We propose captopril as an alternative therapy for PTE. Seven hypertensive PTE patients, aged 42±10 years with stable renal function, were investigated to exclude primary or secondary polycythemia. All patients manifested true erythrocytosis [red blood cells (RBC) mass>20% of predicted level] with concomitant increases in hematocrit and hemoglobin levels. Captopril was introduced in gradually increasing doses up to 75 mg/day under careful monitoring of blood pressure and renal function. Weekly follow-up was arranged to evaluate drug efficacy. After captopril, a significant reduction with normalization of the RBC mass (42±4 vs 31±5 ml/kg; P<0.005) was observed. The RBC counts and hematocrit and hemoglobin levels also decreased. One patient had recurrent erythrocytosis after captopril withdrawal. Captopril may be a simple, effective, and non aggressive treatment for postrenal transplant erythremia.     

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      

Posttransplant erythrocytosis

Posttransplant erythrocytosis (PTE) is defined as a persistently elevated hematocrit to a level greater than 51% after renal transplantation. It occurs in 10% to 15% of graft recipients and usually develops 8 to 24 months after engraftment. Spontaneous remission of established PTE is observed in one fourth of the patients within 2 years from onset, whereas in the remaining three fourths it persists for several years, only to remit after loss of renal function from rejection. Predisposing factors include male gender, retention of native kidneys, smoking, transplant renal artery stenosis, adequate erythropoiesis prior to transplantation, and rejection-free course with well-functioning renal graft. Just as in other forms of erythrocytosis, a substantial number (approximately 60%) of patients with PTE experience malaise, headache, plethora, lethargy, and dizziness. Thromboembolic events occur in 10% to 30% of the cases; 1% to 2% eventually die of associated complications. Posttransplant erythrocytosis results from the combined trophic effect of multiple and interrelated erythropoietic factors. Among them, endogenous erythropoietin appears to play the central role. Persistent erythropoietin secretion from the diseased and chronically ischemic native kidneys does not conform to the normal feedback regulation, thereby establishing a form of "tertiary hypererythropoietinemia." However, erythropoietin levels in most PTE patients still remain within the "normal range," indicating that erythrocytosis finally ensues by the contributory action of additional growth factors on erythroid progenitors, such as angiotensin II, androgens, and insulin-like growth factor 1 (IGF-1). Inactivation of the renin-angiotensin system (RAS) by an angiotensin-converting enzyme (ACE) inhibitor, or an angiotensin II type 1 AT1 receptor blocker represents the most effective, safe, and well-tolerated therapeutic modality.     

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.     

Erythropoietin deficiency and inhibition of erythropoiesis in renal insufficiency

The relative importance of erythropoietin (Ep) and inhibition of erythropoiesis in the anemia of chronic renal insufficiency has been investigated. Sixty patients with varying degrees of renal insufficiency, 40 normal subjects and 40 patients with anemia and normal renal function, were studied. Erythroid (CFU-E) and granulocytic (CFU-GM) progenitor cell colony formation were assayed in fetal mouse liver and human bone marrow cultures, respectively. Erythropoietin was measured by radioimmunoassay. Hematocrit and plasma creatinine concentration correlated with the degree of serum inhibition of CFU-E formation (r = 0.69, P less than 0.001, and r = 0.62, P less than 0.001, respectively). Serum erythropoietin levels in patients with renal insufficiency (34.4 +/- 6.7 mU/ml) were slightly higher than normal values (23.1 +/- 0.98 mU/ml), but showed no relationship to plasma creatinine, hematocrit, or inhibition of CFU-E formation. In contrast, serum erythropoietin concentrations increased exponentially as the hematocrit decreased below 32% (r = 0.61, P less than 0.001), and CFU-E formation was stimulated by serum in anemia patients with normal renal function. Studies of granulopoiesis showed uremic sera supported in vitro CFU-GM growth more efficiently than sera from normal subjects. These results suggest that inhibition of erythroid, but not granulocytic, progenitor cell formation, in addition to a relative erythropoietin deficiency, are the primary factors responsible for the anemia of chronic renal failure.     

Post-transplant erythrocytosis and immunosuppression with cyclosporin: a case-control study

Review of 142 renal transplant recipients treated with cyclosporin and prednisolone revealed 23 patients with post-transplant erythrocytosis. The clinical characteristics of these patients were compared with 23 cyclosporin/prednisolone-treated control subjects matched for age, sex, and duration of transplant. Erythrocytosis developed between 6 weeks and 30 months (median 12 months) after transplant. It persisted in 16 patients and resolved spontaneously in five. In two patients the decrease in haematocrit was associated with acute leukaemia in one and sudden deterioration of renal function in the other. In the study group there were fewer HLA (A, B and DR) mismatches (P less than 0.05) and greater pretransplant haematocrit (P less than 0.01) than in the control group. Other clinical factors--previous allografts, panel reactive cytotoxic antibodies, duration and type of dialysis, transplant function, pre- and post-transplant blood pressure, number of rejection episodes, cyclosporin concentration and dose, smoking habits and use of diuretics--did not differ significantly between the two groups. In our experience, erythrocytosis in cyclosporin-treated patients is a relatively common phenomenon and does not, in general, resolve spontaneously. It is unrelated to transplant function or rejection episodes but affects patients with well-matched kidneys and elevated pretransplant haematocrit values.     

Erythroid Progenitor Growth in Erythrocytosic Transplanted Patients

In 55 patients who underwent renal transplantation, erythrocytosis (E) was observed in 6. In all patients, the growth of erythroid progenitors [burst-forming unit erythroid (BFU-e)], using mononuclear blood cells, was evaluated in in vitro cultures. The results showed a significant increase of serum erythropoietin (s-Ep) in erythrocytosis and in nonerythrocytosis patients with a subsequent decrease when hematocrit (Hct) and hemoglobin (Hb) reached high levels, showing a recovery of a feedback control system. Notwithstanding the diminution of s-Ep, six patients demonstrated further progressive rise of the Hct and Hb to a final state of E. The in vitro BFU-e cultures from these patients showed a noticeable sensitivity to progressively reduced doses of Ep and also the capacity to develop a few colonies when the medium was Ep-free. These results were not verified using peripheral blood depleted of monocyte and/or T lymphocyte cells. Therefore, in transplanted patients with erythrocytosis, it is possible that particular cellular interactions stimulate an early hyperproliferation of BFU-e with a greater Ep sensitivity and at least partly the capacity to grow also in the absence of Ep.     

Insulin-like growth factor I: a modulator of erythropoiesis in uraemic patients?

Anaemia is a feature almost invariably complicating chronic renal failure. Its pathophysiology is multifactorial but the most important cause is erythropoietin (Epo) deficiency. However, either no relation or even a weakly positive relation generally exists between serum immunoreactive (i) Epo and haematocrit values in uraemic anaemia, whereas in anaemias of non-renal origin the correlation is most often strongly negative. Recent evidence indicates that growth hormone also stimulates erythropoiesis. Moreover, late erythroid progenitor cells (CFU-E) require insulin and/or insulin-like growth factor I (IGF-I) for development in vitro. IGF-I has been shown to have a synergistic action with Epo. We have measured serum iEpo and IGF-I levels in 17 haemodialysis patients with severe hyperparathyroidism (mean +/- SEM serum iPTH, 988 +/- 88 pg/ml). Mean age and duration of dialysis treatment were 46.1 +/- 3.4 and 8.8 +/- 1.0 years respectively. Mean haematocrit and haemoglobin values wer 28.1 +/- 1.7% and 9.39 +/- 0.54 g/dl respectively. Mean serum iEpo and IGF-I levels were 20.3 +/- 4.7 mU/ml and 320 +/- 20 ng/ml respectively (normal values for serum iEpo and IGF-I, 17.9 +/- 6 mU/ml and 91 +/- 23 ng/ml respectively). We found that serum IGF-I concentrations were well correlated with haematocrit values (r = 0.68, n = 15, P less than 0.004) whereas serum iEpo values were not (r = 0.41, n = 12, P = 0.18). IGF-I could therefore be an important factor regulating erythropoiesis in uraemic patients, at least when associated with severe hyperparathyroidism.