Recombinant human erythropoietin independence in chronic hemodialysis patients: clinical features, iron homeostasis and erythropoiesis

Functional erythropoietin-hepcidin axis in recombinant human erythropoietin independent haemodialysis patients

AIM

Relatively few haemodialysis (HD) patients remain independent of recombinant human erythropoietin ('rHU-EPO free patients'). We investigated the role of EPO and hepcidin, two key hormones involved in anaemia.

METHODS

We report a monocentric case-control series. Iron status, EPO and hepcidin levels were analysed in 15 Adult HD (Age > 18 years) with a stable haemoglobin (Hb) level that have not received rHU-EPO for at least 6 months (=rHU-EPO free patients); and in 60 controls with a stable rHU-EPO dose and Hb level.

RESULTS

The rHU-EPO free patients had a higher Hb level compared to controls (12.1 ± 0.99 g/dL vs 11.1 ± 0.73, P = 0.0014), and a lower ferritin level (183 ± 102 vs 312 ± 166 ng/mL, P = 0.001). Hepcidin levels were lower in the rHU-EPO free patients (12.53 ± 10.46 ng/mL) compared to the controls (37.95 ± 34.33 ng/mL), P = 0.0033. Hepcidin levels correlated significantly with ferritin levels; but neither with transferrin saturation, C-reactive protein nor EPO levels. Unsupervised analysis revealed that rHU-EPO free patients had a specific clinical/biological profile (presence of renal cyst, longer dialysis vintage, lower ferritin, and EPO and hepcidin levels compared to the control group). Finally, we showed that a lower ferritin level might be a surrogate marker of a lower hepcidin status in this population.

CONCLUSION

Recombinant human erythropoietin free patients seem to restore the EPO-hepcidin axis that is critical for erythropoiesis. A specific combination of clinical and biological parameters may help to detect future rHU-EPO free patients.

Naturally nonanemic dialysis patients: Who are they?

Introduction Not only anemia, but also erythropoiesis stimulating agent (ESA)s for treating anemia may adversely affect prognosis of chronic hemodialysis patients. Various features of naturally (with no ESA usage) nonanemic patients may be useful for defining several factors in the pathogenesis of anemia. Methods Data, retrieved from the European Clinical Database (EuCliD)-Turkey on naturally nonanemic prevalent chronic hemodialysis patients (n: 201) were compared with their anemic (those who required ESA treatment) counterparts (n: 3948). Findings Mean hemoglobin values were 13.5 ± 0.8 and 11.5 ± 0.9 g/dL in nonanemic and anemic patients, respectively (P < 0.001). Nonanemia status was associated with younger age, male gender, longer dialysis vintage, nondiabetic status, more frequent hepatitis-C virus seropositivity and more frequent arteriovenous fistula usage. Serum ferritin and CRP levels and urea reduction ratio were higher in ESA-requiring patients. One (99%) and two (95.3%) years survival rates of the "naturally nonanemic" patients were superior as compared to anemics (91.0% and 82.6%, respectively), (P < 0.001). Discussion "Naturally nonanemic" status is associated with better survival in prevalent chronic hemodialysis patients; underlying mechanisms in this favorable outcome should be investigated by randomized controlled trials including large number of patients.

Renal erythropoietin-producing cells in health and disease

Erythropoietin (Epo) is an indispensable erythropoietic hormone primarily produced from renal Epo-producing cells (REPs). Epo production in REPs is tightly regulated in a hypoxia-inducible manner to maintain tissue oxygen homeostasis. Insufficient Epo production by REPs causes renal anemia and anemia associated with chronic disorders. Recent studies have broadened our understanding of REPs from prototypic hypoxia-responsive cells to dynamic fibrogenic cells. In chronic kidney disease, REPs are the major source of scar-forming myofibroblasts and actively produce fibrogenic molecules, including inflammatory cytokines. Notably, myofibroblast-transformed REPs (MF-REPs) recover their original physiological properties after resolution of the disease insults, suggesting that renal anemia and fibrosis could be reversible to some extent. Therefore, understanding the plasticity of REPs will lead to the development of novel targeted therapeutics for both renal fibrosis and anemia. This review summarizes the regulatory mechanisms how hypoxia-inducible Epo gene expression is attained in health and disease conditions.

Prevalence and related factors of the absence of anemia among Chinese chronic hemodialysis patients: a multicenter cross-sectional study

BACKGROUND

Some chronic hemodialysis (HD) patients can maintain normal hemoglobin levels without requiring erythropoiesis-stimulating agents (ESAs). However, the prevalence and the factors associated with this condition in Chinese chronic HD patients have not been reported. The aim of this study was to investigate clinical features, iron metabolism, and other characteristics to survey the prevalence rate and the related factors of this condition among Chinese chronic HD patients.

METHODS

A total of 1,318 chronic HD patients participated in this study. The patients were classified into a non-ESA group (n = 11) and an ESA group (n = 1,307). The r-HuEPO-independent (non-ESA) HD patients were defined as having hemoglobin greater than 12 g/dl for more than 6 months without r-HuEPO injection, blood transfusion, or androgen therapy. Epidemiological and laboratory data were collected. Renal sonography was also performed on each patient to evaluate the formation of renal and liver cysts, and the number and size of the cysts were recorded.

RESULTS

Approximately 0.84 % of all HD patients were found to be r-HuEPO independent. The non-ESA group had a higher proportion of men (79.6 vs. 58.3 %), a longer duration of renal replacement therapy (RRT) (8.6 ± 6.1 vs. 5.1 ± 3.3 years), a higher prevalence of adult polycystic kidney disease (APKD) (46.3 vs. 9.7 %), a higher prevalence of hepatitis C virus (HCV) liver disease (26.2 vs. 3.2 %, P < 0.01), and had older patients (63.3 ± 13.6 vs. 49.6 ± 13.5 years). Endogenous erythropoietin levels in the non-ESA group were significantly higher than those in the ESA group (61.8 ± 27.1 vs. 29.3 ± 11.7 mU/ml). Non-ESA patients had a significantly higher number of renal (38.1 vs. 13.2 %) and hepatic cysts (9.3 vs. 1.9 %), which were also larger in size (2.9 ± 1.6 vs. 1.3 ± 0.3 cm) compared with those of patients in the ESA group. No significant difference in iron metabolism was found between two groups. In the multivariate Cox analysis, the independent predictor factors for the absence of anemia in these HD patients were the number of renal cysts >6 cysts (95 % CI 1.058-1.405; P = 0.00), endogenous erythropoietin levels (95 % CI 1.139-1.361; P = 0.05), HCV+ liver disease (95 % CI 1.129-1.316; P = 0.01), and time on RRT (95 % CI 1.019-1.263; P = 0.05).

CONCLUSIONS

To our knowledge, this study is the first to report on r-HuEPO independence among Chinese HD patients. The prevalence among Chinese chronic HD patients is significantly lower than that reported in the literature. Factors contributing to this condition are complex and multiple. The frequency of this condition is higher in men and in older patients with long-term RRT, in patients with HCV+ liver disease, and in APKD patients. This condition is associated with increased endogenous erythropoietin production and the presence of renal and hepatic cysts.

Plasticity of renal erythropoietin-producing cells governs fibrosis

CKD progresses with fibrosis and erythropoietin (Epo)-dependent anemia, leading to increased cardiovascular complications, but the mechanisms linking Epo-dependent anemia and fibrosis remain unclear. Here, we show that the cellular phenotype of renal Epo-producing cells (REPs) alternates between a physiologic Epo-producing state and a pathologic fibrogenic state in response to microenvironmental signals. In a novel mouse model, unilateral ureteral obstruction-induced inflammatory milieu activated NFκB and Smad signaling pathways in REPs, rapidly repressed the Epo-producing potential of REPs, and led to myofibroblast transformation of these cells. Moreover, we developed a unique Cre-based cell-fate tracing method that marked current and/or previous Epo-producing cells and revealed that the majority of myofibroblasts are derived from REPs. Genetic induction of NFκB activity selectively in REPs resulted in myofibroblastic transformation, indicating that NFκB signaling elicits a phenotypic switch. Reversing the unilateral ureteral obstruction-induced inflammatory microenvironment restored the Epo-producing potential and the physiologic phenotype of REPs. This phenotypic reversion was accelerated by anti-inflammatory therapy. These findings demonstrate that REPs possess cellular plasticity, and suggest that the phenotypic transition of REPs to myofibroblasts, modulated by inflammatory molecules, underlies the connection between anemia and renal fibrosis in CKD.

Iron overdose: a contributor to adverse outcomes in randomized trials of anemia correction in CKD

Administration of intravenous iron to supplement erythropoiesis stimulating agents (ESAs) has become a common practice in the management of anemia in patients with end-stage renal disease. Randomized clinical trials of anemia correction in this population have shown more adverse outcomes in CKD and ESRD patients assigned to the higher hemoglobin targets. Retrospective analysis of these trials suggests that morbidity is higher in subjects who fail to achieve the designated hemoglobin target and are typically exposed to higher doses of ESAs and iron than those that easily achieve the intended targets. Intravenous iron administration circumvents the natural biologic mechanisms for handling and utilization of iron. There is in vitro and in vivo evidence that intravenous iron preparations can cause oxidative stress, endothelial dysfunction, inflammation, impaired immunity, and renal injury. Since iron overload is known to promote endothelial dysfunction, cardiovascular disease, and immune dysfunction which are the leading causes of premature mortality in CKD and ESRD patients, it is imperative to exercise caution with the use of IV iron preparations in this population. The present review is intended to provide a brief overview of the potential adverse effects of the overzealous use of these agents.

Naturally occurring higher hemoglobin concentration does not increase mortality among hemodialysis patients

A small percentage of hemodialysis patients maintain higher hemoglobin concentrations without transfusion or erythropoietic therapy. Because uncertainty exists regarding the effects of higher hemoglobin concentration on mortality and quality of life among hemodialysis patients, studying this group of patients with sufficient endogenous erythropoietin may provide additional insights. The prospective, observational Dialysis Outcomes and Practice Patterns Study provides an opportunity to investigate this group. Among 29,796 patients in 12 nations, 545 (1.8%) maintained hemoglobin concentrations >12 g/dl for 4 months without erythropoietic support. This subset tended to be male, to have a longer duration of end-stage renal disease, and to not dialyze via a catheter. Cystic disease as the underlying cause of renal failure was over-represented in this group but was present in only 25%. Lung disease, smoking, and cardiovascular disease were associated with increased likelihood of naturally higher hemoglobin concentration. Quality-of-life scores were not higher among this subset compared with the other patients. Unadjusted mortality risk for patients with hemoglobin >12 g/dl and no erythropoietic therapy was lower than for the other patients, but after thorough adjustment for case mix, there was no difference between groups (relative risk, 0.98; 95% CI 0.80 to 1.19). These data show that naturally occurring hemoglobin concentration >12 g/dl does not associate with increased mortality among hemodialysis patients.