Impact of conditioning and engraftment on iron status in hematopoietic stem cell transplantation: Contribution of labile plasma iron

Hepcidin in Children and Adults with Acute Leukemia or Undergoing Hematopoietic Cell Transplantation: A Systematic Review

Objectives: The association between hepcidin and acute leukemia (AL) or hematopoietic cell transplantation (HCT) in children and adults remains obscure. We aimed to assess this potential relationship through a systematic review of observational studies. Methods: An electronic search of three databases, including PubMed, Scopus, and Web of Science Core Collection, was performed up to 31 March 2022. Two independent reviewers assessed the search results according to predetermined inclusion and exclusion criteria, following PRISMA guidelines. Results: Of the 3607 titles identified, 13 studies published between 2008 and 2021 met the inclusion criteria. Most studies included a moderate number of participants and controls and used enzyme-linked immunosorbent assay (ELISA) to determine serum hepcidin levels. The principal findings: (1) serum hepcidin levels in patients with AL or undergoing HCT are increased compared to controls, regardless of the patient’s age and the phase of disease treatment; (2) AL therapy and HCT significantly influence serum hepcidin levels; (3) serum hepcidin may predict a worse outcome in patients with AL and post-HCT. Conclusions: This systematic review provides an overview of observational studies that deal with the association of hepcidin with AL and HCT. Although disturbances in iron metabolism are common in AL and HCT, and hepcidin seems to play a cardinal role in their modulation, more extensive research is needed.

Transferrin saturation as a surrogate marker for assessment of labile nontransferrin bound iron in chronic liver disease

BACKGROUND

Increased transferrin saturation (TS) and ferritin are common in hereditary hemochromatosis (HH) but also in chronic liver diseases (CLD). Nontransferrin bound iron (NTBI) is believed to be associated with iron-induced cell damage. We aimed to evaluate NTBI in CLD and their relationship with liver damage.

METHODS

Two groups of patients were studied. Group 1 (G1): 94 CLD patients from an Outpatient Hepatology Unit. Group 2 (G2): 36 healthy individuals form a Medical Checkup Clinic. Transferrin iron-binding capacity, TS, ferritin, AST, ALT, and red cell count were performed using standard tests. NTBI was assessed as enhanced labile plasma iron (eLPi). Levels of eLPi less than 0.4 µmol/l were considered within the normal range.

RESULTS

Prevalence of increased iron tests (elevated TS and ferritin) was 14% in G1 and 5.5% in G2 ( P = 0.19). Positive NTBI was found in 12 patients (11 in G1 and 1 in G2). Positivity to NTBI was associated with increased iron tests ( P = 0.03), cirrhosis ( P = 0.03) and AST index (ASTI) ( P = 0.03). NTBI was associated with TS of more than 70% ( P = 0.002) but not to elevated ferritin ( P = 0.74). Variables strongly associated with a positive NTBI in univariate analysis (TS > 70%, cirrhosis and ASTI) were submitted to binary regression analysis. TS of more than 70% was the only independent predictive factor ( P = 0.049; odds ratio, 6.8).

CONCLUSION

NTBI was associated with TS in CLD, but not with ferritin. NTBI testing could be useful for CLD patients with increased iron tests. Alternatively, a TS of more than 70% can be used as a surrogate marker.

Iron Toxicity and Chelation Therapy in Hematopoietic Stem Cell Transplant

Many patients with hematologic malignancies receive RBC transfusion support, which often causes systemic and tissue iron toxicity. Because of their compromised bone marrow function, hematopoietic stem cell transplant (HSCT) recipients are especially vulnerable to excess iron levels. Iron toxicity may compromise transplant engraftment and eventually promote relapse by mediating oxidative and genotoxic stress in hematopoietic stem cells (HSCs) and further impairing the already dysfunctional bone marrow microenvironment in HSCT recipients. Iron toxicity is thought to be primarily mediated by its ability to induce reactive oxygen species and trigger inflammation. Elevated iron levels in the bone marrow can decrease the number of HSCs and progenitor cells, as well as their clonogenic potential, alter mesenchymal stem cell differentiation, and inhibit the expression of chemokines and adhesion molecules involved in hematopoiesis. In vivo, in vitro, and clinical studies support the concept that iron chelation therapy may limit iron toxicity in the bone marrow and promote hematologic improvement and engraftment in HSCT recipients. This review will provide an overview of the current knowledge of the detrimental impact of iron toxicity in the setting of HSCT in patients with hematologic malignancies and the use of iron restriction approaches to improve transplant outcome.

Controversies on the Consequences of Iron Overload and Chelation in MDS

Many patients with MDS are prone to develop systemic and tissue iron overload in part as a consequence of disease-immanent ineffective erythropoiesis. However, chronic red blood cell transfusions, which are part of the supportive care regimen to correct anemia, are the major source of iron overload in MDS. Increased systemic iron levels eventually lead to the saturation of the physiological systemic iron carrier transferrin and the occurrence of non-transferrin-bound iron (NTBI) together with its reactive fraction, the labile plasma iron (LPI). NTBI/LPI-mediated toxicity and tissue iron overload may exert multiple detrimental effects that contribute to the pathogenesis, complications and eventually evolution of MDS. Until recently, the evidence supporting the use of iron chelation in MDS was based on anecdotal reports, uncontrolled clinical trials or prospective registries. Despite not fully conclusive, these and more recent studies, including the TELESTO trial, unravel an overall adverse action of iron overload and therapeutic benefit of chelation, ranging from improved hematological outcome, reduced transfusion dependence and superior survival of iron-loaded MDS patients. The still limited and somehow controversial experimental and clinical data available from preclinical studies and randomized trials highlight the need for further investigation to fully elucidate the mechanisms underlying the pathological impact of iron overload-mediated toxicity as well as the effect of classic and novel iron restriction approaches in MDS. This review aims at providing an overview of the current clinical and translational debated landscape about the consequences of iron overload and chelation in the setting of MDS.

Iron Toxicity and Hemopoietic Cell Transplantation: Time to Change the Paradigm

The issue of iron overload in hemopoietic cell transplantation has been first discussed in the field of transplantation for thalassemia. Thalassemia major is characterized by ineffective erythropoiesis and hemolysis leading to severe anemia. Patients require regular blood transfusion therefore they develop iron overload causing organ damage and hematopoietic cell transplantation (HCT) is a consolidated reliably curative option.

In this category of patients an important issue for transplant outcome is the iron burden before transplant and in the long-life post-transplant. Nevertheless today the concept of the impact of iron overload / toxicity on the outcome of HCT has been extended to other diseases characterized by periods of variable duration of transfusion dependence.

Recent preclinical data has shown how increased production of reactive oxygen species (ROS) resulting under iron overload condition, could impair the stem cells clonality capacity, proliferation and maturation. Also, microenvironment cells could be affected through this mechanism. For this reason, iron overload is becoming an important issue also in the engraftment period post-transplant.

The aim of this review is to update consolidated knowledge about the role of iron overload/iron toxicity in the HCT setting in non-malignant and in malignant diseases introducing the concept of exposition of free toxic iron forms and related cellular damage in the different stage of transplant.