Ultrastructure and cell cycle distribution of erythropoietic cells in heterozygotes and homozygotes for haemoglobin E

Iron metabolism in heterozygotes for hemoglobin E (HbE), alpha-thalassemia 1, or beta-thalassemia and in compound heterozygotes for HbE/beta-thalassemia

BACKGROUND

Despite large populations carrying traits for thalassemia in countries implementing universal iron fortification, there are few data on the absorption and utilization of iron in these persons.

OBJECTIVE

We aimed to determine whether iron absorption or utilization (or both) in women heterozygous for beta-thalassemia, alpha-thalassemia 1, or hemoglobin E (HbE) differed from that in control subjects and compound HbE/beta-thalassemia heterozygotes.

DESIGN

In Thai women (n = 103), red blood cell indexes, iron status, non-transferrin-bound iron, and growth differentiation factor 15 were measured, and body iron was calculated. Fractional iron absorption was measured from meals fortified with isotopically labeled ((57)Fe) Fe sulfate, and iron utilization was measured by the infusion of ((58)Fe) Fe citrate.

RESULTS

Iron utilization was approximately 15% lower in alpha-thalassemia 1 or beta-thalassemia heterozygotes than in controls. When corrected for differences in serum ferritin, absorption was significantly higher in the alpha- and beta-thalassemia groups, but not the HbE heterozygotes, than in controls. HbE/beta-thalassemia compound heterozygotes had lower iron utilization and higher iron absorption and body iron than did controls. Nontransferrin-bound iron and growth differentiation factor 15 were higher in the compound heterozygotes, but not in the other groups, than in the controls.

CONCLUSIONS

In alpha-thalassemia 1 and beta-thalassemia heterozygotes with ineffective erythropoesis, dietary iron absorption is not adequately down-regulated, despite a modest increase in body iron stores. In populations with a high prevalence of these traits, a program of iron fortification could include monitoring for possible iron excess and for iron deficiency.

Increased circulating activated endothelial cells, vascular endothelial growth factor, and tumor necrosis factor in thalassemia

An increased number of circulating endothelial cells (CECs) was demonstrated in alpha- and beta-thalassemic patients, beta-thalassemia/hemoglobin E (BE), both splenectomized (BE[S]) and non-splenectomized (BE[NS]), had higher numbers of CECs than alpha-thalassemia, both HbH (alpha-thal l/alpha-thal 2; H) and HbH with hemoglobin Constant Spring (alpha-thal 1/CS; H/CS). CECs were also increased in heterozygous HbE (EA) and homozygous HbE (EE). The highest level of tumor necrosis factor-alpha (TNF-alpha) was found in HbH/CS patients, whereas the highest levels of vascular endothelial growth factor (VEGF) was observed in BE[S] patients. Significant decreases, in protein C and protein S levels were found in both alpha- and beta-thalassemia compared with normal. Good correlations between the numbers of CEC and TNF-alpha, VEGF, protein C, and protein S levels were demonstrated in this study. In addition, markers for endothelial cell activation and injury (intercellular adhesion molecule-1, ICAM-1/CD54; vascular cell adhesion molecule-1, VCAM-1/CD106; and E-selectin, ELAM-1/CD62E) were detected on the surface of isolated CECs using immunofluorescence technique. Appearance of CECs with markers for endothelial cell activation, together with increased levels of TNF-alpha and VEGF and decreased levels of protein C and protein S in the circulation, may account for the propensity of vascular perturbation in thalassemic subjects.

The congenital dyserythropoietic anaemias

Congenital dyserythropoietic anaemias (CDA) are a category of rare genetic diseases that affect erythropoiesis. Dyserythropoiesis is associated with abnormal erythroblasts and leads to altered red cells, the amount of which is insufficient. There are three main, well-defined CDAs, CDA I, II and III. Their characterization is based on a careful examination of the bone marrow under light and electron microscopes. In addition, a number of rare or unique forms of dyserythropoiesis have been reported. At least with respect to CDA I to III, the clinical evaluation is reaching an ever increasing refinement: age of discovery, determinants of iron overload and/or biliary complications. Over the past few years, a more promising breakthrough has been the localization of the genes responsible for CDA I, II and III, that is, 15q15.1-q15.3, 20q11.2 and 15q21-q25, respectively. Epidemiological studies have now become possible. The identification of the genes is pending.

Congenital dyserythropoietic anaemias: clinical features, haematological morphology and new biochemical data

Three types of congenital dyserythropoietic anaemia (CDA) were originally identified on the basis of the pattern of dysplastic changes in the erythroblasts and the results of the acidified serum lysis test (Ham test). These were designated CDA types I, II and III. Several other types have been described subsequently and new forms continue to be reported. Some patients with CDA develop iron overload even without repeated blood transfusion and may present with the complications of severe iron overload. Dysmorphic features are seen in some cases, especially of CDA type I. In CDA type II, incomplete processing of N-linked oligosaccharides leads to a marked reduction of polylactosamines associated with band 3 of the red cell membrane. A few cases of CDA type III develop lymphoid neoplasms. Some of the Swedish cases of CDA type III have developed a retinal abnormality characterized by angioid streaks and macular degeneration. The chromosomal localizations of the disease gene in CDA types I and II and in the Swedish family with CDA type III are now known, but the identities of the mutant genes are still unknown. Cases of CDA type I have shown a partial haematological response to interferon-alpha, however the biochemical basis of this response is unclear. An important step in the diagnosis of sporadic cases of CDA is the exclusion of known causes of acquired dyserythropoiesis.

Erythroblast- and erythrocyte-bound antibodies in alpha and beta thalassaemia syndromes

Thirty-five Thai patients with various alpha-thalassaemia (alpha-thal 1/alpha-thal 2, alpha-thal 1/HbCS, HbCS/HbCS) and beta-thalassaemia (beta-thal/HbE, severe and mild form, HbE/HbE) syndromes were examined for the presence of immunoglobulins and C3d on o-tolidine positive erythroblasts in the bone marrow, and for the amounts of IgG of some specificities bound to circulating erythrocytes. In mild, but not in severe beta-thal/HbE and in alpha-thalassaemia, the percentages of Ig-positive erythroblasts were significantly higher than in controls and correlated well with the percentage of IgG-positive erythroblasts. By contrast, the percentages of IgM and C3d positive erythroblasts were low and similar in thalassaemic and control marrows. A substantial proportion of thalassaemic patients showed more erythrocyte-bound IgG than controls, but statistically significant elevations were seen only in severe beta-thal/HbE. Within a particular syndrome erythrocyte-bound IgG was more abundant in splenectomized than non-splenectomized subjects. It showed specificity for spectrin in some beta-thalassaemic patients and for band 3 protein in several individuals with alpha- or beta-thalassaemia. The results suggest that IgG antibodies play a role in the haemolysis of thalassaemia and that they are likely to be involved in the ineffective erythropoiesis in at least some of the syndromes studied.

Congenital dyserythropoietic anaemia with novel intra-erythroblastic and intra-erythrocytic inclusions

A hitherto undescribed form of congenital dyserythropoietic anaemia is reported. The patient was severely anaemic and hydropic at birth and is now 8 years old. She has a moderate normochromic normocytic anaemia. HbF level of 50%, reticulocyte count of 5-12% and hyperbilirubinaemia. Bone marrow smears showed intense normoblastic erythroid hyperplasia with morphological evidence of dyserythropoiesis; the most common dysplastic features were basophilic stippling of polychromatic erythroblasts and erythrocytes and marked abnormalities of nuclear shape in polychromatic erythroblasts. Electron microscope studies showed that some polychromatic erythroblasts and several erythrocytes contained inclusions which were rounded, elongated or irregular in outline or were doughnut-shaped. These inclusions consisted of compact masses of tubules and saccules which may represent smooth endoplastic reticulum together with Golgi cisternae. The ultrastructural studies also revealed peculiar membrane-bound cylindrical structures in a rare late erythroblast, and phagocytosed erythroblasts within some macrophages. The technique of combined Feulgen microspectrophotometry and 3H-thymidine autoradiography demonstrated a pile-up of early polychromatic erythroblasts in the G1 and G2 phases of the cell cycle, indicating a prolongation of, or an arrest at, these phases. Furthermore, nearly a quarter of all erythroblasts failed to incorporate 3H-leucine into protein. Thus the anaemia appeared to be due to a combination of disordered erythroblast function, increased ineffectiveness of erythropoiesis and peripheral haemolysis. The primary defect may be an excessive synthesis or impaired degradation of intracytoplasmic membranes.

Ultrastructure and cell cycle distribution of bone marrow cells in protein-energy malnutrition

Bone marrow aspirates from four children with kwashiorkor and three with marasmus were studied using the techniques of electron microscopy and combined Feulgen microspectrophotometry and 3H-thymidine autoradiography. The majority of the erythroblasts were ultrastructurally normal, the distribution of the early polychromatic erythroblasts between the various stages of the cell cycle was normal or almost normal, and the macrophages did not contain ingested erythroblasts. Since erythropoietin production has been shown to be normal in protein-energy malnutrition, these findings suggest that at least in some cases of PEM the impairment of erythropoiesis results primarily from an abnormality in the erythroid progenitor cell pool rather than from dyserythropoiesis and ineffective erythropoiesis. In one afebrile and apparently uninfected patient with marasmus, a substantial proportion of the neutrophil granulocytes and their more mature precursors contained electron-dense, myelin-containing intracytoplasmic structures which were presumed to be abnormal primary granules. In four of the patients, the 3H-thymidine labelling index of the neutrophil promyelocyte-myelocyte pool was increased. In addition, in all of the cases, neutrophils at various stages of degradation were readily found within the cytoplasm of some of the macrophages. Thus, whereas the techniques employed did not reveal a major disturbance in the morphologically recognizable precursor cells of the erythroid series in PEM, they demonstrated some abnormalities in such cells of the neutrophil series.

Studies of erythroblast function in congenital dyserythropoietic anaemia, type I: evidence of impaired DNA, RNA, and protein synthesis and unbalanced globin chain synthesis in ultrastructurally abnormal cells

Two patients with congenital dyserythropoietic anaemia, type I (CDA) were studied. Their blood reticulocytes showed unbalanced globin chain synthesis with increased alpha:beta globin chain synthesis ratios. A high proportion of the erythroblasts displayed the characteristic "Swiss cheese" abnormality of the nuclear chromatin and some also showed cytoplasmic intrusions lined with nuclear membrane within the nucleus. Occasional erythroblast profiles contained intracytoplasmic inclusions that were ultrastructurally indistinguishable from precipitated alpha chains. The technique of combined Feulgen microspectrophotometry and 3H-thymidine autoradiography showed gross abnormalities of proliferation in the early polychromatic erythroblasts. The proliferative abnormalities included an arrest of DNA synthesis after the progress of cells through part of the S phase and the formation of several mononucleate and binucleate cells with hypertetraploid total DNA contents. The bone marrow cells gave a normal deoxyuridine suppressed value, indicating that there was no impairment of the methylation of deoxyuridylate. Electron microscope autoradiographic studies showed that a high proportion of the erythroblasts with the "Swiss cheese" nuclear abnormality suffered from a severe impairment, or arrest of DNA, RNA, and protein synthesis.