Effects of four species of interferon-alpha on cultured erythroid progenitors from congenital dyserythropoietic anaemia type I

The in vitro effects of interferon (IFN)-alpha on erythroid progenitor cells derived from the peripheral blood of five patients with congenital dyserythropoietic anaemia (CDA) type I and seven healthy adults were studied. Ficol-hypaque-separated mononuclear cells were cultured for 14 d in StemGEM-1d medium with 0, 1, 10 and 100 U/ml of recombinant IFN-alpha2a, recombinant IFN-alpha2b, the genetically-engineered hybrid molecule IFN-alpha(1-8) or the laboratory-designed molecule IFN-alpha(consensus). Erythroid bursts and colonies were counted, picked and processed for electron microscopy. In the experiments employing IFN-alpha2a there were no differences in the numbers of erythroid bursts or colonies between four patients with CDA type I and seven healthy adults. All five patients with CDA type I showed the 'Swiss-cheese' ultrastructural abnormality of the heterochromatin in a proportion of the erythroblasts when the progenitor cells were cultured in the absence of added IFN-alpha. A statistically significant reduction in the proportion of erythroblasts showing the 'Swiss-cheese' defect was seen when the erythroid progenitors were cultured in the presence of 0.01-0.5 U/ml IFN-alpha2a (five patients), or 0.1 U/ml of IFN-alpha2b (two patients). In contrast, no reduction was seen in cultures containing 0.1-100 U/ml of either IFN-alpha(1-8) or IFN-alpha(consensus) or 20 microM hydroxyurea (two patients). The partial correction of the 'Swiss-cheese' abnormality by low concentrations of IFN-alpha2a in vitro provides an experimental model with which the mechanisms underlying the haematological response that occurs after the in vivo administration of this species of IFN-alpha may be investigated.

Congenital dyserythropoiesis with intererythroblastic chromatin bridges and ultrastructurally-normal erythroblast heterochromatin: a new disorder

Two non-anaemic subjects, a father and daughter, with a new form of congenital dyserythropoiesis are reported. The features of their disorder are: (1) an abnormal blood film with basophilic stippling of red cells and oval macrocytes, (2) various dysplastic changes in the erythroblasts, including internuclear chromatin bridges, (3) ultrastructurally-normal erythroblast heterochromatin, (4) normal serum thymidine kinase activity, and (5) a probable autosomal dominant inheritance. The last three features distinguish this disorder from CDA type I.

Transient increase in the alpha3-isoform of Na,K-ATPase in rat erythroblastic cells

Using immunoelectron microscopy and isoform-specific antibodies against Na,K-ATPase to study changes in Na,K-ATPase in rat erythroblastic cells during maturation, we unexpectedly observed numerous antigenic sites against the alpha3-isoform in the cytoplasmic phase. There was an increase in the number of alpha3-isoforms after denucleation of the erythroblast. The increase was transient. As the reticulocyte matured into a red blood cell, the number of alpha3-isoforms was reduced drastically. This alpha3-isoform was distributed in a reticular pattern resembling the double layers of endoplasmic reticulum. Western blot analysis confirms the presence of the alpha3-isoform in these cells. X-ray microanalysis of the erythroid series of cells in the bone marrow shows that sodium concentration in the young reticulocyte is higher than that in the nucleated erythroblast. The reason for the transient increase in this pump protein is not clear. It is possible that the increase in sodium concentration in the reticulocyte plays a role in the increase in pump protein synthesis.

Effects of colchicine on the enucleation of erythroid cells and macrophages in the liver of mouse embryos: ultrastructural and three-dimensional studies

Enucleation is the last event in the development of a definitive erythroid line, and extruded nuclei are phagocytosed by macrophages. Both colchicine and cytochalasin have been known to exert a great influence on the enucleation process, but the relationship between enucleation and these agents has not yet been clearly revealed in vivo. Our aim was to clarify the significance of the enucleation in liver erythropoiesis and macrophage phagocytosis by colchicine and cytochalasin administration to embryonic mice. Pregnant mice were intraperitoneally injected with colchicine or cytochalasin at 13 days of gestation. Embryonic livers were removed at intervals of 3, 6 and 12 h after injection for processing for light and electron microscopy, and, to obtain three-dimensional morphology of erythroids at enucleation, computer-aided reconstructions were performed by light microscopy. Colchicine injections had cytolytic effects on hepatocytes and macrophages, and numerous erythroblasts were observed in the process of enucleation after colchicine injection. However, the extruding nuclei were irregularly shaped, and some erythroblasts at mitosis showed extreme peripheralization of their chromosomal masses and cell membrane constriction. Enucleation behavior could also be observed in immature erythroblasts. Liver macrophages engulfed extruded nuclei and erythroblasts in mitosis. Cytochalasin injections, on the other hand, had no significant effect on embryonic livers. The progress of erythroblast mitosis was clearly stopped by colchicine injection, and numerous erythroblasts at mitosis were extruding their nuclear compartment. Following colchicine injection, erythroid enucleation also took place in immature erythroblasts, and mitotic erythroids were phagocytosed. In enucleation, more attention should be paid to hematopoietic environmental factors than to hemopoietic cell factors.

Ultrastructural abnormalities of bone marrow erythroblasts in refractory anemia

Ultrastructural abnormalities of erythroblasts in 30 patients with refractory anemia (RA) according to FAB classification were studied. Nuclear clefts, iron-laden mitochondria, and myelin figures in cytoplasm were most frequently observed. Eleven patients (36.7%) with nuclear clefts of erythroblasts had a higher platelet count and higher incidence of cytogenetic abnormalities linked to poor prognosis than the patients without nuclear clefts. They also had a higher frequency of leukemic transformation and shorter survival than the patients without nuclear clefts. The nuclear clefts of erythroblasts, which are the result of impairment of DNA metabolism or nuclear formation and fusion during mitosis, may be one of the adverse prognostic factors for patients with RA.

[Congenital dyserythropoietic anemia morphologically type I with a positive HEMPAS phenomenon]

A patient with clinical and morphological anaemia of type I is described. Surprisingly, the Ham's test yield positive with 2 of 20 compatible serum. Only other such case is recorded in the literature. We revised the literature and comment the unclassified cases reported.

Parvovirus particles in a fetal-heart with myocarditis: ultrastructural and immunohistochemical study

We report on the occurrence of parvovirus particles and VP1 (84 kDa) and VP2 (58 kDa) viral antigens in the heart of a case of fatal myocarditis in a fetus of a 26 year old women. Numerous cells containing intranuclear inclusions were identified within the blood vessels of the heart in a close apposition to muscle fibers. These cells were characterized by plentiful mitochondria and were consistent with erythroblasts. Typically, inclusions consisted of electrondense marginated chromatin and granular and amorphous "cores". At higher magnification, parvovirus particles, approximately 23 nm in diameter, were visualized either as relatively small clusters or forming large paracrystalline arrays. Virus buds were never observed. In addition, unusual membrane proliferation was seen. These findings support a notion that parvovirus may invade the fetal heart.

Observations on the relationship between gamma-globin chain content and globin chain precipitation in thalassaemic erythroblasts and on the composition of erythroblastic inclusions in HbE/beta-thalassaemia

Electron microscope immunocytochemical studies were performed on the bone marrow from 2 patients each with beta-thalassaemia major and beta-thalassaemia intermedia and 4 patients with HbE/beta-thalassaemia, using the immunogold technique. Studies of sections that were reacted with mouse monoclonal antibodies against human gamma-globin chains showed the presence of large quantities of gamma-chains in several erythroblasts and marrow reticulocytes containing large amounts of precipitated globin chains. At least in these cells, substantial gamma-chains synthesis did not protect against the formation of erythroblastic inclusions, indicating that factors other than the rate of gamma-chain synthesis influence the extent of globin-chain precipitation. Studies of sections of marrow that were reacted with a rabbit polyclonal antibody against human alpha-globin chains and a mouse monoclonal antibody against human beta-globin chains showed that the erythroblastic inclusions in HbE/beta-thalassaemia did not contain detectable quantities of HbE and consisted only of precipitated alpha-globin chains. Thus, the generally milder phenotype of HbE/beta-thalassaemia cannot be attributed to co-precipitation of HbE and excess free alpha-globin chains.

Chromatin condensation in erythropoiesis resolved by multipixel spectral imaging: differentiation versus apoptosis

Chromatin condensation and nuclear organization of May-Grunwald-Giemsa (MGG)-stained normal erythropoietic bone marrow cells and apoptotic red cell precursors were resolved by spectral bio-imaging. Multipixel spectra were obtained from single cells displaying a range of wavelengths of both transmitted and absorbed light. Two groups of spectra, of low- and high-intensity transmitted light, were revealed in the nuclei of each cell. The absorbance spectra served for the reconstruction of "absorbance images" depicting the affinity of MGG stain for the chromatin of proerythroblasts and of basophilic, polychromatic, and orthochromatic normoblasts. The localization of different spectral components in the nuclei was resolved employing two mathematical methods, spectral similarity mapping and principal component analysis. Novel structures of high symmetry revealing windmill-like organization were detected in basophilic, polychromatic, and orthochromatic normoblast cells. Matching structures were detected in apoptotic normoblasts obtained from an agnogenic myeloid metaplasia patient. Apoptosis was associated with a gradual breakdown of the ordered arrays in the nucleus. We propose that DNA cleavage may lead to fragmentation of the symmetrical windmill-like superstructure of the basic nuclear domains.

Origin of the central cells of erythroblastic islands in fetal mouse liver: ultrahistochemical studies of membrane-bound glycoconjugates

To clarify the origin of the central cells in hepatic erythroblastic islands, glycoconjugates on the surface of cellular constituents in fetal mice liver were ultrahistochemically examined using lectin staining. At 11 days of gestation, the cells derived from mesenchyme in fetal liver, including sinusoidal macrophages, endothelial cells, and erythropoietic cells, bound Griffonia simplicifolia isoagglutinin I-B4 (GS-I-B4), but hepatocytes lacked binding sites for the isolectin. Scavenger macrophages in the hepatic cords at 13 days of gestation and the central cells in the erythroblastic islands at 15 days of gestation also bound GS-I-B4. Hepatocytes, however, exhibited no GS-I-B4 binding site at any gestational day. At 11 days of gestation, none of the cells in fetal liver had binding sites for soybean agglutinin (SBA), but cells derived from mesenchyme acquired these binding sites at 13 days of gestation. The central cells in the erythroblastic islands also bound SBA, but hepatocytes did not bind the lectin at all. The central cells in the erythroblastic islands can be considered to belong to a mesenchymal cell lineage, and primitive sinusoidal macrophages at 11 days of gestation are possible precursors of these central cells.

Electron microscopic study of erythroblastic islands obtained by 'tissue-stamp culture' method

A new 'tissue-stamp culture' method was developed for stamping proliferating erythroblasts of mouse spleens on collagen-coated coverslips after inducing haemolytic anaemia by administration of 1-acetyl-2-phenylhydrazine, and then adherent splenic cells were cultured for a few days. We could obtain many erythroblastic islands, where cultured erythroblasts were located over macrophages and were proliferated synchronously for 10-30 h, and then the erythroblasts were differentiated and enucleated after 30-50 h in the presence of erythropoietin. To observe three-dimensional structures of the erythroblastic islands, a scanning electron microscope was used for the cultured cells treated with critical point-drying method. Immature wrinkled erythroblasts with many micropinocytic pits were attached to the central area of the flattened macrophages with many cytoplasmic projections, though matured erythroblasts were localized on their peripheral areas. Moreover, cytoplasmic projections of underlying macrophages, which were attached to the matured erythroblasts, were decreased in number. At a late stage, deep cytoplasmic invaginations of erythroblasts observed at a middle stage became shallow after their enucleation and flattened to form their concave shapes. This 'tissue-stamp culture' system would be useful for studying specific interaction between stromal macrophages and haematopoietic cells.

Erythroblastic inclusions in dominantly inherited beta thalassemias

While the precipitation of unstable variant beta-globin chains has been implicated as a major pathogenic mechanism in dominantly inherited beta thalassemia, their instability and presence in intra-erythroblastic inclusions have not been conclusively shown. We report the investigation of two cases of dominantly inherited beta thalassemia due to heterozygosity for the beta-codon 121 G-T mutation. In one case, we were able to demonstrate the presence of an abnormal beta-globin chain in both peripheral blood reticulocytes and bone marrow erythroblasts, and to assess its stability in relation to the substantial amounts of mutant beta mRNA transcript. The serum transferrin receptor (TfR) level was markedly increased, an indication of increased erythropoietic activity. In both cases, we could show by immunoelectron microscopy that the intra-erythroblastic inclusion bodies, a prominent feature of diseases in this category, contained not only precipitated alpha-globin chains, but also beta chains. The data confirm previous suggestions that the cellular pathology underlying this group of beta thalassemias is related to the synthesis of highly unstable beta-globin chain variants, which fail to form functional tetramers and precipitate intracellularly with the concomitant excess alpha chains, leading to increased ineffective erythropoiesis.

Malignant lymphoma in congenital dyserythropoietic anaemia type III

A 60 year old woman with congenital dyserythropoietic anaemia (CDA) type III developed a malignant T cell lymphoma with cutaneous and widespread nodal involvement. Bone marrow aspirates showed erythroid hyperplasia and dyserythropoiesis with multinucleate erythroblasts and gigantoblasts, in keeping with CDA type III. Electron microscopy showed multinucleate erythroblasts with notably irregular nuclear outlines and intranuclear clefts. The development of malignant lymphoma in this patient, together with a documented high prevalence of monoclonal gammopathy and multiple myeloma and a single case of Hodgkin's disease, may indicate an increased incidence of lymphoproliferative disease in CDA type III.

Composition of the intra-erythroblastic precipitates in thalassaemia and congenital dyserythropoietic anaemia (CDA): identification of a new type of CDA with intra-erythroblastic precipitates not reacting with monoclonal antibodies to alpha- and beta-globin chains

Ultrathin sections of bone marrow cells from two patients with homozygous beta-thalassaemia, two patients with haemoglobin H (HbH) disease, a patient with congenital dyserythropoietic anaemia (CDA) type III and two patients with severe congenital dyserythropoietic anaemia of an unusual type were reacted with mouse monoclonal antibodies against various globin chains and the reaction visualized using a gold-labelled goat antibody against mouse IgG. The multiple rounded intra-erythroblastic inclusions found in homozygous beta-thalassaemia reacted with the monoclonal antibody against alpha-globin chains but not beta-globin chains, thus confirming that they consisted of precipitated alpha-globin chains. The branching intra-erythroblastic inclusions found in HbH disease and CDA type III reacted with the monoclonal antibody against beta-globin chains but not alpha-globin chains, indicating that they consisted of precipitated beta-globin chains. The two patients with severe CDA had been transfusion-dependent since infancy, had a normal alpha:beta globin chain synthesis ratio or parents with normal red cell indices, displayed prominent dysplastic changes in their erythroblasts, and had intra-erythroblastic inclusions resembling those seen in homozygous beta-thalassaemia. However, unlike those in beta-thalassaemia, the inclusions in these two patients did not react with the monoclonal antibody against either alpha- or beta-globin chains. The inclusions reacted with antibody against zeta-globin chains, but detailed studies in one of the patients indicated that the antigen involved was not zeta-globin. These patients have features not reported in the condition known as dominantly inherited inclusion body beta-thalassaemia and appear to suffer from a novel type of CDA in which the intra-erythroblastic inclusions may consist of some non-globin protein or structurally-abnormal alpha-globin chains.

The molecular basis of the sideroblastic anemias

The sideroblastic anemias display remarkable clinical and hematologic heterogeneity but share in common mitochondrial iron loading as evidence of unhinging between intracellular iron metabolism and heme biosynthesis. Molecular defects responsible for this unhinging have now been identified and appear to display matching heterogeneity. Mutations in the erythroid-specific ALA synthase 2 (ALAS2) gene cause microcytic anemia, whereas mitochondrial DNA deletions are responsible for Pearsons syndrome with a macrocytic anemia. The molecular basis for other causes including X-linked non-ALAS2-associated autosomal inheritance and for the more frequent acquired forms of this disorder awaits discovery. Speculation about their causes includes disturbed intracellular iron homeostasis involving iron-responsive factors involved in the translational control of ALAS2 and in certain nuclear and mitochondrial genes important for erythroid mitochondrial metabolism.

Clinical features and studies of erythropoiesis in Israeli Bedouins with congenital dyserythropoietic anemia type I

Congenital dyserythropoietic anemia (CDA) type I is a rare macrocytic anemia of unknown etiology. In the present study, we redefined the clinical and laboratory picture of CDA type I, some of its pathogenic aspects, and the association with thalassemia-like features in 20 patients, all of whom belong to one Bedouin tribal group and are probably descended from a common ancestor. In each case ultrastructural studies of bone marrow (BM) erythroblasts showed the classic morphological findings of CDA type I. Serological tests for CDA type II were negative. The clinical picture was variable, but mostly benign. Some patients displayed elevated hemoglobin A2 levels or high ratio of alpha- to non-alpha- globin. However, neither family studies nor complete sequence analysis of the beta-globin was compatible with beta-thalassemia. Increased erythropoiesis was manifested by a high number of BM erythroid burst-forming units. Serum erythropoietin was also elevated. BM flow cytometry studies demonstrated arrest of erythroid precursors in the S phase of the cell cycle. The ultrastructural morphological features of the erythroid precursors, showing peripheral chromatin condensation, suggest apoptosis. Additional studies are indicated to define the molecular basis of this disease.

[Scanning and transmission microscopic observations on circulating primitive erythroblasts of yolk sac origin in the mouse embryo]

The earliest hemopoietic tissues which appear during the ontogeny of mammals are the blood islands of the yolk sac, and the blood cells produced therein begin to circulate between the embryo and visceral yolk sac at the establishment of the circulatory system. Primitive erythroblasts derived from the yolk sac have a short life span of only several days, and they form a majority of the embryonic blood cells prior to the start of liver hemopoiesis. To clarify cell fragmentation of primitive erythroblasts at the ultrastructural level, using 18 embryos of ICR-mice at 10 and 11 days of gestation, we observed circulating erythroblasts by scanning and transmission electron microscopy. The circulating erythroblasts generally had an irregularly ovoid contour, and they showed a great deal of micropinocytosis on their cell surface. The nuclei of the erythroblasts were round and possessed one or two nucleoli which were in contact with the nuclear membrane. Their nuclear chromatin was dispersed, and the cytoplasm was rich in polyribosomes and mitochondria. The majority of circulating erythroblasts were at the stage of either basophilic or polychromatophilic erythroblasts. Cytoplasmic projections could occasionally be seen extending from the erythroblast surface, and some of the projections appeared to be liberated into the vascular lumen as cell fragments. On the basis of their size and shape, the cytoplasmic projections could be classified into three types; finger-like projections, vesicular projections and microvesicular projections. The finger-like projections were approximately 1 micron in diameter and 3 microns in length. The vesicular projections, connected with the cell by a narrow stalk, were teardrop in shape, and approximately 0.8 microns in diameter and 1.5 microns in length. The microvesicular projections were approximately 0.2 microns in diameter and 0.2-0.5 microns in length. The finger-like projections had micropinocytotic invaginations on their surface, but no invaginations could be seen on the vesicular and microvesicular projections. Not only the finger-like but also the vesicular projections contained cytoplasmic matrix with a few polyribosomes. The microvesicular projections, on the other hand, occasionally contained myelinic-like figures. These projections were seen on the surface of erythroblasts at various maturation stages. The cytoplasmic fragments released from the erythroblasts were engulfed and eliminated from the embryonic peripheral blood by intravascular macrophages. The fragmentation of cytoplasmic projections was considered to be related to the development of microfilaments involved in the cytoskeleton of the erythroid elements.

[Extreme increase in the blood erythroblast count in a patient with iron-deficiency anemia and asplenia]

Bone marrow stress can provoke the presence of high erythroblast count in peripheral blood of patients with splenectomy, but is very rare in patients with normal spleen. Hypoxia occurring in patients with severe ferropenic anaemia could originate the occasional presence of erythroblasts in peripheral blood. An associated pathology should be excluded if there is a high normoblast count. We present the case of a 40 years old woman with ferropenic anaemia and a very high normoblast count. Hyperplastic polips were found in the gastric tissue as the cause for her anaemia. The absence of spleen explained the presence of erytroblasts. Further studies excluded the possibility of hemoglobinopathy and bone marrow studies were normal. Treatment with iron was successfully in correcting the hemoglobin levels and the normoblasts disappeared from peripheral blood also. A careful examination of the peripheral blood film and, specially the presence of Howell-Jolly bodies is the cornerstone of the possible diagnosis confirmed with the appropriate radiological studies.

[Abundant erythroblastic islands in bone marrow aspirate in a case of polycythemia vera. Various considerations on this anatomo-functional structure]

Despite the initial description, more than 30 years ago, of an erythroblastic island (EI), little is known about the mechanisms of union and interaction between the different cells of this anatomical and functional bone marrow structure. The observation of entire Els is extremely uncommon in normal bone marrow aspirates because of their dispersion during spread. A case report is described in which a 73-year-old woman, diagnosed 20 years ago with polycythaemia vera, showed multiple Els in a bone marrow aspirate. Their immunophenotyping revealed deficiency of several integrins. The ultrastructural study indicated a marked erythroblastic rophalocytosis. A hypothesis is suggested in view of these observations.

The paradox of Ferrata and the fate of the extruded red cell nucleus: two problems concerning erythropoiesis in the human

A critical analysis of the present erythropoietic pathway reveals two problems which require resolving. One is the paradox of the basophilic erythroblast, and the other is the fate of the extruded red cell nucleus. The problems can be overcome if erythropoiesis is looked at differently, and the orthochromatic normoblast considered to arise directly from a denuded stem cell nucleus as has been previously suggested. The orthochromatic normoblast extrudes its nucleus leaving behind a reticulocyte. The extruded but functionally impaired nucleus of the orthochromatic normoblast then gives rise to a polychromatic normoblast, a defective cell. The poorly made cytoplasm of the polychromatic normoblast is shed and its nucleus, now non-functional, undergoes complete dissolution into an aggregate of ultrafine particles. The theory has the advantage that the fate of the extruded red cell nucleus can be explained without having to introduce phagocytosis by macrophages and all the immunological difficulties which this entails. The new pathway does away with the basophilic erythroblast as a haemoglobin-producing cell, and it is argued that the cell instead is a ferritin storage cell, and that erythropoiesis is the result of two separate but interdependent pathways, a ferritin storage pathway and a haemoglobin production pathway. Evidence is put forward to support the new pathways.

alpha-Interferon therapy for congenital dyserythropoiesis type I

We report the case of a 28-year-old female followed for congenital dyserythropoiesis type I which required repeated transfusions. Alpha-2a interferon treatment was started because of post-transfusion chronic viral hepatitis type C. Following this treatment, haemoglobin level increased and reached normal value during the 24 weeks of interferon treatment. When interferon therapy was stopped, haemoglobin level returned to previous values, requiring more transfusions. Resumption of interferon therapy resulted again in a complete normalization of haemoglobin level. Erythrokinetic studies demonstrated a striking reduction of the ineffective erythropoiesis, and electron microscopy study a reduction in nuclear structure abnormalities. To our knowledge, this is the first report of the efficacy of interferon in congenital dyserythropoiesis.