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PubMed1998

Anemia in children with cancer is associated with decreased erythropoietic activity and not with inadequate erythropoietin production.

A defect in erythropoietin (EPO) production has been advocated as being the main cause of anemia presented at time of diagnosis or during treatment by adults with solid tumors. On the basis of this defect, anemic cancer patients, both adults and children, have been treated with recombinant human EPO (rHuEPO). To further elucidate the pathophysiology of anemia in children with cancer, we measured serum soluble transferrin receptor (sTfR), a quantitative marker of erythropoiesis, and serum EPO at time of diagnosis and during chemotherapy in children suffering from solid tumor or leukemia. We determined serum EPO in 111 children (55 leukemia, 56 solid tumors) at time of diagnosis. In the last 44 patients (23 leukemia and 21 solid tumors), sTfR levels were also measured. Serum EPO together with sTfR levels were also determined in 60 children receiving chemotherapy (29 leukemia, 31 solid tumors). These results were compared with those obtained from appropriate control groups. In all patients, we found a highly significant correlation between the logarithm of EPO (log[EPO]) and the hemoglobin (Hb) level. In all subsets of patients, sTfR levels were inappropriately low for the degree of anemia. Neither leukemic nor solid tumor groups showed a significant inverse relationship between log(sTfR) and the Hb level as would be expected in anemic patients with appropriate marrow response. Thus, in children with cancer, anemia is associated with a decreased total bone marrow erythropoietic activity which, in contrast to what has been reported in anemic cancer adults, is not related to defective EPO production.

Adolescent↗
PubMed1998

Expression and bioactivity of recombinant canine erythropoietin.

OBJECTIVE: To produce recombinant canine erythropoietin (rcEPO) and compare its biological activity with that of recombinant human EPO (rhEPO). ANIMALS: C57BL/6J mice. PROCEDURE: The gene encoding cEPO was isolated from a genomic library and subcloned into an eucaryotic expression vector. Production of rcEPO was achieved by stable transfection of the expression construct into Chinese hamster ovary cells. Biological activity was evaluated in vitro by analyzing the mitogenic activity of rcEPO on murine erythroid progenitor cells. In vivo bioactivity was assessed in mice by measuring the ability of rcEPO to increase blood reticulocyte counts. RESULTS: Size and glycosylation of rcEPO expressed in Chinese hamster ovary cells were similar to values for commercial rhEPO. Canine and human EPO stimulated proliferation of murine erythroid progenitor cells in vitro and murine reticulocytosis in vivo in a dose-dependent manner. CONCLUSIONS: Comparable biological activity was observed for rcEPO and rhEPO in the 2 murine-based assay systems studied. By avoiding interspecies variation in protein structure and the resulting potential for immunogenicity, rcEPO should represent a better option than rhEPO for treatment of dogs with erythropoietin-dependent anemia. CLINICAL RELEVANCE: Therapeutic use of rhEPO in companion animals is limited by its immunogenicity and the resulting potential to induce pure red cell aplasia. Development and availability of species-specific EPO preparations should avoid this problem.

Animals↗
PubMed1996

Opposing effects of the basic helix-loop-helix transcription factor SCL on erythroid and monocytic differentiation.

The SCL gene (also called Tal-1 or TCL5) was identified because of its association with chromosomal translocations in childhood T-cell lymphoid leukemias. SCL codes for a basic helix-loop-helix (bHLH) factor that can function as a transcriptional activator or repressor. In the adult, SCL expression is restricted to hematopoietic cells and tissues, but its function in the process of lineage commitment is unknown. The present study was designed to address the role of SCL in hematopoietic cell differentiation. SCL expression was determined in primary hematopoietic cells through the screening of cDNA samples obtained by reverse transcription-polymerase chain reaction (RT-PCR) from single cells at different stages of differentiation. SCL RNA expression was highest in bipotential and committed erythroid precursors and diminished with subsequent maturation to proerythroblasts and normoblasts. In contrast, SCL mRNA was low to undetectable in precursors of granulocytes and monocytes and their maturing progeny. The same pattern of expression was observed after erythroid or monocytic differentiation of a bipotent cell line, TF-1, in that SCL mRNA levels remained elevated during erythroid differentiation and were downregulated with monocytic differentiation. Accordingly, TF-1 was chosen as a model to investigate the functional significance of this divergent pattern of SCL expression in the two lineages. Four independent clones stably transfected with an SCL expression vector exhibited enhanced spontaneous and delta-aminolevulinic acid-induced erythroid differentiation as measured by glycophorin expression and hemoglobinization, consistent with the view that SCL is a positive regulator of erythroid differentiation. Furthermore, constitutive SCL expression interfered with monocytic differentiation, as assessed by the generation of adherent cells and the expression of Fc gamma RII in response to TPA. These results suggest that the downregulation of SCL may be required for monocytic differentiation.

Adult↗
PubMed1986

Genotype-limited changes in platelet and erythroid kinetics in Friend-virus-infected allophenic mice.

We report here results suggesting that cells of the megakaryocytic lineage or uncommitted precursor cells may be targets for Friend-virus-induced proliferation, and that genetic differences (other than Fv-2) between strains C57BL/6 and DBA/2 affect the susceptibility of these cells to Friend virus. The evidence suggesting this was derived from experiments with C57BL/6 in equilibrium DBA/2 allophenic mice. Within the first few weeks following infection of these mice with the polycythemic NB-tropic strain of Friend virus (FV-P), we observed a rapid shift in the genotypic composition of both red cells and platelets in favor of those of the DBA/2 genotype. Infection with the anemia-inducing strain of Friend virus (FV-A) also resulted in preferential production of DBA/2 strain erythrocytes, but its effect on platelet kinetics was nil. The FV-P- and FV-A-induced change in red cell composition is consistent with the view that erythroid precursors are target cells for Friend virus and that viral infection preferentially stimulates proliferation of susceptible strain (DBA/2) erythroid precursors. As for the platelet shifts induced by FV-P (and not FV-A), we believe the changes in platelet mosaicism also could be caused by viral-induced proliferation of DBA/2 platelet precursors, or more primitive progenitors, over the C57BL/6 ones. Thus, these results implicate the existence of nonerythroid target cells for FV-P-induced proliferation, as well as the existence of genetic differences between strains C57BL/6 and DBA/2 that modulate the responsiveness of such cells to infection.

Animals↗
PubMed1996

Ferritin uptake by human erythroid precursors is a regulated iron uptake pathway.

Iron delivery to mammalian cells is traditionally ascribed to diferric transferrin (Tf). We recently reported that human erythroid precursor cells possess specific membranes receptors that bind and internalize acid isoferritin. Here we show that ferritin uptake by these cells is highly regulated and that the internalized ferritin-iron is used for home synthesis and thus, this process could constitute a physiological pathway for iron assimilation. Ferritin was internalized by a specific, saturable process, distinct from the uptake of iron associated with albumin. Ferritin uptake downregulated transferrin-receptor expression, indicating that internalized ferritin-iron was recognized as an integral part of the cellular iron content. Ferritin receptor expression was coordinated to cell development and was tightly regulated by cellular iron status. Receptor abundance was increased by iron-depletion and decreased by iron-loading, while the affinity of the ferritin receptor for acid isoferritin remained nearly constant (kd = 4.1 +/- 0.5 x 10(-6) mol/L). Under all experimental conditions, ferritin- and transferrin-receptor expression was closely coordinated, suggesting that these pathways possess a common regulatory element. It is concluded that ferritin uptake by erythroid cells constitutes an iron uptake pathway in addition to the classical transferrin uptake pathway.

Apoferritins↗
PubMed2004

Specific features of the erythroid hemopoietic stem in CBA/CaLac mice with neuroses demonstrating good and poor learning capacities.

We studied changes in the erythroid hemopoietic stem in CBA/CaLac mice with experimental neuroses demonstrating good and poor learning capacities (conflict situation and paradoxical sleep deprivation followed by training in a 3-arm T-maze). The animals with different learning capacities exhibited pronounced hyperplasia of the erythroid hemopoietic stem in response to neurosis. Activation of the erythron in good learners was related to acceleration of division and maturation of erythroid precursors and enhanced formation of cell complexes containing central macrophage. In poor learners hyperplasia of the erythroid hemopoietic stem under conditions of conflict situation manifested in activation of proliferation and differentiation (against the background of decreased count of erythroid and mixed complexes in the bone marrow), while after paradoxical sleep deprivation followed by T-maze training this hyperplasia was associated with increased formation of additional hemopoietic islets (against the background of desynchronization of division and maturation of erythroid precursor cells).

Animals↗
PubMed1990

Migration of stem cells and progenitors between marrow and spleen following thiamphenicol treatment of mice.

Recovery of hemopoiesis was studied after a 3-day treatment with the antibiotic thiamphenicol (TAP). A contrasting behavior of the spleen colony-forming units (CFU-S), granulocyte-macrophage colony-forming units (CFU-GM), erythroid burst-forming units (BFU-E), and erythroid colony-forming units (CFU-E) numbers in the bone marrow versus those in the spleen was found. Whereas the cell numbers reached nadirs in the marrow, they peaked 30 to 100-fold above control values in the spleen on day 4. Simultaneously the number of CFU-S, BFU-E, and CFU-GM, but not of CFU-E, increased drastically in the peripheral blood. The tritiated thymidine kill of the splenic CFU-S was too small to explain the endogenous splenic production of these cells. A quantitative analysis further revealed that an effective erythropoiesis was established in the spleen. As a consequence, the first part of a reticulocytosis was mainly due to the splenic contribution, whereas the second part predominantly originated from a delayed marrow erythropoiesis. In contrast, the CFU-GM of the spleen did not effectively differentiate into granuloid precursors. The bulk of the granuloid production occurred in the marrow. The best explanation for these results is a net migration of CFU-S, BFU-E, and CFU-GM from the marrow to the spleen during early recovery, and a back-migration of CFU-GM to the marrow later in the recovery phase. These observations indicate a link between migration of hemopoietic cells and their differentiation at the two hemopoietic sites.

Animals↗
PubMed1993

Proliferating cell nuclear antigen expression by erythroid precursors in normal bone marrow, in reactive lesions and in polycythaemia rubra vera.

Using a sequential double-immunostaining technique, a morphometric analysis was performed on routinely processed bone marrow trephines from 20 patients with secondary (reactive) polycythaemia and 28 patients with polycythaemia rubra vera to determine the proliferation capacity of erythropoiesis. Monoclonal antibodies PC10--anti-proliferating cell nuclear antigen (PCNA)--and Ret40f--anti-glycophorin C--were employed. For comparison with the PCNA-labelling index, in a pilot study, Ki-67 was additionally used on frozen-section material. In comparison with normal bone marrow (15 patients) morphometric and statistical evaluation revealed a numerical increase in erythroid precursors (pro-, erythro- and normoblasts) in secondary polycythaemia and to a pronounced degree in polycythaemia rubra vera. In comparison with secondary polycythaemia and the control group, in polycythaemia rubra vera there was a significant enhancement of proliferation according to PCNA-staining reactivity in all haematopoietic cell elements and particularly in the erythroid series. Evaluation of PCNA v. Ki-67 immunostaining disclosed only a slight difference, which could be mainly attributed to various modalities of antigen expression during the cell cycle. Our findings are in keeping with in vitro studies on cultured erythroid progenitor cells and, in problematic cases, may present a valuable aid in differentiation between reactive lesions and polycythaemia rubra vera.

Antibodies, Monoclonal↗
PubMed1993

Cytokine-induced selective expansion and maturation of erythroid versus myeloid progenitors from purified cord blood precursor cells.

To study the role of different cytokine combinations on the proliferation and differentiation of highly purified primitive progenitor cells, a serum-free liquid culture system was used in combination with phenotypic and functional analysis of the cells produced in culture. CD34+ CD45RAlo CD71lo cells, purified from umbilical cord blood by flow cytometry and cell sorting, were selected for this study because of their high content of clonogenic cells (34%), particularly multipotent progenitors (CFU-MIX, 12% of all cells). Four cytokine combinations were tested: (1) mast cell growth factor (MGF; a c-kit ligand) and interleukin-6 (IL-6); (2) MGF, IL-6, IL-3, and erythropoietin (Epo); (3) MGF, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF)/IL-3 fusion protein (FP), macrophage colony-stimulating factor (M-CSF), and granulocyte-CSF (G-CSF); and (4) MGF, IL-6, FP, M-CSF, G-CSF, and Epo. Maximum numbers of erythroid progenitors (BFU-E, up to 55-fold increase) and mature erythroid cells were observed in the presence of MGF, IL-6, IL-3, and Epo, whereas maximum levels of myeloid progenitors (CFU-C, up to 70-fold increase) and mature myeloid cells were found in cultures supplemented with MGF, IL-6, FP, M-CSF, and G-CSF. When MGF, IL-6, FP, M-CSF, G-CSF, and Epo were present, maximum levels of both erythroid and myeloid progenitors and their progeny were observed. These results indicate that specific cytokine combinations can act directly on primitive hematopoietic cells resulting in significant expansion of progenitor cell numbers and influencing their overall patterns of proliferation and differentiation. Furthermore, the observations presented in this study suggest that the cytokine combinations used were unable to bias lineage commitment of multipotent progenitors, but rather had a permissive effect on the development of lineage-restricted clonogenic cells.

Antigens, CD↗
PubMed1993

[Polycythemia: primary or secondary? The differential diagnostic value of stem cell cultures].

Cultures of hematopoietic precursor cells can be helpful in differentiating between primary polycythemia (polycythaemia vera, PV) and reactive secondary polycythemia: in PV erythroid precursors form hemoglobinized colonies in the absence of added erythropoietin (epo) (= endogenous erythroid colonies), whereas in normals and in patients with secondary polycythemia, formation of erythroid colonies is dependent on added epo. We have performed cultures of peripheral blood precursors from 132 patients with elevated hemoglobin in the presence/absence of added epo. In 48/132 patients we assumed that PV was the cause of polycythemia. In 80/132 patients no endogenous colonies appeared and the polycythemia was judged secondary. 23 PV patients were examined repeatedly. In 18 of them the first diagnosis was confirmed by subsequent cultures; in 5 cases endogenous colonies, which had been present in the first cultures, were no longer detectable. A questionnaire on the subsequent clinical course was sent to 108 treating physicians. 77 questionnaires were answered correctly and returned. In 86% of these patients, our culture diagnosis of PV was either confirmed or another myeloproliferative disorder had been found as a cause of endogenous colonies. In 14% our diagnosis of PV had been false positive. On the other hand, our diagnosis of secondary polycythemia was confirmed in 85% of the patients; its most frequent cause was cigarette smoking and chronic bronchitis and only rarely was it associated with heart or kidney disease. 5/77 patients had persistently elevated Hb without an evident cause, and in 3/77 the Hb normalized spontaneously.(ABSTRACT TRUNCATED AT 250 WORDS)

Colony-Forming Units Assay↗
PubMed1999

Function of caspases in regulating apoptosis caused by erythropoietin deprivation in erythroid progenitors.

Erythropoietin (EP) is required by late stage erythroid progenitor cells to prevent apoptosis. In a previous study (Gregoli and Bondurant, 1997, Blood 90:630-640), it was shown that rapid proteolytic conversion of procaspase 3 to the fully activated enzyme occurred when erythroblasts were deprived of EP for as little as 2 h. In the present study, protein and mRNA analyses of erythroblasts indicated the presence of the proenzyme precursors of caspases 1, 2, 3, 5, 6, 7, 8, and 9. The effects of various caspase inhibitors on caspase 3 processing and on apoptosis were examined. These inhibitors were benzyloxycarbonyl (z-) and fluoromethyl-ketone (FMK) derivatives of peptides that serve as substrates for selected caspases. z-VAD-FMK, t-butoxycarbonyl-aspartate-FMK (Boc-D-FMK), and z-IETD-FMK blocked the initial cleavage of procaspase 3, while z-DEVD-FMK, z-VEID-FMK, and z-VDVAD-FMK did not block the initial cleavage but had some effect on blocking apoptosis. The peptide inhibitor z-FA-FMK, which inhibits cathepsins B and L but is not known to inhibit caspases, altered caspase 3 processing to a final 19 kDa large subunit that appeared to retain enzymatic activity. The action of z-FA-FMK in preventing the usual conversion to a 1 7 kDa subunit suggests the possibility that a noncaspase protease may be involved in caspase 3 processing. Studies with the peptide inhibitors and EP were done to determine the short- and long-term effectiveness of the caspase inhibitors in protecting EP-deprived cells from apoptosis. Although several of the inhibitors were effective, z-IETD-FMK was studied most extensively because of its specificity for enzymes which cleave procaspase 3 at aspartate 175 (IETD175). Large percentages of EP-deprived erythroblasts treated with z-IETD-FMK appeared morphologically normal and negative by a DNA strand breakage (TUNEL) assay at 24 h (75%) compared to EP-deprived controls (10%) which were not treated with inhibitor. However, inhibitor-treated erythroid progenitors deprived of EP for 24 h and then resupplied with EP showed only a modest improvement in long-term survival compared to cells which did not receive the caspase inhibitor during the 24 h EP deprivation. Thus, while the manifestations of apoptosis were delayed in most cells by inhibiting caspase activity, the processes initiating the loss of cell viability due to EP deprivation were irreparablein the majority of the cells and eventually led to their deaths.

Amino Acid Sequence↗
PubMed1999

High incidence of transiently appearing complement-sensitive bone marrow precursor cells in patients with severe aplastic anemia--A possible role of high endogenous IL-2 in their suppression.

In a prospective long-term study on the incidence of paroxysmal nocturnal hemoglobinuria (PNH), 115 consecutive patients with severe aplastic anemia (SAA), 97 treated with antilymphocyte globulin (ALG) and 18 with bone marrow transplantation (BMT), were observed over a period of 4-18 years and tested for the presence of complement-sensitive hematopoietic precursor cells with the bone marrow (BM) sucrose test. Sixteen (14%) of the ALG-treated patients developed clinical signs of PNH between 0.5 and 8 years after treatment. Complement-sensitive BM precursors were found in 89% of the SAA patients at some time during their disease, but in none of 18 normal donors. At diagnosis, their proportion was significantly higher in patients who later developed PNH than in patients who later achieved disease-free complete remission (CR). After ALG, the abnormal population was found in both groups, but it was gradually replaced by normal precursors in remission patients. After BMT, the complement-sensitive population decreased to very low numbers in patients with a stable graft, but increased again in 3 patients upon graft rejection. Mimicking the PNH defect by enzymatic removal of glycosyl-phosphatidylinositol (GPI)-linked proteins from CD34+ cells resulted in their complement sensitivity, suggesting that the BM sucrose test identifies precursor cells carrying the PNH defect. In 66 patients, white blood cells (WBC) in peripheral blood (PB) were examined for GPI-deficient populations by flow cytometry (FACS). Ten patients with signs of clinical or laboratory PNH had over 25% complement-sensitive precursor cells in the BM and a GPI-deficient WBC population in the PB. Of 56 SAA patients without PNH, 8 had an abnormal population detectable with both tests, 26 only with the BM sucrose test, 4 only with PB FACS analysis, and in 18, no abnormal cells were detected with either test. In search for parameters which might explain why in some patients the abnormal population expands, while it regresses or disappears in others, we tested the release of IL-2 as a parameter of immune competence. At diagnosis, IL-2 release was approximately 50% of normal in patients who later developed PNH, while it was double the normal value in patients who later achieved CR. We conclude that the majority of SAA patients transiently harbor complement-sensitive precursor cells in the BM. Patients with more than 25% abnormal BM precursors and low endogenous IL-2 release are at risk of progression to clinical PNH.

Anemia, Aplastic↗
PubMed1993

Blast colony-forming cells in myelodysplastic syndrome: decreased potential to generate erythroid precursors.

In vitro colony-forming abilities of highly purified primitive hematopoietic cells in eight cases of myelodysplastic syndrome (MDS) were studied using the blast cell colony assay. Blast cell colony formation from seven normal bone marrow (NBM) samples was studied in parallel. Blast cell colonies were formed in 7/8 cases of MDS, the numbers not significantly differing from those generated by NBM. In contrast the more mature hematopoietic progenitors (granulocyte-erythroid-macrophage-megakaryocyte colony-forming unit, CFU-GEMM; erythroid burst-forming units, BFU-E; granulocyte colony-forming units, CFU-G; eosinophilic colony-forming units, CFU-Eo) were severely depressed in numbers in MDS marrow. After replating of blast cell colonies in secondary cultures, colonies were obtained in 5/8 MDS cases. A marked difference was evident in the composition of the secondary colonies between MDS and normal marrow. Whereas secondary colonies derived from normal blast cell colonies consisted of about 45% of erythroid cells, MDS blast colonies generated mainly colonies of the granulocytic-monocytic lineage and no erythroid colonies. The normal quantitative level of CFU-blast progenitors in MDS in the context of their impaired ability to generate lineage specific progeny upon secondary plating suggests that the incompetence of maturation of MDS may reside in the CFU-blast progenitor cell being incapable of properly responding to growth factor stimulation.

Adult↗
PubMed1991

Antisense myb inhibition of purified erythroid progenitors in development and differentiation is linked to cycling activity and expression of DNA polymerase alpha.

These studies aimed to determine the expression and functional role of c-myb in erythroid progenitors with different cycling activities. In the first series of experiments the erythroid burst-forming unit (BFU-E) and colony-forming unit (CFU-E) populations from adult peripheral blood (PB), bone marrow (BM), and embryonic-fetal liver (FL) were treated with either c-myb antisense oligomers or 3H-thymidine (3H-TdR). A direct correlation was always observed between the inhibitory effect of anti-myb oligomers and the level of cycling activity. Thus, the inhibitory effect of antisense c-myb on the number of BFU-E colonies was 28.3% +/- 15.8% in PB, 53.4% +/- 9.3% in BM, and 68.2% +/- 24.5% in FL. Both adult and embryonic CFU-E were markedly inhibited (73.2% +/- 10.4% and 74.2% +/- 12.7%). Using highly purified PB progenitors, we observed a similar pattern, although with slightly lower inhibitory effects. In the 3H-TdR suicide assay the killing index of BFU-E was 8.9% +/- 4.2% in PB, 29.4% +/- 6.5% in BM, and 40.1% +/- 9.6% in FL. The values for adult and embryonic CFU-E were 55.7% +/- 7.9% and 60.98% +/- 6.6%, respectively. We then investigated the kinetics of c-myb mRNA level during the erythroid differentiation of highly purified adult PB and FL BFU-E, as evaluated in liquid-phase culture by reverse transcription-polymerase chain reaction. Adult erythroid precursors showed a gradual increase of c-myb mRNA from day 4 through day 8 of culture and a sharp decrease at later times, whereas the expression of c-myb mRNA and protein in differentiation embryonic precursors peaked 2 days earlier. In both cases, c-myb mRNA level peaked at the CFU-E stage of differentiation. Finally, highly purified adult PB BFU-E were stimulated into cycling by a 3-day treatment with interleukin-3 in liquid phase: both the sensitivity to c-myb antisense oligomers and the 3H-TdR suicide index showed a gradual, strictly parallel increase. Under the same experimental conditions a progressive increase of the mRNA level of DNA polymerase alpha was observed. These observations suggest that in early erythroid differentiation c-myb activation is associated with the progression of progenitors into the S phase of the cell cycle, as well as to the synthesis of DNA polymerase alpha.

Antisense Elements (Genetics)↗
PubMed1997

Differential modulation of adhesion markers with ex vivo expansion of human umbilical CD34+ progenitor cells.

The effect of different expansion protocols on the expression levels of CD49dw/CD29 (VLA-4), CD11a/CD18 (LFA-1), CD31 (PECAM-1), CD44, and CD34 was determined after cord blood CD34+ cells were cultured for defined periods with the following: 1) A growth factor mix (GFmix) containing interleukin (IL)-1, IL-3, IL-6, kit ligand (KL), G-CSF, GM-CSF, and erythropoietin (Epo); 2) IL-3 + KL; and 3) HS-5 (a human stromal cell line supernatant) + KL. Before culturing, cord blood CD34+ cells (> 95% purity) were 94 +/- 5% CD31+, 98 +/- 1% CD44+, 66 +/- 29% VLA-4+, and 68 +/- 18% LFA-1+ (mean +/- SEM). Immunophenotyping and morphological examination of pre- and post-cultured cells indicated that GFmix preferentially supported erythroid development, while IL-3+KL and HS-5+KL preferentially supported myeloid development. Similar to what other investigators have reported, there was an absolute increase in CD34+ cell numbers as well as clonogenic precursors with ex vivo expansion. However, the majority of clonogenic precursors post-expansion expressed CD34 antigen at reduced levels. Examination of adhesion molecules indicated that a majority of cells cultured with GFmix expressed PECAM-1 and LFA-1 at undetectable levels, but PECAM-1 and LFA-1 levels remained essentially unchanged when cells were cultured with IL-3+KL and HS-5+KL. Overall VLA-4 expression levels slightly increased and CD44 expression levels were more heterogeneous with ex vivo expansion. Nevertheless, LFA-1, VLA-4, PECAM-1, and CD44 expression levels remained essentially unchanged on cultured progeny retaining a CD34 phenotype, independent of the culture system used. Together these results indicate that differential modulation of adhesion markers occur with different culture conditions, yet adhesion receptor expression levels on progeny cells retaining a CD34 phenotype are essentially maintained independent of the culture conditions. And although there is an absolute increase in CD34+ cells after ex vivo expansion, a majority of clonogenic precursors have reduced levels of CD34 antigen.

Antigens, CD↗
PubMed2002

Inappropriate expression of hepcidin is associated with iron refractory anemia: implications for the anemia of chronic disease.

The anemia of chronic disease is a prevalent, poorly understood condition that afflicts patients with a wide variety of diseases, including infections, malignancies, and rheumatologic disorders. It is characterized by a blunted erythropoietin response by erythroid precursors, decreased red blood cell survival, and a defect in iron absorption and macrophage iron retention, which interrupts iron delivery to erythroid precursor cells. We noted that patients with large hepatic adenomas had severe iron refractory anemia similar to that observed in anemia of chronic disease. This anemia resolved spontaneously after adenoma resection or liver transplantation. We investigated the role of the adenomas in the pathogenesis of the anemia and found that they produce inappropriately high levels of hepcidin mRNA. Hepcidin is a peptide hormone that has been implicated in controlling the release of iron from cells. We conclude that hepcidin plays a major, causative role in the anemia observed in our subgroup of patients with hepatic adenomas, and we speculate that it is important in the pathogenesis of the anemia of chronic disease in general.

Adenoma, Liver Cell↗
PubMed2002

Disruption of Smad5 gene leads to enhanced proliferation of high-proliferative potential precursors during embryonic hematopoiesis.

SMAD proteins are downstream signal transducers of the transforming growth factor beta (TGF-beta) superfamily, which serve as pleiotropic regulators in embryonic and adult hematopoiesis. SMAD5, initially considered to mediate bone morphogenetic proteins (BMPs) signals, can also transduce the inhibitory signal of TGF-beta1 on proliferation of hematopoietic progenitors derived from human bone marrow. To define its specific role in regulation of primitive multipotential progenitors during early embryonic hematopoiesis, we examined Smad5(-/-) yolk sacs at E9.0 to 9.5 and detected an elevated number of high-proliferative potential colony-forming cells (HPP-CFCs) with enhanced replating potential. To exclude the possible influence of microenvironmental deficit on embryonic hematopoiesis in vivo, we performed in vitro embryonic stem (ES) cell differentiation assay and investigated the HPP-CFCs in particular. Smad5(-/-) embryoid bodies (EBs) contained an elevated number of blast colony-forming cells (BL-CFCs), the in vitro equivalent of hemangioblast, in contrast to reduced proliferation of primitive erythroid precursors (Ery/Ps) within the mutant EBs. More importantly, profoundly increased frequency of HPP-CFCs, featured with a gene-dosage effect, was detected within day 6 Smad5(-/-) EBs compared with the wild type. In addition, Smad5(-/-) HPP-CFCs displayed enhanced self-renewal capacity and decreased sensitivity to TGF-beta1 inhibition, suggesting a critical role of Smad5 in TGF-beta1 regulation of embryonic HPP-CFCs. Consistently, reverse transcription-polymerase chain reaction analysis detected alterations of the transcription factors including GATA-2 and AML1 as well as cytokine receptors in Smad5(-/-) HPP-CFC colonies. Together, these data define an important function of SMAD5 in negative regulation of high-proliferative potential precursors during embryonic hematopoiesis.

Animals↗
PubMed1990

Tumor necrosis factor exerts dose-dependent effects on erythropoiesis and myelopoiesis in vivo.

Recombinant human tumor necrosis factor alpha (TNF) administered i.v. to Lewis rats as a daily low dose for 1 week induces an erythroid hyperplasia of late normoblasts. Although the erythroid marrow compartment is hyperplastic, the morphology of the normoblasts is dysplastic and there is no accompanying increase in circulating red blood cells, suggesting a state of ineffective erythropoiesis. TNF administered on the same daily schedule as a high dose induces an erythroid hypoplasia of late normoblasts and a peripheral anemia with decreases in the hematocrit and hemoglobin. A tremendous myeloid hyperplasia is noted in rats treated with high-dose TNF, and the mechanism of the erythroid anemia may be in part due to the increase in neutrophils. In support of the hypothesis that the erythroid anemia may be partly myelophthisic in nature, a decrease in marrow lymphocytes was also noted. On the other hand, the dysplastic morphology of the late erythroid precursors in rats treated with low-dose TNF would also be consistent with a destructive effect of TNF on erythroid precursors as a mechanism of TNF-related anemia. In light of the in vitro inhibitory effects of TNF on erythropoiesis and myelopoiesis as reported by previous investigators, the erythroid and myeloid hyperplasia noted in vivo most likely represent indirect effects.

Anemia↗