Cell Mechanics Based Computational Classification of Red Blood Cells Via Machine Intelligence Applied to Morpho-Rheological Markers

Despite fluorescent cell-labelling being widely employed in biomedical studies, some of its drawbacks are inevitable, with unsuitable fluorescent probes or probes inducing a functional change being the main limitations. Consequently, the demand for and development of label-free methodologies to classify cells is strong and its impact on precision medicine is relevant. Towards this end, high-throughput techniques for cell mechanical phenotyping have been proposed to get a multidimensional biophysical characterization of single cells. With this motivation, our goal here is to investigate the extent to which an unsupervised machine learning methodology, which is applied exclusively on morpho-rheological markers obtained by real-time deformability and fluorescence cytometry (RT-FDC), can address the difficult task of providing label-free discrimination of reticulocytes from mature red blood cells. We focused on this problem, since the characterization of reticulocytes (their percentage and cellular features) in the blood is vital in multiple human disease conditions, especially bone-marrow disorders such as anemia and leukemia. Our approach reports promising label-free results in the classification of reticulocytes from mature red blood cells, and it represents a step forward in the development of high-throughput morpho-rheological-based methodologies for the computational categorization of single cells. Besides, our methodology can be an alternative but also a complementary method to integrate with existing cell-labelling techniques.

Genetic manipulation of cell line derived reticulocytes enables dissection of host malaria invasion requirements

Investigating the role that host erythrocyte proteins play in malaria infection is hampered by the genetic intractability of this anucleate cell. Here we report that reticulocytes derived through in vitro differentiation of an enucleation-competent immortalized erythroblast cell line (BEL-A) support both successful invasion and intracellular development of the malaria parasite Plasmodium falciparum. Using CRISPR-mediated gene knockout and subsequent complementation, we validate an essential role for the erythrocyte receptor basigin in P. falciparum invasion and demonstrate rescue of invasive susceptibility by receptor re-expression. Successful invasion of reticulocytes complemented with a truncated mutant excludes a functional role for the basigin cytoplasmic domain during invasion. Contrastingly, knockout of cyclophilin B, reported to participate in invasion and interact with basigin, did not impact invasive susceptibility of reticulocytes. These data establish the use of reticulocytes derived from immortalized erythroblasts as a powerful model system to explore hypotheses regarding host receptor requirements for P. falciparum invasion.

Plasmodium vivax Infection Impairs Regulatory T-Cell Suppressive Function During Acute Malaria

The balance between pro- and antiinflammatory mechanisms is essential to limit immune-mediated pathology, and CD4+ forkhead box P3 (Foxp3+) regulatory T cells (Treg) play an important role in this process. The expression of inhibitory receptors regulates cytokine production by Plasmodium vivax-specific T cells. Our goal was to assess the induction of programmed death-1 (PD-1) and cytotoxic T-lymphocyte antigen (CTLA-4) on Treg during malaria and to evaluate their function. We found that P. vivax infection triggered an increase in circulating Treg and their expression of CTLA-4 and PD-1. Functional analysis demonstrated that Treg from malaria patients had impaired suppressive ability and PD-1+Treg displayed lower levels of Foxp3 and Helios, but had higher frequencies of T-box transcription factor+ and interferon-gamma+ cells than PD-1-Treg. Thus malaria infection alters the function of circulating Treg by triggering increased expression of PD-1 on Treg that is associated with decreased regulatory function and increased proinflammatory characteristics.

A regenerative erythropoietic response does not increase the frequency of Pig-a mutant reticulocytes and erythrocytes in Sprague-Dawley rats

The in vivo rodent Pig-a mutation assay is a sensitive test to identify exposure to mutagenic substances, and has been proposed as an assay for the identification of impurities for pharmaceuticals. Red blood cells (RBCs) and reticulocytes (RETs) are analyzed by flow cytometry after exposure to potentially mutagenic chemicals for cells deficient in the cell surface anchored protein CD59, representing mutation in the X-linked Pig-a gene. The full potential of the assay as well as its limitations are currently being explored. The current study investigated the effects of regenerative erythropoietic bone marrow responses on the frequency of Pig-a mutated reticulocytes (RET^CD59- ) and erythrocytes (RBC^CD59- ). We hypothesized that a robust regenerative erythropoietic response would not increase the basal frequency of RET^CD59- or RBC^CD59- cells. Two groups of six male Sprague-Dawley rats either had 2 mL of blood sampled each day via an indwelling catheter over a period of 5 days or were minimally sampled for hematology and used as controls. Blood was also then collected and evaluated 5, 18, and 49 days after the initial bleed period for the number of Pig-a mutant cells in either the RET or RBC population. Despite the expected decrease in hematocrit and the correlative increase in reticulocytes after bleeding, no increase in the number of Pig-a mutant cells was observed in male Sprague-Dawley rats that were bled for five consecutive days. These results indicate that changes in erythropoiesis and hematology parameters in rats appear to have no effect on the background levels of Pig-a mutated RETs and RBCs. Environ. Mol. Mutagen. 59:91-95, 2018. © 2017 Wiley Periodicals, Inc.

Monoclonal gammopathy-associated pure red cell aplasia

Pure red cell aplasia (PRCA) is a rare disorder characterized by inhibition of erythroid precursors in the bone marrow and normochromic, normocytic anaemia with reticulocytopenia. Among 51 PRCA patients, we identified 12 (24%) patients having monoclonal gammopathy, monoclonal gammopathy of undetermined significance or smouldering multiple myeloma, with presence of monoclonal protein or abnormal serum free light chains and atypical bone marrow features of clonal plasmacytosis, hypercellularity and fibrosis. Thus far, three patients treated with anti-myeloma based therapeutics have responded with reticulocyte recovery and clinical transfusion independence, suggesting plasma cells play a key role in the pathogenesis of this specific monoclonal gammopathy-associated PRCA.

A Chemical Screening Approach to Identify Novel Key Mediators of Erythroid Enucleation

Erythroid enucleation is critical for terminal differentiation of red blood cells, and involves extrusion of the nucleus by orthochromatic erythroblasts to produce reticulocytes. Due to the difficulty of synchronizing erythroblasts, the molecular mechanisms underlying the enucleation process remain poorly understood. To elucidate the cellular program governing enucleation, we utilized a novel chemical screening approach whereby orthochromatic cells primed for enucleation were enriched ex vivo and subjected to a functional drug screen using a 324 compound library consisting of structurally diverse, medicinally active and cell permeable drugs. Using this approach, we have confirmed the role of HDACs, proteasomal regulators and MAPK in erythroid enucleation and introduce a new role for Cyclin-dependent kinases, in particular CDK9, in this process. Importantly, we demonstrate that when coupled with imaging analysis, this approach provides a powerful means to identify and characterize rate limiting steps involved in the erythroid enucleation process.

Human erythrocyte PIG-A assay: an easily monitored index of gene mutation requiring low volume blood samples

This laboratory has previously described a method for scoring the incidence of rodent blood Pig-a mutant phenotype erythrocytes using immunomagnetic separation in conjunction with flow cytometric analysis (In Vivo MutaFlow®). The current work extends this approach to human blood. The frequencies of CD59- and CD55-negative reticulocytes (RET(CD59-/CD55-)) and erythrocytes (RBC(CD59-/CD55-)) serve as phenotypic reporters of PIG-A gene mutation. Immunomagnetic separation was found to provide an effective means of increasing the number of reticulocytes and erythrocytes evaluated. Technical replicates were utilized to provide a sufficient number of cells for precise scoring while at the same time controlling for procedural accuracy by allowing comparison of replicate values. Cold whole blood samples could be held for at least one week without affecting reticulocyte, RET(CD59-/CD55-) or RBC(CD59-/CD55-) frequencies. Specimens from a total of 52 nonsmoking, self-reported healthy adult subjects were evaluated. The mean frequency of RET(CD59-/CD55-) and RBC(CD59-/CD55-) were 6.0 × 10(-6) and 2.9 × 10(-6), respectively. The difference is consistent with a modest selective pressure against mutant phenotype erythrocytes in the circulation, and suggests advantages of studying both populations of erythrocytes. Whereas intra-subject variability was low, inter-subject variability was relatively high, with RET(CD59-/CD55-) frequencies differing by more than 30-fold. There was an apparent correlation between age and mutant cell frequencies. Taken together, the results indicate that the frequency of human PIG-A mutant phenotype cells can be efficiently and reliably estimated using a labeling and analysis protocol that is well established for rodent-based studies. The applicability of the assay across species, its simplicity and statistical power, and the relatively non-invasive nature of the assay should benefit myriad research areas involving DNA damage, including studies of environmental factors that modify "spontaneous" mutation frequencies.

Supplemental dietary folic acid has no effect on chromosome damage in erythrocyte progenitor cells of mice

Folate deficiency can cause chromosome damage, which could result from reduced de novo thymidylate synthesis or DNA hypomethylation. High folic acid intake has been hypothesized to inhibit folate-dependent one-carbon metabolism, which could also lead to DNA damage. A large proportion of the general population may have high folic acid intakes. In this study, 2 experiments were conducted to examine the effects of folate on chromosome damage. First, male mice were fed folic acid-deficient (D) (0 mg folic acid/kg diet), control (C) (2 mg/kg), or folic acid-supplemented (S) (6 mg folic acid/kg diet) diets from weaning to maturity. Second, female mice were fed the D, C, or S diet throughout pregnancy, lactation, and breeding for 3 generations; male mice from the F3 generation were fed the same diet as their mothers from weaning, producing D, C, and S F3 male mice. RBC micronucleus frequencies, a measure of chromosome damage or aneuploidy, were determined for both experimental groups. In mice fed diets from weaning to maturity, erythrocyte micronucleus frequency was 24% greater in D compared with C mice. F3 mice fed diet D had 260% and 174% greater reticulocyte and erythrocyte micronucleus frequencies compared with F3 C mice, respectively. The S diets did not affect micronucleus frequency, suggesting that excess folic acid at this level does not promote or protect against chromosome damage. The results suggest that chronic exposure to folic acid at the levels similar to those achieved through fortification is unlikely to be clastogenic or aneugenic.

The erythroid niche: molecular processes occurring within erythroblastic islands

Erythroblasts terminally differentiate within specialized niches composed of erythroblast islands nesting in extracellular matrix proteins. A number of adhesion molecules active in erythroid island attachments have been identified. We have recently observed a receptor/counter receptor interaction that appears to maintain island integrity: erythroid ICAM-4 interacting with macrophage alphaV integrin. When ICAM-4/alphaV binding is blocked, a 70% decrease in islands is observed. Moreover, erythroblastic islands are markedly decreased in ICAM-4 null mice. Using erythropoietin to examine whether ICAM-4/alphaV binding plays a role in stress erythropoiesis, we found that the reticulocyte response is different in ICAM-4 null mice compared to control mice. We speculate that this may be a reflection of the baseline decrease in island number in the ICAM-4 null mice. Erythroblast enucleation also occurs within the erythroid niche. Earlier, we examined whether abnormal protein sorting during nuclear extrusion creates the deficiencies of membrane proteins that are well described in hereditary spherocytosis (HS) and hereditary elliptocytosis (HE). We observed that whereas glycophorin C partitions to reticulocytes in normal mouse cells, it sorts to extruding nuclei in murine hereditary elliptocytosis cells. Additionally, in a murine model of hereditary spherocytosis, band 3, glycophorin A and RhAG partition to both nuclei and reticulocytes, while in normal cells these three proteins distribute predominantly to reticulocytes. Hence, it appears that abnormal protein sorting generates specific protein deficiencies in hereditary elliptocytosis and hereditary spherocytosis.

Modular domains of the Dicistroviridae intergenic internal ribosome entry site

The intergenic region internal ribosome entry site (IGR IRES) of the Dicistroviridae viral family can directly assemble 80S ribosomes and initiate translation at a non-AUG codon from the ribosomal A-site. These functions are directed by two independently folded domains of the IGR IRES. One domain, composed of overlapping pseudoknots II and III (PKII/III), mediates ribosome recruitment. The second domain, composed of PKI, mimics a tRNA anticodon-codon interaction to position the ribosome at the ribosomal A-site. Although adopting a common secondary structure, the dicistrovirus IGR IRESs can be grouped into two classes based on distinct features within each domain. In this study, we report on the modularity of the IGR IRESs and show that the ribosome-binding domain and the tRNA anticodon mimicry domain are functionally interchangeable between the Type I and the Type II IGR IRESs. Using structural probing, ribosome-binding assays, and ribosome positioning analysis by toeprinting assays, we show that the chimeric IRESs fold properly, assemble 80S ribosomes, and can mediate IRES translation in rabbit reticulocyte lysates. We also demonstrate that the chimeric IRESs can stimulate the ribosome-dependent GTPase activity of eEF2, which suggests that the ribosome is primed for a step downstream from IRES binding. Overall, the results demonstrate that the dicistrovirus IGR IRESs are composed of two modular domains that work in concert to manipulate the ribosome and direct translation initiation.

Extrusion of Na,K-ATPase and transferrin receptor with lipid raft-associated proteins in different populations of exosomes during reticulocyte maturation in dogs

The present study characterizes canine reticulocyte exosomes. Exosomes are small membrane vesicles involved in membrane remodeling that are released from reticulocytes during the final maturation step of red blood cells. The vesicles collected from reticulocyte culture supernatants by differential centrifugation contained major exosomal proteins including heat shock protein cognate 70 (Hsc70) and transferrin receptors (TfR), consistent with the definition of the exosome. In addition, the Na,K-ATPase alpha-subunit and stomatin, a lipid raft-associated protein, were extruded by the exosome pathway, possibly leading to the absence of these proteins in erythrocytes, while the major protein constituents of erythrocyte membranes, spectrin and band 3 were retained in reticulocytes and not expelled into exosomes. The Na,K-ATPase alpha-subunit, as well as TfR and about half of the stomatin contained in exosomes, was obtained in a detergent-soluble fraction that was distinct from the lipid raft microdomain. Moreover, Na,K-ATPase and a portion of stomatin were distributed differently to Hsc70, TfR, stomatin, and ganglioside GM1 in vesicles separated with sucrose density gradient centrifugation. These results demonstrate that a heterogeneous group of exosomes participates in the loss of Na,K-ATPase and membrane remodeling during reticulocyte maturation in dogs.

Use of Nramp2-transfected Chinese hamster ovary cells and reticulocytes from mk/mk mice to study iron transport mechanisms

OBJECTIVE

We investigated mechanisms involved in iron (Fe) transport by DMT1 (endosomal Fe(II) exporter, encoded by the Nramp2 gene) using wild-type Chinese hamster ovary (CHO) cells and Nramp2-transfected CHO cells, as well as reticulocytes from normal and mk/mk mice that have a defect in DMT1.

MATERIALS AND METHODS

CHO cells and reticulocytes were incubated with 59Fe bound to various ligands. The radioiron was present in its Fe(II) or Fe(III) forms or bound to transferrin (Tf), and the internalized 59Fe measured under varying experimental conditions. Additionally, 125I-Tf interaction with reticulocytes was investigated and 59Fe incorporation into their heme was determined.

RESULTS

Hyperexpression of DMT1 in CHO cells greatly increases their capacity to acquire ferrous iron. Although CHO-Nramp2 cells showed an increase in Fe(III) uptake as compared to CHO cells, they transported Fe(III) with much lower efficacy than Fe(II). In addition to their defect in Fe uptake, mk/mk reticulocytes also showed a decrease in Tf receptor levels.

CONCLUSIONS

Given that CHO cells acquire iron from Fe(II)-ascorbate with much higher rates than from Fe(III)-Tf, Tf-receptor levels represent the rate-limiting step in their iron uptake. As Fe(III) transport by CHO-Nramp2 cells can be inhibited by the impermeable oxidant K3Fe(CN)6, a membrane ferric reductase is probably needed for reduction of Fe(III) to Fe(II), which is then transported by DMT1. DMT1 is not a limiting factor in Fe acquisition by normal reticulocytes and their heme synthesis.

Modeling time variant distributions of cellular lifespans: increases in circulating reticulocyte lifespans following double phlebotomies in sheep

Many pharmacodynamic (PD) models of cellular response assume a single and time invariant lifespan of all cells, despite the existence of a true underlying distribution of cellular lifespans and known changes in the lifespan distributions with time. To account for these features of cellular populations, a time variant cellular lifespan distribution PD model was formulated and theoretical aspects of modeling cellular populations presented. The model extends prior work assuming time variant "point distributions" of cellular lifespans (Freise et al. J Pharmacokinet Pharmacodyn 34:519-547, 2007) and models assuming a time invariant lifespan distribution (Krzyzanski et al. J Pharmacokinet Pharmacodyn 33:125-166, 2006). The formulated time variant lifespan distribution model was fitted to endogenous plasma erythropoietin (EPO), reticulocyte, and red blood cell (RBC) concentrations in sheep phlebotomized on two occasions, 8 days apart. The time variant circulating reticulocyte lifespan was modeled as a truncated and scaled Weibull distribution, with the location parameter of the distribution non-parametrically represented by an end constrained quadratic spline function. The formulated time variant lifespan distribution model was compared to the identical time invariant distribution, time variant "point distribution", and time invariant "point distribution" cellular lifespan models. Parameters of the time variant lifespan distribution model were well estimated with low standard errors. The mean circulating reticulocyte lifespan was estimated at 0.304 days, which rapidly increased over 3-fold following the first phlebotomy to a maximum of 1.03 days (P = 0.009). On average, the percentage of erythrocytes being released as reticulocytes maximally increased an estimated two-fold following the phlebotomies. The primary features of immature RBC physiology were captured by the model and gave results consistent with other estimates in sheep and humans. The comparison of the four lifespan models gave similar parameter estimates of the stimulation function and fits to the RBC data. However, the time invariant models fit the reticulocyte data poorly, while the time variant "point distribution" cellular lifespan model gave physiologically unrealistic estimates of the changes in the circulating reticulocyte lifespan under stress erythropoiesis. Thus the underlying physiology must be considered when selecting the most appropriate cellular lifespan model and not just the goodness-of-fit criteria. The proposed PD model and the numerical implementation allows for a flexible framework to incorporate time variant lifespan distributions when modeling populations of cells whose production or stimulation depends on endogenous growth factors and/or exogenous drugs.

Evaluation of reticulocyte parameters in iron deficiency, vitamin B(12) deficiency and beta-thalassemia minor patients

The aim of this study was to test the clinical utility of reticulocyte parameters in differential diagnosis in iron deficiency anemia (IDA), vitamin B(12) deficiency (B12) and beta-thalassemia minor (TM). We analyzed the percentage of reticulocyte, absolute reticulocyte count, mean content hemoglobin of reticulocyte (CHr), mean corpuscular volume of reticulocyte (MCVr), corpuscular hemoglobin concentration mean of reticulocyte (CHCMr), MCVr/MCV ratio, CHr/CH ratio and CHCMr/CHCM ratio in healthy donors (n = 34), iron deficiency (IDA) (n = 41), vitamin B(12) deficiency (B12) (n = 22), and TM (n = 34). This study demonstrates that the cutoff value of CHr was 25.7 as indicative of IDA (85.4% sensitivity, 97.1% specificity). CHr and MCVr may be useful for TM (cutoff value < or = 24.8 for CHr) and B12 (>102.1, cutoff value for MCVr), respectively. Sensitivity and specificity of these parameters were 90.9, 86.4% and 97.1, 82.4%, respectively. CHCMr is useful to differentiate IDA and TM from B12. While CHr was low value in microcytic groups (mean 21.8 +/- 3.3 for IDA, 21.0 +/- 2.9 for TM), it was high in B12 (mean 32.1 +/- 5.7). However, that of CHr/CH ratio was only significantly in IDA group compared with the control (P < 0.05, mean 0.98). Therefore, there are limitations regarding CHr and CHr/CH ratio differential diagnosis in microcytic and macrocytic groups. CHr, MCVr, and CHCMr are not sufficiently sensitive and specific to differentiate TM from IDA. We conclude that measurement of reticulocyte count and parameters may be a very useful implement in the diagnosis of IDA and TM.

Reticulocyte haemoglobin content vs. soluble transferrin receptor and ferritin index in iron deficiency anaemia accompanied with inflammation

Ferritin concentration, as a parameter of iron status that is commonly used in the diagnosis of iron deficiency anaemia (IDA), often has limited values if the iron deficiency is accompanied by inflammatory disease. This study evaluated the value of reticulocyte haemoglobin content (CHr) and soluble transferrin receptor-ferritin index (sTfR/F) in the diagnosis of IDA and differential diagnosis of IDA and anaemia of chronic disease. The study included 66 nonanaemic individuals as controls, 86 patients with IDA divided into noninflammatory and inflammatory subgroups, and 32 patients with anaemia of chronic disease. Blood count, iron, transferrin saturation, total iron binding capacity, ferritin, C-reactive protein, sTfR and CHr were determined. Receiver operator characteristic curve analysis showed very high discriminating power for CHr, soluble transferrin receptor (sTfR) and sTfR/F in the diagnosis of IDA. In patients with anaemia of chronic disease these parameters showed no significant difference from the control. CHr and sTfR enabled recognition of iron deficiency and were not affected by acute phase reaction. They are sensitive markers of body iron status with additional value to conventional tests for the detection of iron deficiency.

Method of determination of the reticulocyte age distribution from flow cytometry count by a structured-population model

BACKGROUND

A flow cytometry count of reticulocytes (RET) provides information about distribution of signal emitted by reticulocyte RNA. A new method of determination of the RNA degradation rate in RET is provided. This technique allows one to determinate the age distribution of RET.

METHODS

The method is based on a series of flow cytometry counts of cultured RET. From those counts, the changes of signal distribution of RET over time are obtained. The RNA degradation rate of individual RET is then resolved based on changes in the signal distribution of the whole population of cells. The obtained relation between signal and age allows obtaining a RET age density that can be used to characterize RET age distribution and age dependence of processes that control the population dynamics.

RESULTS

The total maturation time of RET in rats is 3 days. The median time that a homeostatic RET spends in blood or before it becomes a mature RBC is about 0.6 days, whereas a stress RET needs 0.8 days.

CONCLUSIONS

The proposed method provides means for studies in vivo RET dynamics using age-structured models.

Enhanced susceptibility to suicidal death of erythrocytes from transgenic mice overexpressing erythropoietin

Eryptosis, a suicidal death of mature erythrocytes, is characterized by decrease of cell volume, cell membrane blebbing, and breakdown of cell membrane asymmetry with phosphatidylserine exposure at the cell surface. Triggers of eryptosis include increased cytosolic Ca(2+) activity, which could result from activation of Ca(2+)-permeable cation channels. Ca(2+) triggers phosphatidylserine exposure and activates Ca(2+)-sensitive K(+) channels, leading to cellular K(+) loss and cell shrinkage. The cation channels and thus eryptosis are stimulated by Cl(-) removal and inhibited by erythropoietin. The present experiments explored eryptosis in transgenic mice overexpressing erythropoietin (tg6). Erythrocytes were drawn from tg6 mice and their wild-type littermates (WT). Phosphatidylserine exposure was estimated from annexin binding and cell volume from forward scatter in fluorescence-activated cell sorting (FACS) analysis. The percentage of annexin binding was significantly larger and forward scatter significantly smaller in tg6 than in WT erythrocytes. Transgenic erythrocytes were significantly more resistant to osmotic lysis than WT erythrocytes. Cl(-) removal and exposure to the Ca(2+) ionophore ionomycin (1 microM) increased annexin binding and decreased forward scatter, effects larger in tg6 than in WT erythrocytes. The K(+) ionophore valinomycin (10 nM) triggered eryptosis in both tg6 and WT erythrocytes and abrogated differences between genotypes. An increase of extracellular K(+) concentration to 125 mM blunted the difference between tg6 and WT erythrocytes. Fluo-3 fluorescence reflecting cytosolic Ca(2+) activity was larger in tg6 than in WT erythrocytes. In conclusion, circulating erythrocytes from tg6 mice are sensitized to triggers of eryptosis but more resistant to osmotic lysis, properties at least partially due to enhanced Ca(2+) entry and increased K(+) channel activity.

Reticulocyte Maturation Parameters Are Reliable Early Predictors of Hematopoietic Engraftment after Allogeneic Stem Cell Transplantation

Early detection of donor-derived hematopoietic restoration after allogeneic stem cell transplantation (allo-SCT) is a crucial issue in the management of heavily immunocompromised patients. The aim of this prospective study was to validate our previously defined cutoff values for reticulocyte maturation parameters as early predictors of hematopoietic engraftment. Importantly, the effect of clinical variables in reticulocyte engraftment was also sought. For this purpose, we prospectively studied 136 consecutive patients undergoing allo-SCT from related (n = 89) or unrelated (n = 47) donors. High fluorescence reticulocytes (RETH), immature reticulocyte fraction (IRF), mean fluorescence index (MFI), and mean reticulocyte volume (MRV) were automatically measured in peripheral blood samples drawn on a daily basis. We previously defined reticulocyte engraftment when MFI > or =10, RETH > or =3%, IRF > or =10%, and MRV > or =110 fL. Median neutrophil engraftment was 18 days (range, 10-35 days); for reticulocyte parameters, the values were 14 days for IRF (range, 7-45 days), 14 days for MFI (range, 7-43 days), 15 days for RETH (range, 7-43 days), and 21 days for MRV (range, 9-74 days). These differences reached statistical significance for MFI and IRF when compared with standard neutrophil recovery, even when analyzing siblings or unrelated donors separately. In univariate analysis, donor-recipient ABO disparity adversely influenced erythroid engraftment (P = .04 for IRF, P = .03 for MFI), but the infusion of >2.9 x 10(6)/kg of CD34+ cells was associated with a shorter time to reach erythroid engraftment (P = .02 for IRF and MFI). In Cox regression analysis, > or =100/microL neutrophils and IRF > or =10% were predictive parameters for standard neutrophil engraftment. Based on these findings, we suggest that serial measurement of IRF or MFI should be routinely used to trace hematopoietic restoration after allo-SCT because these preceded standard neutrophil recovery by a median of 4 days and are therefore very useful to make clinical decisions.

A detailed study of time-dependent changes in human red blood cells: from reticulocyte maturation to erythrocyte senescence

The use of microfabrication technology in the study of biological systems continues to grow rapidly in both prevalence and ascendancy. Customised microdevices that provide superior results than traditional macroscopic methods can be designed in order to investigate specific cell types and cellular processes. This study showed the benefit of this approach in precisely characterising the progressive losses of surface area and haemoglobin (Hb) content by the human red blood cell (RBC), from newborn reticulocyte to senescent erythrocyte. The high-throughput, multiparametric measurements made on individual cells with a specialised microdevice enabled, for the first time, delineation and quantification of the losses that occur during the two stages of the human RBC lifespan. Data acquired on tens of thousands of red cells showed that nearly as much membrane area is lost during the 1-2 d of reticulocyte maturation (c. 10-14%) as in the subsequent 4 months of erythrocyte ageing (c. 16-17%). The total decrease in Hb over the red cell lifespan is also estimated (c. 15%) and a model describing the complete time-course of diminishing mean RBC area and Hb is proposed. The relationship between the losses of Hb and area, and their possible influence on red cell lifespan, are discussed.

Exosomes: a common pathway for a specialized function

Exosomes are membrane vesicles that are released by cells upon fusion of multivesicular bodies with the plasma membrane. Their molecular composition reflects their origin in endosomes as intraluminal vesicles. In addition to a common set of membrane and cytosolic molecules, exosomes harbor unique subsets of proteins linked to cell type-associated functions. Exosome secretion participates in the eradication of obsolete proteins but several findings, essentially in the immune system, indicate that exosomes constitute a potential mode of intercellular communication. Release of exosomes by tumor cells and their implication in the propagation of unconventional pathogens such as prions suggests their participation in pathological situations. These findings open up new therapeutic and diagnostic strategies.

Assessment of survival of aging erythrocyte in circulation and attendant changes in size and CD147 expression by a novel two step biotinylation method

Three intravenous injections (1mg each) of biotin-X-NHS (BXN) given at 24h intervals labeled all circulating erythrocytes with biotin in C57Bl/6 mice. After 5 days, administration of another i.v. injection of BXN (0.6mg) resulted in the labeling of erythrocytes released in blood circulation after the first biotinylation step, with a lower intensity of biotin. The older erythrocyte population with high intensity of biotin (biotin(high) population) and the later population of newly formed erythrocytes with lower intensity of biotin (biotin(low) population) could be stained with streptavidin-APC (SAv) and identified by flow cytometry. Using the double biotinylation technique, we could examine the survival and age related changes in biotin(low) population of erythrocytes that was released in circulation during a defined time period (5 days). Our results indicate that the percentage of Biotin(low) erythrocytes in circulation remained static for 10 days after the second biotinylation step and than started to decline steadily with time. Mean fluorescence intensity of biotin label on surviving biotin(low) population of erythrocytes however remained stable. These results suggest that after 15 days of release in blood, erythrocytes may undergo random destruction. Furthermore, forward scatter as well as CD147 expression of Biotin(low) population also declined with age. Double biotinylation technique described in this communication offers an easy method for tracking age related changes in populations of erythrocytes released in circulation during a defined period of time.

Multivesicular bodies and autophagy in erythrocyte maturation

During reticulocyte maturation, hematopoietic progenitors undergo numerous changes to reach the final functional stage which concludes with the release of reticulocytes and erythrocytes into circulation. During this process some proteins, which are not required in the mature stage, are sequestered in the internal vesicles present in multivesicular bodies (MVBs). These small vesicles are known as exosomes because they are released into the extracellular medium by fusion of the MVB with the plasma membrane. Interestingly, during this maturation process some organelles, such as mitochondria and endoplasmic reticulum, are wrapped in double membrane vacuoles and degraded via autophagy. We have demonstrated in human leukemic K562 cells a role for calcium and Rab11 in the biogenesis of MVBs and exosome release. Here we discuss evidence indicating that K562 cells present a high basal level of autophagy, and that there is an association between MVBs and autophagosomes, suggesting a role for the autophagic pathway in the maturation process of this cell type.

[On the biophysics characteristics of reticulocytes]

This paper reports an in vivo study on the biophysics characteristics of reticulocytes. Anemia was induced by injection of phenylhydrazine in rabbits. The measurements, including electrophoresis rate, hematolytic rate, fluorescent polarization and the changing anisotropic value, were performed in vivo for 72 hours in the process of reticulocytes growing into erythrocytes. It was shown that there were obvious changes in the biophysics characteristics of reticulocytes in this course. Therefore, the findings are of significance to basic, theoretical and clinical studies.

Is it more effective for highly trained swimmers to live and train at 1200 m than at 1850 m in terms of performance and haematological benefits?

OBJECTIVES

The effects of living and training have not been compared at different altitudes in well trained subjects.

METHODS

Nine international swimmers lived and trained for 13 days similarly at 1200 m (T1200) and 1850 m (T1850). The two altitude training periods were separated by six weeks of sea level training. Before and after each training trip, subjects performed, at an altitude of 1200 m, an incremental exercise test to exhaustion of 5 x 200 m swims and a maximal test over 2000 m.

RESULTS

There was no difference in Vo(2)max after each training trip: the before values were 58.5 (5.6) and 60.4 (6.7) ml/kg/min and the after values were 56.2 (5.2) and 57.1 (4.7) ml/kg/min for T1200 and T1850 respectively. The 2000 m performance had improved during T1200 (1476 (34) to 1448 (45) seconds) but not during T1850 (1458 (35) v 1450 (33) seconds). Mean cell volume increased during T1850 (86.6 (2.8) to 88.7 (2.9) microm(3)) but did not change during T1200 (85.6 (2.9) v 85.7 (2.9) microm(3)). The proportion of reticulocytes decreased during T1200 (15.2 (3.8)% to 10.3 (3.4)%) and increased during T1850 (9.3 (1.6)% to 11.9 (3.5)%).

CONCLUSIONS

The short term effects of 13 days of training at 1200 m on swimming performance appear to be greater than the same type of training for the same length of time at 1850 m. As mean cell volume and proportion of reticulocytes only increased during training at 1850 m, the benefits of training at this altitude may be delayed and appear later on.

Studies on the biomechanical properties of maturing reticulocytes

We investigated the biomechanical properties of reticulocytes obtained from an animal model of hemolytic anemia induced by antibody injection. The hemorheological indices, membrane viscoelasticity, membrane fluidity, and the secondary structure of membrane proteins of the reticulocytes were monitored continuously during the course of their maturation into erythrocytes. The results indicate that reticulocytes had lower deformability, lower membrane fluidity, greater viscoelastic modulus and lesser proportions of alpha-helices and beta-sheets in protein secondary structures than mature erythrocytes. All these indices approached to the level of normal erythrocytes when reticulocytes transformed during maturation. The results help to enhance our understanding of the biomechanical properties of the reticulocytes in their maturing process with clinical diagnosis significances.

Diurnal normobaric moderate hypoxia raises serum erythropoietin concentration but does not stimulate accelerated erythrocyte production

This study was performed to examine the effect of diurnal normobaric hypoxia on hematological parameters. Eleven healthy male volunteers were randomly selected to be in either the hypoxic group (n=6) or the control group (n=5). The hypoxic group was exposed to 8 h of normobaric hypoxia in hypoxic tent systems that elicited a target peripheral O(2) saturation of 81+/-2% on three consecutive days. The control group spent three consecutive 8-h days in modified tent systems that delivered normoxic air into the tent. Venous blood samples were collected before the exposure (days -5, 0), after each day of the exposure (days 1, 2, 3), and for 3 weeks after the exposure (days 7, 10, 13, 17, 24). Serum erythropoietin concentration significantly increased from 9.1+/-3.3 U.L(-1) to 30.7+/-8.6 U.L(-1) in the hypoxic group. Although there were significant increases in hematocrit (4%), hemoglobin concentration (5%), red blood cell count (4%) on day 7 in the hypoxic group, these observations were likely due to dehydration or biological variation over time. There was no significant change in early erythropoietic markers (reticulocyte counts or serum ferritin concentration), which provided inconclusive evidence of accelerated erythroid differentiation and proliferation. The results suggest that the degree of hypoxia was sufficient to stimulate increased erythropoietin production and release. However, the duration of hypoxic exposure was insufficient to propagate the erythropoietic cascade.

Changes in erythropoiesis, iron metabolism and oxidative stress after half-marathon

OBJECTIVE

In marathon runners changes in red blood cell count, haematocrit and haemoglobin in relation to haemodilution have been reported. Moreover, it has been hypothesized that strenuous exercise induces oxidant stress through several different mechanisms. This study investigated the haematological variables, iron status and oxidative indices before, immediately and 48 h after a race in 8 healthy trained males aged 33-44 years running a 21-km marathon in 79 +/- 3 min.

METHODS

The haematological parameters were determined by standard procedures. Erythropoietin and soluble-transferrin receptor were evaluated immunoenzymatically. Nontransferrin-bound iron (NTBI) was assayed by high-performance liquid chromatography after nitrilotriacetic acid chelation. Malonyldialdehyde (MDA) concentration was assayed colorimetrically.

RESULTS

The total number of reticulocytes rose significantly after the run with a significant increase in the high-RNA-content fraction (14 +/- 5, p < 0.0006). Erythropoietin rose by 26% (15.0 +/- 2.8 mU/ml, p < 0.004) and by 25% (14.9 +/- 2.13 mU/ml, p < 0.02) immediately and 48 h after the race, respectively. Serum iron and serum ferritin remained unchanged but NTBI and serum MDA increased significantly immediately after running (1.16 +/- 0.40 mmol/l, p < 0.0008; 0.76 +/- 0.16 mmol/l, p < 0.0001). Significant positive correlations at any time between MDA and polymorphonuclear neutrophils (p = 0.0005), MDA and NTBI (p = 0.0018), polymorphonuclear neutrophils and NTBI (p = 0.0008) and between lactate dehydrogenase and NTBI (p = 0.0212) were observed.

CONCLUSIONS

The erythropoietic changes observed in marathon runners are the results of several interacting mechanisms that involve either the haemopoietic system per se or erythrocyte haemolysis and oxidative stress.

Core erythropoietin receptor signals for late erythroblast development

Critical signals for erythroblast formation are transduced by activated, tyrosine-phosphorylated erythropoietin receptor (EpoR) complexes. Nonetheless, steady-state erythropoiesis is supported effectively by EpoR alleles that are deficient in cytoplasmic phosphotyrosine sites. To better define core EpoR action mechanisms, signaling capacities of minimal PY-null (EpoR-HM) and PY343-retaining (EpoR-H) alleles were analyzed for the first time in bone marrow-derived erythroblasts. Jak2 activation via each allele was comparable. Stat5 (and several Stat5-response genes) were induced via EpoR-H but not via EpoR-HM. Stat1 and Stat3 activation was nominal for all EpoR forms. For both EpoR-HM and EpoR-H, Akt and p70S6-kinase activation was decreased multifold, and JNK activation was minimal. ERKs, however, were hyperactivated uniquely via EpoR-HM. In vivo, Epo expression in EpoR-HM mice was elevated, while Epo-induced reticulocyte production was diminished. In vitro, EpoR-HM erythroblast maturation also was attenuated (based on DNA content, forward-angle light scatter, and hemoglobinization). These EpoR-HM-specific defects were corrected not only upon PY343 site restoration in EpoR-H, but also upon MEK1,2 inhibition. Core EpoR PY site-independent signals for erythroblast formation therefore appear to be Stat5, Stat1, Stat3, p70S6-kinase, and JNK independent, but ERK dependent. Wild-type signaling capacities, however, depend further upon signals provided via an EpoR/PY343/Stat5 axis.

Four-base codon-mediated incorporation of non-natural amino acids into proteins in a eukaryotic cell-free translation system

Various four-base codons have been shown to work for the introduction of non-natural amino acids into proteins in an Escherichia coli cell-free translation system. Here, a four-base codon-mediated non-natural mutagenesis was applied to a eukaryotic rabbit reticulocyte cell-free translation system. Mutated streptavidin mRNAs containing four-base codons were prepared and added to a rabbit reticulocyte lysate in the presence of tRNAs that were aminoacylated with a non-natural amino acid and had the corresponding four-base anticodons. A Western blot analysis of translation products indicated that the four-base codons CGGU, CGCU, CCCU, CUCU, CUAU, and GGGU were efficiently decoded by the aminoacyl-tRNAs having the corresponding four-base anticodons. In contrast, the four-base codons AGGU, AGAU, CGAU, UUGU, UCGU, and ACGU were not decoded. The stop codon-derived four-base codons UAGU, UAAU, and UGAU were found to be inefficient, whereas the amber codon UAG and opal codon UGA were efficient for the incorporation of non-natural amino acids. The application of the expanded genetic code in a eukaryotic cell-free system opens the possibility of a four-base codon-mediated incorporation of non-natural amino acids into proteins in living eukaryotic cells.

Supramaximal exercise mobilizes hematopoietic progenitors and reticulocytes in athletes

Marathon runners show increased circulating CD34+ cell counts and postexercise release of interleukin-6 (IL-6), granulocyte-colony stimulating factor (G-CSF) and flt3-ligand (Bonsignore MR, Morici G, Santoro A, Pegano M, Cascio L, Bonnano A, Abate P, Mirabella F, Profita M, Insalaco G, Gioia M, Vignola AM, Majolino I, Testa U, and Hogg JC. J Appl Physiol 93: 1691–1697, 2002). In the present study we hypothesized that supramaximal (“all-out”) exercise may acutely affect circulating progenitors and reticulocytes and investigated possible mechanisms involved. Progenitor release was measured by flow cytometry ( n = 20) and clonogenic assays ( n = 6) in 20 young competitive rowers (13 M, 7 F, age ± SD: 17.1 ± 2.1 yr, peak O2consumption: 56.5 ± 11.4 ml·min−1·kg−1) at rest and shortly after 1,000 m “all-out.” Release of reticulocytes, cortisol, muscle enzymes, neutrophil elastase, and several cytokines/growth factors was measured. Supramaximal exercise doubled circulating CD34+ cells (rest: 7.6 ± 3.0, all-out: 16.3 ± 9.1 cells/μl, P < 0.001), and increased immature reticulocyte fractions; AC133+ cells doubled, suggesting release of angiogenetic precursors. Erythrocyte burst forming units and colony forming units for granulocytes-monocytes and all blood series increased postexercise by 3.4-, 5.5-, and 4.8-fold, respectively ( P < 0.01 for all). All-out rowing acutely increased plasma cortisol, neutrophil elastase, flt3-ligand, hepatocyte growth factor, VEGF, and transforming growth factor-β1, and decreased erythropoietin; K-ligand, stromal-derived factor-1, IL-6, and G-CSF were unchanged. Therefore, all-out exercise is a physiological stimulus for progenitor release in athletes. Release of reticulocytes and proangiogenetic cells and mediators suggests tissue hypoxia as possibly involved in progenitor mobilization.

In vitro assays of substrate degradation induced by high-risk HPV E6 oncoproteins

The high-risk mucosal human papillomavirus E6 proteins were the first viral proteins that were shown to use the ubiquitin proteasome pathway for the inactivation of their cellular target proteins. The first substrate to be identified was the p53 tumor suppressor protein, and since then many other substrates for E6-induced degradation have been described. All of these require the presence of high-risk mucosal E6 together with the E1, E2, and E3 enzymes of the ubiquitin pathway. This activity of E6, although complex, is nonetheless amenable to in vitro analysis. Many different protocols have been described over the years for performing these assays. In this chapter we describe the most easily used and robust procedure that is routinely used in our laboratory.

Changes in the mutagenic and estrogenic activities of bisphenol A upon treatment with nitrite

Bisphenol A (4,4'isopropylidenediphenol: BPA), an endocrine-disrupting chemical, is contained in food-packaging and can-coating agents as well as in dental sealants. Nitrite is present in vegetables, fish and tap water as an ingredient or contaminant, and also in human saliva. Here, we explored the possible generation of genotoxicity from the reactions of BPA and nitrite under acidic conditions, a situation simulating the stomach. We determined the changes in the mutagenic and estrogenic activities of BPA before and after nitrite treatment. Untreated BPA did not exhibit any mutagenicity. However, the mixture of BPA and sodium nitrite after incubation at pH 3.0 showed strong mutagenic activity toward Salmonella typhimurium strains TA 100 and TA 98 either with or without a metabolic activation system (S9 mix). The clastogenic properties of nitrite-treated and untreated BPA were analyzed by a micronucleus test with male ICR mice. A single gastric intubation of nitrite-treated BPA induced a significantly higher frequency of micronucleated reticulocytes (MNRETs) in mice. The results of analysis of electron spin resonance (ESR) suggest that the expression of the mutagenic activity of nitrite-treated BPA is related to the generation of radicals in the reaction mixture. By applying 1H and 13C NMR, AB-MS and APCI/LC/MS, we identified two compounds 3-nitrobisphenol A and 3,3'-dinitro-bisphenol A. These compounds were synthesized by the reaction of BPA with nitric acid. 3,3'-Dinitro-bisphenol induced a significantly greater frequency of MNRETs in male ICR mice. By applying a green fluorescent protein (GFP)-reporter expression system and an estrogen R(alpha) competitor screening kit, we found that nitrite-treated BPA and 3,3'-dinitro-bisphenol A showed weak estrogenic activity compared to that of untreated BPA.

Pharmacodynamic Analysis of Changes in Reticulocyte Subtype Distribution in Phlebotomy-Induced Stress Erythropoiesis

Changes in the reticulocyte subtype distribution (high, medium and low reticulocytes count (HR, MR, LR)) measured by flow cytometry following phlebotomy-induced stress erythropoiesis (abruptly dropping hemoglobin to 3-4 g/dl over 4-5 hr) and the pharmacodynamic (PD) relationship to the stimulated erythropoietin (EPO) was investigated in sheep. A PD model was developed that describes the relationship between EPO and the reticulocyte maturity distribution fractions (r=0.95+/-0.02, mean +/- SD). The lag-time between EPO activation of erythroid progenitor cells and the subsequent increase in the least mature HR fraction in the peripheral circulation was 0.72 +/- 0.08 days. The mean transition times (in days) for all three reticulocyte fractions changed at baseline from, T(HR) : 0.09 +/- 0.06, T(MR) : 0.06 +/- 0.04, and T(LR) : 0.46 +/- 0.24 to T(HR) : 0.13 +/- 0.08, T(MR) : 0.29 +/- 0.15, and T(LR) : 2.3 +/- 0.24 under stress erythropoiesis. The total mean residence time for a reticulocyte in the peripheral circulation, T(total) (T(HR) + T(MR) + T(LR)), increased from 0.60 +/- 0.33 days under basal to 2.8 +/- 0.09 days during stress erythropoiesis. The statistically significant increase observed for T(LR) and T(total) supports the hypothesis that stress erythropoiesis perturbs the mean reticulocyte transition times. A correlation analysis between various new, proposed metrics involving the HR, MR and LR fractions and the total reticulocyte count, with the latter indicative of stress erythropoiesis at higher total counts, revealed a highly significant correlation indicating these new metrics may be a valuable adjunct to the reticulocyte maturation index (RMI) and the immature reticulocyte fractions index (IRF) previously used in assessing erythropoietic activity in response to anemia.

Isolation and characterization of a glucose/mannose/rhamnose-specific lectin from the knife bean Canavalia gladiata

A lectin with specificity toward mannose, glucose, and rhamnose has been isolated from the legumes of the knife bean Canavalia gladiata. The lectin is composed of two identical 30-kDa subunits with substantial N-terminal sequence similarity to Concanavalin A (Con A). It was purified by affinity chromatography on Affi-gel blue gel, ion exchange chromatography on Mono S, and gel filtration by fast protein liquid chromatography on Superdex 200. Compared with Con A, knife bean lectin started to stimulate [methyl-(3)H]thymidine uptake by mouse splenocytes at a lower concentration, and more potently inhibited proliferation of L1210 leukemia cells. In contrast to Con A, the mitogenic activity of knife bean lectin toward mouse splenocytes, but not its antiproliferative activity toward tumor cells, could be abrogated by 250 mM glucose. Both mitogenic and antiproliferative activities of Con A were abolished by glucose. The lectin inhibited HIV-1 reverse transcriptase with an IC(50) of 35 microM and cell-free translation in a rabbit reticulocyte lysate system with an IC(50) of 2.08 microM. The lectin did not exhibit antifungal activity.

Effect of blood reticulocyte concentration on electrophoretic mobility of erythrocytes in rats

In intact rats electrokinetic characteristics of erythrocytes weakly depended on the intensity of erythropoiesis. This dependence became significant when the degree of erythropoiesis approached the upper limit of variations. Electrophoretic mobility of erythrocytes progressively decreased with increasing blood reticulocyte count. Subpopulations of erythrocytes with low mobility in electric field accumulated in the blood. Our results indicate that erythrocytes whose electrokinetic potential is similar to the mean mobility of circulating cells migrate from the bone marrow into the circulation under normal conditions.

Pilot study for comparison of reticulocyte-micronulei with lymphocyte-micronuclei in human biomonitoring

Biomonitoring tries to determine the consequences for humans of exposures to environmental or pharmaceutical agents. Different end points have been employed to assess the burden of genomic damage. This is the first report comparing a recently introduced new end point, the reticulocyte-micronuclei analyzed by flow cytometry with the widely used lymphocyte-micronucleus assay, applied to two exposure scenarios leading to enhanced genomic damage. Radioiodine therapy was chosen to represent a short time exposure and hemodialysis treatment in end-stage renal failure was chosen to represent a chronic exposure. The results show that iodine radiation induced measurable genomic damage in the lymphocyte-micronucleus assay as well as in the reticulocyte-micronucleus test. Of two groups of patients under hemodialysis treatment, a reduced genomic damage was found with the lymphocyte-micronucleus test, but not with the reticulocyte-micronucleus test in the group undergoing daily hemodialysis, which removes uremic toxins more efficiently as compared to conventional hemodialysis, the treatment applied in the other group. The limited life-span of reticulocytes may make them less suitable for accumulation of chronic low level damage than lymphocytes. In conclusion, the lymphocyte-micronucleus test may be applicable to more exposure situations (including low chronic exposure), but the reticulocyte-micronucleus assay may be easier to perform in a clinical setting. The latter reflects a more rapid reduction of genomic damage after an acute exposure.

Monitoring the content of reticulocyte hemoglobin (CHr) as the progression of anemia in nondialysis chronic renal failure (CRF) patients

BACKGROUND

We previously showed that the content of reticulocyte hemoglobin (CHr) is a reliable measure of iron status in chronic dialysis patients with erythrocytopoiesis. The CHr was significantly correlated with conventional parameters of iron deficiency in dialysis patients. We attempted to utilize the measurement of CHr levels to monitor iron status and clarify the changes in iron levels that occur as renal anemia progresses in patients with chronic renal failure (CRF).

METHODS

We measured CHr, iron parameters, and the intrinsic erythropoietin (EPO) concentration in nondialysis CRF patients who visited our outpatient clinic (n=211). Iron deficiency was defined according to the transferrin saturation (TSAT) and ferritin levels. Conventional red blood cell parameters and CHr levels were measured using an ADVIA120 autoanalyzer (Bayer Medical, USA).

RESULTS

The mean CHr value of the nondialysis CRF patients (creatinine clearance less than 70 mL/min) was 32.3 pg, which was not significantly different from that of the dialysis patients. Significant correlations were found between CHr and ferritin levels (r=0.042, p<0.0403) and CHr and TSAT levels (r=0.040, p<0.0157). A positive correlation was observed between the CHr and serum creatinine levels. Nondialysis CRF patients treated with recombinant human EPO (rHuEPO) at a dose of 24,000 U/month exhibited lower CHr levels, compared with those of other patients who received less than 24,000 U/month.

CONCLUSION

CHr is an easily measurable and trustworthy marker of iron status in nondialysis CRF patients. Moreover, the CHr level was also sensitive to iron alterations in nondialysis CRF patients receiving rHuEPO treatment, and thus, the CHr value could likely provide useful information regarding the need for iron supplementation.

Analysis of human reticulocyte genes reveals altered erythropoiesis: potential use to detect recombinant human erythropoietin doping

BACKGROUND AND OBJECTIVES

Enhancement of oxygen delivery to tissues is associated with improved sporting performance. One way of enhancing oxygen delivery is to take recombinant human erythropoietin (rHuEpo), which is an unethical and potentially dangerous practice. However, detection of the use of rHuEpo remains difficult in situations such as: i) several days after the end of treatment ii) when a treatment with low doses is conducted iii) if the rHuEpo effect is increased by other substances. In an attempt to detect rHuEpo abuse, we selected erythroid gene markers from a SAGE library and analyzed the effects of rHuEpo administration on expression of the HBB, FTL and OAZ genes.

DESIGN AND METHODS

Ten athletes were assigned to the rHuEpo or placebo group. The rHuEpo group received subcutaneous injections of rHuEpo (50 UI/kg three times a week, 4 weeks; 20 UI/kg three times a week, 2 weeks). HBB, FTL and OAZ gene profiles were monitored by real time-polymerase chain reaction (PCR) quantification during and for 3 weeks after drug administration.

RESULTS

The global analysis of these targeted genes detected in whole blood samples showed a characteristic profile of subjects misusing rHuEpo with a increase above the threshold levels. The individual analysis of OAZ mRNA seemed indicative of rHuEpo treatment.

INTERPRETATION AND CONCLUSIONS

The performance-enhancing effect of rHuEpo treatment is greater than the duration of hematologic changes associated with rHuEpo misuse. Although direct electrophoretic methods to detect rHuEpo have been developed, recombinant isoforms of rHuEpo are not detectable some days after the last subcutaneous injection. To overcome these limitations indirect OFF models have been developed. Our data suggest that, in the near future, it will be possible to consolidate results achievable with the OFF models by analyzing selected erythroid gene markers as a supplement to indirect methods.

Associations between serum transferrin receptor concentrations and erythropoietic activities according to body iron status

This study investigated the associations between serum transferrin receptor (sTfR) concentrations and erythropoietic activities during 3 stages of iron deficiency in humans. Serum iron markers, fluorescent intensity of reticulocytes, and sTfR concentrations were measured in 227 prepubescent children, age 9 to 12 yr. Reticulocyte subpopulations were analyzed by flow cytometry and sTfR concentrations were measured by enzyme immunoassay. Mean values of middle-fluorescence reticulocytes (MFR), reticulocyte maturity index (RMI), and sTfR concentrations were significantly higher in iron-deficiency anemia subjects than in healthy controls. Reticulocyte subpopulations increased gradually, as body iron status diminished; the mean values of MFR and RMI in subjects with serum ferritin concentrations < 4.0 microg/L were 3-fold higher than those in healthy controls (p < 0.01). Correlation coefficients of MFR and RMI vs log ferritin values (r = 0.43 and r = 0.42) were higher than those of MFR and RMI vs sTfR concentrations (r = 0.24 and r = 0.27) in iron-deficiency anemia subjects. In summary, iron deficiency leads to increased production of immature reticulocytes. Erythropoietic activity is more closely associated with log ferritin values than with sTfR concentrations in iron-deficiency anemia.

Time and temperature dependant changes in red blood cell analytes used for testing recombinant erythropoietin abuse in sports

There has been a long debate since the introduction of blood analysis prior to major sports events, to find out whether blood samples should be analysed right away on the site of competition or whether they should be transported and analysed in an anti-doping laboratory. Therefore, it was necessary to measure blood samples and compare the results obtained right after the blood withdrawal with those obtained after a few hours delay. Furthermore, it was interesting to determine the effect of temperature on the possible deterioration of red blood cell analytes used for testing recombinant erythropoietin abuse. Healthy volunteers were asked to give two blood samples and one of these was kept at room temperature whereas the second one was put into a refrigerator. On a regular basis, the samples were rolled for homogenisation and temperature stabilisation and were analysed with the same haematological apparatus. The results confirmed that blood controls prior to competition should be performed as soon as possible with standardised pre-analytical conditions to avoid too many variations notably on the haematocrit and the reticulocyte count. These recommendations should ideally also be applied to the all the blood controls compulsory for the medical follow up, otherwise unexplainable values could be misinterpreted and could for instance lead to a period of incapacity.

What determines whether mammalian ribosomes resume scanning after translation of a short upstream open reading frame?

If the 5'-proximal AUG triplet in a mammalian mRNA is followed by a short open reading frame (sORF), a significant fraction of ribosomes resume scanning after termination of sORF translation, and reinitiate at a downstream AUG. To examine the underlying mechanism, we examined reinitiation in vitro using a series of mRNAs that differed only in the 5'-untranslated region (UTR). Efficient reinitiation was found to occur only if the eIF4F complex, or at a minimum the central one-third fragment of eIF4G, participated in the primary initiation event at the sORF initiation codon. It did not occur, however, when sORF translation was driven by the classical swine fever virus or cricket paralysis virus internal ribosome entry sites (IRESs), which do not use eIF4A, 4B, 4E, or 4G. A critical test was provided by an mRNA with an unstructured 5'-UTR, which is translated by scanning but does not absolutely need eIF4G and eIF4A: There was efficient reinitiation in a standard reticulocyte lysate, when initiation would be largely driven by eIF4F, but no reinitiation in an eIF4G-depleted lysate. These results suggest that resumption of scanning may depend on the interaction between eIF4F (or the eIF4G central domain) and the ribosome being maintained while the ribosome translates the sORF.

Visualization and mechanism of assembly of a glucocorticoid receptor.Hsp70 complex that is primed for subsequent Hsp90-dependent opening of the steroid binding cleft

A minimal system of five proteins, hsp90, hsp70, Hop, hsp40, and p23, assembles glucocorticoid receptor (GR).hsp90 heterocomplexes and causes the simultaneous opening of the steroid binding cleft to access by steroid. The first step in assembly is the ATP-dependent and hsp40 (YDJ-1)-dependent formation of a GR.hsp70 complex that primes the receptor for subsequent ATP-dependent activation by hsp90, Hop, and p23. This study focuses on three aspects of the GR priming reaction with hsp70. First, we have visualized the primed GR.hsp70 complexes by atomic force microscopy, and we find the most common stoichiometry to be 1:1, with some complexes of a size approximately 1:2 and a few complexes of larger size. Second, in a recent study of progesterone receptor priming, it was shown that hsp40 binds first, leading to the notion that it targets hsp70 to the receptor. We show here that hsp40 does not perform such a targeting function in priming the GR. Third, we focus on a short amino-terminal segment of the ligand binding domain that is required for GR.hsp90 heterocomplex assembly. By using two glutathione S-transferase (GST)/ligand binding domain fusions with (GST/520C) and without (GST/554C) hsp90 binding and steroid binding activity, we show that the priming step with hsp70 occurs with GST/554C, and it is the subsequent assembly step with hsp90 that is defective.

Determination of the elastic shear modulus of cultured human red blood cells

In this study we investigated the mechanical properties of in vitro cultured red blood cells (RBCs) in a liquid system. We used human umbilical cord blood as a highly efficient source of hematopoietic stem cells (HS). Our first goal was to establish an optimal medium composition in order to yield finally differentiated RBCs, i.e. enucleated and hemoglobin-filled cells. Different stages of cell differentiation were distinguished based on morphological observations and flow cytometry measurements. By means of the micropipette aspiration technique we estimated the deformability characteristics of the cultured cells. Up to the stage of oxiphilic normoblasts they readily deformed. Reticulocytes and mature RBCs showed an enhanced stiffness as compared to RBCs obtained from donors.

Soluble transferrin receptor and immature reticulocytes are not useful for distinguishing iron-deficiency anemia from heterozygous beta-thalassemia

Iron deficiency and heterozygous beta-thalassemia are important causes of hypochromic-microcytic anemia. Two laboratory parameters are suggested for the differentiation of such anemia. High-fluorescence reticulocyte counts and soluble transferrin receptor levels were determined in iron-deficiency anemia patients (n = 49) and heterozygous beta-thalassemia patients (n = 43). There was no significant difference in high-fluorescence reticulocyte and soluble transferrin receptor values between the two groups, but a correlation was observed between high-fluorescence reticulocytes and soluble transferrin receptors in iron-deficiency anemia, probably due to increased receptor synthesis as a response to decreased iron content in erythrocytes.

[Evolutionary and bone marrow recovery indicators in bone marrow transplantation after total body irradiation]

Oxidative stress and reticulocyte maturity index (RMI) were studied in 27 patients who underwent bone marrow transplantation (BMT). Plasmatic lipoperoxide levels of those patients with unfavorable evolution were significantly increased on days 12-14 post-transplant (median 1.83 microM, range 0.78-5.82) compared with preconditioning levels (median 1.05 microM, range 0.36-1.84) (p < 0.05). Patients with favorable evolution revealed significantly higher lipoperoxide levels during conditioning regime (median 1.42 microM, range 0.31-4.50) (p < 0.05). Starting from the 3rd post-transplant week a significant and continuous decrease was observed, with a median of 0.77 microM (range 0.21-1.48 p < 0.05) for the 3rd, and a median of 0.60 microM (range 0.11-1.48 for the 4th week (p < 0.01). A significant increase in total antioxidant activity was observed in the three patients who died up to the 35 days post-transplant. Recovery of bone marrow function was detected by RMI after a median time of 17 days (range 11-24) post-allogeneic transplantation. The threshold established for absolute neutrophil count was achieved after a median of 21 days (range 14-28) (p < 0.001). An increase of plasma lipoperoxides on days 12-14 post-transplant may be a predictive value of unfavourable evolution. RMI was the earlier indicator of engraftment in allogeneic BMT.

Early prediction of response to intravenous iron supplementation by reticulocyte haemoglobin content and high-fluorescence reticulocyte count in haemodialysis patients

BACKGROUND

Optimal response to recombinant human erythropoietin (rHuEpo) in haemodialysis (HD) patients requires provision of sufficient available iron. However, a balance between iron requirements and supplements remains a challenge in clinical practice. Reticulocyte parameters, i.e. reticulocyte haemoglobin content (CHr) and reticulocytes in a high-fluorescence intensity region (HFR), have been shown to be accurate predictors of iron-deficient erythropoiesis as compared with traditional markers. Therefore, the aim of this study was to appraise the diagnostic power of these two parameters in the early prediction of response to intravenous iron (IVFE) medications in HD patients receiving rHuEpo.

METHODS

Sixty-five HD patients with a serum ferritin level of <500 microg/l and on rHuEpo therapy for >6 months were enrolled for IVFE supplementation (100 mg iron saccharate three times a week for 4 weeks, then 100 mg every 2 weeks for 5 months). Haemoglobin, haematocrit, serum ferritin, transferrin saturation, reticulocyte count, percentage of hypochromic red cells, CHr and HFR were measured before and following iron supplementation. Response was defined as a rise in haematocrit of >3% and/or a reduction in rHuEpo dose of >30% over the baseline values at the end of the study.

RESULTS

Forty-two patients had a dramatic response to IVFE therapy with a 13.5% increase in mean haematocrit and a 38% reduction in rHuEpo dose at the end of the study (P<0.001). This paralleled a statistically significant rise in CHr and HFR (P<0.001). Univariate analyses showed that ferritin (P<0.010) and CHr (P<0.001) at baseline, changes in CHr (DeltaCHr(2W), P<0.001) and HFR (DeltaHFR(2W), P<0.010) at 2 weeks, as well as changes in CHr (DeltaCHr(4W), P<0.001) and HFR (DeltaHFR(4W), P<0.001) at 4 weeks, strongly correlated with response to IVFE supplementation. Stepwise discriminant analysis disclosed that DeltaCHr(4W) in conjunction with DeltaHFR(4W) exhibited an r(2) value of 0.531 (P<0.001) to predict response to IVFE therapy. Analyses by receiver operating characteristic curves and logistic regression further revealed that DeltaCHr(4W) at a cut-off value of >1.2 pg and DeltaHFR(4W) of >500/microl were more specific to the status of iron-deficient erythropoiesis following IVFE medications. Combined use of the two cut-off values allowed for the highest accuracy in the early prediction of the response to IVFE therapy, with a sensitivity of 96% and a specificity of 100%.

CONCLUSIONS

Our study shows that changes in CHr and HFR at either 2 or 4 weeks are superior to the conventional erythrocyte and iron metabolism indices and may serve as reliable parameters to detect iron-deficient erythropoiesis in HD patients undergoing rHuEpo therapy. During aggressive IVFE treatment, early identification of non-responsiveness and subsequent discontinuation of treatment can avoid the inadvertent iron-related toxicity due to over-treatment.

Effects of phenylhydrazine or recombinant human erythropoietin on deformability and activity of dehydrogenase glucose-6-phosphate and acetylcholinesterase in Wistar rats blood enriched in reticulocytes

Deformability and activity of the enzymes: acetylcholinesterase (AChE) and dehydrogenase glucose-6-phosphate (G-6-PD), were assayed for RBC enriched in immature reticulocytes. Reticulocytosis was evoked by administration of two different drugs: recombinant human erythropoietin (rHuEPO) and phenylhydrazine (PHZ) to two groups of Wistar rats. After treatment with the former compound, a group of animals exhibited 17.33% reticulocytes in blood whereas a group of rats treated with the latter drug reached 57.66% of these cells in blood. A marked decrease in RBC deformability was found in both groups of animals. AChE did not significantly change activity neither in PHZ-treated nor in rHuEPO-treated rats, whereas G-6-PD activity was significantly decreased in the PHZ-treated group.