Human erythrocytes' perplexing behaviour: erythrocytic microRNAs.

Erythrocytes have the potential role in erythropoiesis and disease diagnosis. Thought to have lacked nucleic acid content, mammalian erythrocytes are nevertheless able to function for 120-140 days, metabolize heme, maintain oxidative stress, and so on. Mysteriously, erythrocytes proved as largest repositories of microRNAs (miRNAs) some of which are selectively retained and function in mature erythrocytes. They have unique expression patterns and have been found to be linked to specific conditions such as sickle cell anaemia, high-altitude hypoxia, chronic mountain sickness, cardiovascular and metabolic conditions as well as host-parasite interactions. They also have been implicated in cell storage-related damage and the regulation of its survival. However, the mechanism by which miRNAs function in the cell remains unclear. Investigations into the molecular mechanism of miRNAs in erythrocytes via extracellular vesicles have provided important clues in research studies on Plasmodium infection. Erythrocytes are also the primary source of circulating miRNAs but, how they affect the plasma/serum miRNAs profiles are still poorly understood. Erythrocyte-derived exosomal miRNAs, can interact with various body cell types, and have easy access to all regions, making them potentially crucial in various pathophysiological conditions. Which can also improve our understanding to identify potential treatment options and discovery related to non-invasive diagnostic markers. This article emphasizes the importance of erythrocytic miRNAs while focusing on the enigmatic behaviour of erythrocytes. It also sheds light on how this knowledge may be applied in the future to enhance the state of erythrocyte translational research from the standpoint of erythrocytic miRNAs.

Renal anemia: from relative insufficiency of EPO to imbalance of erythropoiesis and eryptosis.

Chronic kidney disease has emerged as a major health issue both in China and worldwide. Renal anemia frequently occurs in patients with chronic kidney disease, and its severity and incidence rate increase as the disease progresses. Over the last 30 years, the administration of exogenous EPO and EPO stimulants has been employed to alleviate renal anemia, suggesting that a relative deficiency in EPO may be a primary cause. However, this approach has overshadowed other contributing factors, particularly eryptosis, which results from the reduced lifespan of red blood cells. Numerous studies reveal that there are nephrogenic and extrarenal EPO secretion indicating that an absolute deficiency of EPO is not always present in patients. Therefore, this paper speculates that renal anemia may arise when EPO-driven erythropoiesis fails to adequately compensate for aggravating eryptosis. Other factors including iron metabolism disorder, uremic toxin accumulation, inflammatory state, oxidative stress, and secondary hyperparathyroidism affect EPO reactivity bone marrow hematopoiesis and eryptosis, leading to an imbalance between red blood cell production and destruction, and cause anemia ultimately. More further studies on the pathogenesis and treatment of renal anemia would be expected to provide evidence to support our opinion.

Reference intervals and percentiles for soluble transferrin receptor and sTfR/log ferritin index in healthy children and adolescents.

OBJECTIVES: Soluble transferrin receptor (sTfR) is a marker of both erythropoiesis and iron status and is considered useful for detecting iron deficiency, especially in inflammatory conditions, but reference intervals covering the entire pediatric age spectrum are lacking. METHODS: We studied 1,064 (48.5 % female) healthy children of the entire pediatric age spectrum to determine reference values and percentiles for sTfR and the ratio of sTfR to log-ferritin (sTfR-F index) using a standard immunoturbidimetric assay. RESULTS: Soluble TfR levels were highly age-specific, with a peak in infancy and a decline in adulthood, whereas the sTfR-F index was a rather constant parameter. There were positive linear relationships for sTfR with hemoglobin (Hb) (p=0.008) and transferrin (females p<0.001; males p=0.003). A negative association was observed between sTfR and ferritin in females (p<0.0001) and for transferrin saturation and mean corpuscular volume (MCV) in both sexes (both p<0.0001). We found a positive relationship between sTfR and body height, body mass index (BMI) and inflammatory markers (CrP p<0.0001; WBC p=0.0172), while sTfR-F index was not affected by inflammation. CONCLUSIONS: Soluble TfR values appear to reflect the activity of infant erythropoiesis and to be modulated by inflammation and iron deficiency even in a healthy cohort.

The effect of erythropoiesis­stimulating agents on lung cancer patients: a meta­analysis.

Previous studies have demonstrated that erythropoiesis-stimulating agents (ESAs) can reduce anemia and improve quality of life in cancer patients, but ESAs may increase mortality. Therefore, we conducted a meta-analysis of randomized controlled trials (RCT) comparing the effect and risk of ESAs about the prevention or treatment of anemia in cancer patients. Four databases including PubMed, Embase, Web of science and Cochrane Library were searched for published RCTS on ESAs in the treatment of anemia in lung cancer patients from 2000 to 2023. Endpoints including mortality, incidence of thrombotic vascular events, blood transfusion requirement, and incidence of adverse events. Our meta-analysis included 8 studies, with a sample size of 4240 patients, including 2548 patients in the ESAs group and 1692 patients in the control group. The risk of mortality was lower in patients using ESAs than control group (RR 0.96, 95% CI 0.92-0.99, P = 0.02). But there was no significant difference in the risk of mortality between the patients using ESAs and controls (RR 0.99, 95% CI 0.92-1.06, P = 0.69) after removing Pere 2020. Subgroup analysis found that patients diagnosed with small cell lung cancer (SCLC) (RR 1.00, 95% CI 0.92-1.08, P = 0.16) or non-small cell lung cancer (NSCLC) (RR 1.01, 95% CI 0.87-1.17, P = 0.13) were no significant difference in mortality rate. The thrombotic vascular events increase in patients using ESAs than control group (RR 1.40, 95% CI 1.13-1.72, P = 0.002). The blood transfusion requirement of ESAs group was lower than control group (RR 0.56, 95% CI 0.44-0.72, P < 0.00001). And the subgroups of Darbepoetin alfa (RR 0.57, 95% CI 0.41-0.79, P = 0.003) and Epoetin alfa (RR 0.68, 95% CI 0.47-0.99, P = 0.01) had lower transfusion requirements than the control group. In the SCLC subgroup (RR 0.51, 95% CI 0.40-0.65, P = 0.34), blood transfusion requirements were lower in the ESAs group, but there was no significant difference between the subgroup of patients with NSCLC (RR 0.61, 95% CI 0.36-1.04, P = 0.009). There was no statistically significant difference between the two groups in the incidence of adverse reactions (RR 0.98, 95% CI 0.95-1.00, P = 0.10). In conclusion, ESAs does not increase the mortality of lung cancer patients or may reduce the risk of death, and can reduce the need for blood transfusion, although ESA can increase the incidence of thrombotic vascular adverse events.Registration PROSPERO CRD42023463582.

Treatment of Anemia Associated with Chronic Kidney Disease: Plea for Considering Physiological Erythropoiesis.

Traditionally, the treatment of anemia associated with chronic kidney disease (CKD) involves prescribing erythropoiesis-stimulating agents (ESAs) or iron preparations. The effectiveness and safety of ESAs and iron have been established. However, several clinical issues, such as hyporesponsiveness to ESAs or defective iron utilization for erythropoiesis, have been demonstrated. Recently, a new class of therapeutics for renal anemia known as hypoxia-inducible factor (HIF)/proline hydroxylase (PH) inhibitors has been developed. Several studies have reported that HIF-PH inhibitors have unique characteristics compared with those of ESAs. In particular, the use of HIF-PH inhibitors may maintain target Hb concentration in patients treated with a high dose of ESAs without increasing the dose. Furthermore, several recent studies have demonstrated that patients with CKD with defective iron utilization for erythropoiesis had a high risk of cardiovascular events or premature death. HIF-PH inhibitors increase iron transport and absorption from the gastrointestinal tract; thus, they may ameliorate defective iron utilization for erythropoiesis in patients with CKD. Conversely, several clinical problems, such as aggravation of thrombotic and embolic complications, diabetic retinal disease, and cancer, have been noted at the time of HIF-PH inhibitor administration. Recently, several pooled analyses of phase III trials have reported the non-inferiority of HIF-PH inhibitors regarding these clinical concerns compared with ESAs. The advantages and issues of anemia treatment by ESAs, iron preparations, and HIF-PH inhibitors must be fully understood. Moreover, patients with anemia and CKD should be treated by providing a physiological erythropoiesis environment that is similar to that of healthy individuals.

Differential regulation by CD47 and thrombospondin-1 of extramedullary erythropoiesis in mouse spleen.

Extramedullary erythropoiesis is not expected in healthy adult mice, but erythropoietic gene expression was elevated in lineage-depleted spleen cells from Cd47-/- mice. Expression of several genes associated with early stages of erythropoiesis was elevated in mice lacking CD47 or its signaling ligand thrombospondin-1, consistent with previous evidence that this signaling pathway inhibits expression of multipotent stem cell transcription factors in spleen. In contrast, cells expressing markers of committed erythroid progenitors were more abundant in Cd47-/- spleens but significantly depleted in Thbs1-/- spleens. Single-cell transcriptome and flow cytometry analyses indicated that loss of CD47 is associated with accumulation and increased proliferation in spleen of Ter119-CD34+ progenitors and Ter119+CD34- committed erythroid progenitors with elevated mRNA expression of Kit, Ermap, and Tfrc. Induction of committed erythroid precursors is consistent with the known function of CD47 to limit the phagocytic removal of aged erythrocytes. Conversely, loss of thrombospondin-1 delays the turnover of aged red blood cells, which may account for the suppression of committed erythroid precursors in Thbs1-/- spleens relative to basal levels in wild-type mice. In addition to defining a role for CD47 to limit extramedullary erythropoiesis, these studies reveal a thrombospondin-1-dependent basal level of extramedullary erythropoiesis in adult mouse spleen.

Mitochondrial regulation of erythropoiesis in homeostasis and disease.

Erythroid cells undergo a highly complex maturation process, resulting in dynamic changes that generate red blood cells (RBCs) highly rich in haemoglobin. The end stages of the erythroid cell maturation process primarily include chromatin condensation and nuclear polarization, followed by nuclear expulsion called enucleation and clearance of mitochondria and other organelles to finally generate mature RBCs. While healthy RBCs are devoid of mitochondria, recent evidence suggests that mitochondria are actively implicated in the processes of erythroid cell maturation, erythroblast enucleation and RBC production. However, the extent of mitochondrial participation that occurs during these ultimate steps is not completely understood. This is specifically important since abnormal RBC retention of mitochondria or mitochondrial DNA contributes to the pathophysiology of sickle cell and other disorders. Here we review some of the key findings so far that elucidate the importance of this process in various aspects of erythroid maturation and RBC production under homeostasis and disease conditions.

Angelica sinensis polysaccharides promote extramedullary stress erythropoiesis via ameliorating splenic glycolysis and EPO/STAT5 signaling-regulated macrophages.

Conventional treatments exhibit various side effects on chronic stress anemia. Extramedullary stress erythropoiesis is a compensatory mechanism, which may effectively counteract anemia. Angelica sinensis polysaccharides (ASP) are the main active ingredient found in Angelica sinensis and exhibit antioxidant and hematopoietic effects. However, the effects of ASP on extramedullary stress erythropoiesis remain to be unclear. Here, we demonstrated the protective effects of ASP on chemotherapeutic drug 5-fluorouracil (5-FU)-induced decline in peripheral blood parameters such as RBC counts, HGB, HCT, and MCH, and the decline of BFU-E colony enumeration in the bone marrow. Meanwhile, ASP promoted extramedullary erythropoiesis, increasing cellular proliferation in the splenic red pulp and cyclin D1 protein expression, abrogating phase G0/G1 arrest of c-kit+ cells in mouse spleen. RT-qPCR and immunohistochemistry further revealed that ASP increased macrophage chemokine Ccl2 genetic expression and the number of F4/80+ macrophages in the spleen. The colony-forming assay showed that ASP significantly increased splenic BFU-E. Furthermore, we found that ASP facilitated glycolytic genes including Hk2, Pgk1, Pkm, Pdk1, and Ldha via PI3K/Akt/HIF2α signaling in the spleen. Subsequently, ASP declined pro-proinflammatory factor IL-1ß, whereas upregulating erythroid proliferation-associated genes Gdf15, Bmp4, Wnt2b, and Wnt8a. Moreover, ASP facilitated EPO/STAT5 signaling in splenic macrophages, thus enhancing erythroid lineage Gata2 genetic expression. Our study indicated that ASP may improve glycolysis, promoting the activity of splenic macrophages, subsequently promoting erythroid progenitor cell expansion. Additionally, ASP facilitates erythroid differentiation via macrophage-mediated EpoR/STAT5 signaling; suggesting it might be a promising strategy for stress anemia treatment.

Effect of Preoperative Recombinant Human Erythropoietin on the Need for Blood Transfusion and Surgical Outcomes in Adult Patients Undergoing Cardiac Surgery: A Systematic Review and Meta-Analysis with Trial Sequential Analysis.

This study aimed to examine the value of preoperative recombinant human erythropoietin (rhEPO) administration to adults undergoing elective cardiac surgery. Databases were searched for randomized controlled trials (RCTs) comparing rhEPO plus standard treatment versus standard treatment only. Primary outcomes were the need for and volume of homologous blood transfusion (HBT). Secondary outcomes were the lengths of intensive care unit (ICU) and hospital stay and the incidence of major adverse events. There was very low certainty that rhEPO is associated with a reduction in the need for HBT, with a number needed to treat of 5.6 (95% confidence interval [CI], 3.9-12.5), and low certainty that it is associated with a moderate reduction in HBT volume (Hedges g = -0.55; 95% CI, -0.79 to -0.32). Meta-regression revealed that studies with a higher proportion of females or older patients demonstrated less benefit of rhEPO in terms of reduced consumption of HBT. Trial sequential analysis showed that rhEPO was superior to standard treatment only for reducing the need for and volume of HBT. Regarding secondary outcomes, there was moderate certainty that rhEPO is associated with a limited reduction in the length of ICU (Hedges g = -0.10; 95% CI, -0.19 to -0.01) and hospital stay (Hedges g = -0.13; 95% CI = -0.25 to -0.02), and low certainty for increased risk of myocardial infarction, with a number needed to harm of 36.1 (95% CI, 17.9-127.4). More well-designed, adequately powered RCTs are needed to draw conclusions regarding the value of rhEPO.

Transcription Factor TAL1 in Erythropoiesis.

Lineage-specific transcription factors (TFs) regulate differentiation of hematopoietic stem cells (HSCs). They are decisive for the establishment and maintenance of lineage-specific gene expression programs during hematopoiesis. For this they create a regulatory network between TFs, epigenetic cofactors, and microRNAs. They activate cell-type specific genes and repress competing gene expression programs. Disturbance of this process leads to impaired lineage fidelity and diseases of the blood system. The TF T-cell acute leukemia 1 (TAL1) is central for erythroid differentiation and contributes to the formation of distinct gene regulatory complexes in progenitor cells and erythroid cells. A TAL1/E47 heterodimer binds to DNA with the TFs GATA-binding factor 1 and 2 (GATA1/2), the cofactors LIM domain only 1 and 2 (LMO1/2), and LIM domain-binding protein 1 (LDB1) to form a core TAL1 complex. Furthermore, cell-type-dependent interactions of TAL1 with other TFs such as with runt-related transcription factor 1 (RUNX1) and Kruppel-like factor 1 (KLF1) are established. Moreover, TAL1 activity is regulated by the formation of TAL1 isoforms, posttranslational modifications (PTMs), and microRNAs. Here, we describe the function of TAL1 in normal hematopoiesis with a focus on erythropoiesis.

Erythroid Krüppel-Like Factor (KLF1): A Surprisingly Versatile Regulator of Erythroid Differentiation.

Erythroid Krüppel-like factor (KLF1), first discovered in 1992, is an erythroid-restricted transcription factor (TF) that is essential for terminal differentiation of erythroid progenitors. At face value, KLF1 is a rather inconspicuous member of the 26-strong SP/KLF TF family. However, 30 years of research have revealed that KLF1 is a jack of all trades in the molecular control of erythropoiesis. Initially described as a one-trick pony required for high-level transcription of the adult HBB gene, we now know that it orchestrates the entire erythroid differentiation program. It does so not only as an activator but also as a repressor. In addition, KLF1 was the first TF shown to be directly involved in enhancer/promoter loop formation. KLF1 variants underlie a wide range of erythroid phenotypes in the human population, varying from very mild conditions such as hereditary persistence of fetal hemoglobin and the In(Lu) blood type in the case of haploinsufficiency, to much more serious non-spherocytic hemolytic anemias in the case of compound heterozygosity, to dominant congenital dyserythropoietic anemia type IV invariably caused by a de novo variant in a highly conserved amino acid in the KLF1 DNA-binding domain. In this chapter, we present an overview of the past and present of KLF1 research and discuss the significance of human KLF1 variants.

Perioperative Patient Blood Management (excluding obstetrics): Guidelines from the French National Authority for Health.

The French National Authority for Health (HAS) recently issued guidelines for patient blood management (PBM) in surgical procedures. These recommendations are based on three usual pillars of PBM: optimizing red cell mass, minimizing blood loss and optimizing anemia tolerance. In the preoperative period, these guidelines recommend detecting anemia and iron deficiency and taking corrective measures well in advance of surgery, when possible, in case of surgery with moderate to high bleeding risk or known preoperative anemia. In the intraoperative period, the use of tranexamic acid and some surgical techniques are recommended to limit bleeding in case of high bleeding risk or in case of hemorrhage, and the use of cell salvage is recommended in some surgeries with a major risk of transfusion. In the postoperative period, the limitation of blood samples is recommended but the monitoring of postoperative anemia must be carried out and may lead to corrective measures (intravenous iron in particular) or more precise diagnostic assessment of this anemia. A "restrictive" transfusion threshold considering comorbidities and, most importantly, the tolerance of the patient is recommended postoperatively. The implementation of a strategy and a program for patient blood management is recommended throughout the perioperative period in healthcare establishments in order to reduce blood transfusion and length of stay. This article presents an English translation of the HAS recommendations and a summary of the rationale underlying these recommendations.

Momelotinib versus Continued Ruxolitinib or Best Available Therapy in JAK Inhibitor-Experienced Patients with Myelofibrosis and Anemia: Subgroup Analysis of SIMPLIFY-2.

INTRODUCTION: Some Janus kinase (JAK) inhibitors such as ruxolitinib and fedratinib do not address and may worsen anemia in patients with myelofibrosis. In these cases, the JAK inhibitor may be continued at a reduced dose in an effort to maintain splenic and symptom control, with supportive therapy and/or red blood cell (RBC) transfusions added to manage anemia. This post hoc descriptive analysis of the phase 3 SIMPLIFY-2 trial evaluated the relative benefits of this approach versus switching to the JAK1/JAK2/activin A receptor type 1 inhibitor momelotinib in patients for whom anemia management is a key consideration. METHODS: SIMPLIFY-2 was a randomized (2:1), open-label, phase 3 trial of momelotinib versus best available therapy (BAT; 88.5% continued ruxolitinib) in JAK inhibitor-experienced patients with myelofibrosis (n = 156). Patient subgroups (n = 105 each) were defined by either baseline (1) hemoglobin (Hb) of < 100 g/L or (2) non-transfusion independence (not meeting the criteria of no transfusions and no Hb of < 80 g/L for the previous 12 weeks); outcomes have been summarized descriptively. RESULTS: In both subgroups of interest, week 24 transfusion independence rates were higher with momelotinib versus BAT/ruxolitinib: baseline Hb of < 100 g/L, 22 (33.3%) versus 5 (12.8%); baseline non-transfusion independent, 25 (34.7%) versus 1 (3.0%). Mean Hb levels over time were also generally higher in both subgroups with momelotinib, despite median transfusion rates through week 24 with momelotinib being comparable to or lower than with BAT/ruxolitinib. Spleen and symptom response rates with momelotinib in these subgroups were comparable to the intent-to-treat population, while rates with BAT/ruxolitinib were lower. CONCLUSION: In patients with moderate-to-severe anemia and/or in need of RBC transfusions, outcomes were improved by switching to momelotinib rather than continuing ruxolitinib and using anemia supportive therapies. TRIAL REGISTRATION: ClinicalTrials.gov: NCT02101268.

Patients with the rare blood cancer myelofibrosis often experience symptoms such as tiredness, an increase in the size of their spleens (an organ involved in filtering the blood), and anemia (too few red blood cells). One type of treatment for myelofibrosis, called a Janus kinase (JAK) inhibitor, can help patients to feel better and reduce the size of their spleens, but some JAK inhibitors do not help with anemia and may make it worse. In those situations, patients may continue to take their JAK inhibitor but also receive another type of treatment, called an anemia supportive therapy, and may also receive red blood cell transfusions. This study compared 2 treatment approaches, continuing the JAK inhibitor ruxolitinib and adding an anemia supportive therapy and/or transfusions versus switching to another treatment called momelotinib, in 2 groups of patients from a clinical trial: (1) patients with levels of hemoglobin (a red blood cell protein) at the start of the trial that indicated that they had anemia, and (2) patients who were already receiving red blood cell transfusions at the start of the trial. In both groups, more patients did not need red blood cell transfusions anymore at week 24 with momelotinib, and their hemoglobin levels on average became higher over time. More patients also had improvements in spleen size and symptoms with momelotinib. Overall, outcomes were improved by switching to momelotinib rather than continuing ruxolitinib and using supportive therapies and/or red blood cell transfusions to treat anemia.

A spotlight on using HIF-PH inhibitors in renal anemia.

INTRODUCTION: Erythropoiesis-stimulating agents (ESAs) together with iron supplementation had been the standard treatment for anemia in chronic kidney disease (CKD) for the past decades. Recently, hypoxia-inducible factor-prolyl hydroxylase inhibitors (HIF-PHIs) have attracted attention as a novel treatment option. AREAS COVERED: This review summarizes the effectiveness and the safety of HIF-PHIs based on previous clinical trials and discusses points to consider for their clinical use. EXPERT OPINION: The results from clinical trials demonstrate that HIF-PHIs are non-inferior to ESAs in terms of the efficacy to maintain or improve blood hemoglobin levels. However, concerns about adverse events including cardiovascular outcomes, thrombotic events, and tumor progression have prevented HIF-PHIs from being widely approved for clinical use. Also, long-term safety has not been demonstrated yet. Practically, HIF-PHIs should be used with caution in patients with a history of thrombosis or active malignancy. Patients without them may be preferable for HIF-PHIs if those are bothered with regular injections of ESAs or are hyporesponsive to ESAs without obvious reasons, provided that the drugs were approved in the country. Even so, clinicians must take caution for signs of adverse events such as heart failure after prescribing the drugs.

Cardiomyocyte crosstalk with endothelium modulates cardiac structure, function, and ischemia-reperfusion injury susceptibility through erythropoietin.

Erythropoietin (EPO) exerts non-canonical roles beyond erythropoiesis that are developmentally, structurally, and physiologically relevant for the heart as a paracrine factor. The role for paracrine EPO signalling and cellular crosstalk in the adult is uncertain. Here, we provided novel evidence showing cardiomyocyte restricted loss of function in Epo in adult mice induced hyper-compensatory increases in Epo expression by adjacent cardiac endothelial cells via HIF-2α independent mechanisms. These hearts showed concentric cellular hypertrophy, elevated contractility and relaxation, and greater resistance to ischemia-reperfusion injury. Voluntary exercise capacity compared to control hearts was improved independent of any changes to whole-body metabolism or blood O2 content or delivery (i.e., hematocrit). Our findings suggest cardiac EPO had a localized effect within the normoxic heart, which was regulated by cell-specific EPO-reciprocity between cardiomyocytes and endothelium. Within the heart, hyper-compensated endothelial Epo expression was accompanied by elevated Vegfr1 and Vegfb RNA, that upon pharmacological pan-inhibition of VEGF-VEGFR signaling, resulted in a paradoxical upregulation in whole-heart Epo. Thus, we provide the first evidence that a novel EPO-EPOR/VEGF-VEGFR axis exists to carefully mediate cardiac homeostasis via cardiomyocyte-endothelial EPO crosstalk.

Global Transcriptomic and Characteristics Comparisons between Mouse Fetal Liver and Bone Marrow Definitive Erythropoiesis.

Erythropoiesis occurs first in the yolk sac as a transit "primitive" form, then is gradually replaced by the "definitive" form in the fetal liver (FL) during fetal development and in the bone marrow (BM) postnatally. While it is well known that differences exist between primitive and definitive erythropoiesis, the similarities and differences between FL and BM definitive erythropoiesis have not been studied. Here we performed comprehensive comparisons of erythroid progenitors and precursors at all maturational stages sorted from E16.5 FL and adult BM. We found that FL cells at all maturational stages were larger than their BM counterparts. We further found that FL BFU-E cells divided at a faster rate and underwent more cell divisions than BM BFU-E. Transcriptome comparison revealed that genes with increased expression in FL BFU-Es were enriched in cell division. Interestingly, the expression levels of glucocorticoid receptor Nr3c1, Myc and Myc downstream target Ccna2 were significantly higher in FL BFU-Es, indicating the role of the Nr3c1-Myc-Ccna2 axis in the enhanced proliferation/cell division of FL BFU-E cells. At the CFU-E stage, the expression of genes associated with hemoglobin biosynthesis were much higher in FL CFU-Es, indicating more hemoglobin production. During terminal erythropoiesis, overall temporal patterns in gene expression were conserved between the FL and BM. While biological processes related to translation, the tricarboxylic acid cycle and hypoxia response were upregulated in FL erythroblasts, those related to antiviral signal pathway were upregulated in BM erythroblasts. Our findings uncovered previously unrecognized differences between FL and BM definitive erythropoiesis and provide novel insights into erythropoiesis.

Identifying and Analyzing Low Energy Availability in Athletes: The Role of Biomarkers and Red Blood Cell Turnover.

Low energy availability (LEA) is a growing concern that can lead to several problems for athletes. However, adaptation to LEA occurs to maintain balance over time, making diagnosis difficult. In this review, we categorize LEA into two phases: the initial phase leading to adaptation and the phase in which adaptation is achieved and maintained. We review the influence of LEA on sports performance and health and discuss biomarkers for diagnosing LEA in each phase. This review also proposes future research topics for diagnosing LEA, with an emphasis on the recently discovered association between red blood cell turnover and LEA.

Erythropoiesis in the mammalian embryo.

Red blood cells (RBCs) comprise a critical component of the cardiovascular network, which constitutes the first functional organ system of the developing mammalian embryo. Examination of circulating blood cells in mammalian embryos revealed 2 distinct types of erythroid cells- large, nucleated 'primitive' erythroblasts followed by smaller, enucleated 'definitive' erythrocytes. This review describes the current understanding of primitive and definitive erythropoiesis gleaned from studies in mouse and human embryos and induced pluripotent stem cells (iPSCs). Primitive erythropoiesis in the mouse embryo comprises a transient wave of committed primitive erythroid progenitors (primitive erythroid colony-forming cells, EryP-CFC) in the early yolk sac that generates a robust cohort of precursors that mature in the bloodstream and enucleate. In contrast, definitive erythropoiesis has 2 distinct developmental origins. The first comprises a transient wave of definitive erythroid progenitors (burst-forming units erythroid, BFU-E) that emerge in the yolk sac and seed the fetal liver where they terminally mature to provide the first definitive RBCs. The second comprises hematopoietic stem cell (HSC)-derived BFU-E that terminally mature at sites colonized by HSCs particularly the fetal liver and subsequently the bone marrow. Primitive and definitive erythropoiesis are derived from endothelial identity precursors with distinct developmental origins. While they share prototypical transcriptional regulation, they are also characterized by distinct lineage-specific factors. The exquisitely timed, sequential production of primitive and definitive erythroid cells is necessary for the survival and growth of the mammalian embryo.

Creg1 Regulates Erythroid Development via TGF-ß/Smad2-Klf1 Axis in Zebrafish.

Understanding the regulation of normal erythroid development will help to develop new potential therapeutic strategies for disorders of the erythroid lineage. Cellular repressor of E1A-stimulated genes 1 (CREG1) is a glycoprotein that has been implicated in the regulation of tissue homeostasis. However, its role in erythropoiesis remains largely undefined. In this study, it is found that CREG1 expression increases progressively during erythroid differentiation. In zebrafish, creg1 mRNA is preferentially expressed within the intermediate cell mass (ICM)/peripheral blood island (PBI) region where primitive erythropoiesis occurs. Loss of creg1 leads to anemia caused by defective erythroid differentiation and excessive apoptosis of erythroid progenitors. Mechanistically, creg1 deficiency results in reduced activation of TGF-ß/Smad2 signaling pathway. Treatment with an agonist of the Smad2 pathway (IDE2) could significantly restore the defective erythroid development in creg1-/- mutants. Further, Klf1, identified as a key target gene downstream of the TGF-ß/Smad2 signaling pathway, is involved in creg1 deficiency-induced aberrant erythropoiesis. Thus, this study reveals a previously unrecognized role for Creg1 as a critical regulator of erythropoiesis, mediated at least in part by the TGF-ß/Smad2-Klf1 axis. This finding may contribute to the understanding of normal erythropoiesis and the pathogenesis of erythroid disorders.

The heterogeneity of erythroid cells: insight at the single-cell transcriptome level.

Erythroid cells, the most prevalent cell type in blood, are one of the earliest products and permeate through the entire process of hematopoietic development in the human body, the oxygen-transporting function of which is crucial for maintaining overall health and life support. Previous investigations into erythrocyte differentiation and development have primarily focused on population-level analyses, lacking the single-cell perspective essential for comprehending the intricate pathways of erythroid maturation, differentiation, and the encompassing cellular heterogeneity. The continuous optimization of single-cell transcriptome sequencing technology, or single-cell RNA sequencing (scRNA-seq), provides a powerful tool for life sciences research, which has a particular superiority in the identification of unprecedented cell subgroups, the analyzing of cellular heterogeneity, and the transcriptomic characteristics of individual cells. Over the past decade, remarkable strides have been taken in the realm of single-cell RNA sequencing technology, profoundly enhancing our understanding of erythroid cells. In this review, we systematically summarize the recent developments in single-cell transcriptome sequencing technology and emphasize their substantial impact on the study of erythroid cells, highlighting their contributions, including the exploration of functional heterogeneity within erythroid populations, the identification of novel erythrocyte subgroups, the tracking of different erythroid lineages, and the unveiling of mechanisms governing erythroid fate decisions. These findings not only invigorate erythroid cell research but also offer new perspectives on the management of diseases related to erythroid cells.