Concise review: stem cell-based approaches to red blood cell production for transfusion

An Optimized Human Erythroblast Differentiation System Reveals Cholesterol-Dependency of Robust Production of Cultured Red Blood Cells Ex Vivo

The generation of cultured red blood cells (cRBCs) ex vivo represents a potentially unlimited source for RBC transfusion and other cell therapies. Human cRBCs can be generated from the terminal differentiation of proliferating erythroblasts derived from hematopoietic stem/progenitor cells or erythroid precursors in peripheral blood mononuclear cells. Efficient differentiation and maturation into cRBCs highly depend on replenishing human plasma, which exhibits variable potency across donors or batches and complicates the consistent cRBC production required for clinical translation. Hence, the role of human plasma in erythroblast terminal maturation is investigated and uncovered that 1) a newly developed cell culture basal medium mimicking the metabolic profile of human plasma enhances cell growth and increases cRBC yield upon erythroblast terminal differentiation and 2) LDL-carried cholesterol, as a substitute for human plasma, is sufficient to support erythroid survival and terminal differentiation ex vivo. Consequently, a chemically-defined optimized medium (COM) is developed, enabling robust generation of cRBCs from erythroblasts of multiple origins, with improved enucleation efficiency and higher reticulocyte yield, without the need for supplementing human plasma or serum. In addition, the results reveal the crucial role of lipid metabolism during human terminal erythropoiesis.

Detection of CRISPR/Cas9-Mediated Fetal Hemoglobin Reactivation in Erythroblasts Derived from Cord Blood-Hematopoietic Stem Cells

Reactivation of the fetal hemoglobin (HbF) in adult erythroid cells via genome editing is a strategy for the treatment of β-thalassemia and sickle cell disease. In related reports, the reactivation of HbF is regularly examined in erythroblasts which are generated from the adult CD34+ hematopoietic stem and progenitor cells (HSPCs). However, the procurement of adult HSPCs, either from the bone-marrow (BM) or from mobilized peripheral-blood (mPB), is difficult. Cord-blood (CB) is a readily available source of HSPCs. CB-HSPCs, however, produce high quantities of HbF following differentiation into the erythroid lineage-a potential drawback in such studies. Here, we have edited the BCL11A enhancer (a well-characterized HbF-quantitative trait loci or QTL) via CRISPR/Cas9 in order to determine whether HbF reactivation could be detected in CB-HSPC-derived erythroblasts. In the edited erythroblasts, insertion/deletion (indel) frequencies of 74.0-80.4% and BCL11A RNA reduction levels of 92.6 ± 5.1% (P < 0.0001) were obtained. In turn, the γ/β-globin transcript ratios were increased from 11.3 ± 1.1-fold to 77.1 ± 2.0-fold, i.e., by 6.8-fold (P < 0.0001)-and the HbF% levels increased from 34.3% in the control population to 43.5% in the BCL11A edited erythroblasts. Our results suggest that γ-globin/HbF reactivation via genome editing can be detected in CB-HSPCs generated erythroblasts-rendering CB-HSPCs a useful model for similar studies.

Generation of Rh D-negative blood using CRISPR/Cas9

Blood supply shortages, especially the shortage of rare blood types, threaten the current medical system. Research on stem cells has shed light on in vitro blood cell manufacturing. The in vitro production of universal red blood cells (RBCs) from induced pluripotent stem cells (iPSCs) has become the focus of transfusion medicine. To obtain O-type Rh D-negative blood, we developed O-type Rh D-negative human (h)iPSCs using homology-directed repair (HDR)-based CRISPR/Cas9. HuAiPSCs derived from human umbilical arterial endothelial cells and showing haematopoietic differentiation preferences were selected for gene modification. Guide RNAs (gRNAs) were selected, and a donor template flanked by gRNA-directed homologous arms was set to introduce a premature stop code to RHD exon 2. CRISPR/Cas9 gene editing has resulted in the successful generation of an RHD knockout cell line. The HuAiPSC-A1-RHD-/- cell line was differentiated into haematopoietic stem/progenitor cells and subsequently into erythrocytes in the oxygen concentration-optimized differentiation scheme. HuAiPSC-A1-RHD-/- derived erythrocytes remained positive for the RBC markers CD71 and CD235a. These erythrocytes did not express D antigen and did not agglutinate in the presence of anti-Rh D reagents. In conclusion, taking the priority of haematopoietic preference hiPSCs, the HDR-based CRISPR/Cas9 system and optimizing the erythroid-lineage differentiation protocol, we first generated O-type Rh D-negative universal erythrocytes from RHD knockout HuAiPSCs. Its production is highly efficient and shows great potential for clinical applications.

Human Endometrium Derived Induced Pluripotent Stem Cells Are Amenable to Directed Erythroid Differentiation

BACKGROUND

A protocol for using human endometrium derived induced pluripotent stem cells (iPSCs) to derive hematopoietic and erythroid lineages will be elaborated, through a two-phase culture system.

METHODS

Discarded endometrial tissues were obtained from women receiving hysterectomy in their 4th to 5th decade due to benign uterine conditions. pCE-Sox2, Oct4, Klf4, L-Myc and Lin28 episomal vectors were used to electrotransfect the endometrial stromal cells. The first 8 days involves commitment to hematopoietic stem cells through embryoid body with robust expansion on murine bone marrow stromal cells. The second phase involves feeder free conditions with hydrocortisone, stem cell factor, interleukin-3, and recombinant EPO. After 22 days of feeder free culture, the expression profiles of CD235a+, CD34+, CD43+ and CD 71+ were analyzed by flow cytometry and Wright-Giemsa staining for differential counting. The oxygen carrying capacity of cultured RBCs was measured using a hemoxanalyser.

RESULTS

As a result of inducing these cells via co-culture with murine stromal fibroblasts, all endometrium derived iPSCs were differentiated into erythroblasts with a stable yield of approximately 80% for polychromatic and orthochromatic normoblasts. The protocol for complete induction of erythroid lineage cells starting from human endometrial tissue via iPS cells has been optimized.

CONCLUSION

Successful directed erythroid differentiation has occurred from human endometrium-derived iPS cells. A comprehensive process of actually deriving iPS cells using discarded surgical hysterectomy specimens to the erythroid fate has significance in that the scope of using human iPSC cell lines for tissue regeneration could be expanded in the future.

Generation of red blood cells from stem cells: Achievements, opportunities and perspectives for malaria research

Parasites of the genus Plasmodium that cause malaria survive within humans by invasion of, and proliferation within, the most abundant cell type in the body, the red blood cell. As obligate, intracellular parasites, interactions between parasite and host red blood cell components are crucial to multiple aspects of the blood stage malaria parasite lifecycle. The requirement for, and involvement of, an array of red blood cell proteins in parasite invasion and intracellular development is well established. Nevertheless, detailed mechanistic understanding of host cell protein contributions to these processes are hampered by the genetic intractability of the anucleate red blood cell. The advent of stem cell technology and more specifically development of methods that recapitulate in vitro the process of red blood cell development known as erythropoiesis has enabled the generation of erythroid cell stages previously inaccessible in large numbers for malaria studies. What is more, the capacity for genetic manipulation of nucleated erythroid precursors that can be differentiated to generate modified red blood cells has opened new horizons for malaria research. This review summarises current methodologies that harness in vitro erythroid differentiation of stem cells for generation of cells that are susceptible to malaria parasite invasion; discusses existing and emerging approaches to generate novel red blood cell phenotypes and explores the exciting potential of in vitro derived red blood cells for improved understanding the broad role of host red blood cell proteins in malaria pathogenesis.

Erythroid Differentiation of Induced Pluripotent Stem Cells Co-cultured with OP9 Cells for Diagnostic Purposes

Background

Reagent red blood cells (RBCs) are prepared from donated whole blood, resulting in various combinations of blood group antigens. This inconsistency can be resolved by producing RBCs with uniform antigen expression. Induced pluripotent stem cells (iPSCs) generated directly from mature cells constitute an unlimited source for RBC production. We aimed to produce erythroid cells from iPSCs for diagnostic purposes. We hypothesized that cultured erythroid cells express surface antigens that can be recognized by blood group antibodies.

Methods

iPSCs were co-cultured with OP9 stromal cells to stimulate differentiation into the erythroid lineage. Cell differentiation was examined using microscopy and flow cytometry. Hemoglobin electrophoresis and oxygen-binding capacity testing were performed to verify that the cultured erythroid cells functioned normally. The agglutination reactions of the cultured erythroid cells to antibodies were investigated to confirm that the cells expressed blood group antigens.

Results

The generated iPSCs showed stemness characteristics and could differentiate into the erythroid lineage. As differentiation progressed, the proportion of nucleated RBCs increased. Hemoglobin electrophoresis revealed a sharp peak in the hemoglobin F region. The oxygen-binding capacity test results were similar between normal RBCs and cultured nucleated RBCs. ABO and Rh-Hr blood grouping confirmed similar antigen expression between the donor RBCs and cultured nucleated RBCs.

Conclusions

We generated blood group antigen-expressing nucleated RBCs from iPSCs co-cultured with OP9 cells that can be used for diagnostic purposes. iPSCs from rare blood group donors could serve as an unlimited source for reagent production.

Reticulocyte Maturation

Changes to the membrane proteins and rearrangement of the cytoskeleton must occur for a reticulocyte to mature into a red blood cell (RBC). Different mechanisms of reticulocyte maturation have been proposed to reduce the size and volume of the reticulocyte plasma membrane and to eliminate residual organelles. Lysosomal protein degradation, exosome release, autophagy and the extrusion of large autophagic–endocytic hybrid vesicles have been shown to contribute to reticulocyte maturation. These processes may occur simultaneously or perhaps sequentially. Reticulocyte maturation is incompletely understood and requires further investigation. RBCs with membrane defects or cation leak disorders caused by genetic variants offer an insight into reticulocyte maturation as they present characteristics of incomplete maturation. In this review, we compare the structure of the mature RBC membrane with that of the reticulocyte. We discuss the mechanisms of reticulocyte maturation with a focus on incomplete reticulocyte maturation in red cell variants.

Generation of 'designer erythroblasts' lacking one or more blood group systems from CRISPR/Cas9 gene-edited human-induced pluripotent stem cells

Despite the recent advancements in transfusion medicine, red blood cell (RBC) alloimmunization remains a challenge for multiparous women and chronically transfused patients. At times, diagnostic laboratories depend on difficult-to-procure rare reagent RBCs for the identification of different alloantibodies in such subjects. We have addressed this issue by developing erythroblasts with custom phenotypes (Rh null, GPB null and Kx null/Kell low) using CRISPR/Cas9 gene-editing of a human induced pluripotent stem cell (hiPSC) parent line (OT1-1) for the blood group system genes: RHAG, GYPB and XK. Guide RNAs were cloned into Cas9-puromycin expression vector and transfected into OT1-1. Genotyping was performed to select puromycin-resistant hiPSC KOs. CRISPR/Cas9 gene-editing resulted in the successful generation of three KO lines, RHAG KO, GYPB KO and XK KO. The OT1-1 cell line, as well as the three KO hiPSC lines, were differentiated into CD34+ CD41+ CD235ab+ hematopoietic progenitor cells (HPCs) and subsequently to erythroblasts. Native OT1-1 erythroblasts were positive for the expression of Rh, MNS, Kell and H blood group systems. Differentiation of RHAG KO, GYPB KO and XK KO resulted in the formation of Rh null, GPB null and Kx null/Kell low erythroblasts, respectively. OT1-1 as well as the three KO erythroblasts remained positive for RBC markers-CD71 and BAND3. Erythroblasts were mostly at the polychromatic/ orthochromatic stage of differentiation. Up to ~400-fold increase in erythroblasts derived from HPCs was observed. The availability of custom erythroblasts generated from CRISPR/Cas9 gene-edited hiPSC should be a useful addition to the tools currently used for the detection of clinically important red cell alloantibodies.

Industrially Compatible Transfusable iPSC-Derived RBCs: Progress, Challenges and Prospective Solutions

Amidst the global shortfalls in blood supply, storage limitations of donor blood and the availability of potential blood substitutes for transfusion applications, society has pivoted towards in vitro generation of red blood cells (RBCs) as a means to solve these issues. Many conventional research studies over the past few decades have found success in differentiating hematopoietic stem and progenitor cells (HSPCs) from cord blood, adult bone marrow and peripheral blood sources. More recently, techniques that involve immortalization of erythroblast sources have also gained traction in tackling this problem. However, the RBCs generated from human induced pluripotent stem cells (hiPSCs) still remain as the most favorable solution due to many of its added advantages. In this review, we focus on the breakthroughs for high-density cultures of hiPSC-derived RBCs, and highlight the major challenges and prospective solutions throughout the whole process of erythropoiesis for hiPSC-derived RBCs. Furthermore, we elaborate on the recent advances and techniques used to achieve cost-effective, high-density cultures of GMP-compliant RBCs, and on their relevant novel applications after downstream processing and purification.

Blood Pharming – eine realistische Option?

Die Bluttransfusion ist ein wesentlicher und unersetzlicher Teil der modernen Medizin. Jedoch stellt vor allem bei Patienten mit sehr seltenen Blutgruppenkonstellationen der Mangel an Blutprodukten auch heute noch ein wichtiges Gesundheitsproblem weltweit dar. Um diesem Problem entgegenzutreten, versucht man seit einiger Zeit künstlich rote Blutzellen zu generieren. Diese haben potenzielle Vorteile gegenüber Spenderblut, wie z. B. ein verringertes Risiko für die Übertragung von Infektionskrankheiten. Diese Übersicht fasst die aktuellen Entwicklungen über den Prozess der Erythropoese, die Expansionsstrategien der erythrozytären Zellen, der verschiedenen Quellen für ex vivo expandierte Erythrozyten, die Hürden für die klinische Anwendung und die zukünftigen Möglichkeiten der Anwendung zusammen.

BMI1 enables extensive expansion of functional erythroblasts from human peripheral blood mononuclear cells

Transfusion of red blood cells (RBCs) from ABO-matched but genetically unrelated donors is commonly used for treating anemia and acute blood loss. Increasing demand and insufficient supply for donor RBCs, especially those of universal blood types or free of known and unknown pathogens, has called for ex vivo generation of functional RBCs by large-scale cell culture. However, generating physiological numbers of transfusable cultured RBCs (cRBCs) ex vivo remains challenging, due to our inability to either extensively expand primary RBC precursors (erythroblasts) or achieve efficient enucleation once erythroblasts have been expanded and induced to differentiation and maturation. Here, we report that ectopic expression of the human BMI1 gene confers extensive expansion of human erythroblasts, which can be derived readily from adult peripheral blood mononuclear cells of either healthy donors or sickle cell patients. These extensively expanded erythroblasts (E3s) are able to proliferate exponentially (>1 trillion-fold in 2 months) in a defined culture medium. Expanded E3 cells are karyotypically normal and capable of terminal maturation with approximately 50% enucleation. Additionally, E3-derived cRBCs can circulate in a mouse model following transfusion similar to primary human RBCs. Therefore, we provide a facile approach of generating physiological numbers of human functional erythroblasts ex vivo.

Differentiation of human induced pluripotent stem cells into erythroid cells

During the last years, several strategies have been made to obtain mature erythrocytes or red blood cells (RBC) from the bone marrow or umbilical cord blood (UCB). However, UCB-derived hematopoietic stem cells (HSC) are a limited source and in vitro large-scale expansion of RBC from HSC remains problematic. One promising alternative can be human pluripotent stem cells (PSCs) that provide an unlimited source of cells. Human PSCs, including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), are self-renewing progenitors that can be differentiated to lineages of ectoderm, mesoderm, and endoderm. Several previous studies have revealed that human ESCs can differentiate into functional oxygen-carrying erythrocytes; however, the ex vivo expansion of human ESC-derived RBC is subjected to ethical concerns. Human iPSCs can be a suitable therapeutic choice for the in vitro/ex vivo manufacture of RBCs. Reprogramming of human somatic cells through the ectopic expression of the transcription factors (OCT4, SOX2, KLF4, c-MYC, LIN28, and NANOG) has provided a new avenue for disease modeling and regenerative medicine. Various techniques have been developed to generate enucleated RBCs from human iPSCs. The in vitro production of human iPSC-derived RBCs can be an alternative treatment option for patients with blood disorders. In this review, we focused on the generation of human iPSC-derived erythrocytes to present an overview of the current status and applications of this field.

Large-scale in vitro production of red blood cells from human peripheral blood mononuclear cells

Transfusion of donor-derived red blood cells (RBC) is the most common form of cellular therapy. Donor availability and the potential risk of alloimmunization and other transfusion-related complications may, however, limit the availability of transfusion units, especially for chronically transfused patients. In vitro cultured, customizable RBC would negate these concerns and further increase precision medicine. Large-scale, cost-effective production depends on optimization of culture conditions. We developed a defined medium and adapted our protocols to good manufacturing practice (GMP) culture requirements, which reproducibly provided pure erythroid cultures from peripheral blood mononuclear cells without prior CD34+ isolation, and a 3 × 107-fold increase in erythroblasts in 25 days (or from 100 million peripheral blood mononuclear cells, 2 to 4 mL packed red cells can be produced). Expanded erythroblast cultures could be differentiated to CD71dimCD235a+CD44+CD117-DRAQ5- RBC in 12 days. More than 90% of the cells enucleated and expressed adult hemoglobin as well as the correct blood group antigens. Deformability and oxygen-binding capacity of cultured RBC was comparable to in vivo reticulocytes. Daily RNA sampling during differentiation followed by RNA-sequencing provided a high-resolution map/resource of changes occurring during terminal erythropoiesis. The culture process was compatible with upscaling using a G-Rex bioreactor with a capacity of 1 L per reactor, allowing transition toward clinical studies and small-scale applications.

Early Career Scientists' Guide to the Red Blood Cell - Don't Panic!

Why should we take interest in studying red blood cells? This mini review attempts to answer this question and highlights the problems that authors find most appealing in this dynamic research area. It addresses the early career scientists who are just starting their independent journey and facing tough times. Despite unlimited access to information, the exponential development of computational and intellectual powers, and the seemingly endless possibilities open to talented and ambitious early career researchers, they soon realize that the pressure of imminent competition for financial support is hard. They have to hit deadlines, produce data, publish, report, teach, manage, lead groups, and remain loving family members at the same time. Are these countless hardships worth it? We think they are. Despite centuries of research, red blood cells remain a mysterious and fascinating study objects. These cells bring together experts within the family of the European Red Cell Society and beyond. We all share our joy for the unknown and excitement in understanding how red cells function and what they tell us about the microenvironments and macroenvironments they live in. This review is an invitation to our colleagues to join us on our quest.

Human induced pluripotent stem cell line banking for the production of rare blood type erythrocytes

Background

The in vitro production of mature human red blood cells (RBCs) from induced pluripotent stem cells (iPSCs) has been the focus of research to meet the high demand for blood transfusions. However, limitations like high costs and technological requirements restrict the use of RBCs produced by iPSC differentiation to specific circumstances, such as for patients with rare blood types or alloimmunized patients. In this study, we developed a detailed protocol for the generation of iPSC lines derived from peripheral blood of donors with O D-positive blood and rare blood types (D–and Jr(a-)) and subsequent erythroid differentiation.

Methods

Mononuclear cells separated from the peripheral blood of O D-positive and rare blood type donors were cultured to produce and expand erythroid progenitors and reprogrammed into iPSCs. A 31-day serum-free, xeno-free erythroid differentiation protocol was used to generate reticulocytes. The stability of iPSC lines was confirmed with chromosomal analysis and RT-PCR. Morphology and cell counts were determined by microscopy observations and flow cytometry.

Results

Cells from all donors were successfully used to generate iPSC lines, which were differentiated into erythroid precursors without any apparent chromosomal mutations. This differentiation protocol resulted in moderate erythrocyte yield per iPSC.

Conclusions

It has previously only been hypothesized that erythroid differentiation from iPSCs could be used to produce RBCs for transfusion to patients with rare blood types or who have been alloimmunized. Our results demonstrate the feasibility of producing autologous iPSC-differentiated RBCs for clinical transfusions in patients without alternative options.

Valid Presumption of Shiga Toxin-Mediated Damage of Developing Erythrocytes in EHEC-Associated Hemolytic Uremic Syndrome

The global emergence of clinical diseases caused by enterohemorrhagic Escherichia coli (EHEC) is an issue of great concern. EHEC release Shiga toxins (Stxs) as their key virulence factors, and investigations on the cell-damaging mechanisms toward target cells are inevitable for the development of novel mitigation strategies. Stx-mediated hemolytic uremic syndrome (HUS), characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal injury, is the most severe outcome of an EHEC infection. Hemolytic anemia during HUS is defined as the loss of erythrocytes by mechanical disruption when passing through narrowed microvessels. The formation of thrombi in the microvasculature is considered an indirect effect of Stx-mediated injury mainly of the renal microvascular endothelial cells, resulting in obstructions of vessels. In this review, we summarize and discuss recent data providing evidence that HUS-associated hemolytic anemia may arise not only from intravascular rupture of erythrocytes, but also from the extravascular impairment of erythropoiesis, the development of red blood cells in the bone marrow, via direct Stx-mediated damage of maturing erythrocytes, leading to “non-hemolytic” anemia.

Membrane Rearrangements in the Maturation of Circulating Human Reticulocytes

Red blood cells (RBCs) begin their circulatory life as reticulocytes (Retics) after their egress from the bone marrow where, as R1 Retics, they undergo significant rearrangements in their membrane and intracellular components, via autophagic, proteolytic, and vesicle-based mechanisms. Circulating, R2 Retics must complete this maturational process, which involves additional loss of significant amounts of membrane and selected membrane proteins. Little is known about the mechanism(s) at the basis of this terminal differentiation in the circulation, which culminates with the production of a stable biconcave discocyte. The membrane of R1 Retics undergoes a selective remodeling through the release of exosomes that are enriched in transferrin receptor and membrane raft proteins and lipids, but are devoid of Band 3, glycophorin A, and membrane skeletal proteins. We wondered whether a similar selective remodeling occurred also in the maturation of R2 Retics. Peripheral blood R2 Retics, isolated by an immunomagnetic method, were compared with mature circulating RBCs from the same donor and their membrane protein and lipid content was analyzed. Results show that both Band 3 and spectrin decrease from R2 Retics to RBCs on a "per cell" basis. Looking at membrane proteins that are considered as markers of membrane rafts, flotillin-2 appears to decrease in a disproportionate manner with respect to Band 3. Stomatin also decreases but in a more proportionate manner with respect to Band 3, hinting at a heterogeneous nature of membrane rafts. High resolution lipidomics analysis, on the contrary, revealed that those lipids that are typically representative of the membrane raft phase, sphingomyelin and cholesterol, are enriched in mature RBCs with respct to Retics, relative to total cell lipids, strongly arguing in favor of the selective retention of at least certain subclasses of membrane rafts in RBCs as they mature from Retics. Our hypothesis that rafts serve as additional anchoring sites for the lipid bilayer to the underlying membrane-skeleton is corroborated by the present results. It is becoming ever more clear that a proper lipid composition of the reticulocyte is necessary for the production of a normal mature RBC.

Ultrasound-induced molecular delivery to erythrocytes using a microfluidic system

Preservation of erythrocytes in a desiccated state for storage at ambient temperature could simplify blood transfusions in austere environments, such as rural clinics, far-forward military operations, and during space travel. Currently, storage of erythrocytes is limited by a short shelf-life of 42 days at 4 °C, and long-term preservation requires a complex process that involves the addition and removal of glycerol from erythrocytes before and after storage at -80 °C, respectively. Natural compounds, such as trehalose, can protect cells in a desiccated state if they are present at sufficient levels inside the cell, but mammalian cell membranes lack transporters for this compound. To facilitate compound loading across the plasma membrane via ultrasound and microbubbles (sonoporation), a polydimethylsiloxane-based microfluidic device was developed. Delivery of fluorescein into erythrocytes was tested at various conditions to assess the effects of parameters such as ultrasound pressure, ultrasound pulse interval, microbubble dose, and flow rate. Changes in ultrasound pressure and mean flow rate caused statistically significant increases in fluorescein delivery of up to 73 ± 37% (p < 0.05) and 44 ± 33% (p < 0.01), respectively, compared to control groups, but no statistically significant differences were detected with changes in ultrasound pulse intervals. Following freeze-drying and rehydration, recovery of viable erythrocytes increased by up to 128 ± 32% after ultrasound-mediated loading of trehalose compared to control groups (p < 0.05). These results suggest that ultrasound-mediated molecular delivery in microfluidic channels may be a viable approach to process erythrocytes for long-term storage in a desiccated state at ambient temperatures.

Purifying stem cell-derived red blood cells: a high-throughput label-free downstream processing strategy based on microfluidic spiral inertial separation and membrane filtration

Cell-based therapeutics, such as in vitro manufactured red blood cells (mRBCs), are different to traditional biopharmaceutical products (the final product being the cells themselves as opposed to biological molecules such as proteins) and that presents a challenge of developing new robust and economically feasible manufacturing processes, especially for sample purification. Current purification technologies have limited throughput, rely on expensive fluorescent or magnetic immunolabeling with a significant (up to 70%) cell loss and quality impairment. To address this challenge, previously characterized mechanical properties of umbilical cord blood CD34+ cells undergoing in vitro erythropoiesis were used to develop an mRBC purification strategy. The approach consists of two main stages: (a) a microfluidic separation using inertial focusing for deformability-based sorting of enucleated cells (mRBC) from nuclei and nucleated cells resulting in 70% purity and (b) membrane filtration to enhance the purity to 99%. Herein, we propose a new route for high-throughput (processing millions of cells/min and mls of medium/min) purification process for mRBC, leading to high mRBC purity while maintaining cell integrity and no alterations in their global gene expression profile. Further adaption of this separation approach offers a potential route for processing of a wide range of cellular products.

Cholesterol Deficiency Causes Impaired Osmotic Stability of Cultured Red Blood Cells

Ex vivo generation of red blood cells (cRBCs) is an attractive tool in basic research and for replacing blood components donated by volunteers. As a prerequisite for the survival of cRBCs during storage as well as in the circulation, the quality of the membrane is of utmost importance. Besides the cytoskeleton and embedded proteins, the lipid bilayer is critical for membrane integrity. Although cRBCs suffer from increased fragility, studies investigating the lipid content of their membrane are still lacking. We investigated the membrane lipid profile of cRBCs from CD34⁺ human stem and progenitor cells compared to native red blood cells (nRBCs) and native reticulocytes (nRETs). Ex vivo erythropoiesis was performed in a well-established liquid assay. cRBCs showed a maturation grade between nRETs and nRBCs. High-resolution mass spectrometry analysis for cholesterol and the major phospholipid classes, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, sphingomyelin and lysophosphatidylcholin, demonstrated severe cholesterol deficiency in cRBCs. Although cRBCs showed normal deformability capacity, they suffered from increased hemolysis due to minimal changes in the osmotic conditions. After additional lipid supplementation, especially cholesterol during culturing, the cholesterol content of cRBCs increased to a subnormal amount. Concurrently, the osmotic resistance recovered completely and became comparable to that of nRETs. Minor differences in the amount of phospholipids in cRBCs compared to native cells could mainly be attributed to the ongoing membrane remodeling process from the reticulocyte to the erythrocyte stage. Obtained results demonstrate severe cholesterol deficiency as a reason for enhanced fragility of cRBCs. Therefore, the supplementation of lipids, especially cholesterol during ex vivo erythropoiesis may overcome this limitation and strengthens the survival of cRBCs ex vivo and in vivo.

Differential disruption of autoinhibition and defect in assembly of cytoskeleton during cell division decide the fate of human DIAPH1-related cytoskeletopathy

Background

Diaphanous-related formin 1 (DIA1), which assembles the unbranched actin microfilament and microtubule cytoskeleton, is encoded by DIAPH1. Constitutive activation by the disruption of autoinhibitory interactions between the N-terminal diaphanous inhibitory domain (DID) and C-terminal diaphanous autoregulatory domain (DAD) dysregulates DIA1, resulting in both hearing loss and blood cell abnormalities.

Methods and results

Here, we report the first constitutively active mutant in the DID (p.A265S) of humans with only hearing loss and not blood cell abnormality through whole exome sequencing. The previously reported DAD mutants and our DID mutant (p.A265S) shared the finding of diminished autoinhibitory interaction, abnormally upregulated actin polymerisation activity and increased localisations at the plasma membrane. However, the obvious defect in the DIA1-driven assembly of cytoskeleton ‘during cell division’ was only from the DAD mutants, not from p.A265S, which did not show any blood cell abnormality. We also evaluated the five DID mutants in the hydrophobic pocket since four of these five additional mutants were predicted to critically disrupt interaction between the DID and DAD. These additional pathogenic DID mutants revealed varying degrees of defect in the DIA1-driven cytoskeleton assembly, including nearly normal phenotype during cell division as well as obvious impaired autoinhibition, again coinciding with our key observation in DIA1 mutant (p.A265S) in the DID.

Conclusion

Here, we report the first mutant in the DID of humans with only hearing loss. The differential cell biological phenotypes of DIA1 during cell division appear to be potential determinants of the clinical severity of DIAPH1-related cytoskeletopathy in humans.

Hepatic progenitors of the fetal liver: Interactions with hematopoietic stem cells

The aim of this review is to summarize and give an overview on the findings of signaling between hepatic and hematopoietic progenitors of the liver. To date, there are not many findings published in the field, and the aim of this review is to cover all current publications in this area. The liver is the main site of hematopoiesis during fetal development. However, little is known about how hepatic and other non-hematopoietic progenitors potentially influence hematopoiesis and vice versa. The concurrent peaks of hepatic and hematopoietic progenitor proliferation during development indicate interactions that could possibly be mediated through cell-cell contact, extracellular matrices, cytokines and growth factors, or other signaling molecules. For example, hepatic progenitors, such as hepatic stem cells and hepatoblasts, possess characteristic surface markers that can be cleaved, giving rise to fragments of various lengths. A surface molecule of hepatoblasts has been demonstrated to play an essential role in hematopoiesis. Particularly, these effects on hematopoiesis were distinct, depending on whether it was membrane-bound or cleaved. In this review, the various hepatic and hematopoietic progenitor cell types are concisely described, and the current findings of their potential interactions are summarized.

Review: In vitro generation of red blood cells for transfusion medicine: Progress, prospects and challenges

In vitro generation of red blood cells (RBCs) has the potential to circumvent the shortfalls in global demand for blood for transfusion applications. The conventional approach for RBC generation has been from differentiation of hematopoietic stem cells (HSCs) derived from cord blood, adult bone marrow or peripheral blood. More recently, RBCs have been generated from human induced pluripotent stem cells (hiPSCs) as well as from immortalized adult erythroid progenitors. In this review, we highlight the recent advances to RBC generation from these different approaches and discuss the challenges and new strategies that can potentially make large-scale in vitro generation of RBCs a feasible approach.

The Shape Shifting Story of Reticulocyte Maturation

The final steps of erythropoiesis involve unique cellular processes including enucleation and reorganization of membrane proteins and the cytoskeleton to produce biconcave erythrocytes. Surprisingly this process is still poorly understood. In vitro erythropoiesis protocols currently produce reticulocytes rather than biconcave erythrocytes. In addition, immortalized lines and iPSC-derived erythroid cell suffer from low enucleation and suboptimal final maturation potential. In light of the increasing prospect to use in vitro produced erythrocytes as (personalized) transfusion products or as therapeutic delivery agents, the mechanisms driving this last step of erythropoiesis are in dire need of resolving. Here we review the elusive last steps of reticulocyte maturation with an emphasis on protein sorting during the defining steps of reticulocyte formation during enucleation and maturation.

A Universal Approach to Correct Various HBB Gene Mutations in Human Stem Cells for Gene Therapy of Beta-Thalassemia and Sickle Cell Disease

Beta-thalassemia is one of the most common recessive genetic diseases, caused by mutations in the HBB gene. Over 200 different types of mutations in the HBB gene containing three exons have been identified in patients with β-thalassemia (β-thal) whereas a homozygous mutation in exon 1 causes sickle cell disease (SCD). Novel therapeutic strategies to permanently correct the HBB mutation in stem cells that are able to expand and differentiate into erythrocytes producing corrected HBB proteins are highly desirable. Genome editing aided by CRISPR/Cas9 and other site-specific engineered nucleases offers promise to precisely correct a genetic mutation in the native genome without alterations in other parts of the human genome. Although making a sequence-specific nuclease to enhance correction of a specific HBB mutation by homology-directed repair (HDR) is becoming straightforward, targeting various HBB mutations of β-thal is still challenging because individual guide RNA as well as a donor DNA template for HDR of each type of HBB gene mutation have to be selected and validated. Using human induced pluripotent stem cells (iPSCs) from two β-thal patients with different HBB gene mutations, we devised and tested a universal strategy to achieve targeted insertion of the HBB cDNA in exon 1 of HBB gene using Cas9 and two validated guide RNAs. We observed that HBB protein production was restored in erythrocytes derived from iPSCs of two patients. This strategy of restoring functional HBB gene expression will be able to correct most types of HBB gene mutations in β-thal and SCD. Stem Cells Translational Medicine 2018;7:87-97.

High-throughput assessment of mechanical properties of stem cell derived red blood cells, toward cellular downstream processing

Stem cell products, including manufactured red blood cells, require efficient sorting and purification methods to remove components potentially harmful for clinical application. However, standard approaches for cellular downstream processing rely on the use of specific and expensive labels (e.g. FACS or MACS). Techniques relying on inherent mechanical and physical properties of cells offer high-throughput scalable alternatives but knowledge of the mechanical phenotype is required. Here, we characterized for the first time deformability and size changes in CD34+ cells, and expelled nuclei, during their differentiation process into red blood cells at days 11, 14, 18 and 21, using Real-Time Deformability Cytometry (RT-DC) and Atomic Force Microscopy (AFM). We found significant differences (p < 0.0001; standardised mixed model) between the deformability of nucleated and enucleated cells, while they remain within the same size range. Expelled nuclei are smaller thus could be removed by size-based separation. An average Young's elastic modulus was measured for nucleated cells, enucleated cells and nuclei (day 14) of 1.04 ± 0.47 kPa, 0.53 ± 0.12 kPa and 7.06 ± 4.07 kPa respectively. Our identification and quantification of significant differences (p < 0.0001; ANOVA) in CD34+ cells mechanical properties throughout the differentiation process could enable development of new routes for purification of manufactured red blood cells.

Large-Scale Ex Vivo Generation of Human Red Blood Cells from Cord Blood CD34+ Cells

The ex vivo generation of human red blood cells on a large scale from hematopoietic stem and progenitor cells has been considered as a potential method to overcome blood supply shortages. Here, we report that functional human erythrocytes can be efficiently produced from cord blood (CB) CD34⁺ cells using a bottle turning device culture system. Safety and efficiency studies were performed in murine and nonhuman primate (NHP) models. With the selected optimized culture conditions, one human CB CD34⁺ cell could be induced ex vivo to produce up to 200 million erythrocytes with a purity of 90.1% ± 6.2% and 50% ± 5.7% (mean ± SD) for CD235a⁺ cells and enucleated cells, respectively. The yield of erythrocytes from one CB unit (5 million CD34⁺ cells) could be, in theory, equivalent to 500 blood transfusion units in clinical application. Moreover, induced human erythrocytes had normal hemoglobin content and could continue to undergo terminal maturation in the murine xenotransplantation model. In NHP model, xenotransplantation of induced human erythrocytes enhanced hematological recovery and ameliorated the hypoxia situation in the primates with hemorrhagic anemia. These findings suggested that the ex vivo-generated erythrocytes could be an alternative blood source for traditional transfusion products in the clinic. Stem Cells Translational Medicine 2017;6:1698-1709.

Production of Gene-Corrected Adult Beta Globin Protein in Human Erythrocytes Differentiated from Patient iPSCs After Genome Editing of the Sickle Point Mutation

Human induced pluripotent stem cells (iPSCs) and genome editing provide a precise way to generate gene-corrected cells for disease modeling and cell therapies. Human iPSCs generated from sickle cell disease (SCD) patients have a homozygous missense point mutation in the HBB gene encoding adult β-globin proteins, and are used as a model system to improve strategies of human gene therapy. We demonstrate that the CRISPR/Cas9 system designer nuclease is much more efficient in stimulating gene targeting of the endogenous HBB locus near the SCD point mutation in human iPSCs than zinc finger nucleases and TALENs. Using a specific guide RNA and Cas9, we readily corrected one allele of the SCD HBB gene in human iPSCs by homologous recombination with a donor DNA template containing the wild-type HBB DNA and a selection cassette that was subsequently removed to avoid possible interference of HBB transcription and translation. We chose targeted iPSC clones that have one corrected and one disrupted SCD allele for erythroid differentiation assays, using an improved xeno-free and feeder-free culture condition we recently established. Erythrocytes from either the corrected or its parental (uncorrected) iPSC line were generated with similar efficiencies. Currently ∼6%-10% of these differentiated erythrocytes indeed lacked nuclei, characteristic of further matured erythrocytes called reticulocytes. We also detected the 16-kDa β-globin protein expressed from the corrected HBB allele in the erythrocytes differentiated from genome-edited iPSCs. Our results represent a significant step toward the clinical applications of genome editing using patient-derived iPSCs to generate disease-free cells for cell and gene therapies. Stem Cells 2015;33:1470-1479.

Killing the hypnozoite--drug discovery approaches to prevent relapse in Plasmodium vivax

The eradication of malaria will only be possible if effective, well-tolerated medicines kill hypnozoites in vivax and ovale malaria, and thus prevent relapses in patients. Despite progress in the 8-aminoquinoline series, with tafenoquine in Phase III showing clear benefits over primaquine, the drug discovery challenge to identify hypnozoiticidal or hypnozoite-activating compounds has been hampered by the dearth of biological tools and assays, which in turn has been limited by the immense scientific and logistical challenges associated with accessing relevant human tissue and sporozoites. This review summarises the existing drug discovery series and approaches concerning the goal to block relapse.

Induced pluripotent stem cells in hematology: current and future applications

Reprogramming somatic cells into induced pluripotent stem (iPS) cells is nowadays approaching effectiveness and clinical grade. Potential uses of this technology include predictive toxicology, drug screening, pathogenetic studies and transplantation. Here, we review the basis of current iPS cell technology and potential applications in hematology, ranging from disease modeling of congenital and acquired hemopathies to hematopoietic stem and other blood cell transplantation.