Assessment of Red Blood Cell-Mediated Microvascular Occlusion in Sickle Cell Disease By a Novel Electrical Impedance-Based Microfluidic Device

Introduction: Sickle cell disease (SCD) is a recessive genetic disorder caused by the mutated sickle hemoglobin (HbS) in red blood cells (RBCs). HbS polymerizes in a hypoxic environment, which leads to increased adhesiveness and decreased deformability of RBCs, and ultimately contributes to microvascular occlusion in SCD. As RBC deformability and the associated microvascular occlusion are predictors of individual microcirculatory health, previous studies have developed microfluidic devices for deformability-based RBC sorting in microscale flow, albeit with relatively low throughput. An easy-to-use, point-of-care assay to rapidly assess RBC-mediated microvascular occlusion can be clinically useful in examining the outcome of novel targeted and curative therapies, such as anti-sickling drugs and gene therapies, for patients with SCD. Here, we present an electrical impedance-based microfluidic device and functional assessment of RBC-mediated microvascular occlusion in SCD. Methods: Venous blood samples were collected in EDTA from subjects with homozygous SCD (HbSS, N=12) and controls (HbAA, N=5) under consent in an IRB-approved protocol. Microfluidic devices were fabricated using standard photolithography and polydimethylsiloxane (PDMS) micro-molding protocols. The microchannel consisted of micropillar arrays forming microcapillaries from 3-12 μm, with each array coupled with a pair of gold electrodes on the channel bottom surface (Figure 1A). Two 40-μm-wide side passageways mimicking the anastomoses in the capillary bed were designed to prevent microchannel upstream clogging (Figure 1A inset). A macroscopic view of the device is shown in Figure 1B. The 12-μm array was designed to filter large-cell aggregates and was excluded from our analysis. An impedance analyzer coupled with a custom printed-circuit board was used to record the electrical impedance at a spot frequency of 10 kHz. Prior to the experiments, the microchannel was blocked and rinsed to prevent non-specific adhesion of blood cells. Thereafter, the initial electrical impedance reading of each array was obtained. RBCs suspended at 20% hematocrit in PBS were then perfused through the microchannel under the same inlet pressure for 20 min. Next, the microchannel was washed and a second electrical impedance reading was obtained. The microchannel was then imaged under an inverted microscope, and occlusions of each array were manually quantified. The electrical impedance and occlusion results are reported as percent changes. Data are reported as mean ± standard deviation (SD). Pearson's correlation coefficient (PCC) was used to derive correlation statistics. Results: We observed increased microcapillary occlusion caused by HbSS- vs. HbAA-containing RBCs (Figure 1C, mean microcapillary occlusion percentage ± SD (%) = 24.33 ± 16.88 vs. 5.01 ± 1.25 for 3-μm array, 6.05 ± 4.09 vs. 2.19 ± 0.59 for 4-μm array, 2.77 ± 2.59 vs. 0.82 ± 0.82 for 6-μm array, 1.08 ± 2.28 vs. 0 ± 0 for 8-μm array, and 0.42 ± 1.14 vs. 0 ± 0 for 10-μm array). Similarly, we observed elevated electrical impedance change induced by HbSS- vs. HbAA-containing RBCs (Figure 1D, mean electrical impedance change ± SD (%) = 12.03 ± 8.97 vs. 2.44 ± 0.84 for 3-μm array, 1.79 ± 1.65 vs. 0.91 ± 0.42 for 4-μm array, 0.88 ± 1.14 vs. 0.58 ± 0.67 for 6-μm array, 0.16 ± 0.31 vs. 0.32 ± 0.37 for 8-μm array, and 0.06 ± 0.16 vs. 0.05 ± 0.17 for 10-μm array). Moreover, we found that the electrical impedance changes of individual arrays exhibited a significant correlation to the occlusion percentage within the corresponding arrays (Figure 1E, PCC = 0.9817, N = 85, p < 0.001). Conclusions: Findings suggest that a novel microfluidic platform integrated with micropillar arrays and electrical impedance readout can be used for standardized in vitro functional assessment of RBC-mediated microvascular occlusion in SCD. Electrical impedance change due to RBC-mediated microcapillary occlusion may serve as a new parameter for monitoring RBC health and function without the need for high-resolution microscopic imaging. RBC mediated microcapillary occlusion may serve as a new parameter to assess the clinical efficacy of treatments that improve RBC deformability and rheology, such as hemoglobin modifying drugs, anti-sickling agents, and therapies with curative intent. Disclosures Maji: Xatek Inc.: Patents & Royalties. An:Hemex Health, Inc.: Patents & Royalties. Ahuja:Genentech: Consultancy, Honoraria; Sanofi Genzyme: Consultancy, Honoraria; XaTek, Inc.: Consultancy, Patents & Royalties, Research Funding. Little:BioChip Labs: Patents & Royalties: SCD Biochip (patent, no royalties); Hemex Health, Inc.: Patents & Royalties: Microfluidic electropheresis (patent, no royalties); Bluebird Bio: Research Funding; GBT: Research Funding; GBT: Membership on an entity's Board of Directors or advisory committees; NHLBI: Research Funding. Mohseni:Xatek Inc.: Consultancy, Patents & Royalties, Research Funding. Suster:Xatek Inc.: Consultancy, Patents & Royalties, Research Funding. Gurkan:BioChip Labs: Patents & Royalties; Xatek Inc.: Patents & Royalties; Dx Now Inc.: Patents & Royalties; Hemex Health, Inc.: Consultancy, Current Employment, Patents & Royalties, Research Funding.

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Microfluidic electrical impedance assessment of red blood cell mediated microvascular occlusion

Lab on a Chip ◽

10.1039/d0lc01133a ◽

2021 ◽

Author(s):

Yuncheng Man ◽

Debnath Maji ◽

Ran An ◽

Sanjay Ahuja ◽

Jane A Little ◽

...

Keyword(s):

Sickle Cell Disease ◽

Blood Cell ◽

Red Blood Cells ◽

Sickle Cell ◽

Red Blood Cell ◽

Blood Cells ◽

Electrical Impedance ◽

Cell Disease ◽

Blood Disorders

Alterations in the deformability of red blood cells (RBCs), occurring in hemolytic blood disorders such as sickle cell disease (SCD), contributes to vaso-occlusion and disease pathophysiology. However, there are few...

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High-Throughput Mirna Analysis Suggests Pro-Inflammatory Profile in Sickle Cell Disease

Blood ◽

10.1182/blood-2018-99-110812 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 1077-1077

Author(s):

Matthew Cannon ◽

Sarah Glass ◽

Sidney Smith ◽

Melanie Heinlein ◽

Rosa Lapalombella ◽

...

Keyword(s):

Chronic Pain ◽

Steady State ◽

Sickle Cell Disease ◽

Red Blood Cells ◽

Sickle Cell ◽

Blood Cells ◽

Research Funding ◽

Red Cell ◽

Cell Disease ◽

Acute Crisis

Abstract BACKGROUND: Mature circulating red blood cells, though devoid of a nucleus, have been shown to contain an abundance of miRNAs. Further, it has been shown that sickle cell patient-derived RBCs have a dramatic difference in miRNA content than normal RBCs. Given that a range of miRNAs are involved in the regulation of immunity, including the release of inflammatory mediators, we hypothesize that miRNAs enriched in circulating red blood cells function to prolong the inflammatory state in sickle cell disease. Further, we hypothesize that these miRNAs can be used as biomarkers for use in the clinic to predict crisis and differentiate acute versus chronic pain. Exploring this miRNA enrichment in circulating red blood cells in sickle cell patients will provide practical insight for the inflammation state and will inform characteristics of patients who may need greater care in the clinic. METHODS: Twenty steady state patients were recruited and categorized according to their chronic pain status and crisis frequency per year. Whole blood was drawn during routine visits to the OSU Wexner Medical Center Hematology Clinic. Additionally, whole blood was drawn from five patients either in acute pain crisis (recruited prior to crisis) or within a few days of crisis. Samples were subject to double gradient centrifugation and red cells were resuspended in Trizol and cryopreserved. MiRNAs were isolated from red cell Trizol suspensions using a commercial isolation kit (QIAGEN Cat#217004). Isolated miRNAs were then subject to a NanoString Human miR (v3) expression assay. Differential expression analysis was conducted to compare miRNAs with at least 1.5 fold difference (p = 0.05) between steady state and acute crisis. Target prediction and GO ontology analysis was performed for statistically significant miRNAs using DIANA Tools mirPath v3. Follow-up qPCRs were performed using TaqMan Advanced miRNA cDNA Synthesis Kit (Cat#A28007) and TaqMan Advanced miRNA Assays (Cat#A25576) to validate the decreased expression of miRNAs. Additional qPCRs were performed using TaqMan Gene Expression Assays (Cat#4331182) to investigate mRNA regulatory effects of significant miRNAs in the total red cell population. Western blots were also performed to investigate regulatory effects of these miRNAs at the protein level. RESULTS & CONCLUSION: Comparison of RBC miRNA profiles from patients during acute crisis to those in steady state shows several significantly decreased (>1.5 fold) miRNAs in crisis. Among these miRs we have found previously uncharacterized miRNAs, hsa-miR-2116-5p and hsa-miR-302d-3p. DIANA tools miRNA analysis software predicts these miRNAs to be involved in regulation of cell-to-cell adhesion pathways through gene transcripts such as Protocadherin Beta 6 (PCDHB6) and Neural Cell Adhesion Molecule 2 (NCAM2). Interestingly, inspection of miRNA predicted targets that fall under significant GO terms also predicts several individual miRNAs to regulate inflammatory response and nociceptive signaling gene transcripts like A20 (TNFAIP3) and Cathepsin S (CTSS). Validation of these miRNAs was performed via qPCR for 5 out of the 6 significantly decreased miRNAs. Of the 5 miRNAs tested, hsa-miR-2116-5p, hsa-miR-302d-3p, and hsa-miR-1246 were validated as having decreased expression in acute crisis patients compared to steady state. qPCRs were then performed to probe for miRNA based regulation of top predicted target mRNA transcripts. Both CTSS and TNFAIP3 showed increased expression of mRNA transcripts in acute crisis patient red cells as compared to steady state. Next, western blot analysis was performed on red cell protein lysate. Interestingly, this analysis revealed a pattern in activated CTSS expression that was independent of acute crisis. Steady state patients reporting chronic pain showed increased activated CTSS compared to those without chronic pain. Activated CTSS was not found in red cell lysates from three normal, non-SCD donors. Taken together, these results suggest that red blood cells may play a larger role in inflammation and pain responses in sickle cell disease than previously thought. Further these results suggest activated CTSS as a potential biomarker for differentiating chronic pain in patients. Follow-up studies are underway to further stratify and investigate these findings. Disclosures Desai: University of Pittsburgh: Research Funding; Ironwood: Other: Adjudication Committee; NIH: Research Funding; FDA: Research Funding; Selexy/Novartis: Research Funding; Pfizer: Research Funding.

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ML-0207/ASP8731: A Novel BACH1 Inhibitor That Induces Fetal Hemoglobin in Treatment of Sickle Cell Disease

Blood ◽

10.1182/blood-2021-151606 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 854-854

Author(s):

Selva Nataraja ◽

Maneet Singh ◽

Shilpa Demes ◽

Lyndsay Olson ◽

Jeff Stanwix ◽

...

Keyword(s):

Sickle Cell Disease ◽

Red Blood Cells ◽

Heme Oxygenase ◽

Sickle Cell ◽

Blood Cells ◽

Research Funding ◽

Heme Oxygenase 1 ◽

Cell Disease ◽

Nrf2 Pathway ◽

F Cells

Abstract Sickle cell disease (SCD) is a genetic disorder caused by a point mutation in the β-globin subunit resulting in hemoglobin S (HbS). Following deoxygenation of red blood cells, HbS forms polymers that can promote hemolysis and the release of free heme that cause pro-oxidative and pro-inflammatory stress, vaso-occlusive pain crises, and ischemia-reperfusion pathophysiology. Heme also functions as an intracellular activator of antioxidant and globin gene expression. Heme binds to the transcriptional repressor BTB and CNC homolog 1 (BACH1), which relieves BACH1's repression of gene transcription. The release of BACH1 repression increases the binding of nuclear factor erythroid 2-related factor 2 (NRF2) to antioxidant response elements (ARE) and the cell-specific transcription of antioxidant genes such as heme oxygenase-1 (HMOX1), glutathione reductase (GR), solute carrier family 7 member 11 (SLC7A11), and NAD(P)H dehydrogenase [quinone] 1 (NQO1). We have previously shown that pharmacologic activation of the NRF2 pathway in SCD mice provides protection against heme-induced vascular occlusion, is anti-inflammatory, and decreases hepatic necrosis. NRF2 activation also promotes erythroid expression of the A-gamma (HBG1) and G-gamma (HBG2) globins, which are subunits of hemoglobin F (HbF) that replace β S-globins and thus increase HbF and decrease HbS in red blood cells. Thus, BACH1 inhibitors have the potential to increase expression of antioxidant and HbF genes and prevent or reduce SCD-related pathophysiology, resulting in reduction of hemolysis, inflammation, and vaso-occlusive pain crises. Mitobridge is currently developing ML-0207/ASP8731, a highly potent, selective small molecule inhibitor of BACH1 capable of activating the Nrf2 pathway in human and murine models and investigated the ability of ML-0207 to modulate antioxidant and anti-inflammatory genes and induce HbF in human translational cellular models and a preclinical murine model of SCD. ML-0207 induced mRNA expression of Nrf2 target genes HGB1, HBG2, HMOX1, SLC7A11, GCLM, and NQO1 in human bone marrow-derived CD34+ cells differentiated to erythrocytes. We observed 2-fold increases in both the percentage and number of CD71+/HbF+ erythrocytes by FACS using 1 µM ML-0207 and 10 μM HU compared to DMSO control (Figure 1A). The combination of ML-0207 and HU induced significantly more HbF+ erythrocytes compared to each drug alone (Figure 1B). In a single healthy CD34+ donor non-responsive to 10 µM HU, we observed ML-0207 was able to significantly induce CD71+/HbF+ cells at 1 & 3 µM (Figure 1C). In Townes SCD mice, there were significant increases in heme oxygenase 1 and decreases in VCAM-1, ICAM-1, and decreases in phospho-p65 NF-ĸB protein. Furthermore, we observed a significant reduction in hemin-induced vaso-occlusion and an increase in the percentage of F-cells. The increases in F-cells were accompanied by increases in blood A-gamma globin and erythrocytes and decreases in leukocytes. Taken together, these data support BACH1 inhibitors as potential novel and effective treatments for SCD patients. Figure 1 Figure 1. Disclosures Nataraja: Mitobridge: Current Employment. Singh: Mitobridge: Current Employment. Demes: Astellas: Current Employment. Olson: Mitobridge: Current Employment. Stanwix: Mitobridge: Current Employment. Biddle: Rheos Medicine: Current Employment. Vercellotti: Mitobridge, an Astellas Company: Consultancy, Research Funding; CSL Behring: Research Funding. Belcher: Mitobridge/Astellas: Consultancy, Research Funding; CSL Behring: Research Funding.

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Optimized Beta-Globin Expression and Enucleation from Induced Red Blood Cells for In Vitro Modeling of Sickle Cell Disease

Blood ◽

10.1182/blood-2018-99-114136 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 2359-2359

Author(s):

Tolulope O Rosanwo ◽

Melissa Kinney ◽

Martha A Clark ◽

Linda T Vo ◽

R. Grant Rowe ◽

...

Keyword(s):

Sickle Cell Disease ◽

Red Blood Cells ◽

Sickle Cell ◽

Blood Cells ◽

Research Funding ◽

Disease Modeling ◽

Sequencing Analysis ◽

Beta Globin ◽

Cell Disease

Abstract Human induced pluripotent stem cells (hiPSCs) hold remarkable capacity for disease modeling and the development of novel therapeutic treatments for sickle cell disease (SCD). hiPSCs can theoretically produce all cell types including induced red blood cells (iRBCs). Sickle cell patients, in particular, could benefit from autologous, engineered red blood cells (RBCs). Many patients possess rare Rh phenotypes, are allo-sensitized to blood products and are at risk of iron overload from recurrent transfusions. Therefore, the generation of personalized iRBCs is attractive. Yet, in vitro iRBC production has been hampered by an inability of these cells to differentiate into terminally-mature, enucleated, beta globin-expressing RBCs. Here, we describe updated strategies to improve in vitro production of iRBCs. hiPSCs from sickle cell patients as well as those with normal hemoglobin were differentiated into hematopoietic stem progenitor cells (HSPCs) and immortalized via the overexpression of a previously characterized set of transcription factors promoting self-renewal and multipotency under the control of a doxycycline-regulated promoter. Utilizing an in vitro protocol incorporating increasing concentrations of human plasma, HSPCs differentiated from these lines proceed through terminal erythroid differentiation, including the formation of CD71-/GlyA+/α4 integrin-/Band 3+ cells. Plasma-stimulated iRBCs achieved robust enucleation (11-60.7%) and underwent fetal to adult globin-switching. Further, nearly 21% of the enucleated iRBCs were RNA negative erythrocytes 5-8 microns in diameter. RNA sequencing analysis reveals similar transcriptional profiles between iRBCs and peripheral blood CD34+- derived cultured RBCs (cRBCs) yet distinct differences between SCD and WT iRBCs. SCA iRBCs have increased extracellular matrix organization, cell-cell adhesive properties and up-regulation of hypoxia-response genes. Heme metabolism, DNA repair, fatty acid metabolism and oxidative phosphorylation are all impaired in SCD iRBCs. Assessment of cell physiology exposes membrane damage in SCD iRBCs with increased phalloidin permeability in comparison to wild type controls. Intriguingly, SCD iRBCs co-expressing gamma and beta-globin also demonstrate sickling under hypoxic conditions. With the development of expandable source of erythroid progenitors capable of producing mature red cells, we now aim to utilize this platform for robust disease modeling and autologous cell therapy. Figure. Figure. Disclosures Heeney: Pfizer: Research Funding; Sancilio Pharmaceuticals: Consultancy, Research Funding; Astra Zeneca: Consultancy, Research Funding; Ironwood: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Vertex/Crisper: Other: Data Monitoring Committee.

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Increased Procoagulant Activity of Red Blood Cells from Patients with Homozygous Sickle Cell Disease and β-Thalassemia

Thrombosis and Haemostasis ◽

10.1055/s-0038-1650577 ◽

1996 ◽

Vol 76 (03) ◽

pp. 322-327 ◽

Cited By ~ 73

Author(s):

Dominique Helley ◽

Amiram Eldor ◽

Robert Girot ◽

Rolande Ducrocq ◽

Marie-Claude Guillin ◽

...

Keyword(s):

Sickle Cell Disease ◽

Red Blood Cells ◽

Sickle Cell ◽

Blood Cells ◽

Annexin V ◽

Mean Value ◽

Procoagulant Activity ◽

Dependent Manner ◽

Cell Disease ◽

Homozygous Sickle Cell Disease

SummaryIt has recently been proved that, in vitro, red blood cells (RBCs) from patients with homozygous β-thalassemia behave as procoagulant cells. The procoagulant activity of β-thalassemia RBCs might be the result of an increased exposure of procoagulant phospholipids (i. e. phosphatidylserine) in the outer leaflet of the membrane. In order to test this hypothesis, we compared the catalytic properties of RBCs of patients with β-thalassemia and homozygous sickle cell disease (SS-RBCs) with that of controls. The catalytic parameters (Km, kcat) of prothrombin activation by factor Xa were determined both in the absence and in the presence of RBCs. The turn-over number (kcat) of the reaction was not modified by normal, SS- or (3-thalassemia RBCs. The Km was lower in the presence of normal RBCs (mean value: 9.1 µM) than in the absence of cells (26 µM). The Km measured in the presence of either SS-RBCs (mean value: 1.6 µM) or β-thalassemia RBCs (mean value: 1.5 pM) was significantly lower compared to normal RBCs (p <0.001). No significant difference was observed between SS-RBCs and p-thalassemia RBCs. Annexin V, a protein with high affinity and specificity for anionic phospholipids, inhibited the procoagulant activity of both SS-RBCs and (3-thalassemia RBCs, in a dose-dependent manner. More than 95% inhibition was achieved at nanomolar concentrations of annexin V. These results indicate that the procoagulant activity of both β-thalassemia RBCs and SS-RBCs may be fully ascribed to an abnormal exposure of phosphatidylserine at the outer surface of the red cells.

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Role of Adhesion Molecules and Vascular Endothelium in the Pathogenesis of Sickle Cell Disease

Hematology ◽

10.1182/asheducation-2007.1.84 ◽

2007 ◽

Vol 2007 (1) ◽

pp. 84-90 ◽

Cited By ~ 27

Author(s):

Marilyn J. Telen

Keyword(s):

Sickle Cell Disease ◽

Red Blood Cells ◽

Adhesion Molecules ◽

Sickle Cell ◽

Vascular Endothelium ◽

Blood Cells ◽

Cell Disease ◽

Adhesive Interactions ◽

Lines Of Evidence

AbstractA number of lines of evidence now support the hypothesis that vaso-occlusion and several of the sequelae of sickle cell disease (SCD) arise, at least in part, from adhesive interactions of sickle red blood cells, leukocytes, and the endothelium. Both experimental and genetic evidence provide support for the importance of these interactions. It is likely that future therapies for SCD might target one or more of these interactions.

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Electrical Impedance Characterization of Erythrocyte Response to Cyclic Hypoxia in Sickle Cell Disease

ACS Sensors ◽

10.1021/acssensors.9b00263 ◽

2019 ◽

Vol 4 (7) ◽

pp. 1783-1790 ◽

Cited By ~ 3

Author(s):

Jia Liu ◽

Yuhao Qiang ◽

Ofelia Alvarez ◽

E Du

Keyword(s):

Sickle Cell Disease ◽

Sickle Cell ◽

Electrical Impedance ◽

Cell Disease ◽

Impedance Characterization

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Influence of Haptoglobin Polymorphism on Stroke in Sickle Cell Disease Patients

Genes ◽

10.3390/genes13010144 ◽

2022 ◽

Vol 13 (1) ◽

pp. 144

Author(s):

Olivia Edwards ◽

Alicia Burris ◽

Josh Lua ◽

Diana J. Wilkie ◽

Miriam O. Ezenwa ◽

...

Keyword(s):

Oxidative Stress ◽

Sickle Cell Disease ◽

Sickle Cell ◽

Blood Cells ◽

Cell Disease ◽

Free Hemoglobin ◽

Cerebral Tissue ◽

Sickle Hemoglobin ◽

Haptoglobin Polymorphism

This review outlines the current clinical research investigating how the haptoglobin (Hp) genetic polymorphism and stroke occurrence are implicated in sickle cell disease (SCD) pathophysiology. Hp is a blood serum glycoprotein responsible for binding and removing toxic free hemoglobin from the vasculature. The role of Hp in patients with SCD is critical in combating blood toxicity, inflammation, oxidative stress, and even stroke. Ischemic stroke occurs when a blocked vessel decreases oxygen delivery in the blood to cerebral tissue and is commonly associated with SCD. Due to the malformed red blood cells of sickle hemoglobin S, blockage of blood flow is much more prevalent in patients with SCD. This review is the first to evaluate the role of the Hp polymorphism in the incidence of stroke in patients with SCD. Overall, the data compiled in this review suggest that further studies should be conducted to reveal and evaluate potential clinical advancements for gene therapy and Hp infusions.

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COVID Symptoms and COVID Anxiety in Sickle Cell Disease

Blood ◽

10.1182/blood-2020-143054 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 16-17

Author(s):

Wally R Smith ◽

Benjamin Jaworowski ◽

Shirley Johnson ◽

Thokozeni Lipato ◽

Daniel M Sop

Keyword(s):

Sickle Cell Disease ◽

Sickle Cell ◽

Research Funding ◽

Telephone Survey ◽

Cell Disease ◽

Weighted Mean ◽

The Us ◽

Associated Symptoms ◽

At Home

Background Even before the US upswing of the current COVID pandemic, the number of sickle cell disease (SCD) patients coming to hospitals and EDs appeared to fall drastically. This happened despite SCD patients having often been heavy utilizers of the ED and hospital for their iconic vaso-occlusive crises (VOC). Though ambulatory SCD clinics quick converted largely to telehealth in order to comply with stay-at-home orders designed to suppress person-to-person transmission, some SCD patients appeared to avoid care, delay care, or refuse doctors' invitations for care. Presumably patients did so out of COVID fears, but this has not been confirmed in the literature. Further, whether these patients had COVID symptoms but stayed at home has not been studied. As part of quality improvement (QI) to conduct COVID surveillance in an adult sickle cell program, we sought to explain and predict SCD health care utilization patterns we were observing, as well as to determine urgent physical and mental health needs of patients who appeared to be avoiding care. Methods Fifteen staff in the Adult Sickle Cell Medical Home at Virginia Commonwealth University, a large urban academic medical center, conducted a telephone survey ("wellness check"was used when we talked to patients) of all known adults with SCD over 19 days in 2020. A staff member confirmed the patient had SCD, asked permission to proceed, then asked about symptoms consistent with COVID-19. At the end of the telephone survey, respondents wer invited to complete an email survey of sickle cell and COVID-19 utilization attitudes (19-33 items, depending on the response pattern, either drawn from the National Health Interview Survey, from the Adult Sickle Cell Quality of Life Measurement quality of care survey, or drafted by the authors), the Sickle Cell Stress Survey-Adult (SCSS-A, a 10-item previously validated survey), and anxiety and depression (PHQ9 of the PRIME-MD). Results Of 622 adults approached by phone call, 353 responded to the following yes/no screening questions regarding the prior 14 days: fever over 100 F 0/353 (0.00%); cough 3/353(0.01%); difficulty breathing 0/353(0.00%); unexplained shortness of breath 2/353(0.01%); sore throat 2/353 (0.01%); unexplained muscle soreness 2/353(0.01%);contact with anyone who tested positive for COVID-19 2/353(0.01%); testing for COVID 19 6/353(0.02%). For QI purposes, we set a threshold of three or more COVID-associated symptoms or the presence of fever as criteria requiring intense telephone or in-person staff monitoring for the following week. Only three patients met criteria. A total of 219/353 had email surveys sent. Of 63 patients (28.8%) who returned email surveys by June 10, 2020, 35.9% had already managed a "pain attack" at home 4 or more times in the prior 12 months, and 45.5% of these said their bad ER experiences were very or somewhat important in that decision. In the prior 14 days, although 30/64 reported a crisis for at least one day, only 4/64 had visited the Emergency Department for pain. On a 0-10 scale, 21/61 patients endorsed "0" for worry that they would be COVID-infected by going for medical care (weighted mean 3.9), but 18/59 endorsed "10" for worry they were more at risk of COVID because of SCD (weighted mean 6.31), and 22/60 endorsed "10" for worry they would fare worse than others if COVID infected (weighted mean 6.97). Many patients forwent "needed" care (16/62) or delayed "needed" care by at least a day (36/61). Eleven patients met criteria for moderately severe to severe depression on the PHQ-9, and 28/63 somewhat or strongly agreed with the statement "death is always on the back of my mind" on the SCSS-A. Conclusions In adolescents and adults with SCD, many were already reticent to come to the ED for pain, but a significant portion reported delays or avoidance of needed care during the early stages of the US COVID pandemic, and few reported using the ED despite over half reporting at least one crisis day in 14. Patients nonetheless reported very few COVID-associated symptoms. Fears of COVID infection/susceptibility may limit visits for needed sickle cell care among adults. Acknowledgements: Mica Ferlis RN, FNP, Caitlin McManus, RN, FNP, Emily Sushko, RN, FNP, Justin West, RN, Kate Osborne, RN, Stefani Vaughan-Sams, Marla Brannon, BS, Nakeiya Williams, BS Disclosures Smith: GlycoMimetics, Inc.: Consultancy; Emmaeus Pharmaceuticals, Inc.: Consultancy; Novartis, Inc.: Consultancy, Other: Investigator, Research Funding; Global Blood Therapeutics, Inc.: Consultancy, Research Funding; Shire, Inc.: Other: Investigator, Research Funding; NHLBI: Research Funding; Patient-Centered Outcomes Research Institute: Other: Investigator, Research Funding; Health Resources and Services Administration: Other: Investigator, Research Funding; Incyte: Other: Investigator; Pfizer: Consultancy; Ironwood: Consultancy; Novo Nordisk: Consultancy; Imara: Research Funding; Shire: Research Funding.

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Reconstruction of Sickle Cell Disease with Circulating Sickling Red Blood Cells in Novel Humanized Cytokines and Liver Mistrg Mice

Blood ◽

10.1182/blood-2020-141603 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 29-30

Author(s):

Yuanbin Song ◽

Rana Gbyli ◽

Liang Shan ◽

Wei Liu ◽

Yimeng Gao ◽

...

Keyword(s):

Sickle Cell Disease ◽

Mouse Model ◽

Red Blood Cells ◽

Sickle Cell ◽

Blood Cells ◽

Red Cell ◽

Cell Disease ◽

Ineffective Erythropoiesis ◽

Cd34 Cells

In vivo models of human erythropoiesis with generation of circulating mature human red blood cells (huRBC) have remained elusive, limiting studies of primary human red cell disorders. In our prior study, we have generated the first combined cytokine-liver humanized immunodeficient mouse model (huHepMISTRG-Fah) with fully mature, circulating huRBC when engrafted with human CD34+ hematopoietic stem and progenitor cells (HSPCs)1. Here we present for the first time a humanized mouse model of human sickle cell disease (SCD) which replicates the hallmark pathophysiologic finding of vaso-occlusion in mice engrafted with primary patient-derived SCD HSPCs. SCD is an inherited blood disorder caused by a single point mutation in the beta-globin gene. Murine models of SCD exclusively express human globins in mouse red blood cells in the background of murine globin knockouts2 which exclusively contain murine erythropoiesis and red cells and thus fail to capture the heterogeneity encountered in patients. To determine whether enhanced erythropoiesis and most importantly circulating huRBC in engrafted huHepMISTRG-Fah mice would be sufficient to replicate the pathophysiology of SCD, we engrafted it with adult SCD BM CD34+ cells as well as age-matched control BM CD34+ cells. Overall huCD45+ and erythroid engraftment in BM (Fig. a, b) and PB (Fig. c, d) were similar between control or SCD. Using multispectral imaging flow cytometry, we observed sickling huRBCs (7-11 sickling huRBCs/ 100 huRBCs) in the PB of SCD (Fig. e) but not in control CD34+ (Fig. f) engrafted mice. To determine whether circulating huRBC would result in vaso-occlusion and associated findings in SCD engrafted huHepMISTRG-Fah mice, we evaluated histological sections of lung, liver, spleen, and kidney from control and SCD CD34+ engrafted mice. SCD CD34+ engrafted mice lungs showed an increase in alveolar macrophages (arrowheads) associated with alveolar hemorrhage and thrombosis (arrows) but not observed control engrafted mice (Fig. g). Spleens of SCD engrafted mice showed erythroid precursor expansion, sickled erythrocytes in the sinusoids (arrowheads), and vascular occlusion and thrombosis (arrows) (Fig. h). Liver architecture was disrupted in SCD engrafted mice with RBCs in sinusoids and microvascular thromboses (Fig. i). Congestion of capillary loops and peritubular capillaries and glomeruli engorged with sickled RBCs was evident in kidneys (Fig. j) of SCD but not control CD34+ engrafted mice. SCD is characterized by ineffective erythropoiesis due to structural abnormalities in erythroid precursors3. As a functional structural unit, erythroblastic islands (EBIs) represent a specialized niche for erythropoiesis, where a central macrophage is surrounded by developing erythroblasts of varying differentiation states4. In our study, both SCD (Fig. k) and control (Fig. l) CD34+ engrafted mice exhibited EBIs with huCD169+ huCD14+ central macrophages surrounded by varying stages of huCD235a+ erythroid progenitors, including enucleated huRBCs (arrows). This implies that huHepMISTRG-Fah mice have the capability to generate human EBIs in vivo and thus represent a valuable tool to not only study the effects of mature RBC but also to elucidate mechanisms of ineffective erythropoiesis in SCD and other red cell disorders. In conclusion, we successfully engrafted adult SCD patient BM derived CD34+ cells in huHepMISTRG-Fah mice and detected circulating, sickling huRBCs in the mouse PB. We observed pathological changes in the lung, spleen, liver and kidney, which are comparable to what is seen in the established SCD mouse models and in patients. In addition, huHepMISTRG-Fah mice offer the opportunity to study the role of the central macrophage in human erythropoiesis in health and disease in an immunologically advantageous context. This novel mouse model could therefore serve to open novel avenues for therapeutic advances in SCD. Reference 1. Song Y, Shan L, Gybli R, et. al. In Vivo reconstruction of Human Erythropoiesis with Circulating Mature Human RBCs in Humanized Liver Mistrg Mice. Blood. 2019;134:338. 2. Ryan TM, Ciavatta DJ, Townes TM. Knockout-transgenic mouse model of sickle cell disease. Science. 1997;278(5339):873-876. 3. Blouin MJ, De Paepe ME, Trudel M. Altered hematopoiesis in murine sickle cell disease. Blood. 1999;94(4):1451-1459. 4. Manwani D, Bieker JJ. The erythroblastic island. Curr Top Dev Biol. 2008;82:23-53. Disclosures Xu: Seattle Genetics: Membership on an entity's Board of Directors or advisory committees. Flavell:Zai labs: Consultancy; GSK: Consultancy.

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