Severe Sickle Cell Disease Research Articles

Cerebral hemodynamics and oxygen metabolism in patients with milder and severe forms of sickle cell disease and thalassemia.

Silent cerebral infarcts (SCIs) are present in patients with sickle cell disease (SCD) and thalassemia, but the pathophysiology of SCIs is not fully understood. Previous studies mainly focused on cerebral hemodynamics and oxygen metabolism in patients with severe SCD (HbSS/HbSβ°) but not in milder forms of SCD (HbSC/HbSβ+) and thalassemia despite the high prevalence of SCIs in these patients. In this work, we studied the cerebral hemodynamics and oxygen metabolism, and SCI lesion load in 75 severe and 26 mild adult SCD patients, 18 thalassemia patients (as anemic comparison group), and 30 healthy controls before and after a vasodilatory challenge with acetazolamide. Cerebral blood flow was significantly higher in patients with severe SCD and thalassemia compared to patients with mild SCD and controls (p < 0.05). Conversely, oxygen extraction fraction and cerebral metabolic rate of oxygen (CMRO2) were significantly lower in patients with severe SCD and thalassemia compared to other groups (p < 0.01). In contrast, no difference in SCI volumes was found between mild and severe SCD and thalassemia patients. After acetazolamide administration, oxygen delivery increased less in severe SCD and thalassemia patients compared to other groups (p < 0.01) and CMRO2 decreased only in severe SCD patients (p < 0.01). Given the reduced CMRO2 values in severe SCD and thalassemia patients, we conclude that reduced cerebral oxygen consumption in these patient groups is mostly related to anemia. Our data suggest that the pathophysiology of SCIs in patients with milder forms of SCD might be more related to prior episodes of anemia or other sickle cell-related factors.

Sickle cell disease in India: the journey and hope for the future.

India, the most populous nation in the world, also has a high frequency of the sickle hemoglobin (HbS) allele globally. The Arab Indian HbS haplotype in India is characterized by a relatively high percentage of fetal Hb, with widely varying frequencies of α-thalassemia. Hence, sickle cell disease (SCD) in India was perceived to be mild. Advances in the past decade in screening and SCD management have revealed that the severity of SCD in India is comparable to many other parts of the world. Clinical features in India include vaso-occlusive crisis, acute chest syndrome, avascular necrosis, renal involvement, stroke, etc, at a relatively young age. Once a fatal disease of childhood, the majority of patients born with SCD are expected to survive into adulthood, largely because of improvements in comprehensive care programs including newborn screening, penicillin prophylaxis, transcranial Doppler, and hydroxyurea therapy. Several centers are performing hematopoietic stem cell transplants successfully for SCD. To address the urgent need to control and manage SCD in India's population, the Government of India launched the National Sickle Cell Anaemia Elimination Mission, with significant funding for large-scale measures to screen, treat, counsel, educate, and develop technologies and novel therapies and gene therapies.

Effect of voxelotor on cerebral perfusion and cerebral oxygen metabolism and cardiac stress in adult patients with sickle cell disease.

Sickle cell disease (SCD) is complicated by silent cerebral infarcts (SCIs), for which anemia is an important risk factor. Despite normal oxygen delivery (OD), cerebral vascular reserve (CVR), and cerebral metabolic rate of oxygen (CMRO2) are diminished in SCD, possibly causing the formation of SCIs. Voxelotor inhibits polymerization by increasing the hemoglobin oxygen binding, ameliorating hemolytic anemia. Furthermore, anemia is related to cardiac complications. Our aims were to assess the effect of voxelotor on markers of cerebral perfusion, cerebral oxygen metabolism, and markers of cardiac stress in SCD patients. Cerebral hemodynamics and oxygen metabolism were measured with MRI before and after 3 months of voxelotor treatment (1500 mg/day) in 18 adults with SCD (HbSS/HbSβ0-thalassemia). Hemoglobin levels significantly increased (p = .001) and markers of hemolysis decreased (p < .05). OD increased from 6.5 (IQR, 6.0-7.1) mL O2/100 g/min to 8.1 (IQR, 7.2-8.7) mL O2/100 g/min (p = .001). CBF and CVR did not change. CMRO2 decreased from 2.0 (IQR, 1.9-2.1) mL O2/100 g/min to 1.9 (IQR, 1.6-2.1) mL O2/100 g/min (p = .03). N-terminal pro-B type natriuretic peptide (NT-proBNP) levels decreased (p = .048) and maximum tricuspid regurgitation flow velocity (TRVmax) normalized in all but one patient with increased TRVmax. Voxelotor treatment in patients with severe SCD did not decrease CBF despite increased Hb levels. Cerebral oxygen metabolism slightly decreased, despite raised OD, most likely due to drug-induced increase in oxygen binding. Nonetheless, voxelotor improved clinically validated markers of cardiac stress.

Successful Allogeneic Alternative Donor Hematopoietic Stem Cell Transplantation in High-Risk Patients with Severe Sickle Cell Disease

Successful Allogeneic Alternative Donor Hematopoietic Stem Cell Transplantation in High-Risk Patients with Severe Sickle Cell Disease

Health-Related Quality-of-Life Improvements after Exagamglogene Autotemcel in Patients with Severe Sickle Cell Disease

Health-Related Quality-of-Life Improvements after Exagamglogene Autotemcel in Patients with Severe Sickle Cell Disease

Epidemiological profile of severe malaria and sickle cell disease in children at the mother and child university hospital center Jeanne Ebori foundation of libreville from 2020 to 2021

Background: Hemoglobinopathies represent the most common genetic diseases worldwide. In Gabon, the clinico-biological profile of patients with homozygous hemoglobin S or those with AS sickle cell traits, faced with this prevalence of serious malaria, remains unknown today. The objective was to evaluate the complications of severe malaria in SS homozygous sickle cell patients and those carrying AS sickle cell traits. Methods: This is an observational, retrospective study, with descriptive and analytical aims which took place from January 2020 to October 2021. The parameters studied were socio-demographic, clinical and paraclinical data, the diagnosis chosen, therapeutic data and evolution. Results: severe neurological form of malaria was the most common criterion with a frequency of 41.7%, followed by parasitic forms 35.8% and anemic forms 21.8%. Among AS heterozygotes, the most widespread severe form was the neurological form with a frequency of 63.2%, the anemic form 26.3% and parasitic at 10.5%. In homozygous SS subjects, the most widespread severe form was the anemic form with a frequency of 68.1% followed by neurological forms 27.7% and parasitic forms 4.2%. Abdominal pain, prostration, respiratory distress were the main signs in SS homozygotes. In heterozygotes, prostration, convulsion and clinical jaundice were the main signs. A total of 99.8% of our patients were cured. Conclusions: All the electrophoretic profiles identified were subject to this infection which mainly affects heterozygous AS subjects and subjects with the AA electrophoretic profile in its severe neurological form and homozygous SS subjects in its anemic form.

Infrequent Resolution of Vaso-Occlusive Crises in Routine Clinical Care Among Patients Mimicking the Exa-Cel Trial Population: A Cohort Study of Medicaid Enrollees.

The CRISPR-based gene editing therapy exagamglogene autotemcel (exa-cel) recently received FDA approval for patients with severe sickle cell disease (SCD). The approval was based on a phase III trial (CLIMB SCD 121), which showed 97% efficacy of this treatment in eliminating vaso occlusive crises (VOCs) for 12 consecutive months. To help contextualize results from this trial, we aimed to investigate the proportion of patients with severe SCD who remain VOC-free for a 1-year period in routine clinical care. Using Medicaid claims data (2000-2018), we identified a cohort of patients, 12-35 years old with severe SCD, defined by ≥ 2 VOCs per year for 2 consecutive years, who met other exa-cel trial inclusion criteria to mimic a trial-like population. A VOC was identified using ICD diagnosis codes during hospitalization and ER visits. The primary outcome was the proportion of patients with no VOCs during a 1-year follow-up. A total of 7,425 patients with severe SCD [mean (SD) age: 20.5 (6.0) years, 54.6% females, 84% African Americans], had a mean of 5.2 VOCs, 5.1 ER visits and 3.5 hospitalizations per year during the baseline period. The proportion of patients with no VOCs during the 1-year follow-up was 7.7% (95% confidence interval: 7.1%-8.3%). In conclusion, less than one in 12 patients with severe SCD achieved VOC-free status within 1 year in routine clinical care. These findings suggest that the high efficacy observed for exa-cel in the trial, if replicated in routine clinical care, could translate into a significant public health impact.

Genetic variants associated with white blood cell count amongst individuals with sickle cell disease.

Sickle cell disease (SCD) is a Mendelian disorder characterized by a point mutation in the β-globin gene that leads to sickling of erythrocytes. Several studies have shown that absolute neutrophil count is strongly associated with clinical severity of SCD, suggesting an apparent role of white blood cells (WBC) in SCD pathology. However, the mechanism by which genetic variants lead to WBC count differences in SCD patients remains unclear. Genome-wide association (GWA) analyses were carried out amongst a cohort of 2409 Brazil SCD participants. Association of WBC count and genetic markers were investigated in homozygous sickle cell anaemia participants and compound heterozygous sickle cell haemoglobin C participants. GWA analysis showed that variants in genes TERT, ACKR1, and FAM3C are associated with WBC count variation. The well-studied association between WBC count and Duffy null phenotype (variant in ACKR1) in healthy populations was replicated, reinforcing the influence of the SNP rs2814778 (T>C) in WBC count. Genetics plays an important role in regulating WBC count in patients with SCD. Our results point to possible mechanisms involved in WBC count variation and as increased WBC count is associated with more severe SCD, these results could suggest potential therapeutic targets for individuals with SCD.

Knowledge and Experience of In-Home Virtual Reality for Chronic Pain in Sickle Cell Disease

Many adults with sickle cell disease experience chronic, nonvaso-occlusive pain that can benefit from nonpharmacological interventions available for use in the home setting. Virtual reality (VR) has been shown to be effective in decreasing pain in chronic pain conditions and may be useful for home-based self-management of chronic pain in sickle cell. However, the literature lacks studies examining this potential. Additionally, the knowledge and experiences of adults with sickle cell who have tried VR for home-based chronic pain management have not yet been reported. This qualitative, descriptive pilot study explored the knowledge and perceptions of VR among adults with sickle cell and their experience with using in-home VR for chronic pain. Nine participants completed demographic questionnaires and an individual interview that was recorded, transcribed verbatim, and analyzed using thematic analysis. Participants were 21 to 38 years of age, and most were female (88.9%) with a medium or high sickle cell disease severity (88.9%) and a chronic pain-grade classification of grade III (high disability-moderately limiting) or grade IV (high disability-severely limiting) (55.5%). Interview themes, which aligned with the technology acceptance model, were 1) pain beliefs and self-management, 2) VR as another world, and 3) experience of using in-home VR. Based on preliminary data, VR shows promise as a strategy for nonpharmacological management of chronic pain in adults with sickle cell. However, further investigations are warranted to mitigate the challenges and limitations associated with using VR in this capacity. PerspectiveFew evidence-based, nonpharmacological interventions exist for chronic pain in adults with sickle cell disease. This first qualitative, pilot study of in-home VR for chronic pain in adults with sickle cell disease suggests that VR interventions need further exploration as a nonpharmacological strategy for mitigating their pain in the home setting.

PGC-1α agonism induces fetal hemoglobin and exerts antisickling effects in sickle cell disease.

Sickle cell disease is a growing health burden afflicting millions around the world. Clinical observation and laboratory studies have shown that the severity of sickle cell disease is ameliorated in individuals who have elevated levels of fetal hemoglobin. Additional pharmacologic agents to induce sufficient fetal hemoglobin to diminish clinical severity is an unmet medical need. We recently found that up-regulation of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) can induce fetal hemoglobin synthesis in human primary erythroblasts. Here, we report that a small molecule, SR-18292, increases PGC-1α leading to enhanced fetal hemoglobin expression in human erythroid cells, β-globin yeast artificial chromosome mice, and sickle cell disease mice. In SR-18292-treated sickle mice, sickled red blood cells are significantly reduced, and disease complications are alleviated. SR-18292, or agents in its class, could be a promising additional therapeutic for sickle cell disease.

Assessing and Evaluating HbS Concentration in Asymptomatic Sickle Cell Patients and Patients With Sickle Cell Crisis Through High-Performance Liquid Chromatography (HPLC) in a Tertiary Hospital in Central India.

Background Sickle cell disease (SCD) is a significant health concern, particularly due to the variability in disease severity and frequency of crisis episodes among patients. Accurate assessment of HbS concentrations is crucial for understanding the disease's progression and severity. This study aimed to assess and evaluate HbS concentrations in sickle cell patients and those experiencing sickle cell crisis using high-performance liquid chromatography (HPLC). The objectives included screening individuals for SCD, diagnosing the disease using Hb electrophoresis, estimating HbS concentration via HPLC, and comparing HbS concentration values between sickle cell patients and those in crisis. Methods An analytical study design was employed at Jawaharlal Nehru Medical College, Sawangi, Wardha, Maharashtra, involving 80 participants diagnosed with SCD. Data collection included clinical assessments, routine sickling tests, Hb electrophoresis, and HPLC for HbS concentration measurement. Descriptive and inferential statistics were utilized for data analysis, including chi-square tests, Mann-Whitney U tests, and regression analyses. Results Significant differences in HbS concentrations were observed between different patient groups. Individuals with the SS pattern exhibited higher HbS levels than those with the AS pattern (p = 0.001). Non-crisis patients had significantly higher mean HbS concentrations than crisis patients (p = 0.001). A moderate positive correlation (0.476, p = 0.001) was found between HbS concentrations and clinical outcomes. No significant differences in HbS concentrations were noted based on sex or age group. Longitudinal analysis revealed a significant increase in HbS levels over time (p = 0.001). Conclusion The study underscores the importance of HbS concentration measurement in understanding the severity and progression of SCD. HPLC proves to be a valuable tool in accurately estimating HbS levels, aiding in better clinical management of the disease.

Pain sensitisation in patients with sickle cell disease: A preliminary study.

Responses to experimental pain have suggested central and peripheral sensitisation in adult patients with sickle cell disease (SCD). Recent studies have proposed an algometry-derived dynamic measure of pain sensitisation, slowly repeated evoked pain (SREP), which is useful in the discrimination of painful conditions related to central sensitisation. Pain and fatigue are two symptoms that affect the general functioning of patients with SCD most significantly, however, research about experimental dynamic pain measures and their relation to the main symptoms of SCD (pain and fatigue) is still scarce. This preliminary study aimed to test the utility of the SREP protocol for detecting pain sensitisation in patients with SCD, and to evaluate the associations of pain sensitisation, pain threshold, and pain tolerance with the main clinical symptoms of SCD, pain and fatigue. Twenty-two female outpatients with SCD and 20 healthy women participated. Pain threshold, pain tolerance, and pain sensitisation were assessed by algometry in the fingernail. Clinical pain, fatigue, anxiety, depression and pain catastrophizing were evaluated. No group differences were found in pain threshold and tolerance. However, using the SREP protocol, pain sensitisation was greater in patients than in healthy participants, even after controlling for psychological variables and body mass index. Pain threshold and tolerance were inversely associated with fatigue levels in the SCD group, with pain tolerance being the main predictor. Pain threshold and tolerance did not discriminate between patients and healthy individuals, but were useful for predicting fatigue severity in SCD. The SREP protocol provides a useful dynamic measure of pain for the discrimination and detection of enhanced pain sensitisation in patients with SCD, which could contribute to more personalised pain evaluations and treatment for these patients.

Association between fetal hemoglobin, lactate dehydrogenase, and disease severity in patients with sickle cell disease at Bugando Medical Centre, Mwanza, Tanzania.

There is a wide range of clinical manifestations in sickle cell disease (SCD). Despite having the same condition, each person's response to disease complications differs greatly. Individuals can be categorized according to the severity of their diseases to determine which group they fall into and receive the appropriate care based on their needs. The relationship between fetal hemoglobin (HbF), lactate dehydrogenase (LDH), and disease severity in Tanzania is little understood. This investigation sought to ascertain the relationship between HbF, LDH, and disease severity in SCD patients at the Bugando Medical Center. This cross-sectional study was carried out on SCD patients aged 6 months and older at the Bugando Medical Center in Mwanza, Tanzania. A total of 130 SCD patients were enrolled. The clinical history and laboratory test results for SCD patients were recorded on a specially constructed patient report form. The majority of participants (56.9%) were men. For the population under study, more than half (60.8%) of participants had a moderate clinical phenotype (MCP), followed by 31.5% of asymptomatic participants and 7.7% of people with severe clinical phenotypes (SCP). Participants with SCP had substantially higher levels of LDH, with a mean level of 810.97IU/L (95% CI: 559.31-1062.64) and a p-value of 0.005. The severe clinical phenotype exhibited a significantly higher mean HbF score value of 10.09% (95% CI: 7.44-13.74%) with a p-value of 0.024 when compared to the asymptomatic and moderate clinical phenotypes. In SCD patients with SCP compared to ACP and MCP, the HbF levels were higher, but did not show a protective effects, and LDH can be used to predict the severity of SCD.

The CRISPR-Cas System and Clinical Applications of CRISPR-Based Gene Editing in Hematology with a Focus on Inherited Germline Predisposition to Hematologic Malignancies.

Clustered regularly interspaced short palindromic repeats (CRISPR)-based gene editing has begun to transform the treatment landscape of genetic diseases. The history of the discovery of CRISPR/CRISPR-associated (Cas) proteins/single-guide RNA (sgRNA)-based gene editing since the first report of repetitive sequences of unknown significance in 1987 is fascinating, highly instructive, and inspiring for future advances in medicine. The recent approval of CRISPR-Cas9-based gene therapy to treat patients with severe sickle cell anemia and transfusion-dependent β-thalassemia has renewed hope for treating other hematologic diseases, including patients with a germline predisposition to hematologic malignancies, who would benefit greatly from the development of CRISPR-inspired gene therapies. The purpose of this paper is three-fold: first, a chronological description of the history of CRISPR-Cas9-sgRNA-based gene editing; second, a brief description of the current state of clinical research in hematologic diseases, including selected applications in treating hematologic diseases with CRISPR-based gene therapy, preceded by a brief description of the current tools being used in clinical genome editing; and third, a presentation of the current progress in gene therapies in inherited hematologic diseases and bone marrow failure syndromes, to hopefully stimulate efforts towards developing these therapies for patients with inherited bone marrow failure syndromes and other inherited conditions with a germline predisposition to hematologic malignancies.

Exagamglogene autotemcel: a beacon of hope for severe sickle cell disease and thalassemia management

Exagamglogene autotemcel: a beacon of hope for severe sickle cell disease and thalassemia management

Factors Associated with Sickle Cell Crisis Among Sickle Cell Disease Patients Aged ≤15 Years in Three Kenyan Health Facilities

In view of the dearth of definitive therapeutic measures for sickle cell disease (SCD) and its associated crises, the resulting financial burden on parents and caregivers, coupled with psychological distress, social stigma, and other far-reaching consequences, remains incalculable. This research assessed the determinants of sickle cell crises among individuals with SCD aged 15 years and below, focusing on three healthcare facilities in Nairobi County. Using a descriptive cross-sectional design, the study aimed to establish the correlation between SCD crises and various variables in this specific age group within the selected health facilities. Structured interviewer-administered questionnaires, featuring both open-ended and dichotomous questions, were meticulously validated, optimized, and employed to gather pertinent data from the participants. The findings revealed that a majority of SCD patients below 15 years in sampled hospitals were female (52.85%), and the highest incidence of SCD occurred in the age range of 0-5 years (46.63%). Educational attainment among patients predominantly peaked at the primary school level (65.80%), with a minimal 7.77% reaching a secondary school level. Moreover, female caregivers (92.23%) were prevalent among those responsible for SCD patients aged 15 years and below. Primary caregivers, aged between 26- 30 years (37.82%) and 31-35 years (26.42%) were predominately married (75.13%) and engaged in agricultural activities (63.73%). This study revealed that out of the sampled SCD patients under 15 years old, a staggering 83.94% experienced crises related to their sickle cell disease, manifesting as abdominal pains for nearly 70 %, joint discomfort for over 72.22%, acute chest pain occurring approximately 25 %, with bone ache accounting about 32 %. Multiple logistic regression analysis demonstrated that female gender, the age group of 6-10 years, and frequent hospital visits (more than twice a month) significantly increased the log odds for severe SCD crises. Therefore, this study underscores the impact of patient and caregiver factors on the severity of SCD and its crises. Modifying these factors appropriately holds the potential to enhance the prognosis and wellbeing of both patients and caregivers, and strategic interventions must be devised to improve adherence to treatment protocols for SCD patients aged 15 years and below, thereby enhancing prognosis and overall quality of life.

Eosinophilic dialogues: a molecular exploration of sickle cell anemia severity.

Sickle cell anemia (SCA) is a genetically inherited hemoglobinopathy characterized by the abnormal morphology of red blood cells, resulting in vaso-occlusive events and diverse clinical complications. Recent investigations have unveiled a novel dimension in understanding SCA severity through the lens of eosinophilic dialogues. This review article synthesizes current knowledge on the molecular intricacies of eosinophils in the context of SCA, exploring their biology, molecular markers, and interactions with other cellular components. Eosinophil-mediated inflammation and oxidative stress are dissected to elucidate their impact on the disease course. Furthermore, the review evaluates potential therapeutic interventions and outlines future directions in this burgeoning field. The term "Eosinophilic Dialogues" encapsulates the multifaceted molecular exchanges that influence SCA severity, presenting a promising avenue for targeted interventions and improved clinical outcomes. This review serves as a comprehensive resource for researchers, clinicians, and healthcare practitioners engaged in unraveling the complex pathophysiology of SCA and exploring novel therapeutic avenues.

CRISPR-Based Gene Therapies: From Preclinical to Clinical Treatments.

In recent years, clustered regularly interspaced short palindromic repeats (CRISPRs) and CRISPR-associated (Cas) protein have emerged as a revolutionary gene editing tool to treat inherited disorders affecting different organ systems, such as blood and muscles. Both hematological and neuromuscular genetic disorders benefit from genome editing approaches but face different challenges in their clinical translation. The ability of CRISPR/Cas9 technologies to modify hematopoietic stem cells ex vivo has greatly accelerated the development of genetic therapies for blood disorders. In the last decade, many clinical trials were initiated and are now delivering encouraging results. The recent FDA approval of Casgevy, the first CRISPR/Cas9-based drug for severe sickle cell disease and transfusion-dependent β-thalassemia, represents a significant milestone in the field and highlights the great potential of this technology. Similar preclinical efforts are currently expanding CRISPR therapies to other hematologic disorders such as primary immunodeficiencies. In the neuromuscular field, the versatility of CRISPR/Cas9 has been instrumental for the generation of new cellular and animal models of Duchenne muscular dystrophy (DMD), offering innovative platforms to speed up preclinical development of therapeutic solutions. Several corrective interventions have been proposed to genetically restore dystrophin production using the CRISPR toolbox and have demonstrated promising results in different DMD animal models. Although these advances represent a significant step forward to the clinical translation of CRISPR/Cas9 therapies to DMD, there are still many hurdles to overcome, such as in vivo delivery methods associated with high viral vector doses, together with safety and immunological concerns. Collectively, the results obtained in the hematological and neuromuscular fields emphasize the transformative impact of CRISPR/Cas9 for patients affected by these debilitating conditions. As each field suffers from different and specific challenges, the clinical translation of CRISPR therapies may progress differentially depending on the genetic disorder. Ongoing investigations and clinical trials will address risks and limitations of these therapies, including long-term efficacy, potential genotoxicity, and adverse immune reactions. This review provides insights into the diverse applications of CRISPR-based technologies in both preclinical and clinical settings for monogenic blood disorders and muscular dystrophy and compare advances in both fields while highlighting current trends, difficulties, and challenges to overcome.

Mechanisms of Iron-Mediated Renal Injury in a Mouse Model of Sickle Cell Disease

Background: Sickle cell disease (SCD) is a hematologic disorder characterized by polymerization of the mutated hemoglobin S and sickling of red blood cells, leading to hemolysis, release of free heme/iron, and subsequent tissue iron accumulation. The kidney is one of the most frequently affected organs by iron overload, and chronic hemolysis is associated with chronic kidney disease severity in SCD. The potential role of iron overload in causing the observed renal injury in SCD has never been established. The goal of our study is to identify the impact of iron accumulation on the renal phenotype in SCD. We hypothesized that renal iron accumulation causes injury by oxidative stress dependent ferroptosis and/or mitochondrial dysfunction and subsequent kidney damage, that is worse in males than in females. Methods: We used 20-week-old male and female humanized SCD mice (HbSS) and age-matched genetic controls (HbAA). Mice were treated with either vehicle or the iron chelator Deferiprone (DFP, 100 mg/kg/day) for 8 weeks. Urinary excretion of protein and albumin as markers of renal injury were measured. Glomerular filtration rate (GFR) was measured transdermally after injection of FITC-sinistrin. Thiobarbituric acid reactive substance (TBARS) assay was performed for assessment of lipid peroxidation. Mitochondrial bioenergetics was assessed by Oroboros O2k Fluorometer of permeabilized renal cortices. Results: We previously demonstrated comparable iron accumulation in the kidney of male and female mice. However, HbSS males developed a more severe renal injury than females at 20 weeks of age, evidenced by proteinuria (2.52 ± 0.16 vs. 0.55 ± 0.16 mg/24hrs, p=0.0008) and albuminuria (76.44 ± 6.85 vs. 33.9 ± 8.81 μg/24hrs, p=0.0005). There was higher lipid peroxidation, a hallmark of ferroptosis, in the renal cortex of female HbSS than HbAA mice (1.31 ± 0.07 vs. 1.07 ± μM/mg, p=0.04). Bioenergetics studies revealed significantly lower state 3 oxygen consumption rate (108.2 ± 18.1 vs 164.8 ± 9.3 pmol/(s*mg), p=0.05), signifying lower oxidative phosphorylation capacity in HbSS males. In addition, there was significant reduction in state 4◦ respiration (36.4 ± 3.4 vs. 52.8 ± 3.4 pmol/(s*mg), p=0.03) in male HbSS mice. I also detected a decrease in maximum complex IV activity in male HbSS mice (325.5 ± 63.8 vs. 639.5 ± 51.3 pmol/(s*mg), p=0.02). Treatment with DFP improved proteinuria (2.66 ± 0.09 vs. 1.3 ± 0.14 mg/24hrs, p=0.0011) and GFR (165.3 ± 9.4 vs. 236.6 ± 12.6 μl/min, p=0.0058) in male HbSS mice. Conclusion: Iron accumulation causes renal injury which may be attributed to ferroptosis and mitochondrial dysfunction in SCD mice. Funding: NHLBI—R00HL144817 and ASN Norman Siegel Research Grant to MK. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A miniaturized wash-free microfluidic assay for electrical impedance-based assessment of red blood cell-mediated microvascular occlusion

The production of HbS — an abnormal hemoglobin (Hb) — in sickle cell disease (SCD) results in poorly deformable red blood cells (RBCs) that are prone to microcapillary occlusion, causing tissue ischemia and organ damage. Novel treatments, including gene therapy, may reduce SCD morbidity, but methods to functionally evaluate RBCs remain limited. Previously, we presented the microfluidic impedance red cell assay (MIRCA) for rapid assessment of RBC deformability, employing electrical impedance-based readout to measure RBC occlusion of progressively narrowing micropillar openings. We describe herein the design, development, validation, and clinical utility of the next-generation MIRCA assay, featuring enhanced portability, rapidity, and usability. It incorporates a miniaturized impedance analyzer and features a simplified wash-free operation that yields an occlusion index (OI) within 15 min as a new metric for RBC occlusion. We show a correlation between OI and percent fetal hemoglobin (%HbF), other laboratory biomarkers of RBC hemolysis, and SCD severity. To demonstrate the assay’s versatility, we tested RBC samples from treatment-naïve SCD patients in Uganda that yielded OI levels similar to those from hydroxyurea (HU)-treated patients in the U.S., highlighting the role of %HbF in protecting against microcapillary occlusion independent of other pharmacological effects. The MIRCA assay could also identify a subset of HU-treated patients with high occlusion risks, suggesting that they may require treatment adjustments including a second-line therapy to improve their outcomes. This work demonstrates the potential of the MIRCA assay for accelerated evaluation of RBC health, function, and therapeutic effect in an ex vivo model of the microcapillary networks.