Pathology of sickle cell disease

Intravenous Hydration and Associated Outcomes in Patients With Sickle Cell Disease Admitted With Vaso-Occlusive Crises: A Systematic Review

Acute painful vaso-occlusive crisis (VOC) is the common presentation of sickle cell disease (SCD) leading to emergency room visits, admissions, morbidity, mortality, and negative impacts on quality of life. Among various treatment approaches commonly employed to manage the condition, intravenous (IV) hydration is also frequently used in emergency and inpatient settings. Although helpful to overcome dehydration, IV hydration often leads to adverse outcomes like fluid overload, pulmonary edema, increased length of stay, transfer to intensive care unit, new oxygen requirement, etc. Small-scale retrospective studies are conducted to study the outcomes of IV hydration but have failed to conclusively demonstrate its benefits as well as choice of IV fluids, rate of IV fluid replacement, etc. We conduct this review as an attempt to summarize the available evidence on the role and utility of IV hydration in sickle cell crises along with reported adverse outcomes.

Fatty acid nitroalkenes - Multi-target agents for the treatment of sickle cell disease

Sickle cell disease (SCD) is a hereditary hematological disease with high morbidity and mortality rates worldwide. Despite being monogenic, SCD patients display a plethora of disease-associated complications including anemia, oxidative stress, sterile inflammation, vaso-occlusive crisis-related pain, and vasculopathy, all of which contribute to multiorgan dysfunction and failure. Over the past decade, numerous small molecule drugs, biologics, and gene-based interventions have been evaluated; however, only four disease-modifying drug therapies are presently FDA approved. Barriers regarding effectiveness, accessibility, affordability, tolerance, and compliance of the current polypharmacy-based disease-management approaches are challenging. As such, there is an unmet pharmacological need for safer, more efficacious, and logistically accessible treatment options for SCD patients. Herein, we evaluate the potential of small molecule nitroalkenes such as nitro-fatty acid (NO2-FA) as a therapy for SCD. These agents are electrophilic and exert anti-inflammatory and tissue repair effects through an ability to transiently post-translationally bind to and modify transcription factors, pro-inflammatory enzymes and cell signaling mediators. Preclinical and clinical studies affirm safety of the drug class and a murine model of SCD reveals protection against inflammation, fibrosis, and vascular dysfunction. Despite protective cardiac, renal, pulmonary, and central nervous system effects of nitroalkenes, they have not previously been considered as therapy for SCD. We highlight the pathways targeted by this drug class, which can potentially prevent the end-organ damage associated with SCD and contrast their prospective therapeutic benefits for SCD as opposed to current polypharmacy approaches.

A Critical Review of Sickle Cell Disease Burden and Challenges in Sub-Saharan Africa

Sickle cell disease is caused by an abnormality of the β-globin gene and is characterised by sickling of the red blood cells. Globally, sub-Saharan African countries share the highest burden of the disease. This study aimed at critically reviewing studies focusing on challenges of sickle cell anaemia in sub-Saharan Africa. A literature search was carried out in five major databases. Articles that met the inclusion criteria were included in the bibliometric review and critical analysis. A majority of the studies were undertaken in the West African region (85.5%), followed by Central Africa (9.1%). Very few studies had been undertaken in East Africa (3.6%), whilst the Southern African region had the fewest studies (1.8%). Distribution in relation to country revealed that three quarters of the studies were carried out in Nigeria (74.5%), followed by the Democratic Republic of the Congo (9.1%). According to healthcare settings, a strong majority of the studies were undertaken in tertiary health care facilities (92.7%). Major themes that emerged from the review include interventions, cost of treatment, and knowledge about sickle cell disease. Public health awareness and promotion as well as improving the quality of sickle cell centers for prompt management of patients with sickle cell disorder was identified as a critical strategy towards reducing the burden of the disease in sub-Saharan Africa. To achieve this, governments in countries located in this region need to adopt a proactive strategy in addressing gaps that have been identified in this study, as well as instituting other relevant measures, such as continuous media engagement and public health interventions relating to genetic counselling. Reforms in other areas that can help reduce the disease burden, include training of practitioners and equipping sickle cell disease treatment centers according to World Health Organization specifications.

Acute chest syndrome in sickle cell disease/HBE patient, A case report

The presented case will shed some light on one of the rarest complications of HBSE disease, which is acute chest syndrome, and will highlight the management of that complication.

Distinct maternal and fetal pregnancy outcomes in women with sickle cell disease can be predicted using routine clinical and laboratory data

We aimed to identify risk factors for adverse outcomes in pregnancies of women with sickle cell disease (SCD) and develop risk prediction models. Models were derived from a retrospective cohort of pregnant women with SCD and constructed using generalised estimating equation logistic regression, with clustering by woman. Maternal event(s) consisted of acute anaemia; cardiac, pulmonary, hepatobiliary, musculoskeletal, skin, splenic, neurological or renal complications, multi‐organ failure, venous thromboembolism, admission‐requiring vaso‐occlusive events (VOE), red cell transfusion, mortality or hypertensive disorder of pregnancy. Fetal events included preterm birth, small‐for‐gestational‐age or perinatal mortality. Of 199 pregnancies, 71% and 45% resulted in adverse maternal and fetal outcomes respectively. Low first‐trimester haemoglobin, admission‐requiring VOE in the year before pregnancy, multiple transfusions before pregnancy, SCD genotype and previous cardiac complications predicted maternal risk. Younger age and SCD genotype allowed early prediction of fetal risk (model‐F1). Adding maternal event(s) and high lactate dehydrogenase enabled re‐assessment of fetal risk with advancing gestation (model‐F2). Models were well calibrated and moderately discriminative for maternal outcome (c‐statistic 0·81, cross‐validated value 0·79) and fetal outcome (model‐F1 c‐statistic 0·68, cross‐validated value 0·65; model‐F2 c‐statistic 0·72, cross‐validated value 0·68). The models will allow early identification of women with SCD at high risk of adverse events, permitting early targeted interventions and ongoing fetal risk re‐assessment enabling intensification of surveillance and optimisation of delivery timing.

Evidence for Prophylactic Transfusion during Pregnancy for Women with Sickle Cell Disease

The objective of this study was to examine prior studies on maternal and neonatal outcomes with prophylactic compared with emergent blood transfusion in pregnant women with sickle cell disease. A review of the literature was performed. Twenty-one articles were identified and included in the analysis. A generalized linear mixed-effects model was used to analyze the outcomes. Pregnancy outcomes assessed were preeclampsia, pneumonia, pyelonephritis, pain crises, intrauterine growth restriction, neonatal death, perinatal death, and maternal mortality. Women who underwent emergent transfusion were more likely than women who underwent prophylactic transfusion to have the following adverse perinatal outcomes: preterm delivery (adjusted odds ratio [aOR 2.04], 95% confidence interval [CI] 1.14-3.63), pneumonia (aOR 2.98, 95% CI 1.44-6.15), pain crises (aOR 1.67, 95% CI 1.18-2.38), and perinatal death (aOR 1.84, 95% CI 1.06-3.07). Prophylactic transfusion should be reexamined as a potentially beneficial approach to the management of sickle cell disease in pregnancy.

Combined liver-cytokine humanization comes to the rescue of circulating human red blood cells

In vivo models that recapitulate human erythropoiesis with persistence of circulating red blood cells (RBCs) have remained elusive. We report an immunodeficient murine model in which combined human liver and cytokine humanization confer enhanced human erythropoiesis and RBC survival in the circulation. We deleted the fumarylacetoacetate hydrolase (Fah) gene in MISTRG mice expressing several human cytokines in place of their murine counterparts. Liver humanization by intrasplenic injection of human hepatocytes (huHep) eliminated murine complement C3 and reduced murine Kupffer cell density. Engraftment of human sickle cell disease (SCD)-derived hematopoietic stem cells in huHepMISTRGFah ^-/- mice resulted in vaso-occlusion that replicated acute SCD pathology. Combined liver-cytokine-humanized mice will facilitate the study of diseases afflicting RBCs, including bone marrow failure, hemoglobinopathies, and malaria, and also preclinical testing of therapies.

Human genome diversity data reveal that L564P is the predominant TPC2 variant and a prerequisite for the blond hair associated M484L gain-of-function effect

The endo-lysosomal two-pore channel (TPC2) has been established as an intracellular cation channel of significant physiological and pathophysiological relevance in recent years. For example, TPC2-/- mice show defects in cholesterol degradation, leading to hypercholesterinemia; TPC2 absence also results in mature-onset obesity, and a role in glucagon secretion and diabetes has been proposed. Infections with bacterial toxins or viruses e.g., cholera toxin or Ebola virus result in reduced infectivity rates in the absence of TPC2 or after pharmacological blockage, and TPC2-/- cancer cells lose their ability to migrate and metastasize efficiently. Finally, melanin production is affected by changes in hTPC2 activity, resulting in pigmentation defects and hair color variation. Here, we analyzed several publicly available genome variation data sets and identified multiple variations in the TPC2 protein in distinct human populations. Surprisingly, one variation, L564P, was found to be the predominant TPC2 isoform on a global scale. By applying endo-lysosomal patch-clamp electrophysiology, we found that L564P is a prerequisite for the previously described M484L gain-of-function effect that is associated with blond hair. Additionally, other gain-of-function variants with distinct geographical and ethnic distribution were discovered and functionally characterized. A meta-analysis of genome-wide association studies was performed, finding the polymorphisms to be associated with both distinct and overlapping traits. In sum, we present the first systematic analysis of variations in TPC2. We functionally characterized the most common variations and assessed their association with various disease traits. With TPC2 emerging as a novel drug target for the treatment of various diseases, this study provides valuable insights into ethnic and geographical distribution of TPC2 polymorphisms and their effects on channel activity.

Prevalence of Sickle Cell Disease Among School-age Children in Chhattisgarh, India: Predictions, Implications and Interventions

Sickle cell disease (SCD) is a haemoglobin disorder prevalent in Sub-Saharan Africa, Middle East and India. SCD is a major cause of morbidity and low quality of life in Chhattisgarh and other central Indian states. Currently, there is no estimate available for the number of SCD patients and carriers in Chhattisgarh. The Government of Chhattisgarh conducted a screening project for measuring prevalence of SCD among school-age children in the state in October 2007–December 2017 in six districts of the state. Using these screening data, an estimate of prevalence of SCD was made for school-age children in different geographical regions and social categories in Chhattisgarh. The numbers of SCD patients and carriers among school-age children in Chhattisgarh were estimated as 27,101 and 714,483, respectively. Furthermore, 79.64 per cent patients among school-age children, that is, 21,583 patients were estimated to reside in rural areas. The estimates may be of use in designing policies and developing strategies with better coordination and outreach for care of SCD patients. It is call of the time to develop dedicated infrastructure having medical, training, counselling and research facilities in a hierarchical manner comprising dedicated tertiary to primary care facilities in remote rural areas.

Different morphological and gene expression profile in placentas of the same sickle cell anemia patient in pregnancies of opposite outcomes

IMPACT STATEMENT

Environmentally induced changes in placental morphological and molecular phenotypes may provide relevant insight towards pathophysiology of diseases. The rare opportunity to evaluate the same patient, with sickle cell anemia (SCA), in two different pregnancies, of opposite outcomes (one early onset severe preeclampsia (PE) and the other mostly non-complicated) can prove such concept. In addition, the comparison to other conditions of known placental and vascular/inflammatory involvement strengthens such findings. Our results suggest that the clinical association between SCA and PE can be supported by common pathophysiological mechanisms, but that pathways involving response to copper and triglyceride metabolism may be important drivers of the pathophysiology of PE. Future studies using in a larger number of samples should confirm these findings and explore pathways involved in the pathophysiology of PE and its relationship with SCA.

Application of induced pluripotent stem cell technology for the investigation of hematological disorders

Induced pluripotent stem cells (iPSCs) were first described over a decade ago and are currently used in various basic biology and clinical research fields. Recent advances in the field of human iPSCs have opened the way to a better understanding of the biology of human diseases. Disease-specific iPSCs provide an unparalleled opportunity to establish novel human cell-based disease models, with the potential to enhance our understanding of the molecular mechanisms underlying human malignancies, and to accelerate the identification of effective new drugs. When combined with genome editing technologies, iPSCs represent a new approach to study single or multiple disease-causing mutations and model specific diseases in vitro. In addition, genetically corrected patient-specific iPSCs could potentially be used for stem cell based therapy. Furthermore, the reprogrammed cells share patient-specific genetic background, offering a new platform to develop personalized therapy/medicine for patients. In this review we discuss the recent advances in iPSC research technology and their potential applications in hematological diseases. Somatic cell reprogramming has presented new routes for generating patient-derived iPSCs, which can be differentiated to hematopoietic stem cells and the various downstream hematopoietic lineages. iPSC technology shows promise in the modeling of both inherited and acquired hematological disorders. A direct reprogramming and differentiation strategy is able to recapitulate hematological disorder progression and capture the earliest molecular alterations that underlie the initiation of hematological malignancies.

Impaired Collateral Vessel Formation in Sickle Cell Disease

OBJECTIVE

The adaptive response to vascular injury is the formation of functional collateral vessels to maintain organ integrity. Many of the clinical complications associated with sickle cell disease can be attributed to repeated bouts of vascular insufficiency, yet the detailed mechanisms of collateral vessel formation after injury are largely unknown in sickle cell disease. Here, we characterize postischemic neovascularization in sickle cell disease and the role of neutrophils in the production of reactive oxygen species.

APPROACH AND RESULTS

We induced hindlimb ischemia by ligation of the femoral artery in Townes SS (sickle cell) mice compared with AA (wild type) mice. Perfusion recovery, ascertained using LASER (light amplification by stimulated emission of radiation) Doppler perfusion imaging, showed significant diminution in collateral vessel formation in SS mice after hindlimb ischemia (76±13% AA versus 34±10% in SS by day 28; P<0.001; n=10 per group). The incidence of amputation (25% versus 5%) and foot necrosis (80% versus 15%) after hindlimb ischemia was significantly increased in the SS mice. Motor function recovery evaluation by the running wheel assay was also impaired in SS mice (36% versus 97% at 28 days post-hindlimb ischemia; P<0.001). This phenotype was associated with persistent and excessive production of reactive oxygen species by neutrophils. Importantly, neutrophil depletion or treatment with the antioxidant N-acetylcysteine reduced oxidative stress and improved functional collateral formation in the SS mice.

CONCLUSIONS

Our data suggest dysfunctional collateral vessel formation in SS mice after vascular injury and provide a mechanistic basis for the multiple vascular complications of sickle cell disease.

Characterization and Antimicrobial Susceptibility Profile of Bacteraemia Causing Pathogens Isolated from Febrile Children with and without Sickle Cell Disease in Kano, Nigeria

Background and Objectives

Bacterial infection in sickle cell anaemic patients is a major cause of mortality and requires proper treatment with appropriate antibiotics. However, continue defiant of these infections causing pathogens to many antibiotics and inadequate screening methods in overburden health care facilities such as our in Kano, Nigeria necessitates the conduct of this study. A research was therefore conducted to isolate, characterize and test for antimicrobial susceptibility of bacteraemia-causing pathogens from febrile children with and without sickle cell disease in Kano, Nigeria.

Method

A total of 225 venous blood samples from suspected sickle cell anaemic children attending three selected hospitals within Kano metropolis were collected and screened for sickle cell disease, followed by blood culture using automated blood culture system. The bacteria isolated from confirmed febrile SCD and non-SCD children were characterized using microscopic, biochemical and serological techniques. Their susceptibility to commonly used antibiotics was tested using disc diffusion method.

Results

Of the 225 blood specimens screened, 68 (30.22%) were SCD positive, with the highest percentage (16%) among subjects within 1–2 years of age. A total of 11 genera of bacteria were isolated from both SCD and non SCD positive bloods, with Salmonella typhi having highest occurring rate in SCD positive children 27 (39.71%), followed by Streptococcus pneumoniae 10(14.71%), Salmonella Group B 9(13.24%), Staphylococcus aureus 4 (5.88%), and Escherichia coli 3 (4.41%). Majority of the isolates from SCD children 59 (86.76%) were highly susceptible to ciprofloxacin followed by cefuroxime 45 (66.18%), gentamicin 38 (55.88%), ceftriaxone 30 (44.12%), augmentin 39 (57.35%), ampicillin 25 (36.77%) and co-trimoxazole (22.06%).

Conclusion

Bacteraemia in SCD confirmed children in the three hospitals are caused by a combination of 11 genera of bacteria. The lesser rate of bacteraemia was found in non-SCD children. Resistance to commonly used antibiotics is on increase, but treatment with ciprofloxacin and some 3^rd generation cephalosporin are still promising.

Relative adrenal insufficiency in adults with sickle cell disease

Rheological modifications observed in sickle cell anemia are associated with ischemic complications that can cause target organ functional impairment. The objective was to investigate adrenal function of adult patients with sickle cell disease. In this cross-sectional study conducted in a tertiary referral hospital of the capital city of Cameroon, we enrolled ten crisis-free adult patients with sickle cell disease (SCD) and ten age- and sex-matched healthy individuals. We assessed adrenal function by testing basal cortisol levels and 60 min after tetracosactide (Synacthen^®) injection using immuno-chemiluminescence method. Post-stimulatory cortisol was defined as primary endpoint and secondary endpoints include basal cortisol levels, post-stimulatory cortisol increments and the fold increase of cortisol one hour after stimulation. Sickle cell patients had an impairment of adrenal function despite no significant difference between patients' and controls' for basal or post-stimulatory cortisol levels. In fact, one patient in two failed to achieve a two-fold increase in cortisol levels after stimulation (5/10) as opposed to 1 in 10 in the control population (1/10), P = 0.070. The percent increment of cortisol after stimulation was lower in patients versus controls (133 vs 207, P = 0.047). Relative adrenal insufficiency is frequent in sub-Saharan adult patients with sickle cell disease despite normal basal cortisol levels. Our results suggest that adrenal function require further investigation during SCD crises as these represent an important stress and may worsen the prognosis.

Prophylactic transfusion for pregnant women with sickle cell disease: a systematic review and meta-analysis

Prophylactic transfusion in pregnant women with SCD may reduce maternal mortality, vaso-occlusive pain events, and pulmonary complications. Prophylactic transfusion in pregnant women with SCD may similarly reduce perinatal mortality, neonatal death, and preterm birth.

Tumor necrosis factor-superfamily 15 gene expression in patients with sickle cell disease

Objective: The aim of this study was to investigate the relation between tumor necrosis factor-superfamily 15 (TNFSF15) gene expression and clinical findings in children with sickle cell disease (SCD).

Materials and Methods: Forty-nine patients with SCD and 38 healthy controls were included in this study. TNFSF15 gene expression and plasma levels were analyzed. TNFSF15 gene expression was compared in subgroups considering the frequency of painful crises and acute chest syndrome (ACS).

Results: It was found that TNFSF15 gene expression was significantly higher in patients with SCD than the controls (p=0.001), whereas there was no significant difference between the patients with SCD and the control groups considering plasma levels of TNFSF15. TNFSF15 gene expression was also significantly higher in SCD patients with ACS (p=0.008).

Conclusion: These findings suggest that TNFSF15 may have a role in the pathogenesis of SCD presenting with ACS. Further studies on larger groups are needed to determine the function of TNFSF15 in SCD patients with ACS and pulmonary hypertension. Analysis of TNFSF15 expression may also serve as a promising approach in ACS therapy.

The C5 convertase is not required for activation of the terminal complement pathway in murine experimental cerebral malaria

Cerebral malaria (CM) is the most severe manifestation of clinical malaria syndromes and has a high fatality rate especially in the developing world. Recent studies demonstrated that C5(-/-) mice are resistant to experimental CM (ECM) and that protection was due to the inability to form the membrane attack complex. Unexpectedly, we observed that C4(-/-) and factor B(-/-) mice were fully susceptible to disease, indicating that activation of the classical or alternative pathways is not required for ECM. C3(-/-) mice were also susceptible to ECM, indicating that the canonical C5 convertases are not required for ECM development and progression. Abrogation of ECM by treatment with anti-C9 antibody and detection of C5a in serum of C3(-/-) mice confirmed that C5 activation occurs in ECM independent of C5 convertases. Our data indicate that activation of C5 in ECM likely occurs via coagulation enzymes of the extrinsic protease pathway.

Hematopoietic stem cell function in a murine model of sickle cell disease

Previous studies have shown that the sickle environment is highly enriched for reactive oxygen species (ROS). We examined the oxidative effects of sickle cell disease on hematopoietic stem cell function in a sickle mouse model. In vitro colony-forming assays showed a significant decrease in progenitor colony formation derived from sickle compared to control bone marrow (BM). Sickle BM possessed a significant decrease in the KSL (c-kit⁺, Sca-¹⁺, Lineage⁻) progenitor population, and cell cycle analysis showed that there were fewer KSL cells in the G₀ phase of the cell cycle compared to controls. We found a significant increase in both lipid peroxidation and ROS in sickle-derived KSL cells. In vivo analysis demonstrated that normal bone marrow cells engraft with increased frequency into sickle mice compared to control mice. Hematopoietic progenitor cells derived from sickle mice, however, demonstrated significant impairment in engraftment potential. We observed partial restoration of engraftment by n-acetyl cysteine (NAC) treatment of KSL cells prior to transplantation. Increased intracellular ROS and lipid peroxidation combined with improvement in engraftment following NAC treatment suggests that an altered redox environment in sickle mice affects hematopoietic progenitor and stem cell function.