Kinetics of sickle cell biorheology and implications for painful vasoocclusive crisis

We developed a microfluidics-based model to quantify cell-level processes modulating the pathophysiology of sickle cell disease (SCD). This in vitro model enabled quantitative investigations of the kinetics of cell sickling, unsickling, and cell rheology. We created short-term and long-term hypoxic conditions to simulate normal and retarded transit scenarios in microvasculature. Using blood samples from 25 SCD patients with sickle hemoglobin (HbS) levels varying from 64 to 90.1%, we investigated how cell biophysical alterations during blood flow correlated with hematological parameters, HbS level, and hydroxyurea (HU) therapy. From these measurements, we identified two severe cases of SCD that were also independently validated as severe from a genotype-based disease severity classification. These results point to the potential of this method as a diagnostic indicator of disease severity. In addition, we investigated the role of cell density in the kinetics of cell sickling. We observed an effect of HU therapy mainly in relatively dense cell populations, and that the sickled fraction increased with cell density. These results lend support to the possibility that the microfluidic platform developed here offers a unique and quantitative approach to assess the kinetic, rheological, and hematological factors involved in vasoocclusive events associated with SCD and to develop alternative diagnostic tools for disease severity to supplement other methods. Such insights may also lead to a better understanding of the pathogenic basis and mechanism of drug response in SCD.National Institutes of Health (U.S.) (R01HL094270)National Institutes of Health (U.S.) (U01HL114476

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 218, April 1981

This bibliography lists 161 reports, articles, and other documents introduced into the NASA scientific and technical information system in March 1981

Catch Bonds in Sickle Cell Disease: Shear-Enhanced Adhesion of Red Blood Cells to Laminin

Could the phenomenon of catch bonding—force-strengthened cellular adhesion—play a role in sickle cell disease, where abnormal red blood cell (RBC) adhesion obstructs blood flow? Here we investigate the dynamics of sickle RBCs adhering to a surface functionalized with the protein laminin (a component of the extracellular matrix around blood vessels) under physiologically relevant micro-scale flow. First, using total internal reflectance microscopy we characterize the spatial fluctuations of the RBC membrane above the laminin surface before detachment. The complex dynamics we observe suggest the possibility of catch bonding, where the mean detachment time of the cell from the surface initially increases to a maximum and then decreases as a function of shear force. We next conduct a series of shear-induced detachment experiments on blood samples from 25 sickle cell disease patients, quantifying the number and duration of adhered cells under both sudden force jumps and linear force ramps. The experiments reveal that a subset of patients does indeed exhibit catch bonding. By fitting the data to a theoretical model of the bond dynamics, we can extract the mean bond lifetime versus force for each patient. The results show a striking heterogeneity among patients, both in terms of the qualitative behavior (whether or not there is catch bonding) and in the magnitudes of the lifetimes. Patients with large bond lifetimes at physiological forces are more likely to have certain adverse clinical features, like a diagnosis of pulmonary arterial hypertension and intracardiac shunts. By introducing an in vitro platform for fully characterizing RBC-laminin adhesion dynamics, our approach could contribute to the development of patient-specific anti-adhesive therapies for sickle cell disease. The experimental setup is also easily generalizable to studying adhesion dynamics in other cell types, for example leukocytes or cancer cells, and can incorporate disease-relevant environmental conditions like oxygen deprivation

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 192

This bibliography lists 247 reports, articles, and other documents introduced into the NASA scientific and technical information system in March 1979

Sickle Cell Disease Erythrocyte Stiffness and Cytoadhesion Investigated via Atomic Force Microscopy

The biomechanical properties of red blood cells (RBCs), including increased stiffness and abnormal cytoadherence, are integral components in the cascade of events resulting to vasoocclusive episodes (VOEs) in sickle cell disease (SCD). VOEs are the main cause of morbidity in SCD and sickle cell trait (SCT). Using experimental techniques based on atomic force microscopy (AFM), we studied the stiffness and adhesion of RBCs from SCD patients and from subjects with SCT. We found that SCD and SCT RBCs are three-fold stiffer than normal RBCs. Further, a ten-fold increase in the stiffness of sickled RBCs was measured upon deoxygenation. In an effort to rectify the increased stiffness of sickle RBCs, mice were fed a diet supplemented with docosahexanoic acid (DHA), an omega-3 fatty acid. A decrease in RBC stiffness was measured suggesting therapeutic benefits of DHA. Cytoadherence of RBCs to subendothelial laminin via the basal cell adhesion molecule/Lutheran (BCAM/Lu) is implicated in vasculopathy, a common condition in SCD patients. We established the in vitro technique of single-molecule force spectroscopy (SMFS) which enables detection of single BCAM/Lu proteins on the RBC surface via measurement of the unbinding force with laminin. It was shown that epinephrine, acting through the cyclic adenosine monophosphate (cAMP) signaling pathway, increases the population of active BCAM/Lu receptors on SCT RBCs, suggesting a role in exercise-induced VOEs. The sensitivity of the SMFS system was validated in a neuronal system to quantitatively map SK channels and then employed to investigate the effects of cAMP pathway targeting on BCAM/Lu receptor expression on normal and SCD RBCs. We illustrated that A-kinase anchoring proteins are crucial for BCAM/Lu receptor activation. To examine the relevance of results based on SMFS in the cytoadhesion of entire RBCs, single-cell force spectroscopy (SCFS) was established to measure the adhesion of whole cells with a functionalized substrate. We established a correspondence between the SMFS and SCFS results. Both techniques were able to detect significant changes in the adhesive response of RBCs to cAMP pathway modulation and variability was measured amongst human subjects, suggesting that RBCs maintain diverse intracellular levels of tonic protein kinase A

Flow of healthy and sickle red blood cells in microcirculatory conditions : clustering process and self-margination phenomenon

I experimentally characterized the clustering formation of healthy and sickle red blood cells (RBCs) flowing through straight micro-capillaries. The effect of aggregation was also investigated. I found that cluster formation under physiological conditions is most likely caused by a combination of hydrodynamic and macromolecule-induced interactions. Macromolecule-induced interactions are not fully overcome by shear stresses within the physiological range, and they contribute to cluster stability. Moreover, I found that a pronounced bimodal distribution of the cell-to-cell distances in the hydrodynamic clusters is produced. Additionally, I investigated experimentally the collective behavior of oxygenated sickle RBCs and their distribution along cylindrical micro-capillaries with diameters comparable to a human venule or arteriole. I have shown that there is a heterogeneous distribution of RBCs according to their density: low-density cells tend to stay closer to the center of the channel, while most dense cells (also more rigid) self-marginated under defined conditions. Aggregation seems to inhibit self-margination depending on the aggregative factor and patient: dextran allows self-margination in some patients and inhibits it in others. Plasma inhibits self-margination of cells in all cases, highlighting the importance of the plasma proteins and adhesive molecules in the aggregation phenomena.Ich habe experimentell das Aggregationsverhalten gesunder und sichelförmiger roter Blutzellen während des Flusses durch Mikrokapillaren charakterisiert. Der Aggrega- tionseffekt wurde ebenfalls untersucht. Ich habe festgestellt, dass die Aggregation unter physiologischen Bedingungen sehr wahrscheinlich durch eine Kombination aus hydrodynamischen und durch Makromoleküle induzierten Interactionen verursacht wird. Letztere werden in physiologischen Bereichen nicht vollständig durch Scherspannungen beeinflusst überwunden und tragen zur Stabilisierung von Aggregaten bei. Außerdem habe ich gezeigt, dass der Zell-Zell Abstand in hydrodynamischen Aggregaten ausgeprägt bimodal verteilt ist. Zusätzlich habe ich das kollektive Verhalten von sauerstoffreichen sichelförmigen roten Blutzellen und deren Verteilung in zylindrischen Mikrokapillaren mit Durchmessern, die denen von humanen Venulen oder Arteriolen entsprechen, experimentell untersucht. Ich habe gezeigt, dass rote Blutkörperchen abhängig von ihrer Dichte, heterogen verteilt sind: Zellen geringerer Dichte neigen dazu sich näher an der Mitte des Kanals zu befinden, während die meisten Zellen größerer Dichte (die auch höhere Steifigkeit haben) unter definierten Bedingungen zur Kanalwand migrieren. Aggregation scheint Selbst- Margination abhängig vom Aggregationsfaktor und Patienten zu hemmen: Dextran führt bei einigen Patienten zur Selbst-Margination, während es diese bei anderen hemmt. Plasma hemmt die Selbst-Margination in allen Experimenten, was die Bedeutung der Plasmaproteine und Plasmaklebemoleküle für Aggregationsphänomene verdeutlicht

Defining the Clinical Spectrum of Sickle Cell Disease in Tanzania: A Clinico-Epidemiological Study

Introduction: The burden of Sickle Cell Disease (SCD) in Africa is high; having over 75% of annual global births and mortality reaching 95% in childhood. Introduction of interventions, which could prevent 70% of deaths, have been limited because of lack of local evidence. This study described the clinical spectrum of SCD in Tanzania as the first step in providing evidence to guide targeted interventions. Methods: SCD patients attending Muhimbili Hospital in Dar-es-Salaam, Tanzania were recruited between 2004 and 2009. Prospective surveillance of clinical and laboratory information was done at outpatient clinic and during hospitalisation. Specific investigations included blood cultures on all hospitalised SCD patients, Transcranial Doppler (TCD) ultrasonography to measure cerebral blood flow velocity (CBFv) and HPLC to measure levels of foetal haemoglobin (HbF). The outcomes of interest were death, hospitalisation, malaria, bacteraemia and stroke. Results: 1,725 SCD patients [mean age 9.7 (SD 7.9) years; 10% below 2 years] were enrolled with information recorded from 14,000 visits during the study period. 12% of enrolled SCD patients were lost to follow up and 23% of 86 deaths occurred at the hospital. The mortality was 2 deaths/100 person years of observation (PYO); highest under 5 years and independently associated with low haemoglobin (Hazard ratio 0.7 95%CI 0.6-0.8; p0.01). 504 (29%) of the SCD cohort were hospitalised with pain, fever and anaemia as the commonest cause of hospitalisation. SCD patients had less malaria than non-SCD patients at clinic (OR, 0.46; 95% CI, 0.25-0.94; P = .01) and during hospitalisation (OR, 0.53; 95% CI, 0.32-0.86; P = .008). In SCD patients, prevalence of malaria was higher during hospitalisation and associated with severe anaemia and death. 43 out of 890 hospitalisations had bacteraemia (4.8%) with Staphylococcus aureus (28%), non-typhii Salmonella (21%) and Streptococcus pneumoniae (7%) as the most common organisms. The mean CBFv in 372 patients (2 - 16 years) was 132 cm/sec with CBFv > 200cm/sec occurring in 40 (10%) patients. The incidence of stroke was 0.3 per 100PYO; associated with sickle haemoglobin and reticulocyte count but not with CBFv. The mean HbF level in 1,669 SCD patients was 6.3 (SD 4.7) % with no association with mortality and hospitalisation. Conclusion: This study has highlighted the burden of disease to individuals and health system. The findings have important implications for policies to improve healthcare as well as identifying areas for further research

BOIS 412/812: Human Genetics—A Peer Review of Teaching Project Benchmark Portfolio

This portfolio focuses on Human Genetics, an upper-division course taken primarily by biology majors to fulfill elective credit in their degree. This course studies the genetic basis for human variation, with the goal of placing this variation in the context of human evolutionary history and the consequences of this variation for medical understanding and treatments. In Human Genetics, students complete an original synthetic research paper on a human genetic disorder. Through writing this paper, students are expected to learn how to navigate electronic databases and online resources on human genetic diseases, and to read and synthesize the primary scientific literature. This portfolio describes the teaching methods used to guide students through this process. The information and concepts to be taught in Human Genetics are expected to be useful for students going on to do research in a biological field, for those intending to pursue medical and health-related professions, and in general in producing informed and critical citizens who are empowered to make scientifically sound decisions

BOIS 412/812: Human Genetics—A Peer Review of Teaching Project Benchmark Portfolio

This portfolio focuses on Human Genetics, an upper-division course taken primarily by biology majors to fulfill elective credit in their degree. This course studies the genetic basis for human variation, with the goal of placing this variation in the context of human evolutionary history and the consequences of this variation for medical understanding and treatments. In Human Genetics, students complete an original synthetic research paper on a human genetic disorder. Through writing this paper, students are expected to learn how to navigate electronic databases and online resources on human genetic diseases, and to read and synthesize the primary scientific literature. This portfolio describes the teaching methods used to guide students through this process. The information and concepts to be taught in Human Genetics are expected to be useful for students going on to do research in a biological field, for those intending to pursue medical and health-related professions, and in general in producing informed and critical citizens who are empowered to make scientifically sound decisions

NIH Workshop 2018: Towards Minimally Invasive or Noninvasive Approaches to Assess Tissue Oxygenation Pre- and Post-transfusion

Because blood transfusion is one of the most common therapeutic interventions in hospitalized patients, much recent research has focused on improving the storage quality in vitro of donor red blood cells (RBCs) that are then used for transfusion. However, there is a significant need for enhancing our understanding of the efficacy of the transfused RBCs in vivo. To this end, the NIH sponsored a one-and-a-half-day workshop that brought together experts in multiple disciplines relevant to tissue oxygenation (eg, transfusion medicine, critical care medicine, cardiology, neurology, neonatology and pediatrics, bioengineering, biochemistry, and imaging). These individuals presented their latest findings, discussed key challenges, and aimed to identify opportunities for facilitating development of new technologies and/or biomarker panels to assess tissue oxygenation in a minimally-invasive to non-invasive fashion, before and after RBC transfusion