-
[show abstract]
[hide abstract]
ABSTRACT: Sickle cell disease (SCD) is characterized by the abnormal deformation of red blood cells (RBCs) in the deoxygenated condition, as their elongated shape leads to compromised circulation. The pathophysiology of SCD is influenced by both the biomechanical properties of RBCs and their hemodynamic properties in the microvasculature. A major challenge in the study of SCD involves accurate characterization of the biomechanical properties of individual RBCs with minimum sample perturbation. Here we report the biomechanical properties of individual RBCs from a SCD patient using a non-invasive laser interferometric technique. We optically measure the dynamic membrane fluctuations of RBCs. The measurements are analyzed with a previously validated membrane model to retrieve key mechanical properties of the cells: bending modulus; shear modulus; area expansion modulus; and cytoplasmic viscosity. We find that high cytoplasmic viscosity at ambient oxygen concentration is principally responsible for the significantly decreased dynamic membrane fluctuations in RBCs with SCD, and that the mechanical properties of the membrane cortex of irreversibly sickled cells (ISCs) are different from those of the other types of RBCs in SCD.
Acta biomaterialia 07/2012; 8(11):4130-8. · 3.98 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present the anisotropic light scattering of individual red blood cells (RBCs) from a patient with sickle cell disease (SCD). To measure light scattering spectra along two independent axes of elongated-shaped sickle RBCs with arbitrary orientation, we introduce the anisotropic Fourier transform light scattering (aFTLS) technique and measured both the static and dynamic anisotropic light scattering. We observed strong anisotropy in light scattering patterns of elongated-shaped sickle RBCs along its major axes using static aFTLS. Dynamic aFTLS analysis reveals the significantly altered biophysical properties in individual sickle RBCs. These results provide evidence that effective viscosity and elasticity of sickle RBCs are significantly different from those of the healthy RBCs.
Journal of Biomedical Optics 04/2012; 17(4):040501. · 3.16 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The search for predictive indicators of disease has largely focused on molecular markers. However, biophysical markers, which can integrate multiple pathways, may provide a more global picture of pathophysiology. Sickle cell disease affects millions of people worldwide and has been studied intensely at the molecular, cellular, tissue, and organismal level for a century, but there are still few, if any, markers quantifying the severity of this disease. Because the complications of sickle cell disease are largely due to vaso-occlusive events, we hypothesized that a physical metric characterizing the vaso-occlusive process could serve as an indicator of disease severity. Here, we use a microfluidic device to characterize the dynamics of "jamming," or vaso-occlusion, in physiologically relevant conditions, by measuring a biophysical parameter that quantifies the rate of change of the resistance to flow after a sudden deoxygenation event. Our studies show that this single biophysical parameter could be used to distinguish patients with poor outcomes from those with good outcomes, unlike existing laboratory tests. This biophysical indicator could therefore be used to guide the timing of clinical interventions, to monitor the progression of the disease, and to measure the efficacy of drugs, transfusion, and novel small molecules in an ex vivo setting.
Science translational medicine 02/2012; 4(123):123ra26. · 7.80 Impact Factor
-
Florian Leuschner,
Philipp J Rauch,
Takuya Ueno,
Rostic Gorbatov,
Brett Marinelli,
Won Woo Lee,
Partha Dutta,
Ying Wei,
Clinton Robbins,
Yoshiko Iwamoto, [......],
Aleksey Chudnovskiy,
Peter Panizzi,
Edmund Keliher, John M Higgins,
Peter Libby,
Michael A Moskowitz,
Mikael J Pittet,
Filip K Swirski,
Ralph Weissleder,
Matthias Nahrendorf
[show abstract]
[hide abstract]
ABSTRACT: Monocytes (Mo) and macrophages (MΦ) are emerging therapeutic targets in malignant, cardiovascular, and autoimmune disorders. Targeting of Mo/MΦ and their effector functions without compromising innate immunity's critical defense mechanisms first requires addressing gaps in knowledge about the life cycle of these cells. Here we studied the source, tissue kinetics, and clearance of Mo/MΦ in murine myocardial infarction, a model of acute inflammation after ischemic injury. We found that a) Mo tissue residence time was surprisingly short (20 h); b) Mo recruitment rates were consistently high even days after initiation of inflammation; c) the sustained need of newly made Mo was fostered by extramedullary monocytopoiesis in the spleen; d) splenic monocytopoiesis was regulated by IL-1β; and e) the balance of cell recruitment and local death shifted during resolution of inflammation. Depending on the experimental approach, we measured a 24 h Mo/MΦ exit rate from infarct tissue between 5 and 13% of the tissue cell population. Exited cells were most numerous in the blood, liver, and spleen. Abrogation of extramedullary monocytopoiesis proved deleterious for infarct healing and accelerated the evolution of heart failure. We also detected rapid Mo kinetics in mice with stroke. These findings expand our knowledge of Mo/MΦ flux in acute inflammation and provide the groundwork for novel anti-inflammatory strategies for treating heart failure.
Journal of Experimental Medicine 01/2012; 209(1):123-37. · 13.85 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: While Plasmodium falciparum is known to have had a strong effect on human evolution, the time period when P. falciparum first infected ancestors of modern humans has remained uncertain. Recent advances demonstrated that P. falciparum evolved from ancestors of gorilla parasites via host switching. Here, we estimate the range of dates during which this host switch may have occurred. DNA sequences of portions of the mitochondrial cytochrome b gene obtained from gorilla parasites closely related to human P. falciparum were aligned and compared against similar sequences from human P. falciparum. Time estimates were calculated by applying a previously established parasite cytochrome b gene mutation rate (0.012 mutations per site per million years) and by modeling uncertainty in a Monte-Carlo simulation. We estimate a 95% confidence interval for when P. falciparum first infected ancestors of modern humans to be 112,000 and 1,036,000 years ago (median estimate, 365,000 years ago). This confidence interval suggests that P. falciparum first infected human ancestors much more recently than the previous recognized estimate of 2.5 million years ago. The revised estimate may inform our understanding of certain aspects of human-malaria co-evolution. For example, this revised date suggests a closer relationship between the entry of P. falciparum in humans and the appearance of many red blood cell polymorphisms considered to be genetic adaptations to malaria. In addition, the confidence interval lies within the timeframe dating the dawn of Homo sapiens, suggesting that P. falciparum may have undergone host switching as a Plasmodia adaptation specific for our species.
Journal of Molecular Evolution 12/2011; 73(5-6):297-304. · 2.27 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We have used a microfluidic mass sensor to measure the density of single living cells. By weighing each cell in two fluids of different densities, our technique measures the single-cell mass, volume, and density of approximately 500 cells per hour with a density precision of 0.001 g mL(-1). We observe that the intrinsic cell-to-cell variation in density is nearly 100-fold smaller than the mass or volume variation. As a result, we can measure changes in cell density indicative of cellular processes that would be otherwise undetectable by mass or volume measurements. Here, we demonstrate this with four examples: identifying Plasmodium falciparum malaria-infected erythrocytes in a culture, distinguishing transfused blood cells from a patient's own blood, identifying irreversibly sickled cells in a sickle cell patient, and identifying leukemia cells in the early stages of responding to a drug treatment. These demonstrations suggest that the ability to measure single-cell density will provide valuable insights into cell state for a wide range of biological processes.
Proceedings of the National Academy of Sciences 06/2011; 108(27):10992-6. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The systems controlling the number, size, and hemoglobin concentrations of populations of human red blood cells (RBCs), and their dysregulation in anemia, are poorly understood. After release from the bone marrow, RBCs undergo reduction in both volume and total hemoglobin content by an unknown mechanism [Lew VL, et al. (1995) Blood 86:334-341; Waugh RE, et al. (1992) Blood 79:1351-1358]; after ∼120 d, responding to an unknown trigger, they are removed. We used theory from statistical physics and data from the hospital clinical laboratory [d'Onofrio G, et al. (1995) Blood 85:818-823] to develop a master equation model for RBC maturation and clearance. The model accurately identifies patients with anemia and distinguishes thalassemia-trait anemia from iron-deficiency anemia. Strikingly, it also identifies many pre-anemic patients several weeks before anemia becomes clinically detectable. More generally we illustrate how clinical laboratory data can be used to develop and to test a dynamic model of human pathophysiology with potential clinical utility.
Proceedings of the National Academy of Sciences 11/2010; 107(47):20587-92. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A recent large-scale, chemical screening study raised the hypothesis that propranolol may increase the risk of myopathy. We tested this hypothesis in a large population to assess whether (1) propranolol use is associated with an increased risk of myopathy and (2) the concurrent use of propranolol with a statin may further increase risk of myopathy.
New users of propranolol and other beta-blockers (BBs) aged >/=65 were identified using data from Medicare and drug benefit programs in 2 states (1994-2005). The primary end point studied was hospitalization for myopathy or rhabdomyolysis. We used stratified Cox proportional hazards regression to estimate the multivariate-adjusted effect of propranolol compared to other BBs and controlled for demographic variables, risk factors for myopathy, other comorbidities, and health service use measures. We also assessed whether co-use of propranolol and statin further increases the risk, by including an interaction term for use of propranolol and statins.
We identified 9,304 initiators of propranolol and 130,070 initiators of other BBs and found 30 cases of hospitalized myopathy in 15,477 person-years (PYs) of propranolol use and 523 in 343,132 PYs of other BB use. Comparing propranolol with other BB users, the adjusted hazard ratio was 1.45 (95% CI 1.00-2.11) for myopathy and 1.48 (95% CI 0.82-2.67) for rhabdomyolysis. We could not detect interaction between propranolol and statins due to limited power. Similar results were observed when propranolol users were compared to other antihypertensive drug users.
Propranolol may be associated with a 45% increased risk of hospitalized myopathy in the elderly. Our study illustrates how results from in vitro chemical screens can be translated into hypotheses about drug toxicity at the population level.
American heart journal 03/2010; 159(3):428-33. · 4.65 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Blood is a dense suspension of soft non-Brownian cells of unique importance. Physiological blood flow involves complex interactions of blood cells with each other and with the environment due to the combined effects of varying cell concentration, cell morphology, cell rheology, and confinement. We analyze these interactions using computational morphological image analysis and machine learning algorithms to quantify the non-equilibrium fluctuations of cellular velocities in a minimal, quasi-two-dimensional microfluidic setting that enables high-resolution spatio-temporal measurements of blood cell flow. In particular, we measure the effective hydrodynamic diffusivity of blood cells and analyze its relationship to macroscopic properties such as bulk flow velocity and density. We also use the effective suspension temperature to distinguish the flow of normal red blood cells and pathological sickled red blood cells and suggest that this temperature may help to characterize the propensity for stasis in Virchow's Triad of blood clotting and thrombosis.
PLoS Computational Biology 03/2009; 5(2):e1000288. · 5.22 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Red blood cell (RBC) transfusion is unique as a common large-scale intravenous introduction of foreign tissue and provides a valuable opportunity to study human immunologic response to intravenous foreign antigen. Patients receiving RBC transfusions are at risk of forming alloantibodies against donor RBC antigens, and valid estimates of alloimmunization risk are clinically important, but little is known about the factors governing this risk or, more generally, about determinants of human response to intravenous antigen. Here, we mine large electronic patient databases enabling us to model RBC alloimmunization as a stochastic process. We identify a subgroup of transfusion recipients that has a dramatically increased risk of alloimmunization that appears to be genetically determined because it is independent of common disease states, patient age, or the number of alloantibodies already formed, and only weakly dependent on transfusion count.
Blood 07/2008; 112(6):2546-53. · 9.90 Impact Factor
-
Pardis C Sabeti,
David E Reich, John M Higgins,
Haninah Z P Levine,
Daniel J Richter,
Stephen F Schaffner,
Stacey B Gabriel,
Jill V Platko,
Nick J Patterson,
Gavin J McDonald,
Hans C Ackerman,
Sarah J Campbell,
David Altshuler,
Richard Cooper,
Dominic Kwiatkowski,
Ryk Ward,
Eric S Lander
[show abstract]
[hide abstract]
ABSTRACT: The ability to detect recent natural selection in the human population would have profound implications for the study of human history and for medicine. Here, we introduce a framework for detecting the genetic imprint of recent positive selection by analysing long-range haplotypes in human populations. We first identify haplotypes at a locus of interest (core haplotypes). We then assess the age of each core haplotype by the decay of its association to alleles at various distances from the locus, as measured by extended haplotype homozygosity (EHH). Core haplotypes that have unusually high EHH and a high population frequency indicate the presence of a mutation that rose to prominence in the human gene pool faster than expected under neutral evolution. We applied this approach to investigate selection at two genes carrying common variants implicated in resistance to malaria: G6PD and CD40 ligand. At both loci, the core haplotypes carrying the proposed protective mutation stand out and show significant evidence of selection. More generally, the method could be used to scan the entire genome for evidence of recent positive selection.
Nature 11/2002; 419(6909):832-7. · 36.28 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Variation in the human genome sequence is key to understanding susceptibility to disease in modern populations and the history of ancestral populations. Unlocking this information requires knowledge of the patterns and underlying causes of human sequence diversity. By applying a new population-genetic framework to two genome-wide polymorphism surveys, we find that the human genome contains sizeable regions (stretching over tens of thousands of base pairs) that have intrinsically high and low rates of sequence variation. We show that the primary determinant of these patterns is shared genealogical history. Only a fraction of the variation (at most 25%) is due to the local mutation rate. By measuring the average distance over which genealogical histories are typically preserved, these data provide the first genome-wide estimate of the average extent of correlation among variants (linkage disequilibrium). The results are best explained by extreme variability in the recombination rate at a fine scale, and provide the first empirical evidence that such recombination 'hot spots' are a general feature of the human genome and have a principal role in shaping genetic variation in the human population.
Nature Genetics 10/2002; 32(1):135-42. · 35.53 Impact Factor
