nano-rheological biomarkers for patients with sickle cell disease (scd) versus control subjects (other constitutional red blood cell diseases and healthy subjects)

Conditions: Sickle Cell Disease

Summary: numerous pathologies (sickle cell disease, thalassemia, spherocytosis, etc.) lead to changes in the rheological properties of the blood, in particular via alterations in the deformability of red blood cells. these alterations lead to circulatory complications of which an emblematic example is the sickle cell crisis which manifests itself by microcirculatory occlusions. several authors suggest that the deformability of erythrocytes is a key parameter for the diagnosis and monitoring of patients. numerous studies, especially in vitro, show that the mechanical properties of the red blood cell significantly influence its dynamics in flow (blood viscosity, distribution in capillary networks). moreover, concerning the specific problem of vaso-occlusion, the proportion of the most rigid red blood cells is a determining factor of the probability of occlusion more than the average value of this rigidity which can hide great disparities. there is no clinically usable test to assess the alteration of the fine rheology of the red blood cell in a patient. functional tests such as ektacytometry require heavy equipment and teams of specialized biologists; this technique is therefore only available in 3 biological reference centers in france. "mechanical phenotyping" seems to be a potentially simpler and more accessible technique, and has already shown promising prospects in other nosological settings than red blood cell pathologies. today, there is no specific marker of sickle cell vaso-occlusive crisis, nor marker of severity, that would be useful for pathophysiological understanding but also for clinical management.

this study aims to characterize the microfluidic flow and intra-erythrocyte viscosity of sickle cell red blood cells, and to identify specific biological phenotype or clinical severity profiles. the techniques used are microfluidic circuits for the study of flow and molecular rotors for the measurement of intra-erythrocyte viscosity, using deoxygenation cycles in order to model physio-pathological situations. the first part will allow the calibration of the microfluidic techniques used (microfluidic circuit and molecular rotors), testing blood from healthy subjects (without constitutional or acquired red blood cell pathology) and blood from scd patients. the aim is to define the reproducibility and sensitivity of the techniques. a second part is aimed at establishing a rheological profile of the blood of patients with scd in comparison with blood from control subjects, i.e. with other constitutional or acquired red blood cell pathology.

Eligibility criteria:
inclusion criteria for healthy volunteers : 1. patient age ≥ 18 years 2. with social care protection 3. living donor recruited for kidney donation with normal blood count inclusion criteria for sdc patient : 1. patient age ≥ 18 years 2. with social care protection 3. scd patient with documented phenotype: ss, s°, s+, sc, slepore, sorab, sdpundjab, asantilles... with or without specific treatment inclusion criteria for patient with a constitutional non-sickle cell disease of the red blood cell, or an acquired red blood cell disease : 1. patient age ≥ 18 years 2. with social care protection 3. with any of the following conditions : 1. patient being managed for anemia due to martial deficiency, and prior to oral or intravenous replacement therapy 2. patient being followed for myeloproliferative syndrome at diagnosis, and prior to any specific treatment (hemodilution or hydroxycarbamide or other specific treatment) 3. a patient with a mcgre other than a major sickle cell syndrome, whether or not under specific treatment 4. hemoglobinopathy: transfusion-dependent or independent thalassemias (major or intermediate), thalassemias minor, heterozygous sickle cell trait a/s, other heterozygous hemoglobin variants (c, e, lepore...), hyperaffine hemoglobin 5. membrane disorders (hereditary spherocytosis) 6. canalopathies (stomatocytosis with dehydrated or hyperhydrated erythrocytes, melanesian ovalocytosis...) 7. enzyme deficiencies (g6pd, pk, gpi...) exclusion criteria for all patients: 1. patient age \< 18 years 2. subject under guardianship, or subject deprived of freedom 3. linguistic or literacy status not allowing for informed consent despite patient information in "easy to read and understand" format 4. known history of hiv, htlv, syphilis, or positive serology and active viral hepatitis b or c. additional exclusion criteria for healthy volunteers : 5. abnormal blood count, or possible martial deficiency with ferritin levels below 50µg/l, or current treatment with hydroxycarbamide, or transfusion within 4 months prior to inclusion. additional exclusion criteria for scd patient : 5) treatment with hydroxycarbamide started less than 6 months ago 6) anemia with hemoglobin level \<60g/l in the absence of cardiorespiratory pathology, \<70g/l in pregnancy, or in the presence of cardiorespiratory pathology that may alter the tolerance of anemia. additional exclusion criteria for patient with a constitutional non-sickle cell disease of the red blood cell, or an acquired red blood cell disease : 5) anemia with hemoglobin level \<60g/l, \<70g/l in pregnancy, or in the presence of cardio-respiratory pathology that may alter the tolerance of anemia. 6) diagnosis not finalized (in progress), or uncertain nosological framework, or diagnostic wandering.

Keywords: hemorheology microfluidics blood viscosity red blood cell sickle cell disease