Functional and Mechanistic Characterization of Limb Ulcers in Patients With Sickle Cell Disease

Overview

Sickle Cell Disease is the most frequent genetic disease in the world (representing one birth over 1900, in France). The polymerization of the abnormal hemoglobin (i.e., HbS) when deoxygenated is at the origin of a mechanical distortion of red blood cells (RBC) into a crescent-like shape. Sickled RBCs are very fragile and rigid, which lead patients to have severe anemia and to develop frequent and repeated painful vaso-occlusive crises. Furthermore, the repetition of sickling-unsickling cycles causes irreversible damages to the RBCs, which shorten their half-life. Accumulation of free hemoglobin and heme in the plasma is involved in blood vessels lesions in both the macro- and micro- circulation. The resulting vascular dysfunction could explain why limb ulcers are 10 fold more frequent in patients with sickle cell disease compared to the general population and may happen at a younger age. Limb ulcers induce significant morbidity (delay of healing between 9 and 26 weeks in the french cohort), and are associated to significant pain (needing opioid pain-killer) and increase the risk of infection. Cost of care is also increased. Moreover, ulcers induce missed school and work days. Data on cutaneous microcirculation and ulcers physiopathology in patients with sickle cell disease are scarce. We want to realise a microcirculatory and neurological functional study of patients with with and without ulcers and a characterization of biomarkers present in the blood or in the wound fluid which can participate to ulcers physiopathology. To ensure healing, adapted therapeutics are essential. Several strategies are proposed such as: lifestyle measures (venous compression, lower limb elevation, rest), dressings, hyperbaric oxygenotherapy (also used in diabetic ulcers). The project is devoted to study the mechanisms involved in leg ulcers and the effects of therapeutical/behavioral strategies.