Endothelial–Blood Cell Crosstalk in Sickle Cell Disease: molecular Mechanisms of Vaso-Occusion and Multi-Target Therapeutic Strategies

Sickle cell disease (SCD) is a common inherited disorder caused by abnormal hemoglobin S, leading to severe anemia, chronic inflammation, and multi-organ dysfunction. SCD is characterized by increased expression and activation of adhesion molecules on endothelial and blood cells, promoting vascular occlusion and resulting in the hallmark acute pain episodes known as vaso-occlusive crises (VOCs). VOCs can be triggered by a range of biological and environmental factors, including infection, hemolysis, hypoxia, or dehydration, thereby limiting the effectiveness of current therapies. Accordingly, we recently demonstrated that distinct VOC triggers induce specific cell activation in patient samples and mice model, leading to distinct adhesive landscapes and cellular interactions. These observations suggest that VOCs arise through distinct but overlapping biological pathways that remain insufficiently understood. 
This project aims to (i) decipher the molecular and cellular pathways activated during acute VOCs and (ii) assess the efficacy of a multidrug combination in reducing cellular interactions, inflammation, and organ damage in a mouse model.

The PhD work will combine patient-based translational research, mechanistic experiments and preclinical studies. Using the blood sample from patients with SCD, acute VOCs will be studied using the dynamic microfluidic BioChip platform of our lab that reproduces the microvascular environment under physiological flow and allows real-time analysis of blood cell–endothelium interactions. This approach will be integrated with confocal microscopy, computational image analysis, and spectral flow cytometry to characterize multicellular aggregates and neutrophil activation states in different clinical contexts. In the plasma of the patients, a large biomarker panel linked to endothelial activation, cytokines, interferon signaling, and NETosis will also be analyzed. To define the molecular programs associated with crisis onset, the student will perform single-cell RNA sequencing on mature myeloid and endothelial cells collected during acute VOC and after recovery, followed by validation of key pathways by flow cytometry and western blot. Finally, using the comprehensive data collected previously from SCD patients during acute VOC, a combination of drugs will be designed and tested both ex-vivo-using blood from the patients with SCD experiencing VOCs using flow adhesion experiments- and in vivo in a murine model of SCD, in order to reverse the multicellular process of VOCs and to reduce the impact of VOC on organ injury. 
Beyond its scientific objectives, this project will provide the doctoral candidate with strong interdisciplinary training in microfluidics, advanced cellular imaging, computational analysis, flow cytometry, single-cell transcriptomics, biomarker profiling, molecular validation techniques, cell culture and preclinical mouse models. The student will therefore acquire both mechanistic insight into SCD pathophysiology and a broad methodological expertise in vascular biology, inflammation, and translational hematology.

The thesis will be performed in INSERM Unit (UMR S1134) rattached to the University de Paris Cité

For interested students, the PhD project offers an invaluable opportunity to learn about advanced cell biology techniques and translational hematology research. Candidates should have a training in cellular biology or a related discipline, have excellent organizational skills, and a strong interest in cell signaling and blood diseases. A strong emphasis is put towards hard work and scientific discovery.