Our project focuses on the regulatory properties of a subset of microbiota-specific TR1-like regulatory T (Treg) cells, for which we have already shown an unprecedented association with the clinical outcome of patients in various inflammatory diseases, for a therapeutic use in inflammatory bowel diseases (IBD). IBD is a disabling chronic inflammatory process that affects young individuals and causes many life-altering symptoms, and represents a risk factor for colon cancer. Existing treatments are complex, with most people requiring lifelong medications as well as dietary and lifestyle modifications, and some requiring surgery. In this context, the development of new therapeutic approaches appears essential and immunotherapy and cell-based therapy are particularly promising strategies for this disease. Teams from Nantes have a strong expertise in the field of human immunology, mucosal immunology and immunotherapeutic strategies applied to various pathological conditions, including gut inflammatory diseases. They recently identified a novel microbiota-induced Treg subset, associated with good prognosis in IBD patients, thus representing a promising candidate for innovative immunotherapeutic approaches. Based on the limitation to develop immunotherapy approach for human diseases by using animal models due to immune system specificities/differences and ethical considerations, we opted for the development of an ex vivo human preclinical model that will reconstitute the physiological complexity of the human gut. Teams from Strasbourg have a strong experience and already set-up models of organoids in different pathological systems, that will perfectly fit to be used as ex vivo preclinical models for this project. This proposal aims thus at providing a pre-clinical package including i) the proof of concept that a cellular immunotherapy using the identified Tregs subset represents a treatment for IBDs and ii) the reglementary pre-clinical in vitro and in vivo toxicity.

In the human placenta, organ responsible for fetal growth and development, the multinucleated cellular layer, named syncytiotrophoblast (ST) plays a major role. Indeed ST bathing in maternal blood is the site of nutrient exchange and hormone synthesis. ST expands and regenerates all along pregnancy via the recruitment by fusion of underlying mononucleated cytotrophoblast cells. The apical membrane of ST is formed of microvilli which can brake away in the intervillous space. In addition, large ST pieces, called sprouts, are also released in the maternal blood all along pregnancy. Preeclampsia one of the main causes of severe premature births and Intra-Uterine Growth Retardation (IUGR) are two major pregnancy pathologies from placental origin with major socio-economical and human costs. They are associated with a large release of membrane trophoblast necrotic material as well as an abnormal regeneration of the ST. These ST fragments are inflammatory for the maternal endothelial cells. Therefore extensive membrane ruptures occur in physiological and pathological conditions, and must be compensated by efficient processes of membrane repair. Our current understanding of the mechanisms of membrane repair of the human placenta is very poor. Recently, Partner-1 (A. Brisson) has elucidated the function of Annexin-A5 in membrane repair. Annexin-A5 discovered originally in the placenta is the prototype member of the annexins, a family of soluble proteins that share the property of binding to negatively-charged lipid membranes, principally those containing phosphatidylserine (PS) in a Ca2+-dependant manner. According to J. Rand’s hypothesis, proposed fifteen years ago, PS molecules are exposed at the ST membrane surface and Annexin-A5 forms a layer covering the ST surface, which prevents blood coagulation in the intervillous space. Despite its potential interest, this hypothesis is weakly supported by low-resolution immune-histological data. The recent finding that Annexin-A5 occupies a central place in the machinery of membrane repair, which is of vital importance in cell’s life, constitutes a major breakthrough in Annexin-A5 research. This study concludes that Annexin-A5 promotes membrane repair via the formation of 2D arrays at the level of damaged membranes, which prevents the expansion of membrane wound and facilitates the final step of membrane resealing. In view of 1) the role of Annexin-A5 in membrane repair, 2) the extensive membrane damages occurring at the placenta ST membrane and 3) the high Annexin-A5 content of the placenta, we postulate that Annexin-A5 is involved in membrane repair of the ST membrane. The overall aim of the PlacentA5 project is thus to elucidate whether Annexin-A5 is involved in membrane repair of placental ST, and what is its exact role in normal and pathological placentas. The strength of this project is the task force joining two leader teams with unique complementary expertise. Partner 1 (A. Brisson) is a leader in imaging and structure-function studies of Annexin-A5 assemblies. Partner 2 (D. Evain-Brion) is an international reference team in the field of human placenta physiology and human trophoblast differentiation, with a unique expertise in setting in vitro models of human trophoblast differentiation. This project is developed within the RTRS PremUp allowing normal and patholigical placenta collections.