Cardiovascular Immaturity in Extremely Low Gestational Age Newborns: a Fundamental Prospective Study

"Medical abortion performed according to standard practice with cord blood sample (1 to 10ml) collected on EDTA tube before injection of foeto toxic agent.~EDTA tube transfered to laboratory on ambient temperature. Blood sample will be centrifuged to isolate the extracellular vesicles once in the laboratory."

"Foetopathology exam is performed according to standard practice on the day after abortion (H12 to H48 from foetus death).~Investigator will recover 2 horizontal slices (in line with the heart) between 3 and 5 mm thick, including the right and left ventricles put them in a cold physiological saline solution, and transfer them rapidly to the laboratory.~Investigator will also recover segments of the descending aorta (approximately 2cm, between the ductus arteriosus and the celiac trunk) and the left renal artery. The isolated segments will be separated from the fat and connective tissue by the foetopathology team and put in a cold physiological saline solution."

"* From the myocardial samples, 10 µm thick sections will be prepared and slides will be incubated with antibodies directed against proteins of interest (adrenergic receptors, protein kinase A, ryanodine receptor, PDE3, troponin). After washing, fluorescent secondary antibodies will be used and slides will be observed under a fluorescence microscope. Rest of the cardiac tissue will be frozen in liquid nitrogen in order to perform Western blots.~* Vessel samples will be put in a myograph to study contractile function. Concentration-response curves will be constructed by cumulative application of noradrenaline or U46619. For the study of endothelial function, arteries with and without functional endothelium will be pre-contracted to 80% of maximal contraction with U46619. When contraction reaches a plate, cumulative addition of different vasodilating agents will be performed. The vessels will also be cannulated on an arteriograph to assess dilation in response to flow and myogenic tone."