Experimental design

In order to characterize a mouse model of spontaneous degenerative mitral valve disease, two FVB mice strains, provided by Charles River from the Jackson’s Laboratory (FVB/NJ) and Janvier’s laboratories (FVB/NRj) were used and compared to the putative C57BL/6J control. Animals were followed between 12 and 24 weeks of age in parallel groups. For each strain (FVB/NJ, FVB/NRj and C57BL/6J), we built a group of 40 mice (20 for each sex), then divided in 5 males, 5 females, i.e.10 animals per time point, at 12, 16, 20 and 24 weeks of age. At each timepoint body weight, systolic blood pressure and heart rate were measured. Urine was collected to dose 5-hydroxyindoleacetic acid (5-HIAA). A terminal blood collection was performed to make a blood cell count and to dose the cytokine TGF-β1 and the natriuretic peptide, pro-ANP. Then, the heart was collected for histological characterization of the myocardium and mitral valves. All animal care and procedures are in accordance with institutional guidelines and European regulations. The protocol has been submitted to French regulation authorities and ethical committees according to the European guidelines. It has been approved by the Strasbourg’s ethics committee (CREMEAS) and obtained its authorization from the Ministère de l’Enseignement Supérieur, de la Recherche et de l’Innovation (MESRI) with the following registration number 11732–2017121309379999. In an additional set of animals, mice were anesthetized by 2% isoflurane to perform a bleeding time test. After full recovery, they were sedated by 20mg/kg intraperitoneal xylazine (Rompun©) and then euthanized by a lethal intraperitoneal dose of 200 mg/kg pentobarbital (Euthasol©). Blood was immediately collected by direct cardiac puncture and the anterior leaflet of the mitral valve removed. This complementary protocol has been approved by the ethics committee of the Institute of Genetics and Molecular and Cellular Biology (Cometh) and obtained its authorization from the MESRI with the registration number 26957–2020082617147993.