RAPGEF3 and COVID-19: The upstream signaling components EPAC1 RAPGEF3, RAPGEF6, EPAC2 RAPGEF4, and RAPGEF5 were not transcribed in MSCs from mild or severe COVID-19 patients (data not shown).The AKT is a central molecule that triggers other branches of intracellular signaling pathways, including the β-catenin via, which is probably active in vivo in MSCs comparing our data of severe over mild cases.