CD44 and atrial fibrillation: The results showed that MSCs from different AF samples (n = 12) expressed the adhesion molecule CD44 (from 53.9 to 69.9%), high levels of CD90 (Thy-1) (from 69.9 to 91.2%), and mesenchymal-related antigen CD105 (endoglin) (from 49.3 to 61.6%) and were negative for hematopoietic stem cell marker CD34.