Pathway‐specific reporter genes to study stem cell biology

Little is known on the phenotypic characteristics of stem cells (SCs) after they are transplanted to the myocardium, in part due to lack of noninvasive platforms to study SCs directly in the living subject. Reporter gene imaging has played a valuable role in the noninvasive assessment of cell fate in vivo. In this study, we validated a pathway‐specific reporter gene that can be used to noninvasively image the phenotype of SCs transplanted to the myocardium. Rat mesenchymal SCs (MSCs) were studied for phenotypic evidence of myogenic characteristics under in vitro conditions. After markers of myogenic characteristics were identified, we constructed a reporter gene sensor, comprising the firefly luciferase (Fluc) reporter gene driven by the troponin T (TnT) promoter (cardio MSCs had threefold expression in polymerase chain reaction compared to control MSCs) using a two‐step signal amplification strategy. MSCs transfected with TnT‐Fluc were studied and validated under in vitro conditions, showing a strong signal after MSCs acquired myogenic characteristics. Lastly, we observed that cardio MSCs had higher expression of the reporter sensor compared to control cells (0.005 ± 0.0005 vs 0.0025 ± 0.0008 Tnt‐Fluc/ubiquitin‐Fluc, P