Abstract 250: In vivo Kinetics of Embryonic Stem Cell Viability Following Transplantation Into the Injured Murine Myocardium
Background: Embryonic stem cells (ESC) have demonstrated the potential to restore the cardiac function after ischemic injury. Superparamagnetic iron oxide nanoparticles (SPIO) have been widely employed to label cells ex vivo for MRI. However, non-specific intracellular accumulation of SPIO prohibits assessment of the viability of the transplanted cells. To overcome this limitation, a novel MRI reporter gene (RG) has been developed to express antigens on the ESC surface. By employing SPIO-conjugated monoclonal antibody against these antigens (SPIO-MAb), in vivo molecular MRI detects viable ESC in the murine myocardium.
Methods and Results: The MRI RG has been developed to express HA and myc antigens, and firefly luciferase on the ESC surface. Human and mouse ESC were transduced using a lentiviral vector to express the RG (ESC-RG). After incubation of ESC-RG with SPIO-MAb, in vitro MRI generated significant CNR from the viable vs. apoptotic/dying cells (3.98±0.71 vs. 1.35±0.87, p<0.05). Following transplantation of ESC-RG into the murine myocardium, serial cardiac MRI (CMR) was performed pre- and post-intravenous delivery of SPIO-MAb on post-transplantation days 3, 5, 7, 10 and 14. Serial in vivo molecular CMR generated significant MRI signal of ESC survival (pre-CNR: 1.07±0.46 vs. post-CNR: 5.62±2.17, p<0.05, Figure 1⇓) and ESC proliferation suggestive of teratoma formation (2.3+0.67 vs. 5.3±0.46 mm3, p<0.05). Similar increase in luciferase activity (18316+6469 vs. 70750±9995 p/s/cm2/sr, p<0.05) validated the CMR findings.
Conclusions: This novel molecular CMR enabled in vivo assessment of post-transplantation ESC biology.
This research has received full or partial funding support from the American Heart Association, National Center.