Magnetic resonance imaging (MRI) has emerged as one of the predominant modalities to evaluate the effects of stem cells in restoring the injured heart. However, MRI does not assess a fundamental issue in cell therapy, survival of the transplanted cells. The transplanted human embryonic cells (hESCs) must at the very least survive to restore the injured heart. In order to address this issue, this research has conducted the fundamental work to develop a reporter gene as outlined in the proposal and developed a reliable system to evaluate the survival and teratoma formation of the transplanted hESCs.
Using a commercially available genetic construct, the reporter gene was designed to generate specific cell surface tags as a signal of cell survival. Molecular assays demonstrated proper characteristics of the reporter gene and the construct has been inserted into human embryonic stem cells. MRI signal was generated from these cells and this result has been validated by flow cytometry confirming the expression of cell surface tags by the reporter gene in viable human embryonic stem cells. The viable cells expressing this reporter gene were transplanted into mouse heart and MRI signal was generated from the heart of a live mouse.
Based on the above results, the molecular signal was further refined to generate optical signal of cell survival as an additional validation tool. Robust molecular signal of hESC survival was generated following transplantation of the reporter gene transduced hESC into the mouse myocardium. During the no cost extenstion period, detection of hESC survival, proliferation, and early teratoma formation was studied. These biological properties of the transplanted hESCs were monitored accurately. This information will be used to correlate hESC survival/proliferation/teratoma formation with functional restoration of the injured heart.