? Cell transplantation as well as gene therapy both hold promise as potential strategies for treating heart failure. Longitudinal analysis of cell survival and gene therapy remain problematic since current methodology relies on postmortem immunohistology. The long-term goal for this project is to monitor myocardial repair over time in living animal models using novel multimodality imaging technologies. Our primary hypothesis is that noninvasive imaging can be used to optimize delivery and track the survival of stem cells expressing hypoxia inducible factor 1a (HIF-1a) and various imaging reporter genes. We have recently demonstrated the feasibility and reproducibility of imaging cardiac cell implantation using optical bioluminescence and micro positron emission tomography (microPET) in conjunction with reporter gene technology. Therefore, the specific aims of this proposal are logical extensions of our initial findings.
In Aim 1, we will continue to develop an in vivo imaging model for quantifying engraftment of bone marrow derived human mesenchymal stem cell (hMSC) marked with multimodality reporter genes. Ultrasound will be optimized for real-time monitoring of cell delivery and magnetic resonance imaging (MRI) will be optimized for monitoring infarct region and locations of implanted cells. Equally important, cell survival will be correlated with improvement in myocardial function (ultrasound), perfusion ([13N]-NH3), and glucose metabolism ([18F]-FDG). Additional variables of cell delivery route, cell number, etc. will also be studied.
In Aim 2, imaging results will be validated with traditional ex vivo and in vitro assays such as autoradiography, morphometric analysis, immunocytochemical staining, TaqMan PCR, Northerns, and enzyme assays.
In Aim 3 we will deliver a therapeutic gene (HIF-1a) expressed within the hMSC cells to test the hypothesis that co-delivery of an angiogenic gene along with the transplanted cells leads to further improvement of cell survival and improvement in cardiac function. The overall significance of this project is to understand the real-time physiologic state of engrafted stem cells in relationship to myocardial improvement using multi-modality imaging technologies. These findings will add further insights into cell transplant biology and eventually lead to standardized protocols that are reproducible and quantifiable. Furthermore, the methodologies developed in this proposal will help other investigators to implement various models in which imaging of cell survival and cardiac gene therapy are important. ? ? ?
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