Molecular imaging of cardiovascular gene products

Department of Medicine, Stanford University, Palo Alto, California, United States
Journal of Nuclear Cardiology (Impact Factor: 2.94). 08/2004; 11(4):491-505. DOI: 10.1016/j.nuclcard.2004.04.004
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Available from: Joseph C Wu, Mar 23, 2015
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    • "Direct labeling strategies appear to be a good imaging method for detection of cells shortly after transplantation, providing a good signal-to-noise ratio, but less suited for long-term monitoring of stem cell viability [5]. The development of reporter gene strategies made it possible to accurately study the biology of stem cells based on the physiologic activity of transplanted cells [6–10]. In particular the ability of transducing reporter transgenes in non-dividing cells, especially lentivirus was successfully used for reporter gene delivery to the stem cells in many previous studies [11]. "
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    ABSTRACT: Transgenic mouse with a stably integrated reporter gene(s) can be a valuable resource for obtaining uniformly labeled stem cells, tissues, and organs for various applications. We have generated a transgenic mouse model that ubiquitously expresses a tri-fusion reporter gene (fluc2-tdTomato-ttk) driven by a constitutive chicken β-actin promoter. This "Tri-Modality Reporter Mouse" system allows one to isolate most cells from this donor mouse and image them for bioluminescent (fluc2), fluorescent (tdTomato), and positron emission tomography (PET) (ttk) modalities. Transgenic colonies with different levels of tri-fusion reporter gene expression showed a linear correlation between all three-reporter proteins (R(2)=0.89 for TdTomato vs Fluc, R(2)=0.94 for Fluc vs TTK, R(2)=0.89 for TdTomato vs TTK) in vitro from tissue lysates and in vivo by optical and PET imaging. Mesenchymal stem cells (MSCs) isolated from this transgenics showed high level of reporter gene expression, which linearly correlated with the cell numbers (R(2)=0.99 for bioluminescence imaging (BLI)). Both BLI (R(2)=0.93) and micro-PET (R(2)=0.94) imaging of the subcutaneous implants of Tri-Modality Reporter Mouse derived MSCs in nude mice showed linear correlation with the cell numbers and across different imaging modalities (R(2)=0.97). Serial imaging of MSCs transplanted to mice with acute myocardial infarction (MI) by intramyocardial injection exhibited significantly higher signals in MI heart at days 2, 3, 4, and 7 (p<0.01). MSCs transplanted to the ischemic hindlimb of nude mice showed significantly higher BLI and PET signals in the first 2 weeks that dropped by 4(th) week due to poor cell survival. However, laser Doppler perfusion imaging revealed that blood circulation in the ischemic limb was significantly improved in the MSCs transplantation group compared with the control group. In summary, this mouse can be used as a source of donor cells and organs in various research areas such as stem cell research, tissue engineering research, and organ transplantation.
    PLoS ONE 08/2013; 8(8):e73580. DOI:10.1371/journal.pone.0073580 · 3.23 Impact Factor
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    • "To accurately assess stem cell survival in the living subject, it is imperative that a non-invasive imaging strategy is used. Novel developments in non-invasive imaging have allowed us to study transgene expression and the biology of cell therapy, using imaging modalities such as bioluminescence imaging (BLI) (Contag and Ross 2002; Negrin and Contag 2006; Shah et al. 2004; Wu et al. 2004). Our laboratory has previously demonstrated that cell survival can be monitored longitudinally (Rodriguez-Porcel et al. 2005). "
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    ABSTRACT: To investigate the mechanisms underlying the beneficial effect of hypoxia preconditioning (HPC) on mesenchymal stromal cells (MSCs) and optimize novel non-invasive methods to assess the effect of biological interventions aimed to increased cell survival. MSCs from rat femur, with or without HPC, were exposed to hypoxic conditions in cell culture (1% O(2) for 24h) and cell survival (by the LDH release assay and Annexin-V staining) was measured. Oxidant status (conversion of dichloro-fluorescein-DCF- and dihydro-ethidium-DHE-, protein expression of oxidant enzymes) was characterized, together with the mobility pattern of cells under stress. Furthermore, cell survival was assessed non-invasively using state-of-the-art molecular imaging. Compared to controls, Hypoxia resulted in increased expression of the oxidative stress enzyme NAD(P)H oxidase (subunit 67(phox): 0.05 ± 0.01AU and 0.48 ± 0.02AU, respectively, p<0.05) and in the amount of ROS (DCF: 13 ±1 and 42 ± 3 RFU/μg protein, respectively, p<0.05) which led to a decrease in stem cell viability. Hypoxia preconditioning preserved cell biology, as evidenced by preservation of oxidant status (16 ± 1 RFU/μg protein, p<0.05 vs. hypoxia), and cell viability. Most importantly, the beneficial effect of HPC can be assessed non-invasively using molecular imaging. HPC preserves cell viability and function, in part through preservation of oxidant status, and its effects can be assessed using state-of-the-art molecular imaging. Understanding of the mechanisms underlying the fate of stem cells will be critical for the advancement of the field of stem cell therapy.
    Life sciences 11/2010; 88(1-2):65-73. DOI:10.1016/j.lfs.2010.10.023 · 2.70 Impact Factor
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    • "A number of methods are available to track stem cells by molecular imaging. In general, there are two methods to label the cells: (1) direct labeling method, which physically introduce marker(s) into the cells before transplant; (2) indirect labeling method, which genetically introduce reporter gene(s) into the cells before transplant [Wu et al., 2004] "
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    ABSTRACT: Using endothelial cells for therapeutic angiogenesis/vasculogenesis of ischemia diseases has led to exploring human embryonic stem cells (hESCs) as a potentially unlimited source for endothelial progenitor cells. With their capacity for self-renewal and pluripotency, hESCs and their derived endothelial cells (hESC-ECs) may be more advantageous than other endothelial cells obtained from diseased populations. However, hESC-ECs' poor differentiation efficiency and poorly characterized in vivo function after transplantation present significant challenges for their future clinical application. This review will focus on the differentiation pathways of hESCs and their therapeutic potential for vascular diseases, as well as the monitoring of transplanted cells' fate via molecular imaging. Finally, cell enhancement strategies to improve the engraftment efficiency of hESC-ECs will be discussed.
    Journal of Cellular Biochemistry 02/2009; 106(2):194-9. DOI:10.1002/jcb.22003 · 3.26 Impact Factor
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