PET-based reporter gene imaging

In vivo imaging of molecular targets and their function in endocrinology

Imaging is one of the fastest growing fields of study. New technologies and multimodal approaches are increasing the application of imaging to determine molecular targets and functional processes in vivo. The identification of a specific target, transporter, or biological process using imaging has introduced major breakthroughs to the field of endocrinology primarily utilizing computed tomography, magnetic resonance imaging, ultrasonography, positron emission tomography, single-photon emission computed tomography, and optical imaging. This review provides a general background to the specific developments in imaging that pertains to in vivo function and target identification in endocrine-based diseases.

Applications of lentiviral vectors in noninvasive molecular imaging

Noninvasive imaging of molecular-genetic and cellular processes is an effective way to determine the location(s), magnitude, and time variation of action of gene products used for many therapeutic strategies. Lentiviral vectors provide effective means for the delivery, integration, and expression of transgenes in cultured mammalian cells as well as in vivo. Therefore, the combination of lentiviral vector-mediated therapeutic and imaging-targeted reporter gene delivery to various target organs holds promise for the future treatment of diseases. In this chapter, we provide protocols for developing lentiviral vectors that can be utilized for noninvasive monitoring/imaging of reporter gene expression. We have described the procedures to perform cellular assays and animal imaging based on positron emission tomography (PET), optical bioluminescence, and fluorescence reporter genes. The protocols described here are standardized for mouse models, which can also be adapted for other small animal models (e.g., rats).

Potential applications of conventional and molecular imaging to biodefense research

Imaging methods that visualize the structure and function of the living body are widely used in patient care and biomedical research, but their full potential has not yet been applied to the study and treatment of the severe illnesses caused by pathogens of biodefense concern. "Conventional" imaging techniques (e.g., radiography, computed tomography, ultrasound, or magnetic resonance imaging) delineate anatomic changes in tissues, whereas "molecular" methods employ magnetic resonance, positron emission tomography, single-photon emission computed tomography, or optical (fluorescence or bioluminescence) imaging to detect biochemical reactions that accompany pathogen replication or host responses. We review the basic principles of these methods, describe the diseases caused by 6 pathogens classified as category A or B bioterror agents (anthrax, plague, tularemia, filoviral hemorrhagic fever, smallpox, and aerosolized equine encephalitis virus infection), and discuss how imaging could be used to study their pathogenesis in laboratory animals and to diagnose and monitor infection in humans.

Positron emission tomography methods with potential for increased understanding of mental retardation and developmental disabilities

Positron emission tomography (PET) is a technique that enables imaging of the distribution of radiolabeled tracers designed to track biochemical and molecular processes in the body after intravenous injection or inhalation. New strategies for the use of radiolabeled tracers hold potential for imaging gene expression in the brain during development and following interventions. In addition, PET may be key in identifying the physiological consequences of gene mutations associated with mental retardation. The development of high spatial resolution microPET scanners for imaging of rodents provides a means for longitudinal study of transgenic mouse models of genetic disorders associated with mental retardation. In this review, we describe PET methodology, illustrate how PET can be used to delineate biochemical changes during brain development, and provide examples of how PET has been applied to study brain glucose metabolism in Rett syndrome, serotonin synthesis in autism, and GABAA receptors in Angelman's syndrome and Prader-Willi syndrome. Future application of PET scanning in the study of mental retardation might include measurements of brain protein synthesis in fragile X syndrome and tuberous sclerosis complex, two common conditions associated with mental retardation in which cellular mechanisms involve dysregulation of protein synthesis. Mental retardation results in life-long disability, and application of new PET technologies holds promise for a better understanding of the biological underpinnings of mental retardation, with the potential to uncover new treatment options.