Longitudinal Assessment of Lung Cancer Progression in Mice Using the Sodium Iodide Symporter Reporter Gene and SPECT/CT Imaging

In Vivo Stem Cell Imaging Principles and Applications

Stem cells are the foundational cells for every organ and tissue in our body. Cell-based therapeutics using stem cells in regenerative medicine have received attracting attention as a possible treatment for various diseases caused by congenital defects. Stem cells such as induced pluripotent stem cells (iPSCs) as well as embryonic stem cells (ESCs), mesenchymal stem cells (MSCs), and neuroprogenitors stem cells (NSCs) have recently been studied in various ways as a cell-based therapeutic agent. When various stem cells are transplanted into a living body, they can differentiate and perform complex functions. For stem cell transplantation, it is essential to determine the suitability of the stem cell-based treatment by evaluating the origin of stem, the route of administration, in vivo bio-distribution, transplanted cell survival, function, and mobility. Currently, these various stem cells are being imaged in vivo through various molecular imaging methods. Various imaging modalities such as optical imaging, magnetic resonance imaging (MRI), ultrasound (US), positron emission tomography (PET), and single-photon emission computed tomography (SPECT) have been introduced for the application of various stem cell imaging. In this review, we discuss the principles and recent advances of in vivo molecular imaging for application of stem cell research.

Micro-CT acquisition and image processing to track and characterize pulmonary nodules in mice

X-ray computed tomography is a reliable technique for the detection and longitudinal monitoring of pulmonary nodules. In preclinical stages of diagnostic or therapeutic development, the miniaturized versions of the clinical computed tomography scanners are ideally suited for carrying out translationally-relevant research in conditions that closely mimic those found in the clinic. In this Protocol, we provide image acquisition parameters optimized for low radiation dose, high-resolution and high-throughput computed tomography imaging using three commercially available micro-computed tomography scanners, together with a detailed description of the image analysis tools required to identify a variety of lung tumor types, characterized by specific radiological features. For each animal, image acquisition takes 4-8 min, and data analysis typically requires 10-30 min. Researchers with basic training in animal handling, medical imaging and software analysis should be able to implement this protocol across a wide range of lung cancer models in mice for investigating the molecular mechanisms driving lung cancer development and the assessment of diagnostic and therapeutic agents.

Detection and differentiation of murine leukemia virus (MLV) and murine stem cell virus (MSCV) and therefrom derived nucleic acids

Murine leukemia virus (MLV) and murine stem cell virus (MSCV) and derived retroviral vectors are widely used to study retrovirus biology and as tools for gene delivery. The method described here represents a quantitative real time PCR (qPCR) with hydrolysis probe that can be applied within classical qPCR as well as in digital droplet PCR (ddPCR). The method targets a 60 bp long fragment located within the U5 region of the MLV/MSCV genome sequence. For the here described method a LOD95% of 25 copies per PCR reaction (DNA) and 80 copies per PCR reaction (RNA) was determined, and PCR efficiencies of 92.5 % and 98.5 %, respectively, were observed. This method enables the fast and simple titration of viral genomic RNA present in retroviral vector stocks for accurate and consistent transduction experiments. Furthermore, it enables the detection of proviral and transfer plasmid derived DNA sequences and can be modified to differentiate between retroviral RNA and DNA.

Seeing Better and Going Deeper in Cancer Nanotheranostics

Biomedical imaging modalities in clinical practice have revolutionized oncology for several decades. State-of-the-art biomedical techniques allow visualizing both normal physiological and pathological architectures of the human body. The use of nanoparticles (NP) as contrast agents enabled visualization of refined contrast images with superior resolution, which assists clinicians in more accurate diagnoses and in planning appropriate therapy. These desirable features are due to the ability of NPs to carry high payloads (contrast agents or drugs), increased in vivo half-life, and disease-specific accumulation. We review the various NP-based interventions for treatments of deep-seated tumors, involving "seeing better" to precisely visualize early diagnosis and "going deeper" to activate selective therapeutics in situ.

Safe Harbor Targeted CRISPR-Cas9 Tools for Molecular-Genetic Imaging of Cells in Living Subjects

Noninvasive molecular-genetic imaging of cells expressing imaging reporter genes is an invaluable approach for longitudinal monitoring of the biodistribution and viability of cancer cells and cell-based therapies in preclinical models and patients. However, labeling cells with reporter genes often relies on using gene transfer methods that randomly integrate the reporter genes into the genome, which may cause unwanted and serious detrimental effects. To overcome this, we have developed CRISPR-Cas9 tools to edit cells at the adeno-associated virus site 1 (AAVS1) safe harbour with a large donor construct (∼6.3 kilobases) encoding an antibiotic resistance gene and reporter genes for bioluminescence (BLI) and fluorescence imaging. HEK293T cells were transfected with a dual plasmid system encoding the Cas9 endonuclease and an AAVS1-targeted guide RNA in one plasmid, and a donor plasmid encoding a puromycin resistance gene, tdTomato and firefly luciferase flanked by AAVS1 homology arms. Puromycin-resistant clonal cells were isolated and AAVS1 integration was confirmed via PCR and sequencing of the PCR product. In vitro BLI signal correlated well to cell number (R² = 0.9988; p < 0.05) and was stable over multiple passages. Engineered cells (2.5 × 10⁶) were injected into the left hind flank of nude mice and in vivo BLI was performed on days 0, 7, 14, 21, and 28. BLI signal trended down from day 0 to day 7, but significantly increased by day 28 due to cell growth (p < 0.05). This describes the first CRISPR-Cas9 system for AAVS1 integration of large gene constructs for molecular-genetic imaging of cells in vivo. With further development, including improving editing efficiency, use of clinically relevant reporters, and evaluation in other cell populations that can be readily expanded in culture (e.g., immortalized cells or T cells), this CRISPR-Cas9 reporter gene system could be broadly applied to a number of in vivo cell tracking studies.

In Vivo Pulmonary Delivery and Magnetic-Targeting of Dry Powder Nano-in-Microparticles

This brief communication evaluates the cytotoxicity and targeting capability of a dry powder chemotherapeutic. Nano-in-microparticles (NIMs) are a dry powder drug delivery vehicle containing superparamagnetic iron oxide nanoparticles (SPIONs) and either doxorubicin (w/w solids) or fluorescent nanospheres (w/v during formulation; as a drug surrogate) in a lactose matrix. In vitro cytotoxicity was evaluated in A549 adenocarcinoma cells using MTS and LDH assays to assess viability and toxicity after 48 h of NIMs exposure. In vivo magnetic-field-dependent targeting of inhaled NIMs was evaluated in a healthy mouse model. Mice were endotracheally administered fluorescently labeled NIMs either as a dry powder or a liquid aerosol in the presence of an external magnet placed over the left lung. Quantification of fluorescence and iron showed a significant increase in both fluorescence intensity and iron content to the left magnetized lung. In comparison, we observed decreased targeting of fluorescent nanospheres to the left lung from an aerosolized liquid suspension, due to the dissociation of SPIONs and nanoparticles during pulmonary administration. We conclude that dry powder NIMs maintain the therapeutic cytotoxicity of doxorubicin and can be better targeted to specific regions of the lung in the presence of a magnetic field, compared to a liquid suspension.