The figure shows a three-dimensional reconstruction of hybrid fluorescence molecular tomography/x-ray computed tomography (FMT-CT) in a mouse 3 days after coronary artery ligation. The red signal in the infarcted apical myocardium encodes the distribution of a nanoparticle targeted to monocyte/macrophages, which derivatized the fluorochrome. The multimodal imaging approach allows one to noninvasively quantitate infarct inflammation and the quality of tissue repair by optical tomography, while CT imaging provides the exact anatomic location of the molecular signal.
Cold Spring Harb Perspect Biol
Imaging has become an indispensable tool in the study of cancer biology and in clinical prognosis and treatment. The rapid advances in high resolution fluorescent imaging at single cell level and MR/PET/CT image registration, combined with new molecular probes of cell types and metabolic states, will allow the physical scales imaged by each to be bridged. This holds the promise of translation of basic science insights at the single cell level to clinical application. In this article, we describe the recent advances in imaging at the macro- and micro-scale and how these advances are synergistic with new imaging agents, reporters, and labeling schemes. Examples of new insights derived from the different scales of imaging and relevant probes are discussed in the context of cancer progression and metastasis.
J Am Coll Cardiol Img
The aim of this study was to iteratively develop and validate an 18F-labeled small vascular cell adhesion molecule (VCAM)-1 affinity ligand and demonstrate the feasibility of imaging VCAM-1 expression by positron emission tomography–computed tomography (PET-CT) in murine atherosclerotic arteries. Conclusions: 18F-4V allows noninvasive PET-CT imaging of VCAM-1 in inflammatory atherosclerosis, has the dynamic range to quantify treatment effects, and correlates with inflammatory gene expression.
Tumor-associated macrophages (TAM) invade the tumor stroma in many cancers, yet their role is incompletely understood. To visualize and better understand these critical cells in tumor progression, we screened a portfolio of rationally selected, injectable agents to image endogenous TAM ubiquitously in three different cancer models (colon carcinoma, lung adenocarcinoma and soft tissue sarcoma). AMTA680, a functionally derivatized magnetofluorescent nanoparticle, labeled a subset of myeloid cells with a ‘M2’ macrophage phenotype, whereas other neighboring cells, including tumor cells and a variety of other leukocytes, remained unlabeled. AMTA680 or related cell-targeting agents represent appropriate injectable vehicles for in vivo analysis of the tumor microenvironment.
In vivo imaging reveals how proteins and cells function as part of complex regulatory networks in intact organisms, and thereby contributes to a systems-level understanding of biological processes. However, the development of novel in vivo imaging probes remains challenging. Here, we rapidly profile the in vitro binding of nanoparticle imaging probes in multiple samples of defined target vs. background cell types, using primary cell isolates. We apply this approach to the identification of nanoparticle imaging probes that bind endothelial cells, and validate our in vitro findings in human arterial samples, and by in vivo intravital microscopy in mice. Overall, this work presents a generalizable approach to the unbiased discovery of in vivo imaging probes, and may guide the further development of novel endothelial imaging probes
Special Issue: Nanoparticle enhanced imaging - Emerging oncologic applications. Guest-Editor: Dr. Harisinghani
Osteoclasts degrade bone matrix by demineralization followed by degradation of type I collagen through secretion of the cysteine protease, cathepsin K. Current imaging modalities are insufficient for sensitive observation of osteoclast activity, and in vivo live imaging of osteoclast resorption of bone has yet to be demonstrated. Here, we describe a near-infrared fluorescence reporter probe whose activation by cathepsin K is shown in live osteoclast cells and in mouse models of development and osteoclast upregulation. Cathepsin K probe activity was monitored in live osteoclast cultures and correlates with cathepsin K gene expression. In ovariectomized mice, cathepsin K probe upregulation precedes detection of bone loss by micro-computed tomography. These results are the first to demonstrate non-invasive visualization of bone degrading enzymes in models of accelerated bone loss, and may provide a means for early diagnosis of upregulated resorption and rapid feedback on efficacy of treatment protocols prior to significant loss of bone in the patient.
New technologies for imaging molecules, particularly optical technologies, are increasingly being used to understand the complexity, diversity and in vivo behaviour of cancers. Omic approaches are providing comprehensive snapshots of biological indicators, or biomarkers, of cancer, but imaging can take this information a step further, showing the activity of these markers in vivo and how their location changes over time. Advances in experimental and clinical imaging are likely to improve how cancer is understood at a systems level and, ultimately, should enable doctors not only to locate tumours but also to assess the activity of the biological processes within these tumours and to provide on the spot treatment.
The existing paradigms for how immune cells interact with each other and their environment have come largely from static images obtained through histochemistry. As this volume illustrates, an exciting era in immunology is now emerging where the immune response and much of its complexity can be visualized in real time and within the confines of secondary lymphoid tissues in vivo. As the reviews in this issue describe, such studies are altering our perceptions of how, when, where, and for how long immune cells participate in innate and adaptive responses. Our authors show how the advances in and applications of new technologies facilitating imaging of the immune system are destroying old paradigms and writing new ones.
In this study we report on the use of a new, bolus injectable, carboxymethyl-dextran based magnetic nanoparticle (MNP), ferumoxytol, to improve detection in loco-regional lymph nodes by magnetic resonance imaging (MRI). Conclusion: Ferumoxytol is safe and, at the appropriate circulation interval, modulates nodal signal intensity, allowing for identification of malignant nodal involvement by MRI.
Restoring endogenous p53 expression leads to regression of autochthonous lymphomas and sarcomas in mice without affecting normal tissues. The mechanism responsible for tumour regression is dependent on the tumour type, with the main consequence of p53 restoration being apoptosis in lymphomas and suppression of cell growth with features of cellular senescence in sarcomas. These results support efforts to treat human cancers by way of pharmacological reactivation of p53.
J Clin Invest
Colored scanning EM of a human macrophage, the key player in 3 articles featured in the current issue. Lumeng et al. describe a novel subset of macrophages resident in adipose tissue (page 175). Tacke and colleagues (page 185) and Swirski et al. (page 195) both delve further into the roles macrophages play in atherosclerotic plaques. Siamon Gordon synthesizes the findings of the 3 papers in a Commentary beginning on page 89.
This study thus provides a foundation for using Magnetofluorescent nanoparticles (MFNPs) to image genetic and/or pharmacological perturbations of cellular inflammation in experimental atherosclerosis and for the future development of novel targeted nanomaterials for atherosclerosis.
J Biomed Opt
Molecular and cellular mechanisms of atherogenesis and its treatment are largely being unraveled by in vitro techniques. We describe methodology to directly image macrophage cell activity in vivo in a murine model of atherosclerosis using laser scanning fluorescence microscopy (LSFM) and a macrophage-targeted, near-infrared fluorescent (NIRF) magnetofluorescent nanoparticle (MFNP)
Int J Radiat Oncol Biol Phys
A novel magnetic resonance lymphangiographic technique was employed to highlight the likely sites of occult nodal metastasis from prostate cancer. Conclusions: Nodal metastases from prostate cancer are largely localized along the major pelvic vasculature. Defining nodal radiation treatment portals based on vascular rather than bony anatomy may allow for a significant decrease in normal pelvic tissue irradiation and its associated toxicities.
This study was designed to investigate the role of activated H-RAS on the angiogenic phenotype of melanoma that arises in the inducible Tyr/Tet-RAS Ink4a/Arf(-/-) model using in vivo imaging with histopathologic correlation. We show that loss of RAS activity in fully established melanomas led to a reduction in tumor volume, which was preceded by impairment of vascular function as determined by in vivo magnetic resonance imaging.
Here we describe the properties of a luciferase from the copepod marine organism Gaussia princeps. Gaussia luciferase provides a sensitive means of imaging gene delivery and other events in living cells in culture and in vivo, with a unique combination of features including high signal intensity, secretion, and ATP independence, thus being able to report from the cells and their environment in real time.
Cancer Biol Ther
Recent studies have described neuronal progenitor cell recruitment to tumors in vivo, however, the mechanisms mediating this recruitment are not yet understood. Our data suggest that recruitment of C17.2-luc cells to TEC is mediated via SDF- 1a/CXCR4 activation that results in modification of a4-integrin and results in improved recruitment of C17.2-luc cells.
We have developed an imaging agent for real-time endoscopic tumor detection in a murine model using a previously identified phage library-derived colon cancer-specific cyclic peptide and fluorescent moieties. The modified peptide had a 24 minute blood half life and tumoral accumulation was 6.9% of injected dose/g, 7-fold higher than a scrambled control peptide. These results show proof-of-principle that disease-specific library-derived fluorescent probes can be rapidly developed for use in the early detection of cancers by optical means.
Here we report on the synthesis of a novel imaging probe that is specific for HIV-1 protease (PR). The probe was designed to be biocompatible, i.v. injectable, and detectable by fluorescence imaging. These results are the first proof of principle that viral proteases can directly be imaged in vivo.
Using a model of gliosarcoma with stably green fluorescence protein-expressing 9L glioma cells, we explored a multimodal (near-infrared fluorescent and magnetic) nanoparticle as a preoperative magnetic resonance imaging contrast agent and intraoperative optical probe. This prototypical multimodal nanoparticle has unique properties that may allow radiologists and neurosurgeons to see the same probe in the same cells and may offer a new approach for obtaining tumor margins.
We developed a novel, biocompatible, and physiologically inert nanoparticle (highly derivatized cross-linked iron oxide nanoparticle; CLIO-HD) for highly efficient intracellular labeling of a variety of cell types that now allows in vivo MRI tracking of systemically injected cells at near single-cell resolution. Using B16-OVA melanoma and CLIO-HD-labeled OVA-specific CD8+ T cells, we have demonstrated for the first time high resolution imaging of T-cell recruitment to intact tumors in vivo.
The paper by Ntziachristos, et al. describes the use of fluorescence-mediated tomography (FMT) imaging of deep tissues to generate high resolution, quantitative images of biochemical events in living animals. The capability of FMT to provide 3-dimensional images of biochemical events should play a significant role in the development and use of optical imaging technologies in biomedicine.
Contrast enhanced, near infrared optical tomography has the potential to provide a wealth of structural and functional information about biological tissue. The cover artistically illustrates contrast-enhanced NIR tomography when taking measurements with an intensity-modulated source. The photon density wavefronts propagate from the source fiber optic to an obscured, elliptic inclusion within the tissue. Exhibiting enhanced contrast via a specialized fluorescent contrast agent, a series of fluorescent photon density wavefronts propagate from the inclusion to a fiber optic detector, which receives the diagnostic information.