Removing physiological motion from intravital and clinical functional imaging data

Tumor Biomechanics Alters Metastatic Dissemination of Triple Negative Breast Cancer via Rewiring Fatty Acid Metabolism

In recent decades, the role of tumor biomechanics on cancer cell behavior at the primary site has been increasingly appreciated. However, the effect of primary tumor biomechanics on the latter stages of the metastatic cascade, such as metastatic seeding of secondary sites and outgrowth remains underappreciated. This work sought to address this in the context of triple negative breast cancer (TNBC), a cancer type known to aggressively disseminate at all stages of disease progression. Using mechanically tuneable model systems, mimicking the range of stiffness's typically found within breast tumors, it is found that, contrary to expectations, cancer cells exposed to softer microenvironments are more able to colonize secondary tissues. It is shown that heightened cell survival is driven by enhanced metabolism of fatty acids within TNBC cells exposed to softer microenvironments. It is demonstrated that uncoupling cellular mechanosensing through integrin β1 blocking antibody effectively causes stiff primed TNBC cells to behave like their soft counterparts, both in vitro and in vivo. This work is the first to show that softer tumor microenvironments may be contributing to changes in disease outcome by imprinting on TNBC cells a greater metabolic flexibility and conferring discrete cell survival advantages.

Monitoring AKT activity and targeting in live tissue and disease contexts using a real-time Akt-FRET biosensor mouse

Aberrant AKT activation occurs in a number of cancers, metabolic syndrome, and immune disorders, making it an important target for the treatment of many diseases. To monitor spatial and temporal AKT activity in a live setting, we generated an Akt-FRET biosensor mouse that allows longitudinal assessment of AKT activity using intravital imaging in conjunction with image stabilization and optical window technology. We demonstrate the sensitivity of the Akt-FRET biosensor mouse using various cancer models and verify its suitability to monitor response to drug targeting in spheroid and organotypic models. We also show that the dynamics of AKT activation can be monitored in real time in diverse tissues, including in individual islets of the pancreas, in the brown and white adipose tissue, and in the skeletal muscle. Thus, the Akt-FRET biosensor mouse provides an important tool to study AKT dynamics in live tissue contexts and has broad preclinical applications.

Memory of stochastic single-cell apoptotic signaling promotes chemoresistance in neuroblastoma

Gene expression noise is known to promote stochastic drug resistance through the elevated expression of individual genes in rare cancer cells. However, we now demonstrate that chemoresistant neuroblastoma cells emerge at a much higher frequency when the influence of noise is integrated across multiple components of an apoptotic signaling network. Using a JNK activity biosensor with longitudinal high-content and in vivo intravital imaging, we identify a population of stochastic, JNK-impaired, chemoresistant cells that exist because of noise within this signaling network. Furthermore, we reveal that the memory of this initially random state is retained following chemotherapy treatment across a series of in vitro, in vivo, and patient models. Using matched PDX models established at diagnosis and relapse from individual patients, we show that HDAC inhibitor priming cannot erase the memory of this resistant state within relapsed neuroblastomas but improves response in the first-line setting by restoring drug-induced JNK activity within the chemoresistant population of treatment-naïve tumors.

Multiphoton intravital microscopy of rodents

Tissues are heterogeneous with respect to cellular and non-cellular components and in the dynamic interactions between these elements. To study the behaviour and fate of individual cells in these complex tissues, intravital microscopy (IVM) techniques such as multiphoton microscopy have been developed to visualize intact and live tissues at cellular and subcellular resolution. IVM experiments have revealed unique insights into the dynamic interplay between different cell types and their local environment, and how this drives morphogenesis and homeostasis of tissues, inflammation and immune responses, and the development of various diseases. This Primer introduces researchers to IVM technologies, with a focus on multiphoton microscopy of rodents, and discusses challenges, solutions and practical tips on how to perform IVM. To illustrate the unique potential of IVM, several examples of results are highlighted. Finally, we discuss data reproducibility and how to handle big imaging data sets.

Intravital imaging technology guides FAK-mediated priming in pancreatic cancer precision medicine according to Merlin status

Pancreatic ductal adenocarcinoma (PDAC) is a highly metastatic, chemoresistant malignancy and is characterized by a dense, desmoplastic stroma that modulates PDAC progression. Here, we visualized transient manipulation of focal adhesion kinase (FAK), which integrates bidirectional cell-environment signaling, using intravital fluorescence lifetime imaging microscopy of the FAK-based Förster resonance energy transfer biosensor in mouse and patient-derived PDAC models. Parallel real-time quantification of the FUCCI cell cycle reporter guided us to improve PDAC response to standard-of-care chemotherapy at primary and secondary sites. Critically, micropatterned pillar plates and stiffness-tunable matrices were used to pinpoint the contribution of environmental cues to chemosensitization, while fluid flow–induced shear stress assessment, patient-derived matrices, and personalized in vivo models allowed us to deconstruct how FAK inhibition can reduce PDAC spread. Last, stratification of PDAC patient samples via Merlin status revealed a patient subset with poor prognosis that are likely to respond to FAK priming before chemotherapy.

Optimizing metastatic-cascade-dependent Rac1 targeting in breast cancer: Guidance using optical window intravital FRET imaging

Assessing drug response within live native tissue provides increased fidelity with regards to optimizing efficacy while minimizing off-target effects. Here, using longitudinal intravital imaging of a Rac1-Förster resonance energy transfer (FRET) biosensor mouse coupled with in vivo photoswitching to track intratumoral movement, we help guide treatment scheduling in a live breast cancer setting to impair metastatic progression. We uncover altered Rac1 activity at the center versus invasive border of tumors and demonstrate enhanced Rac1 activity of cells in close proximity to live tumor vasculature using optical window imaging. We further reveal that Rac1 inhibition can enhance tumor cell vulnerability to fluid-flow-induced shear stress and therefore improves overall anti-metastatic response to therapy during transit to secondary sites such as the lung. Collectively, this study demonstrates the utility of single-cell intravital imaging in vivo to demonstrate that Rac1 inhibition can reduce tumor progression and metastases in an autochthonous setting to improve overall survival.

Synergistic targeting of BRCA1 mutated breast cancers with PARP and CDK2 inhibition

Basal-like breast cancers (BLBC) are aggressive breast cancers that respond poorly to targeted therapies and chemotherapies. In order to define therapeutically targetable subsets of BLBC we examined two markers: cyclin E1 and BRCA1 loss. In high grade serous ovarian cancer (HGSOC) these markers are mutually exclusive, and define therapeutic subsets. We tested the same hypothesis for BLBC. Using a BLBC cohort enriched for BRCA1 loss, we identified convergence between BRCA1 loss and high cyclin E1 protein expression, in contrast to HGSOC in which CCNE1 amplification drives increased cyclin E1. In cell lines, BRCA1 loss was associated with stabilized cyclin E1 during the cell cycle, and BRCA1 siRNA led to increased cyclin E1 in association with reduced phospho-cyclin E1 T62. Mutation of cyclin E1 T62 to alanine increased cyclin E1 stability. We showed that tumors with high cyclin E1/BRCA1 mutation in the BLBC cohort also had decreased phospho-T62, supporting this hypothesis. Since cyclin E1/CDK2 protects cells from DNA damage and cyclin E1 is elevated in BRCA1 mutant cancers, we hypothesized that CDK2 inhibition would sensitize these cancers to PARP inhibition. CDK2 inhibition induced DNA damage and synergized with PARP inhibitors to reduce cell viability in cell lines with homologous recombination deficiency, including BRCA1 mutated cell lines. Treatment of BRCA1 mutant BLBC patient-derived xenograft models with combination PARP and CDK2 inhibition led to tumor regression and increased survival. We conclude that BRCA1 status and high cyclin E1 have potential as predictive biomarkers to dictate the therapeutic use of combination CDK inhibitors/PARP inhibitors in BLBC.

Cancer Cell Invasion and Metastasis in Zebrafish Models (Danio rerio)

Cancer cell vascular invasion and extravasation at metastatic sites are hallmarks of malignant progression of cancer and associated with poor disease outcome. Here we describe an in vivo approach to study the invasive ability of cancer cells into the vasculature and their hematogenous metastatic seeding in zebrafish (Danio rerio). In one approach, extravasation of fluorescently labeled cancer cells is monitored in zebrafish embryos whose vasculature is marked by a contrasting fluorescent reporter. After injection into the precardiac sinus of 2-day-old embryos, cancer cells can extravasate from the vasculature into tissues over the next few days. Extravasated cancer cells are identified and counted in live embryos via fluorescence microscopy. In a second approach, intravasation of cancer cells can be evaluated by changing their injection site to the yolk sac of zebrafish embryos. In addition to monitoring the impact of drivers of malignant progression, candidate inhibitors can be studied in this in vivo model system for their efficacy as well as their toxicity for the host.

Quantifying and visualising the nuances of cellular dynamics in vivo using intravital imaging

Intravital imaging is a powerful technology used to quantify and track dynamic changes in live cells and tissues within an intact environment. The ability to watch cell biology in real-time 'as it happens' has provided novel insight into tissue homeostasis, as well as disease initiation, progression and response to treatment. In this minireview, we highlight recent advances in the field of intravital microscopy, touching upon advances in awake versus anaesthesia-based approaches, as well as the integration of biosensors into intravital imaging. We also discuss current challenges that, in our opinion, need to be overcome to further advance the field of intravital imaging at the single-cell, subcellular and molecular resolution to reveal nuances of cell behaviour that can be targeted in complex disease settings.

Peripheral-specific Y1 receptor antagonism increases thermogenesis and protects against diet-induced obesity

Obesity is caused by an imbalance between food intake and energy expenditure (EE). Here we identify a conserved pathway that links signalling through peripheral Y1 receptors (Y1R) to the control of EE. Selective antagonism of peripheral Y1R, via the non-brain penetrable antagonist BIBO3304, leads to a significant reduction in body weight gain due to enhanced EE thereby reducing fat mass. Specifically thermogenesis in brown adipose tissue (BAT) due to elevated UCP1 is enhanced accompanied by extensive browning of white adipose tissue both in mice and humans. Importantly, selective ablation of Y1R from adipocytes protects against diet-induced obesity. Furthermore, peripheral specific Y1R antagonism also improves glucose homeostasis mainly driven by dynamic changes in Akt activity in BAT. Together, these data suggest that selective peripheral only Y1R antagonism via BIBO3304, or a functional analogue, could be developed as a safer and more effective treatment option to mitigate diet-induced obesity.

Osteoclasts recycle via osteomorphs during RANKL-stimulated bone resorption

Osteoclasts are large multinucleated bone-resorbing cells formed by the fusion of monocyte/macrophage-derived precursors that are thought to undergo apoptosis once resorption is complete. Here, by intravital imaging, we reveal that RANKL-stimulated osteoclasts have an alternative cell fate in which they fission into daughter cells called osteomorphs. Inhibiting RANKL blocked this cellular recycling and resulted in osteomorph accumulation. Single-cell RNA sequencing showed that osteomorphs are transcriptionally distinct from osteoclasts and macrophages and express a number of non-canonical osteoclast genes that are associated with structural and functional bone phenotypes when deleted in mice. Furthermore, genetic variation in human orthologs of osteomorph genes causes monogenic skeletal disorders and associates with bone mineral density, a polygenetic skeletal trait. Thus, osteoclasts recycle via osteomorphs, a cell type involved in the regulation of bone resorption that may be targeted for the treatment of skeletal diseases.

Nuclear F-actin counteracts nuclear deformation and promotes fork repair during replication stress

Filamentous actin (F-actin) provides cells with mechanical support and promotes the mobility of intracellular structures. Although F-actin is traditionally considered to be cytoplasmic, here we reveal that nuclear F-actin participates in the replication stress response. Using live and super-resolution imaging, we find that nuclear F-actin is polymerized in response to replication stress through a pathway regulated by ATR-dependent activation of mTORC1, and nucleation through IQGAP1, WASP and ARP2/3. During replication stress, nuclear F-actin increases the nuclear volume and sphericity to counteract nuclear deformation. Furthermore, F-actin and myosin II promote the mobility of stressed-replication foci to the nuclear periphery through increasingly diffusive motion and directed movements along the nuclear actin filaments. These actin functions promote replication stress repair and suppress chromosome and mitotic abnormalities. Moreover, we find that nuclear F-actin is polymerized in vivo in xenograft tumours after treatment with replication-stress-inducing chemotherapeutic agents, indicating that this pathway has a role in human disease.

Cellular Plasticity during Metastasis: New Insights Provided by Intravital Microscopy

Metastasis is a highly dynamic process during which cancer and microenvironmental cells undergo a cascade of events required for efficient dissemination throughout the body. During the metastatic cascade, tumor cells can change their state and behavior, a phenomenon commonly defined as cellular plasticity. To monitor cellular plasticity during metastasis, high-resolution intravital microscopy (IVM) techniques have been developed and allow us to visualize individual cells by repeated imaging in animal models. In this review, we summarize the latest technological advancements in the field of IVM and how they have been applied to monitor metastatic events. In particular, we highlight how longitudinal imaging in native tissues can provide new insights into the plastic physiological and developmental processes that are hijacked by cancer cells during metastasis.

Milestones in the development and implementation of FRET-based sensors of intracellular signals: A biological perspective of the history of FRET

Fӧrster resonance energy transfer (FRET) has been described for more than a century. FRET has become a mainstay for the study of protein localization in living cells and tissues. It has also become widely used in the fields that comprise cellular signaling. FRET-based probes have been developed to monitor second messenger signals, the phosphorylation state of peptides and proteins, and subsequent cellular responses. Here, we discuss the milestones that led to FRET becoming a widely used tool for the study of biological systems: the theoretical description of FRET, the insight to use FRET as a molecular ruler, and the isolation and genetic modification of green fluorescent protein (GFP). Each of these milestones were critical to the development of a myriad of FRET-based probes and reporters in common use today. FRET-probes offer a unique opportunity to interrogate second messenger signals and subsequent protein phosphorylation - and perhaps the most effective approach for study of cAMP/PKA pathways. As such, FRET probes are widely used in the study of intracellular signaling pathways. Yet, somehow, the potential of FRET-based probes to provide windows through which we can visualize complex cellular signaling systems has not been fully reached. Hence we conclude by discussing the technical challenges to be overcome if FRET-based probes are to live up to their potential for the study of complex signaling networks.

Using in vivo multiphoton fluorescence lifetime imaging to unravel disease-specific changes in the liver redox state

Multiphoton fluorescence lifetime microscopy has revolutionized studies of pathophysiological and xenobiotic dynamics, enabling the spatial and temporal quantification of these processes in intact organs in vivo. We have previously used multiphoton fluorescence lifetime microscopy to characterise the morphology and amplitude weighted mean fluorescence lifetime of the endogenous fluorescent metabolic cofactor nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) of mouse livers in vivo following induction of various disease states. Here, we extend the characterisation of liver disease models by using nonlinear regression to estimate the unbound, bound fluorescence lifetimes for NAD(P)H, flavin adenine dinucleotide (FAD), along with metabolic ratios and examine the impact of using multiple segmentation methods. We found that NAD(P)H amplitude ratio, and fluorescence lifetime redox ratio can be used as discriminators of diseased liver from normal liver. The redox ratio provided a sensitive measure of the changes in hepatic fibrosis and biliary fibrosis. Hepatocellular carcinoma was associated with an increase in spatial heterogeneity and redox ratio coupled with a decrease in mean fluorescence lifetime. We conclude that multiphoton fluorescence lifetime microscopy parameters and metabolic ratios provided insights into the in vivo redox state of diseased compared to normal liver that were not apparent from a global, mean fluorescence lifetime measurement alone.

Fluorescence lifetime imaging microscopy: fundamentals and advances in instrumentation, analysis, and applications

SIGNIFICANCE

Fluorescence lifetime imaging microscopy (FLIM) is a powerful technique to distinguish the unique molecular environment of fluorophores. FLIM measures the time a fluorophore remains in an excited state before emitting a photon, and detects molecular variations of fluorophores that are not apparent with spectral techniques alone. FLIM is sensitive to multiple biomedical processes including disease progression and drug efficacy.

AIM

We provide an overview of FLIM principles, instrumentation, and analysis while highlighting the latest developments and biological applications.

APPROACH

This review covers FLIM principles and theory, including advantages over intensity-based fluorescence measurements. Fundamentals of FLIM instrumentation in time- and frequency-domains are summarized, along with recent developments. Image segmentation and analysis strategies that quantify spatial and molecular features of cellular heterogeneity are reviewed. Finally, representative applications are provided including high-resolution FLIM of cell- and organelle-level molecular changes, use of exogenous and endogenous fluorophores, and imaging protein-protein interactions with Förster resonance energy transfer (FRET). Advantages and limitations of FLIM are also discussed.

CONCLUSIONS

FLIM is advantageous for probing molecular environments of fluorophores to inform on fluorophore behavior that cannot be elucidated with intensity measurements alone. Development of FLIM technologies, analysis, and applications will further advance biological research and clinical assessments.

Experimental pathology by intravital microscopy and genetically encoded fluorescent biosensors

The invention of two‐photon excitation microscopes widens the potential application of intravital microscopy (IVM) to the broad field of experimental pathology. Moreover, the recent development of fluorescent protein‐based, genetically encoded biosensors provides an ideal tool to visualize the cell function in live animals. We start from a brief review of IVM with two‐photon excitation microscopes and genetically encoded biosensors based on the principle of Förster resonance energy transfer (FRET). Then, we describe how IVM using biosensors has revealed the pathogenesis of several disease models.

Development of a Robust Autofluorescence Lifetime Sensing Method for Use in an Endoscopic Application

Endoscopic autofluorescence lifetime imaging is a promising technique for making quantitative and non-invasive diagnoses of abnormal tissue. However, motion artifacts caused by vibration in the direction perpendicular to the tissue surface in a body makes clinical diagnosis difficult. Thus, this paper proposes a robust autofluorescence lifetime sensing technique with a lens tracking system based on a laser beam spot analysis. Our optical setup can be easily mounted on the head of an endoscope. The variation in distance between the optical system and the target surface is tracked by the change in the spot size of the laser beam captured by the camera, and the lens actuator is feedback-controlled to suppress motion artifacts. The experimental results show that, when using a lens tracking system, the standard deviation of fluorescence lifetime is dramatically reduced. Furthermore, the validity of the proposed method is experimentally confirmed by using a bio-mimicking phantom that replicates the shape, optical parameters, and chemical component distribution of the cancerous tissue.

Multicolor two-photon imaging of in vivo cellular pathophysiology upon influenza virus infection using the two-photon IMPRESS

In vivo two-photon imaging is a valuable technique for studies of viral pathogenesis and host responses to infection in vivo. In this protocol, we describe a methodology for analyzing influenza virus-infected lung in vivo by two-photon imaging microscopy. We describe the surgical procedure, how to stabilize the lung, and an approach to analyzing the data. Further, we provide a database of fluorescent dyes, antibodies, and reporter mouse lines that can be used in combination with a reporter influenza virus (Color-flu) for multicolor analysis. Setup of this model typically takes ~30 min and enables the observation of influenza virus-infected lungs for >4 h during the acute phase of the inflammation and at least 1 h in the lethal phase. This imaging system, which we termed two-photon IMPRESS (imaging pathophysiology research system), is broadly applicable to analyses of other respiratory pathogens and reveals disease progression at the cellular level in vivo.

Fluids and their mechanics in tumour transit: shaping metastasis

Metastasis is a dynamic succession of events involving the dissemination of tumour cells to distant sites within the body, ultimately reducing the survival of patients with cancer. To colonize distant organs and, therefore, systemically disseminate within the organism, cancer cells and associated factors exploit several bodily fluid systems, which provide a natural transportation route. Indeed, the flow mechanics of the blood and lymphatic circulatory systems can be co-opted to improve the efficiency of cancer cell transit from the primary tumour, extravasation and metastatic seeding. Flow rates, vessel size and shear stress can all influence the survival of cancer cells in the circulation and control organotropic seeding patterns. Thus, in addition to using these fluids as a means to travel throughout the body, cancer cells exploit the underlying physical forces within these fluids to successfully seed distant metastases. In this Review, we describe how circulating tumour cells and tumour-associated factors leverage bodily fluids, their underlying forces and imposed stresses during metastasis. As the contribution of bodily fluids and their mechanics raises interesting questions about the biology of the metastatic cascade, an improved understanding of this process might provide a new avenue for targeting cancer cells in transit.

Frontiers in Intravital Multiphoton Microscopy of Cancer

Background

Cancer is a highly complex disease which involves the co-operation of tumor cells with multiple types of host cells and the extracellular matrix. Cancer studies which rely solely on static measurements of individual cell types are insufficient to dissect this complexity. In the last two decades, intravital microscopy has established itself as a powerful technique that can significantly improve our understanding of cancer by revealing the dynamic interactions governing cancer initiation, progression and treatment effects, in living animals. This review focuses on intravital multiphoton microscopy (IV-MPM) applications in mouse models of cancer.

Recent Findings

IV-MPM studies have already enabled a deeper understanding of the complex events occurring in cancer, at the molecular, cellular and tissue levels. Multiple cells types, present in different tissues, influence cancer cell behavior via activation of distinct signaling pathways. As a result, the boundaries in the field of IV-MPM are continuously being pushed to provide an integrated comprehension of cancer. We propose that optics, informatics and cancer (cell) biology are co-evolving as a new field. We have identified four emerging themes in this new field. First, new microscopy systems and image processing algorithms are enabling the simultaneous identification of multiple interactions between the tumor cells and the components of the tumor microenvironment. Second, techniques from molecular biology are being exploited to visualize subcellular structures and protein activities within individual cells of interest, and relate those to phenotypic decisions, opening the door for "in vivo cell biology". Third, combining IV-MPM with additional imaging modalities, or omics studies, holds promise for linking the cell phenotype to its genotype, metabolic state or tissue location. Finally, the clinical use of IV-MPM for analyzing efficacy of anti-cancer treatments is steadily growing, suggesting a future role of IV-MPM for personalized medicine.

Conclusion

IV-MPM has revolutionized visualization of tumor-microenvironment interactions in real time. Moving forward, incorporation of novel optics, automated image processing, and omics technologies, in the study of cancer biology, will not only advance our understanding of the underlying complexities but will also leverage the unique aspects of IV-MPM for clinical use.

Noninvasive in vivo human multiphoton microscopy: a key method in proving nanoparticulate zinc oxide sunscreen safety

We describe the contribution of our in vivo multiphoton microscopy (MPM) studies over the last ten years with DermaInspect^;® (JenLab, Germany), a CE-certified medical tomograph based on detection of fluorescent biomolecules, to the assessment of possible penetration of nanoparticulate zinc oxide in sunscreen through human skin. At the time we started our work, there was a strong movement for the precautionary principle to be applied to the use of nanoparticles in consumer products due to a lack of knowledge. The combined application of different MPM modalities, including spectral imaging, fluorescence lifetime imaging, second harmonic fluorescence generation, and phosphorescence microscopy, has provided overwhelming evidence that nanoparticle zinc oxide particles do not penetrate human skin when applied to various skin types with a range of methods of topical sunscreen application. MPM has also been used to study the viable epidermal morphology and redox state in supporting the safe use of topical zinc oxide nanoparticles. The impact of this work is emphasized by the recent proposed rule by the United States FDA on Sunscreen Drug Products for Over-the-Counter Human Use, which listed only zinc oxide and titanium dioxide of the currently marketed products to be generally recognized as safe and effective.

Textures of the tumour microenvironment

In this review, we present recent findings on the dynamic nature of the tumour microenvironment (TME) and how intravital microscopy studies have defined TME components in a spatiotemporal manner. Intravital microscopy has shed light into the nature of the TME, revealing structural details of both tumour cells and other TME co-habitants in vivo, how these cells communicate with each other, and how they are organized in three-dimensional space to orchestrate tumour growth, invasion, dissemination and metastasis. We will review different imaging tools, imaging reporters and fate-mapping strategies that have begun to uncover the complexity of the TME in vivo.

Fast Fluorescence Lifetime Imaging Reveals the Aggregation Processes of α-Synuclein and Polyglutamine in Aging Caenorhabditis elegans

The nematode worm Caenorhabditis elegans has emerged as an important model organism in the study of the molecular mechanisms of protein misfolding diseases associated with amyloid formation because of its small size, ease of genetic manipulation, and optical transparency. Obtaining a reliable and quantitative read-out of protein aggregation in this system, however, remains a challenge. To address this problem, we here present a fast time-gated fluorescence lifetime imaging (TG-FLIM) method and show that it provides functional insights into the process of protein aggregation in living animals by enabling the rapid characterization of different types of aggregates. Specifically, in longitudinal studies of C. elegans models of Parkinson's and Huntington's diseases, we observed marked differences in the aggregation kinetics and the nature of the protein inclusions formed by α-synuclein and polyglutamine. In particular, we found that α-synuclein inclusions do not display amyloid-like features until late in the life of the worms, whereas polyglutamine forms amyloid characteristics rapidly in early adulthood. Furthermore, we show that the TG-FLIM method is capable of imaging live and non-anaesthetized worms moving in specially designed agarose microchambers. Taken together, our results show that the TG-FLIM method enables high-throughput functional imaging of living C. elegans that can be used to study in vivo mechanisms of protein aggregation and that has the potential to aid the search for therapeutic modifiers of protein aggregation and toxicity.

Label-Free Multiphoton Endomicroscopy for Minimally Invasive In Vivo Imaging

Multiphoton microscopy of cellular autofluorescence and second harmonic generation from collagen facilitates imaging of living cells and tissues without the need for additional fluorescent labels. Here, a compact multiphoton endomicroscope for label-free in vivo imaging in small animals via side-viewing needle objectives is presented. Minimal invasive imaging at cellular resolution is performed in colonoscopy of mice without surgical measures and without fluorescent dyes as a contrast agent. The colon mucosa is imaged repeatedly in the same animal in a mouse model of acute intestinal inflammation to study the process of inflammation at the tissue level within a time period of ten days, demonstrating the capabilities of label-free endomicroscopy for longitudinal studies for the first time.

Tify: A quality-based frame selection tool for improving the output of unstable biomedical imaging

The ability to image biological tissues is critical to our understanding of a range of systems and processes. In the case of in situ living tissue, such imaging is hampered by the innate mechanical properties of the tissue. In many cases, this provides challenges in how to process large amounts of image data which may contain aberrations from movement. Generally, current tools require the provision of reference images and are unable to maintain temporal correlations within an image set. Here, we describe a tool-Tify-which can accurately predict a numerical quality score versus human scoring and can analyse image sets in a manner that allows the maintenance of temporal relationships. The tool uses regression-based techniques to link image statistics to image quality based on user provided scores from a sample of images. Scores calculated by the software correlate strongly with the scores provided by human users. We identified that, in most cases, the software requires users to score between 20-30 frames in order to be able to accurately calculate the remaining images. Importantly, our results suggest that the software can use coefficients generated from consolidated image sets to process images without the need for additional manual scoring. Finally, the tool is able to use a frame windowing technique to identify the highest quality frame from a moving window, thus retaining macro-chronological connections between frames. In summary, Tify is able to successfully predict the quality of images in an image set based on a small number of sample scores provided by end-users. This software has the potential to improve the effectiveness of biological imaging techniques where motion artefacts, even in the presence of stabilisation, pose a significant problem.

Toolbox for In Vivo Imaging of Host-Parasite Interactions at Multiple Scales

Animal models have for long been pivotal for parasitology research. Over the last few years, techniques such as intravital, optoacoustic and magnetic resonance imaging, optical projection tomography, and selective plane illumination microscopy developed promising potential for gaining insights into host-pathogen interactions by allowing different visualization forms in vivo and ex vivo. Advances including increased resolution, penetration depth, and acquisition speed, together with more complex image analysis methods, facilitate tackling biological problems previously impossible to study and/or quantify. Here we discuss advances and challenges in the in vivo imaging toolbox, which hold promising potential for the field of parasitology.

Meeting report: Metastasis Research Society (MRS) 17th Biennial conference and associated Young Investigator Satellite Meeting (YISM) on cancer metastasis

The Metastasis Research Society (MRS) 17th Biennial conference on metastasis was held on the 1st to the 5th of August 2018 at Princeton University, NJ, USA. The meeting was held around themes addressing notable aspects of the understanding and treatment of metastasis and metastatic disease covering basic, translational, and clinical research. Importantly, the meeting was largely supported by our patient advocate partners including Susan G. Komen for the Cure, Theresa's Research Foundation and METAvivor. There were a total of 85 presentations from invited and selected speakers spread across the main congress and presentations from the preceding Young Investigator Satellite Meeting. Presentations are summarized in this report by session topic.