Longitudinal micro-endoscopic monitoring of high-success intramucosal xenografts for mouse models of colorectal cancer

Spectral Multiplexing of Fluorescent Endoscopy for Simultaneous Imaging with Multiple Fluorophores and Multiple Fields of View

Complex clinical procedures and small-animal research procedures can benefit from dual-site imaging provided by multiple endoscopic devices. Here, an endoscopic system is proposed which enables multiple fluorescence microendoscopes to be spectrally multiplexed on a single microscope base, enabling light sources and optical relays to be shared between endoscopes. The presented system is characterized for resolution using USAF-1951 resolution test charts and for modulation transfer function using the slanted edge method. Imaging is demonstrated both directly and with microendoscopes attached. Imaging of phantoms was demonstrated by targeting USAF charts and fiber tissues dyed for FITC and Texas Red fluorescence. Afterwards, simultaneous liver and kidney imaging was demonstrated in mice expressing mitochondrial Dendra2 and injected with Texas Red-dextran. The results indicate that the system achieves high channel isolation and submicron and subcellular resolution, with resolution limited by the endoscopic probe and by physiological movement during endoscopic imaging. Multi-channel microendoscopy provides a potentially low-cost means of simultaneous multiple endoscopic imaging during biological experiments, resulting in reduced animal harm and potentially increasing insight into temporal connections between connected biological systems.

Fluorescence Microscopy-An Outline of Hardware, Biological Handling, and Fluorophore Considerations

Fluorescence microscopy has become a critical tool for researchers to understand biological processes at the cellular level. Micrographs from fixed and live-cell imaging procedures feature in a plethora of scientific articles for the field of cell biology, but the complexities of fluorescence microscopy as an imaging tool can sometimes be overlooked or misunderstood. This review seeks to cover the three fundamental considerations when designing fluorescence microscopy experiments: (1) hardware availability; (2) amenability of biological models to fluorescence microscopy; and (3) suitability of imaging agents for intended applications. This review will help equip the reader to make judicious decisions when designing fluorescence microscopy experiments that deliver high-resolution and informative images for cell biology.

Therapeutic efficacy and gastrointestinal biodistribution of polycationic nanoparticles for oral camptothecin delivery in early and late-stage colorectal tumor-bearing animal model

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the world and is the second leading cause of cancer related deaths. New cases are increasingly diagnosed every day, but current therapeutic options are still insufficient for an effective treatment. In CRC treatment, there is a significant need for alternative treatment approaches that can both prevent relapse and provide strong antimetastatic effects as the intestines and colon are prone to metastasis to neighboring organs and tissues as well as the liver and the lung. In this study, optimized polycationic cyclodextrin (CD) nanoparticles for oral Camptothecin (CPT) delivery were comprehensively examined for in vivo performance in early and late stage tumor bearing mouse model in terms of antitumoral and antimetastatic efficacy of CPT bound to polycationic CD nanoparticles in comparison to free CPT. In addition, the gastrointestinal localization of a single administration of fluorescent dye loaded polycationic CD nanoparticles in the gastrointestinal tract at the end of 24 hours after oral administration was also imaged and evaluated by in vivo imaging system against fluorescent dye intensity. Results showed that survival percentage was significantly improved in CRC-bearing mice compared to oral CPT solution, with significantly reduced colorectal tumor masses and number of liver metastatic foci (p<0.05). It was also possible to differentiate between the effectiveness of nanoparticles in early or late stages of CRC. In vivo imaging studies have also confirmed that polycationic CD nanoparticles are able to deliver the therapeutic load up to the colon and tend to accumulate especially in tumor foci, indicating an effective local treatment strategy. In addition number of liver metastases were significantly decreased with the CPT-loaded polycationic CD nanoparticle formulation in both early and late stage tumor models. These findings indicated that CPT-loaded polycationic CD nanoparticles could be an efficient oral nanocarrier formulation for anticancer molecules that have limited application because of oral bioavailability and stability problems.

Recent advances in intravital microscopy for investigation of dynamic cellular behavior in vivo

Currently, most biological research relies on conventional experimental techniques that allow only static analyses at certain time points in vitro or ex vivo. However, if one could visualize cellular dynamics in living organisms, that would provide a unique opportunity to study key biological phenomena in vivo. Intravital microscopy (IVM) encompasses diverse optical systems for direct viewing of objects, including biological structures and individual cells in live animals. With the current development of devices and techniques, IVM addresses important questions in various fields of biological and biomedical sciences. In this mini-review, we provide a general introduction to IVM and examples of recent applications in the field of immunology, oncology, and vascular biology. We also introduce an advanced type of IVM, dubbed real-time IVM, equipped with video-rate resonant scanning. Since the real-time IVM can render cellular dynamics with high temporal resolution in vivo, it allows visualization and analysis of rapid biological processes.

Mouse models of colorectal cancer: Past, present and future perspectives

Colorectal cancer (CRC) is the third most common diagnosed malignancy among both sexes in the United States as well as in the European Union. While the incidence and mortality rates in western, high developed countries are declining, reflecting the success of screening programs and improved treatment regimen, a rise of the overall global CRC burden can be observed due to lifestyle changes paralleling an increasing human development index. Despite a growing insight into the biology of CRC and many therapeutic improvements in the recent decades, preclinical in vivo models are still indispensable for the development of new treatment approaches. Since the development of carcinogen-induced rodent models for CRC more than 80 years ago, a plethora of animal models has been established to study colon cancer biology. Despite tenuous invasiveness and metastatic behavior, these models are useful for chemoprevention studies and to evaluate colitis-related carcinogenesis. Genetically engineered mouse models (GEMM) mirror the pathogenesis of sporadic as well as inherited CRC depending on the specific molecular pathways activated or inhibited. Although the vast majority of CRC GEMM lack invasiveness, metastasis and tumor heterogeneity, they still have proven useful for examination of the tumor microenvironment as well as systemic immune responses; thus, supporting development of new therapeutic avenues. Induction of metastatic disease by orthotopic injection of CRC cell lines is possible, but the so generated models lack genetic diversity and the number of suited cell lines is very limited. Patient-derived xenografts, in contrast, maintain the pathological and molecular characteristics of the individual patient’s CRC after subcutaneous implantation into immunodeficient mice and are therefore most reliable for preclinical drug development – even in comparison to GEMM or cell line-based analyses. However, subcutaneous patient-derived xenograft models are less suitable for studying most aspects of the tumor microenvironment and anti-tumoral immune responses. The authors review the distinct mouse models of CRC with an emphasis on their clinical relevance and shed light on the latest developments in the field of preclinical CRC models.