Three-dimensional Deep-tissue Functional and Molecular Imaging by Integrated Photoacoustic, Ultrasound, and Angiographic Tomography (PAUSAT)

Non-invasive small-animal imaging technologies, such as optical imaging, magnetic resonance imaging and x-ray computed tomography, have enabled researchers to study normal biological phenomena or disease progression in their native conditions. However, existing small-animal imaging technologies often lack either the penetration capability for interrogating deep tissues (e.g., optical microscopy), or the functional and molecular sensitivity for tracking specific activities (e.g., magnetic resonance imaging). To achieve functional and molecular imaging in deep tissues, we have developed an integrated photoacoustic, ultrasound and angiographic tomography (PAUSAT) system by seamlessly combining light and ultrasound in a non-invasive manner. PAUSAT can perform three imaging functions simultaneously with complementary contrast: high-frequency B-mode ultrasound imaging of tissue morphology, microbubble-enabled acoustic angiography of vasculature, and multi-spectral photoacoustic imaging of molecular probes. PAUSAT can provide three-dimensional (3D) multi-contrast images that are automatically co-registered, with high spatial resolutions at large depth. Using PAUSAT, we conducted proof-of-concept in vivo experiments on various small animal models: monitoring longitudinal development of placenta and embryo during mouse pregnancy, tracking biodistribution and metabolism of near-infrared organic dye on the whole-body scale, and detecting genetically-encoded breast tumor expressing photoswitchable phytochromes. These results have collectively demonstrated that PAUSAT has broad applicability in biomedical research, providing comprehensive structural, functional, and molecular imaging of small animal models.

Persistent luminescence materials for deep photodynamic therapy

Persistent luminescence (PerL) materials continue emitting light long after their excitation has stopped. Prepared in the form of nanoparticles they revealed their full potential as bio-nanoprobes for in vivo small animal imaging in the last 15 years. PerL materials enable to overcome the limitation of weak light penetration in living tissues. As such, they constitute remarkable light mediators to implement photodynamic therapy (PDT) in deep-seated tissues. This article reviews the recent achievements in PerL-mediated PDT in vitro as well as in small animal cancer models in vivo. PerL-mediated PDT is realized through the smart choice of a tandem of a PerL material and a photosensitizer (PS). The physical association of the PerL material and the PS as well as their targeting ability is debated. Implants or mesoporous nanoparticles emerge as particularly valuable cargos that further permit multimodality in imaging or therapy. The diversity of charge-trapping mechanisms in a few PerL materials enables a large versatility in the excitation protocols. Although the PerL agent can be pre-excited by UV light before its introduction into the animal, it also induces effective PDT after simple infrared or visible LED illumination across tissues as well as after a mild X-ray irradiation.

Development of a High-resolution SSR-SPECT System for Preclinical Imaging and Neuroimaging

The utility of animal models in preclinical research has been increasing by the availability of methods for in vivo imaging. In particular, techniques like single photon emission computed tomography (SPECT) show high potential, which is usually limited by spatial resolution. This represents an important parameter influencing scanner design, given the small size of the anatomical structures to be investigated. The purpose of the present work was to assess the performance of a scintigraphic system with improved spatial resolution based on our previous detector by applying the Super Spatial Resolution (SSR). Our dual-head SPECT system is composed of gamma cameras based on the Hamamatsu H13700 position-sensitive photomultiplier tube (PSPMT). In each detector head, the PSPMT is coupled to a 28×28 array of CRY018 scintillation crystals. The pure Tungsten parallel square hole collimator ensures the position sensitivity, and a dedicated resistive chain readout so as an ADC board have been proprietary designed. To finalize the mechanical development of the SSR-SPECT system several tests were carried out. Based on the results obtained in the test phase, a partial review of the mechanical design was performed. Then a dedicated machine handling software was developed, and in particular, a kinematic software debugging and testing was assessed. Finally, several experiments were carried out by using Derenzo phantoms and capillaries filled with radioactive sources. Finally, the performance of our system was evaluated performing small animal imaging studies. The SPECT spatial resolution was experimentally determined to be about 1.6 mm. We reach a resolution of 1.18 mm by applying the SSR based on two images. The results of this study demonstrated the good capability of the system as a suitable tool for preclinical imaging especially in fields like neuroscience for the study of small brain structures.

Qigefang inhibits migration, invasion and metastasis of ESCC by inhibiting Gas6/Axl signaling pathway

Background: In recent years, there is an increasing interest in using Traditional Chinese medicine (TCM) and their patents for the treatment of cancers. Qigefang (QGF) is a TCM formula and has been used for the treatment of metastatic esophageal cancer in China. However, its therapeutic effect on tumors and its mechanism of action are largely unknown. The aim of this study is to explore the role of QGF in the treatment of metastasis of esophageal squamous cell carcinoma（ESCC）. Methods: Human esophageal carcinoma cell line KYSE150 was used for this study. CCK-8 assay was used to determine the cytotoxicity of QGF. The KYSE150 cells were treated with QGF to determine its effect on cell migration (cell scratch assay and imaging) and invasion (Transwell system based with Matrigel assay). Western blotting was used to investigate the effect of QGF on relevant molecules of signaling pathways. A mouse model of lung metastasis of esophageal cancer was established by injecting the KYSE150-Luc cells through the tail vein. Small animal imaging system was used to observe tumor metastasis in the mice. Results: QGF reduced cell migration and invasion of KYSE150 cells. QGF significantly inhibited lung metastasis in nude mice. Further study revealed that the expression of Growth arrest-specific 6 (Gas6), Anexelekto (Axl), N-nuclear factor-kappa B (NF-κB) and matrix metalloproteinase-9 (MMP-9) proteins were decreased both in vitro and in vivo upon treatment with QGF. Conclusion: QGF could prevent invasion and metastasis of esophageal cancer by inhibiting the Gas6/Axl signaling pathway

Bioinspired Long-Wavelength Excitable Near-Infrared AIEdots for Endometriosis Targeting and Image-Guided Surgery

Endometriosis（EM）is a non-cancerous and intractable disease in clinic due to the ambiguity of its etiology and mechanism. Surgical removal of the lesions is more efficient method for EM treatment compared with pharmacological intervention. Intraoperative identification of the endometrial ectopic sites is a prerequisite, however, available probes with high specificity remain limited, owing to lack of specific biomarkers. Here, based on a polypeptide derived from VAR2CSA protein (CSA) and a near-infrared AIE material (TPA-TBZ-2), we prepared a CSA AIEdots capable of labeling the EM lesions by a one-step nanoprecipitation method. The nanodots have an absorbance maximum at 610 nm with a wide emission range from 650 to 850 nm and an absolute quantum yield of up to 34% in the aggregation states. Through in vitro assay, the dots could specifically label endometrioid cells (Ishikawa cells), and flow cytometry experiments showed its specific spectral absorption peak, compared with empty particles and scrambled peptide groups. Next, to verify the ability of the dots to label the ectopic endometrium in vivo, we established a mouse model of endometriosis. After injection the dots into model mouse intravenously for 24 hours, the AIE signaling could be specifically detected at the ectopic lesions in an IVIS small animal imaging system. The CSA AIEdots were further used for image-guided EM resection in vivo and showed a high EM-to-normal tissue signal ratio. Taken together, our AIE nanodots-based EM diagnosis system is a promising candidate for EM development monitoring and surgical navigations. <br>

Bioinspired Long-Wavelength Excitable Near-Infrared AIEdots for Endometriosis Targeting and Image-Guided Surgery

Endometriosis（EM）is a non-cancerous and intractable disease in clinic due to the ambiguity of its etiology and mechanism. Surgical removal of the lesions is more efficient method for EM treatment compared with pharmacological intervention. Intraoperative identification of the endometrial ectopic sites is a prerequisite, however, available probes with high specificity remain limited, owing to lack of specific biomarkers. Here, based on a polypeptide derived from VAR2CSA protein (CSA) and a near-infrared AIE material (TPA-TBZ-2), we prepared a CSA AIEdots capable of labeling the EM lesions by a one-step nanoprecipitation method. The nanodots have an absorbance maximum at 610 nm with a wide emission range from 650 to 850 nm and an absolute quantum yield of up to 34% in the aggregation states. Through in vitro assay, the dots could specifically label endometrioid cells (Ishikawa cells), and flow cytometry experiments showed its specific spectral absorption peak, compared with empty particles and scrambled peptide groups. Next, to verify the ability of the dots to label the ectopic endometrium in vivo, we established a mouse model of endometriosis. After injection the dots into model mouse intravenously for 24 hours, the AIE signaling could be specifically detected at the ectopic lesions in an IVIS small animal imaging system. The CSA AIEdots were further used for image-guided EM resection in vivo and showed a high EM-to-normal tissue signal ratio. Taken together, our AIE nanodots-based EM diagnosis system is a promising candidate for EM development monitoring and surgical navigations. <br>

Design and Implementation of the Pre-Clinical DICOM Standard in Multi-Cohort Murine Studies

The small animal imaging Digital Imaging and Communications in Medicine (DICOM) acquisition context structured report (SR) was developed to incorporate pre-clinical data in an established DICOM format for rapid queries and comparison of clinical and non-clinical datasets. Established terminologies (i.e., anesthesia, mouse model nomenclature, veterinary definitions, NCI Metathesaurus) were utilized to assist in defining terms implemented in pre-clinical imaging and new codes were added to integrate the specific small animal procedures and handling processes, such as housing, biosafety level, and pre-imaging rodent preparation. In addition to the standard DICOM fields, the small animal SR includes fields specific to small animal imaging such as tumor graft (i.e., melanoma), tissue of origin, mouse strain, and exogenous material, including the date and site of injection. Additionally, the mapping and harmonization developed by the Mouse-Human Anatomy Project were implemented to assist co-clinical research by providing cross-reference human-to-mouse anatomies. Furthermore, since small animal imaging performs multi-mouse imaging for high throughput, and queries for co-clinical research requires a one-to-one relation, an imaging splitting routine was developed, new Unique Identifiers (UID’s) were created, and the original patient name and ID were saved for reference to the original dataset. We report the implementation of the small animal SR using MRI datasets (as an example) of patient-derived xenograft mouse models and uploaded to The Cancer Imaging Archive (TCIA) for public dissemination, and also implemented this on PET/CT datasets. The small animal SR enhancement provides researchers the ability to query any DICOM modality pre-clinical and clinical datasets using standard vocabularies and enhances co-clinical studies.

Role of Nuclear Imaging to Understand the Neural Substrates of Brain Disorders in Laboratory Animals: Current Status and Future Prospects

Molecular imaging, which allows the real-time visualization, characterization and measurement of biological processes, is becoming increasingly used in neuroscience research. Scintigraphy techniques such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) provide qualitative and quantitative measurement of brain activity in both physiological and pathological states. Laboratory animals, and rodents in particular, are essential in neuroscience research, providing plenty of models of brain disorders. The development of innovative high-resolution small animal imaging systems together with their radiotracers pave the way to the study of brain functioning and neurotransmitter release during behavioral tasks in rodents. The assessment of local changes in the release of neurotransmitters associated with the performance of a given behavioral task is a turning point for the development of new potential drugs for psychiatric and neurological disorders. This review addresses the role of SPECT and PET small animal imaging systems for a better understanding of brain functioning in health and disease states. Brain imaging in rodent models faces a series of challenges since it acts within the boundaries of current imaging in terms of sensitivity and spatial resolution. Several topics are discussed, including technical considerations regarding the strengths and weaknesses of both technologies. Moreover, the application of some of the radioligands developed for small animal nuclear imaging studies is discussed. Then, we examine the changes in metabolic and neurotransmitter activity in various brain areas during task-induced neural activation with special regard to the imaging of opioid, dopaminergic and cannabinoid receptors. Finally, we discuss the current status providing future perspectives on the most innovative imaging techniques in small laboratory animals. The challenges and solutions discussed here might be useful to better understand brain functioning allowing the translation of preclinical results into clinical applications.