Detection of DSS-induced gastrointestinal mucositis in mice by non-invasive optical near-infrared (NIR) imaging of cathepsin activity

High Spatial and Temporal Resolution NIR-IIb Gastrointestinal Imaging in Mice

Conventional biomedical imaging modalities, including endoscopy, X-rays, and magnetic resonance, are invasive and insufficient in spatial and temporal resolutions for gastrointestinal (GI) tract imaging to guide prognosis and therapy. Here we report a noninvasive method based on lanthanide-doped nanocrystals with ∼1530 nm fluorescence in the near-infrared-IIb window (NIR-IIb, 1500-1700 nm). The rational design of nanocrystals have led to an absolute quantum yield (QY) up to 48.6%. Further benefiting from the minimized scattering through the NIR-IIb window, we enhanced the spatial resolution to ∼1 mm in GI tract imaging, which is ∼3 times higher compared with the near-infrared-IIa (NIR-IIa, 1000-1500 nm) method. The approach also realized a high temporal resolution of 8 frames per second; thus the moment of mice intestinal peristalsis can be captured. Furthermore, with a light-sheet imaging system, we demonstrated a three-dimensional (3D) imaging on the GI tract. Moreover, we successfully translated these advances to diagnose inflammatory bowel disease.

Receptor-mediated targeted drug delivery systems for treatment of inflammatory bowel disease: Opportunities and emerging strategies

Inflammatory bowel disease (IBD) is a chronic intestinal disease with painful clinical manifestations and high risks of cancerization. With no curative therapy for IBD at present, the development of effective therapeutics is highly advocated. Drug delivery systems have been extensively studied to transmit therapeutics to inflamed colon sites through the enhanced permeability and retention (EPR) effect caused by the inflammation. However, the drug still could not achieve effective concentration value that merely utilized on EPR effect and display better therapeutic efficacy in the inflamed region because of nontargeted drug release. Substantial researches have shown that some specific receptors and cell adhesion molecules highly expresses on the surface of colonic endothelial and/or immune cells when IBD occurs, ligand-modified drug delivery systems targeting such receptors and cell adhesion molecules can specifically deliver drug into inflamed sites and obtain great curative effects. This review introduces the overexpressed receptors and cell adhesion molecules in inflamed colon sites and retrospects the drug delivery systems functionalized by related ligands. Finally, challenges and future directions in this field are presented to advance the development of the receptor-mediated targeted drug delivery systems for the therapy of IBD.

Toward Molecular Imaging of Intestinal Pathology

Inflammatory bowel disease (IBD) is defined by a chronic relapsing and remitting inflammation of the gastrointestinal tract, with intestinal fibrosis being a major complication. The etiology of IBD remains unknown, but it is thought to arise from a dysregulated and excessive immune response to gut luminal microbes triggered by genetic and environmental factors. To date, IBD has no cure, and treatments are currently directed at relieving symptoms and treating inflammation. The current diagnostic of IBD relies on endoscopy, which is invasive and does not provide information on the presence of extraluminal complications and molecular aspect of the disease. Cross-sectional imaging modalities such as computed tomography enterography (CTE), magnetic resonance enterography (MRE), positron emission tomography (PET), single photon emission computed tomography (SPECT), and hybrid modalities have demonstrated high accuracy for the diagnosis of IBD and can provide both functional and morphological information when combined with the use of molecular imaging probes. This review presents the state-of-the-art imaging techniques and molecular imaging approaches in the field of IBD and points out future directions that could help improve our understanding of IBD pathological processes, along with the development of efficient treatments.

Near infrared readouts offer sensitive and rapid assessments of intestinal permeability and disease severity in inflammatory bowel disease models

Intestinal permeability and neutrophil activity are closely linked to inflammatory bowel disease (IBD) pathophysiology. Here we discuss two techniques for assessing permeability and neutrophil activity in mouse IBD models using near infrared (NIR) detection. To address the limitation of visible light readouts-namely high background-IRDye 800CW was used to enable rapid, non-terminal measurements of intestinal permeability. The increased sensitivity of NIR readouts for colon permeability is shown using dextran sulfate sodium (DSS) and anti-CD40 murine colitis models in response to interleukin-22 immunoglobulin Fc (IL22Fc) fusion protein and anti-p40 monoclonal antibody treatments, respectively. In addition to enhanced permeability, elevated levels of neutrophil elastase (NE) have been reported in inflamed colonic mucosal tissue. Activatable NIR fluorescent probes have been extensively used for disease activity evaluation in oncologic animal models, and we demonstrate their translatability using a NE-activatable reagent to evaluate inflammation in DSS mice. Confocal laser endomicroscopy (CLE) and tissue imaging allow visualization of spatial NE activity throughout diseased colon as well as changes in disease severity from IL22Fc treatment. Our findings with the 800CW dye and the NE probe highlight the ease of their implementation in preclinical IBD research.

Agonists of the TRAIL Death Receptor DR5 Sensitize Intestinal Stem Cells to Chemotherapy-Induced Cell Death and Trigger Gastrointestinal Toxicity

The combination of TRAIL death receptor agonists and radiochemotherapy to treat advanced cancers continues to be investigated in clinical trials. We previously showed that normal cells with a functional DNA damage response (DDR) upregulate the expression of death-inducing receptor DR5/TRAILR2/TNFRSF10B in a p53-dependent manner that sensitizes them to treatment with DR5 agonists. However, it is unclear if targeting DR5 selectively sensitizes cancer cells to agonist treatment following exposure to DNA-damaging chemotherapy, and to what extent normal tissues are targeted. Here, we show that the combined administration of the DR5 agonistic monoclonal antibody (mAb) and chemotherapy to wild-type mice triggered synergistic gastrointestinal toxicities (GIT) that were associated with the death of Lgr5(+) crypt base columnar stem cells in a p53- and DR5-dependent manner. Furthermore, we confirmed that normal human epithelial cells treated with the human DR5-agonistic mAb and chemotherapeutic agents were also greatly sensitized to cell death. Interestingly, our data also indicated that genetic or pharmacologic targeting of Chk2 may counteract GIT without negatively affecting the antitumor responses of combined DR5 agonist/chemotherapy treatment, further linking the DDR to TRAIL death receptor signaling in normal cells. In conclusion, the combination of DR5-targeting agonistic mAbs with DNA damaging chemotherapy may pose a risk of developing toxicity-induced conditions, and the effects of mAb-based strategies on the dose-limiting toxicity of chemotherapy must be considered when establishing new combination therapies.

Molecular imaging of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a kind of chronic non-specific intestinal inflammatory disease of unknown etiology. Traditional imaging is difficult for early detection of mucosal lesions and is not conducive to early treatment. Colonoscopy is a kind of invasive procedure, and its clinical use is therefore limited. Molecular imaging provides a new approach for early diagnosis of IBD. In this paper, we review recent advances in molecular imaging of IBD.