In vivo MRI virtual colonography in a mouse model of colon cancer

Exceptionally Mild and High-Yielding Synthesis of Vinyl Esters of Alpha-Ketocarboxylic Acids, Including Vinyl Pyruvate, for Parahydrogen-Enhanced Metabolic Spectroscopy and Imaging

Metabolic changes often occur long before pathologies manifest and treatment becomes challenging. As key elements of energy metabolism, α-ketocarboxylic acids (α-KCA) are particularly interesting, e.g., as the upregulation of pyruvate to lactate conversion is a hallmark of cancer (Warburg effect). Magnetic resonance imaging with hyperpolarized metabolites has enabled imaging of this effect non-invasively and in vivo, allowing the early detection of cancerous tissue and its treatment. Hyperpolarization by means of dynamic nuclear polarization, however, is complex, slow, and expensive, while available precursors often limit parahydrogen-based alternatives. Here, we report the synthesis for novel 13C, deuterated ketocarboxylic acids, and a much-improved synthesis of 1-13C-vinyl pruvate-d6, arguably the most promising tracer for hyperpolarizing pyruvate using parahydrogen-induced hyperpolarization by side arm hydrogenation. The new synthesis is scalable and provides a high yield of 52%. We elucidated the mechanism of our Pd-catalyzed trans-vinylation reaction. Hydrogenation with parahydrogen allowed us to monitor the addition, which was found to depend on the electron demand of the vinyl ester. Electron-poor α-keto vinyl esters react slower than "normal" alkyl vinyl esters. This synthesis of 13C, deuterated α-ketocarboxylic acids opens up an entirely new class of biomolecules for fast and cost-efficient hyperpolarization with parahydrogen and their use for metabolic imaging.

Oral fullerene tablets for colorectal cancer therapy based on modulation of tumor inflammatory microenvironments

The development and progression of colorectal cancer (CRC) are highly dependent on the long-term inflammatory microenvironment with immune dysregulation in the colorectum. However, effective therapeutics are limited to targeting CRC. Here, we developed oral fullerene tablets (OFTs) that can act directly on the colorectal site by oral administration and reduce the inflammatory state at the tumor site for effective CRC therapy. In detail, OFTs scavenged reactive oxygen species (ROS), restrained the mutation of the wild-type P53, inhibited the activation of the inflammatory pathway nuclear factor-κB (NF-κB) and the signal transducer and activator of transcription 3 (STAT3) in the colorectum of CRC mice. Subsequently, OFTs could greatly reduce the infiltration of pro-inflammatory M1 macrophages and neutrophils at the tumor site, restoring the inflammatory microenvironment and immune homeostasis in the colorectal region, and ultimately achieving the inhibition of CRC. In addition, there were no significant toxic side effects of the long-term administration of OFTs. Our work provides an effective oral therapeutic strategy for CRC therapy by modulating the colorectal tumor inflammatory microenvironment and sheds light on the route for oral nano-materials in the clinical treatment of CRC.

Visualization of Inflammation in Experimental Colitis by Magnetic Resonance Imaging Using Very Small Superparamagnetic Iron Oxide Particles

Inflammatory bowel diseases (IBD) comprise mainly ulcerative colitis (UC) and Crohn´s disease (CD). Both forms present with a chronic inflammation of the (gastro) intestinal tract, which induces excessive changes in the composition of the associated extracellular matrix (ECM). In UC, the inflammation is limited to the colon, whereas it can occur throughout the entire gastrointestinal tract in CD. Tools for early diagnosis of IBD are still very limited and highly invasive and measures for standardized evaluation of structural changes are scarce. To investigate an efficient non-invasive way of diagnosing intestinal inflammation and early changes of the ECM, very small superparamagnetic iron oxide nanoparticles (VSOPs) in magnetic resonance imaging (MRI) were applied in two mouse models of experimental colitis: the dextran sulfate sodium (DSS)-induced colitis and the transfer model of colitis. For further validation of ECM changes and inflammation, tissue sections were analyzed by immunohistochemistry. For in depth ex-vivo investigation of VSOPs localization within the tissue, Europium-doped VSOPs served to visualize the contrast agent by imaging mass cytometry (IMC). VSOPs accumulation in the inflamed colon wall of DSS-induced colitis mice was visualized in T₂* weighted MRI scans. Components of the ECM, especially the hyaluronic acid content, were found to influence VSOPs binding. Using IMC, co-localization of VSOPs with macrophages and endothelial cells in colon tissue was shown. In contrast to the DSS model, colonic inflammation could not be visualized with VSOP-enhanced MRI in transfer colitis. VSOPs present a potential contrast agent for contrast-enhanced MRI to detect intestinal inflammation in mice at an early stage and in a less invasive manner depending on hyaluronic acid content.

Mapping kidney tubule diameter ex vivo by diffusion MRI

Tubular pathologies are a common feature of kidney disease. Current metrics to assess kidney health, in vivo or in transplant, are generally based on urinary or serum biomarkers and pathological findings from kidney biopsies. Biopsies, usually taken from the kidney cortex, are invasive and prone to sampling error. Tools to directly and noninvasively measure tubular pathology could provide a new approach to assess kidney health. This study used diffusion magnetic resonance imaging (dMRI) as a noninvasive tool to measure the size of the tubular lumen in ex vivo, perfused kidneys. We first used Monte Carlo simulations to demonstrate that dMRI is sensitive to restricted tissue water diffusion at the scale of the kidney tubule. We applied dMRI and biophysical modeling to examine the distribution of tubular diameters in ex vivo, fixed kidneys from mice, rats, and a human donor. The biophysical model to fit the dMRI signal was based on a superposition of freely diffusing water and water diffusing inside infinitely long cylinders of different diameters. Tubular diameters measured by dMRI were within 10% of those measured by histology within the same tissue. Finally, we applied dMRI to investigate kidney pathology in a mouse model of folic-acid-induced acute kidney injury. dMRI detected heterogeneity in the distribution of tubules within the kidney cortex of mice with acute kidney injury compared with control mice. We conclude that dMRI can be used to measure the distribution of tubule diameters in the kidney cortex ex vivo and that dMRI may provide a new noninvasive biomarker of tubular pathology.NEW & NOTEWORTHY Tubular pathologies are a common feature of kidney disease. Current metrics to assess kidney health, in vivo or in transplant, are generally based on urinary or serum biomarkers and pathological findings from kidney biopsies. Diffusion MRI can be used to measure the distribution of tubule diameters in the kidney cortex ex vivo and may provide a new noninvasive biomarker of tubular pathology.

Manganese threonine chelate-a new enteric contrast agent for MRI: a pilot study on rats

Enteric contrast agents are important in gastrointestinal MRI. However, no currently available agent is well established as the standard of care. In this study, in vitro relaxivities of manganese threonine chelate (Mn-Thr), a common nutritional food supplement, were measured at 1.5 T and 3 T with further investigation of its efficacy and safety in vivo as an enteric contrast agent. According to the calculated relaxivities, T₁ W and T₂ W TSE sequences of Mn-Thr solutions at different concentrations were acquired, and the optimal concentration for dark lumen imaging on both T₁ W and T₂ W images was determined in vitro. To validate the optimal concentration in vivo, eight Sprague-Dawley rats were randomly divided into two groups. Each group received rectal injection of either 2.00 g/L (about 3.80 mM) Mn-Thr or saline as an enteric contrast agent and underwent MRI. After a time interval of one week, the same procedures were repeated with the alternative contrast agent. Animals were sacrificed after the second MRI. Tissue manganese quantification and histopathological examination were obtained. Qualitative MR image quality assessments were performed and compared between Mn-Thr and saline. Measured T₁ and T₂ relaxivities of Mn-Thr were significantly higher than those of MnCl₂ in vitro (p < 0.05). At the concentration of 2.00 g/L (about 3.80 mM), Mn-Thr produced a dark lumen on T₁ W and T₂ W images both in vitro and in vivo. Compared with saline, Mn-Thr showed significantly more homogenous luminal signal and increased bowel wall conspicuity in image quality assessments. Tissue manganese concentrations were not significantly different between two groups. Histopathological examinations were normal in both groups. Our data suggest that Mn-Thr possesses favorable paramagnetic properties and can create a homogenous dark lumen on T₁ W and T₂ W images without obvious side effects in healthy rats. As a commercially available nutritional food supplement, Mn-Thr appears to be a promising enteric contrast agent for MRI.

Magnetic Resonance Colonography Enables the Efficacy Assessment of Immune Checkpoint Inhibitors in an Orthotopic Colorectal Cancer Mouse Model

Immune checkpoint inhibitors (ICIs) have become an effective therapeutic option for colorectal cancer and studies on these drugs have therefore increased greatly. Efficacy assessments of ICIs in preclinical orthotopic colorectal cancer using MRI have not been reported however due to the difficulties in conducting colorectal imaging. The purpose of this present study was to investigate the feasibility of using magnetic resonance colonography (MRC) to evaluate the efficacy of an ICI, an anti-PD-L1 antibody, in an orthotopic colorectal cancer mouse model. The mouse model was generated by the engraftment of colorectal cancer cells into the submucosal layer of the colon. Anti-cancer efficacy was assessed by tumor volume and metastatic tumor number analyses, and these values were significantly lower in the PD-L1 antibody-treated group compared to the controls. Histological analyses using H&E and Ki-67 immunohistochemical staining confirmed a highly efficacious tumor growth inhibition and enhanced infiltration by CD4+ and CD8+ lymphocytes in the PD-L1 antibody-treated group. We conclude that MRC has the potential to be used for ICI efficacy assessments against orthotopic colorectal cancer mouse model.

Hyaluronate-Peanut Agglutinin Conjugates for Target-Specific Bioimaging of Colon Cancer

Colon cancer is one of the most common death-related cancers in the world. For treating colon cancer, it is crucial to detect and remove malignant lesions early. Here, we developed hyaluronate (HA)-peanut agglutinin (PNA) conjugates for the bioimaging of colon cancer. The HA-PNA conjugates were successfully synthesized by the coupling reaction between aldehyde-modified HA and the N-terminal amine group of PNA. For diagnostic imaging, rhodamine B (RhoB) was chemically conjugated onto PNA in HA-PNA conjugates. After intraluminal injection of HA-PNA-RhoB conjugates into tumor-bearing mice, small-sized colon cancers could be effectively visualized by ex vivo imaging with an in vivo imaging system (IVIS) and a two-photon microscope. With these results taken together, we could confirm the feasibility of HA-PNA-RhoB conjugates as a bioimaging agent for detecting colon cancers.

Noninvasive Longitudinal Study of a Magnetic Resonance Imaging Biomarker for the Quantification of Colon Inflammation in a Mouse Model of Colitis

BACKGROUND

Colonoscopy is the gold standard to diagnose and follow up the evolution of inflammatory bowel diseases. However, this technique can still present a risk of severe complications, a general discomfort in patients, and its diagnostic value is limited to the visualization of the colon mucosal changes. Magnetic resonance imaging (MRI) is emerging as a noninvasive imaging technique of choice to overcome these limitations. The aim of this work was to evaluate the potential of colon wall thickness measured using MRI as an in vivo imaging biomarker of inflammation for inflammatory bowel disease in an animal model of this disease.

METHODS

On day 0, 2% or 3% Dextran sodium sulfate was added to the drinking water of mice (n = 10/group) for 5 days. Six mice were left as controls. Animals were imaged with colonoscopy and MRI on days 7, 11, and 21 to study the colitis progression. Histology was performed at the end of the protocol.

RESULTS

The colon wall thickness measured in Dextran sodium sulfate-treated animals was shown to be significantly and dose dependently increased compared to controls. Colonoscopy showed similar results and excellently correlated with MRI measurements and histology. The proposed protocol showed high robustness, with negligible interoperator and intraoperator variability.

CONCLUSIONS

The findings of this investigation suggest the feasibility of using MRI for the noninvasive assessment of colon wall thickness as a robust surrogate biomarker for colon inflammation detection and follow-up. The data presented show the potential of MRI in in vivo preclinical longitudinal studies, including testing of new drugs or investigation of inflammatory bowel disease development mechanisms.

Magnetism in living magnetically-induced bacteria

Artificial magnetically-induced bacteria (AMB) exhibited a magnetic dilution during proliferation. The anisotropic magnetic properties of the 1D AMB nanostructure are enhanced similarly to magnetosomes inside the magnetotactic bacteria.

Assessment of colon and bladder crosstalk in an experimental colitis model using contrast-enhanced magnetic resonance imaging

BACKGROUND

Inflammatory bowel disease (IBD) consists of two chronic remitting-relapsing inflammatory disorders in the colon referred to as ulcerative colitis and Crohn's disease (CD). Inflammatory bowel disease affects about 1.4 million Americans. 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis is a widely used model of experimental intestinal inflammation with characteristic transmural and segmental lesions that are similar to CD.

METHODS

Here, we report on the use of contrast-enhanced magnetic resonance imaging (CE-MRI) to monitor in vivo bladder permeability changes resulting from bladder crosstalk following colon TNBS exposure, and TNBS-induced colitis. Changes in MRI signal intensities and histology were evaluated for both colon and bladder regions.

KEY RESULTS

Uptake of contrast agent in the colon demonstrated a significant increase in signal intensity (SI) for TNBS-exposed rats (p < 0.01) compared to controls. In addition, a significant increase in bladder SI for colon TNBS-exposed rats (p < 0.001) was observed compared to saline controls. Histological damage within the colon was observed, however, bladder histology indicated a normal urothelium in rats with TNBS-induced colitis, despite increased permeability seen by CE-MRI.

CONCLUSIONS & INFERENCES

Contrast-enhanced MRI was able to quantitatively measure inflammation associated with TNBS-induced colitis, and assess bladder crosstalk measured as an increase in urothelial permeability. Although CE-MRI is routinely used to assess inflammation with IBD, currently there is no diagnostic test to assess bladder crosstalk with this disease, and our developed method may be useful in providing crosstalk information between organ and tissue systems in IBD patients, in addition to colitis.