3D molecular MR imaging of liver fibrosis and response to rapamycin therapy in a bile duct ligation rat model

The transcription factor mesenchyme homeobox 1 exacerbates hepatic fibrosis by transcriptional activation of connective tissue growth factor

As a chronic condition, liver fibrosis is characterized by diverse etiological factors, and the pivotal event to its pathogenesis is the activation of quiescent hepatic stellate cells (HSCs) into myofibroblasts. Mesenchyme homeobox 1 (MEOX1) is a transcription factors central to cellular development and differentiation. However, the role of MEOX1 signaling in hepatic fibrosis still remains largely unknown. In this study, we investigated the potential role and mechanism of MEOX1 in liver fibrosis using different models in vivo and in vitro. The hepatic expression of MEOX1 exhibited a positive correlation with the degree of fibrosis in patients diagnosed with non-alcoholic steatohepatitis (NASH), as determined through bioinformatics analysis. Furthermore, MEOX1 demonstrated high expression levels in activated HSCs and fibrotic liver tissues induced by methionine and choline-deficient diet (MCD), thioacetamide (TAA), or carbon tetrachloride (CCl4) treatment in C57/BL6 mice. Mechanistically, MEOX1 facilitated HSC activation, proliferation, and migration. The comprehensive analysis of transcriptome sequencing and chromatin immunoprecipitation sequencing data revealed that connective tissue growth factor (CTGF) served as a target gene for MEOX1 in HSCs. Specifically, MEOX1 bound to the promoter region of CTGF and enhanced its transcriptional activity, thereby mediating the exacerbating effect of MEOX1 on hepatic fibrosis. In conclusion, our current findings elucidate the role of MEOX1 in exacerbating hepatic fibrosis progression through transcriptional activation of CTGF. Our findings provide valuable insights into the therapeutic potential of targeting MEOX1 for the treatment of hepatic fibrosis.

FAP-catalyzed in situ self-assembly of magnetic resonance imaging probe for early and precise staging of liver fibrosis

Liver fibrosis is an inevitable stage in the progression of most chronic liver diseases. Early diagnosis and treatment of liver fibrosis are crucial for effectively managing chronic liver conditions. However, there lacks a noninvasive and sensitive imaging method capable of early assessing fibrosis activity. Here, we report a molecular magnetic resonance imaging (MRI) probe for imaging fibroblast activation protein (FAP), which is overexpressed on activated hepatic stellate cells (HSCs) even in very early fibrotic livers. This method relies on FAP-catalyzed in situ self-assembly of its substrate probe that leads to the increase of the rotational correlation time (τR) of probe, thereby notably amplifies T1 MRI signal. Thanks to the superior specificity and efficiency of enzymatic reaction, our method has been validated as highly selective and sensitive to FAP in two liver fibrosis mouse models. By establishing a direct correlation between MRI signals and fibrosis activity, our method enables continuous monitoring of liver fibrotic disease progression and assessment of treatment responses.

Collagen type I PET/MRI enables evaluation of treatment response in pancreatic cancer in pre-clinical and first-in-human translational studies

Pancreatic ductal adenocarcinoma (PDAC) is an invasive and rapidly progressive malignancy. A major challenge in patient management is the lack of a reliable imaging tool to monitor tumor response to treatment. Tumor-associated fibrosis characterized by high type I collagen is a hallmark of PDAC, and fibrosis further increases in response to neoadjuvant chemoradiotherapy (CRT). We hypothesized that molecular positron emission tomography (PET) using a type I collagen-specific imaging probe, 68Ga-CBP8 can detect and measure changes in tumor fibrosis in response to standard treatment in mouse models and patients with PDAC. Methods: We evaluated the specificity of 68Ga-CBP8 PET to tumor collagen and its ability to differentiate responders from non-responders based on the dynamic changes of fibrosis in nude mouse models of human PDAC including FOLFIRNOX-sensitive (PANC-1 and PDAC6) and FOLFIRINOX-resistant (SU.86.86). Next, we demonstrated the specificity and sensitivity of 68Ga-CBP8 to the deposited collagen in resected human PDAC and pancreas tissues. Eight male participant (49-65 y) with newly diagnosed PDAC underwent dynamic 68Ga-CBP8 PET/MRI, and five underwent follow up 68Ga-CBP8 PET/MRI after completing standard CRT. PET parameters were correlated with tumor collagen content and markers of response on histology. Results: 68Ga-CBP8 showed specific binding to PDAC compared to non-binding 68Ga-CNBP probe in two mouse models of PDAC using PET imaging and to resected human PDAC using autoradiography (P < 0.05 for all comparisons). 68Ga-CBP8 PET showed 2-fold higher tumor signal in mouse models following FOLFIRINOX treatment in PANC-1 and PDAC6 models (P < 0.01), but no significant increase after treatment in FOLFIRINOX resistant SU.86.86 model. 68Ga-CBP8 binding to resected human PDAC was significantly higher (P < 0.0001) in treated versus untreated tissue. PET/MRI of PDAC patients prior to CRT showed significantly higher 68Ga-CBP8 uptake in tumor compared to pancreas (SUVmean: 2.35 ± 0.36 vs. 1.99 ± 0.25, P = 0.036, n = 8). PET tumor values significantly increased following CRT compared to untreated tumors (SUVmean: 2.83 ± 0.30 vs. 2.25 ± 0.41, P = 0.01, n = 5). Collagen deposition significantly increased in response to CRT (59 ± 9% vs. 30 ± 9%, P=0.0005 in treated vs. untreated tumors). Tumor and pancreas collagen content showed a positive direct correlation with SUVmean (R2 = 0.54, P = 0.0007). Conclusions: This study demonstrates the specificity of 68Ga-CBP8 PET to tumor type I collagen and its ability to differentiate responders from non-responders based on the dynamic changes of fibrosis in PDAC. The results highlight the potential use of collagen PET as a non-invasive tool for monitoring response to treatment in patients with PDAC.

Simultaneous Positron Emission Tomography and Molecular Magnetic Resonance Imaging of Cardiopulmonary Fibrosis in a Mouse Model of Left Ventricular Dysfunction

BACKGROUND

Aging-associated left ventricular dysfunction promotes cardiopulmonary fibrogenic remodeling, Group 2 pulmonary hypertension (PH), and right ventricular failure. At the time of diagnosis, cardiac function has declined, and cardiopulmonary fibrosis has often developed. Here, we sought to develop a molecular positron emission tomography (PET)-magnetic resonance imaging (MRI) protocol to detect both cardiopulmonary fibrosis and fibrotic disease activity in a left ventricular dysfunction model.

METHODS AND RESULTS

Left ventricular dysfunction was induced by transverse aortic constriction (TAC) in 6-month-old senescence-accelerated prone mice, a subset of mice that received sham surgery. Three weeks after surgery, mice underwent simultaneous PET-MRI at 4.7 T. Collagen-targeted PET and fibrogenesis magnetic resonance (MR) probes were intravenously administered. PET signal was computed as myocardium- or lung-to-muscle ratio. Percent signal intensity increase and Δ lung-to-muscle ratio were computed from the pre-/postinjection magnetic resonance images. Elevated allysine in the heart (P=0.02) and lungs (P=0.17) of TAC mice corresponded to an increase in myocardial magnetic resonance imaging percent signal intensity increase (P<0.0001) and Δlung-to-muscle ratio (P<0.0001). Hydroxyproline in the heart (P<0.0001) and lungs (P<0.01) were elevated in TAC mice, which corresponded to an increase in heart (myocardium-to-muscle ratio, P=0.02) and lung (lung-to-muscle ratio, P<0.001) PET measurements. Pressure-volume loop and echocardiography demonstrated adverse left ventricular remodeling, function, and increased right ventricular systolic pressure in TAC mice.

CONCLUSIONS

Administration of collagen-targeted PET and allysine-targeted MR probes led to elevated PET-magnetic resonance imaging signals in the myocardium and lungs of TAC mice. The study demonstrates the potential to detect fibrosis and fibrogenesis in cardiopulmonary disease through a dual molecular PET-magnetic resonance imaging protocol.

Advances in Noninvasive Molecular Imaging Probes for Liver Fibrosis Diagnosis

Liver fibrosis is a wound-healing response to chronic liver injury, which may lead to cirrhosis and cancer. Early-stage fibrosis is reversible, and it is difficult to precisely diagnose with conventional imaging modalities such as magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, and ultrasound imaging. In contrast, probe-assisted molecular imaging offers a promising noninvasive approach to visualize early fibrosis changes in vivo, thus facilitating early diagnosis and staging liver fibrosis, and even monitoring of the treatment response. Here, the most recent progress in molecular imaging technologies for liver fibrosis is updated. We start by illustrating pathogenesis for liver fibrosis, which includes capillarization of liver sinusoidal endothelial cells, cellular and molecular processes involved in inflammation and fibrogenesis, as well as processes of collagen synthesis, oxidation, and cross-linking. Furthermore, the biological targets used in molecular imaging of liver fibrosis are summarized, which are composed of receptors on hepatic stellate cells, macrophages, and even liver collagen. Notably, the focus is on insights into the advances in imaging modalities developed for liver fibrosis diagnosis and the update in the corresponding contrast agents. In addition, challenges and opportunities for future research and clinical translation of the molecular imaging modalities and the contrast agents are pointed out. We hope that this review would serve as a guide for scientists and students who are interested in liver fibrosis imaging and treatment, and as well expedite the translation of molecular imaging technologies from bench to bedside.

Platelet-derived growth factor receptor β-targeted positron emission tomography imaging for the noninvasive monitoring of liver fibrosis

PURPOSE

Noninvasive quantifying activated hepatic stellate cells (aHSCs) by molecular imaging is helpful for assessing disease progression and therapeutic responses of liver fibrosis. Our purpose is to develop platelet-derived growth factor receptor β (PDGFRβ)-targeted radioactive tracer for assessing liver fibrosis by positron emission tomography (PET) imaging of aHSCs.

METHODS

Comparative transcriptomics, immunofluorescence staining and flow cytometry were used to evaluate PDGFRβ as biomarker for human aHSCs and determine the correlation of PDGFRβ with the severity of liver fibrosis. The high affinity affibody for PDGFRβ (ZPDGFRβ) was labeled with gallium-68 (68Ga) for PET imaging of mice with carbon tetrachloride (CCl4)-induced liver fibrosis. Binding of the [68Ga]Ga-labeled ZPDGFRβ ([68Ga]Ga-DOTA-ZPDGFRβ) for aHSCs in human liver tissues was measured by autoradiography.

RESULTS

PDGFRβ overexpressed in aHSCs was highly correlated with the severity of liver fibrosis in patients and CCl4-treated mice. The 68Ga-labeled ZPDGFRβ affibody ([68Ga]Ga-DOTA-ZPDGFRβ) showed PDGFRβ-dependent binding to aHSCs. According to the PET imaging, hepatic uptake of [68Ga]Ga-DOTA-ZPDGFRβ increased with the accumulation of aHSCs and collagens in the fibrotic livers of mice. In contrast, hepatic uptake of [68Ga]Ga-DOTA-ZPDGFRβ decreased with spontaneous recovery or treatment of liver fibrosis, indicating that the progression and therapeutic responses of liver fibrosis in mice could be visualized by PDGFRβ-targeted PET imaging. [68Ga]Ga-DOTA-ZPDGFRβ also bound human aHSCs and visualized fibrosis in patient-derived liver tissues.

CONCLUSIONS

PDGFRβ is a reliable biomarker for both human and mouse aHSCs. PDGFRβ-targeted PET imaging could be used for noninvasive monitoring of liver fibrosis in mice and has great potential for clinical translation.

Parathyroid hormone receptor-1 signaling aggravates hepatic fibrosis through upregulating cAMP response element-binding protein-like 2

BACKGROUND AND AIMS

Parathyroid hormone receptor-1 (PTH1R) is a class B G protein-coupled receptor central to skeletal development, bone turnover, and calcium homeostasis. However, the role of PTH1R signaling in liver fibrosis is largely unknown. Here, the role of PTH1R signaling in the activation of HSCs and hepatic fibrosis was examined.

APPROACH AND RESULTS

PTH1R was highly expressed in activated HSCs and fibrotic liver by using human liver specimens or carbon tetrachloride (CCl 4 )-treated or methionine and choline-deficient diet (MCD)-fed C57/BL6 mice. The mRNA level of hepatic PTH1R was positively correlated to α-smooth muscle actin in patients with liver cirrhosis. Mice with HSCs-specific PTH1R deletion were protected from CCl 4 , MCD, or western diet, plus low-dose CCl 4 -induced liver fibrosis. Conversely, parathyroid hormone (PTH) aggravated liver fibrosis in CCl 4 -treated mice. Mouse primary HSCs and LX2 cell lines were used for in vitro experiments. Molecular analyses by luciferase reporter assays and chromatin immunoprecipitation assays in combination with mRNA sequencing in HSCs revealed that cAMP response element-binding protein-like 2 (Crebl2), a novel regulator in HSCs treated by PTH that interacted with mothers against decapentaplegic homolog 3 (SMAD3) and increased the transcription of TGFβ in activating HSCs and collagen deposition. In agreement, HSCs-specific Crebl2 deletion ameliorated PTH-induced liver fibrosis in CCl 4 -treated mice.

CONCLUSIONS

In both mouse and human models, we found that PTH1R was highly expressed in activated HSCs and fibrotic liver. PTH1R signaling regulated collagen production in the HSCs through Crebl2/SMAD3/TGFβ regulatory circuits. Blockade of PTH1R signaling in HSCs might help mitigate the development of liver fibrosis.

Biased Quantification of Rat Liver Fibrosis-Meta-Analysis with Practical Recommendations and Clinical Implications

For liver fibrosis assessment, the liver biopsy is usually stained with Masson's trichrome (MT) or picrosirius red (PSR) to quantify liver connective tissue (LCT) for fibrosis scoring. However, several concerns of such semiquantitative assessments have been raised, and when searching for data on the amount of LCT in healthy rats, the results vastly differ. Regarding the ongoing reproducibility crisis in science, it is necessary to inspect the results and methods, and to design an unbiased and reproducible method of LCT assessment. We searched the Medline database using search terms related to liver fibrosis, LCT and collagen, rat strains, and staining methods. Our search identified 74 eligible rat groups in 57 studies. We found up to 170-fold differences in the amount of LCT among healthy Wistar and Sprague-Dawley rats, with significant differences even within individual studies. Biased sampling and quantification probably caused the observed differences. In addition, we also found incorrect handling of liver fibrosis scoring. Assessment of LCT using stereological sampling methods (such as systematic uniform sampling) would provide us with unbiased data. Such data could eventually be used not only for the objective assessment of liver fibrosis but also for validation of noninvasive methods of the assessment of early stages of liver fibrosis.

Molecular MRI quantification of extracellular aldehyde pairs for early detection of liver fibrogenesis and response to treatment

Liver fibrosis plays a critical role in the evolution of most chronic liver diseases and is characterized by a buildup of extracellular matrix, which can progress to cirrhosis, hepatocellular carcinoma, liver failure, or death. Now, there are no noninvasive methods available to accurately assess disease activity (fibrogenesis) to sensitively detect early onset of fibrosis or to detect early response to treatment. Here, we hypothesized that extracellular allysine aldehyde (LysAld) pairs formed by collagen oxidation during active fibrosis could be a target for assessing fibrogenesis with a molecular probe. We showed that molecular magnetic resonance imaging (MRI) using an extracellular probe targeting these LysAld pairs acts as a noninvasive biomarker of fibrogenesis and demonstrated its high sensitivity and specificity in detecting fibrogenesis in toxin- and dietary-induced mouse models, a cholestasis rat model of liver fibrogenesis, and in human fibrotic liver tissues. Quantitative molecular MRI was highly correlated with fibrogenesis markers and enabled noninvasive detection of early onset fibrosis and response to antifibrotic treatment, showing high potential for clinical translation.

Genomic miscellany and allelic frequencies of Plasmodium falciparum msp-1, msp-2 and glurp in parasite isolates

Introduction

The genomic miscellany of malaria parasites can help inform the intensity of malaria transmission and identify potential deficiencies in malaria control programs. This study was aimed at investigating the genomic miscellany, allele frequencies, and MOI of P. falciparum infection.

Methods

A total of 85 P. falciparum confirmed isolates out of 100 were included in this study that were collected from P. falciparum patients aged 4 months to 60 years in nine districts of Khyber Pakhtunkhwa Province. Parasite DNA was extracted from 200µL whole blood samples using the Qiagen DNA extraction kit following the manufacturer’s instructions. The polymorphic regions of msp-1, msp-2 and glurp loci were genotyped using nested PCR followed by gel electrophoresis for amplified fragments identification and subsequent data analysis.

Results

Out of 85 P. falciparum infections detected, 30 were msp-1 and 32 were msp-2 alleles specific. Successful amplification occurred in 88.23% (75/85) isolates for msp-1, 78.9% (67/85) for msp-2 and 70% (60/85) for glurp gene. In msp-1, the K1 allelic family was predominantly prevalent as 66.66% (50/75), followed by RO33 and MAD20. The frequency of samples with single infection having only K1, MAD20 and RO33 were 21.34% (16/75), 8% (6/75), and 10.67% (8/75), respectively. In msp-2, both the FC27 and 3D7 allelic families revealed almost the same frequencies as 70.14% (47/67) and 67.16% (45/67), respectively. Nine glurp RII region alleles were identified in 60 isolates. The overall mean multiplicity of infection for msp genes was 1.6 with 1.8 for msp-1 and 1.4 for msp-2, while for glurp the MOI was 1.03. There was no significant association between multiplicity of infection and age groups (Spearman’s rank coefficient = 0.050; P = 0.6) while MOI and parasite density correlated for only msp-2 allelic marker.

Conclusions

The study showed high genetic diversity and allelic frequency with multiple clones of msp-1, msp-2 and glurp in P. falciparum isolates in Khyber Pakhtunkhwa, Pakistan. In the present study the genotype data may provide valuable information essential for monitoring the impact of malaria eradication efforts in this region.

Multiparameter magnetic resonance imaging of liver fibrosis in a bile duct ligation mouse model

BACKGROUND

Bile duct ligation (BDL) in animals is a classical method for mimicking cholestatic fibrosis. Although different surgical techniques have been described in rats and rabbits, mouse models can be more cost-effective and reproducible for investigating cholestatic fibrosis. Magnetic resonance imaging (MRI) has made great advances for noninvasive assessment of liver fibrosis. More comprehensive liver fibrotic features of BDL on MRI are important. However, the utility of multiparameter MRI to detect liver fibrosis in a BDL mouse model has not been assessed.

AIM

To evaluate the correlation between the pathological changes and multiparameter MRI characteristics of liver fibrosis in a BDL mouse model.

METHODS

Twenty-eight healthy adult male balb/c mice were randomly divided into four groups: sham, week 2 BDL, week 4 BDL, and week 6 BDL. Multiparameter MRI sequences, included magnetic resonance cholangiopancreatography, T1-weighted, T2-weighted, T2 mapping, and pre- and post-enhanced T1 mapping, were performed after sham and BDL surgery. Peripheral blood and liver tissue were collected after MRI. For statistical analysis, Student’s t-test and Pearson’s correlation coefficient were used.

RESULTS

Four mice died after BDL surgery; seven, six, five and six mice were included separately from the four groups. Signal intensities of liver parenchyma showed no difference on TI- and T2-weighted images. Bile duct volume, ΔT1 value, T2 value, and the rate of liver fibrosis increased steadily in week 2 BDL, week 4 BDL and week 6 BDL groups compared with those in the sham group (P < 0.01). Alanine aminotransferase and aspartate transaminase levels initially surged after surgery, followed by a gradual decline over time. Strong correlations were found between bile duct volume (r = 0.84), T2 value (r = 0.78), ΔT1 value (r = 0.62), and hepatic fibrosis rate (all P < 0.01) in the BDL groups.

CONCLUSION

The BDL mouse model induces changes that can be observed on MRI. The MRI parameters correlate with the hepatic fibrosis rate and allow for detection of cholestatic fibrosis.

A Type I Collagen-Targeted MR Imaging Probe for Staging Fibrosis in Crohn's Disease

Fibrostenosis is a serious complication of Crohn's disease (CD), affecting approximately one-half of all patients. Surgical resection is the typical clinical end due to ineffective antifibrotic therapy mainly through anti-inflammatory treatment and fibrosis can be reverted only at early stages. Mover, human fibrotic disorders is known to be associated with aging process. Thus, accurate monitoring of the progression of fibrosis is crucial for CD management as well as can be benefit to aging related fibrosis. The excessive deposition of type I collagen (ColI) is the core point in major complications of fibrosis, including that in patients with CD and aging related fibrosis. Therefore, a MR imaging probe (EP-3533) targeted ColI was employed to stage bowel fibrosis in CD using a rat model and to compare its efficiency with the common MR imaging contrast medium gadopentetatedimeglumine (Gd-DTPA). The bowel fibrotic rat model was established with different degrees of bowel fibrosis, were scanned using a 3.0-T MRI scanner with a specialized animal coil. MRI sequence including T ₁ mapping and T1-weighed imaging were performed before and after injecting the MRI probe (EP-3533 or Gd-DTPA). The T ₁ relaxation time (T ₁ value) and change in the contrast-to-noise ratio (ΔCNR) were measured to evaluate bowel fibrosis. Masson's trichrome staining was performed to determine the severity of fibrosis. EP-3533 offered a better longitudinal relaxivity (r₁) with 67.537 L/mmol·s, which was approximately 13 times that of Gd-DTPA. The T ₁ value on bowel segments was reduced in the images from EP-3533 compared to that from Gd-DTPA (F = 16.478; p < 0.001). Additionally, a better correlation between ΔCNR calculated from EP-3533 imaging and bowel fibrosis (AUC = 0.846) was determined 10 min after enhanced media administration than with Gd-DTPA (AUC = 0.532). The 10th-minute ΔCNR performed using the ColI probe showed the best correlation with the severity of bowel fibrosis (r = 0.538; p = 0.021). Our results demonstrates that targeted MRI probe (EP-3533) supplies a better enhanced effect compared to Gd-DTPA and could be a promising method to evaluate the progression and monitor the therapeutic response of bowel fibrosis.

Rapid Naked-Eye Detection of a Liver Disease Biomarker by Discovering Its Monoclonal Antibody to Functionalize Engineered Red-Colored Bacteria Probes

Glycocholic acid (GCA) is a biomarker for liver diseases, but few facile naked-eye detection methods have been reported to detect it till now. To tackle this challenge, we first prepared a novel monoclonal mouse antibody (mAb) of GCA by a hybridoma technique. The anti-GCA mAb exhibited high specificity, making its cross-reactivity with seven structurally and functionally related GCA analogs negligible. Using this anti-GCA mAb and an engineered red-colored bacterial strain (Staphylococcus aureus, S. aureus), we developed a simple naked-eye visualized method for GCA detection. Toward this goal, S. aureus bacteria were turned red by 5-cyano-2,3-ditolyl tetrazolium chloride treatment and heat treated to an unculturable state, rendering the bacteria as an optical detection probe powerful in in vitro diagnostics. Through the natural binding ability of protein A on the surface of S. aureus and the Fc fragment of a mouse antibody, the anti-GCA antibody was simply conjugated onto S. aureus. Then, the engineered S. aureus served as a red-colored bioprobe for detecting GCA through a coagglutination test. In the presence of GCA, the bioprobes aggregated into dense red-colored eye-visible clusters, enabling the sensitive detection of GCA with a concentration of 0.05-0.10 μg/mL. This naked-eye visualization method only takes a few minutes to detect GCA and avoids the use of expensive equipment. It represents a rapid, convenient, and simple method for detecting GCA to diagnose liver diseases.

MicroSPECT Imaging-Guided Treatment of Idiopathic Pulmonary Fibrosis in Mice with a Vimentin-Targeting 99mTc-Labeled N-Acetylglucosamine-Polyethyleneimine

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic disease with poor prognosis. Evidence has shown that vimentin is a key regulator of lung fibrogenesis. ^99mTc-labeled N-acetylglucosamine-polyethyleneimine (NAG-PEI), a vimentin-targeting radiotracer, was used for the early diagnosis of IPF, and NAG-PEI was also used as a therapeutic small interfering RNA (siRNA) delivery vector for the treatment of IPF in this study. Single-photon emission-computed tomography (SPECT) imaging of bleomycin (BM)- and silica-induced IPF mice with ^99mTc-labeled NAG-PEI was performed to visualize pulmonary fibrosis and monitor the treatment efficiency of siRNA-loaded NAG-PEI, lipopolysaccharide (LPS, a tolerogenic adjuvant), or zymosan (ZYM, an immunostimulant). The lung uptakes of ^99mTc-NAG-PEI in the BM- and silica-induced IPF mice were clearly and directly correlated with IPF progression. The lung uptake of ^99mTc-NAG-PEI in the NAG-PEI/TGF-β1-siRNA treatment group or LPS treatment group was evidently lower than that in the control group, while the lung uptake of ^99mTc-NAG-PEI was significantly higher in the ZYM treatment group compared to that in the control group. These results demonstrate that NAG-PEI is a potent MicroSPECT imaging-guided theranostic platform for IPF diagnosis and therapy.

Use of EP3533-Enhanced Magnetic Resonance Imaging as a Measure of Disease Progression in Skeletal Muscle of mdx Mice

As putative treatments are developed for Duchenne muscular dystrophy (DMD), sensitive, non-invasive measures are increasingly important to quantify disease progression. Fibrosis is one of the histological hallmarks of muscular dystrophy and has been directly linked to prognosis. EP3533 is a novel contrast agent with an affinity to collagen 1 that has demonstrated a significant and high correlation to ex vivo fibrosis quantification. Halofuginone is an established anti-fibrotic compound shown to reduce collagen skeletal muscle fibrosis in murine models of DMD. This experiment explored whether EP3533 could be used to detect signal change in skeletal muscle of mdx mice before and after a 12 week course of halofuginone compared to controls. Four age-matched groups of treated and untreated mice were evaluated: 2 groups of mdx (n = 8 and n = 13, respectively), and 2 groups of BL10 mice (n = 5 and n = 3, respectively). Treated mice received an intraperitoneal injection with halofuginone three times per week for 12 weeks, with the remaining mice being given vehicle. Both mdx groups and the untreated BL10 were scanned at baseline, then all groups were scanned on week 13. All subjects were scanned using a 7T Varian scanner before and after administration of EP3533 using a T1 mapping technique. Mice underwent grip testing in week 13 prior to dissection. Skeletal muscle was used for Masson's trichrome quantification, hydroxyproline assay, and immunofluorescent antibody staining. Untreated mdx mice demonstrated a significant increase in R1 signal from pre- to post-treatment scan in three out of four muscles (gastrocnemius p = 0.04, hamstrings p = 0.009, and tibialis anterior p = 0.01), which was not seen in either the treated mdx or the BL10 groups. Histological quantification of fibrosis also demonstrated significantly higher levels in the untreated mdx mice with significant correlation seen between histology and EP3533 signal change. Forelimb weight adjusted-grip strength was significantly lower in the untreated mdx group, compared to the treated group. EP3533 can be used over time as an outcome measure to quantify treatment effect of an established anti-fibrotic drug. Further studies are needed to evaluate the use of this contrast agent in humans.

Molecular Magnetic Resonance Imaging of Liver Fibrosis and Fibrogenesis Is Not Altered by Inflammation

METHODS

Three groups of mice that develop either mild type 2 inflammation and fibrosis (wild type), severe fibrosis with exacerbated type 2 inflammation (Il10-/-Il12b-/-Il13ra2-/-), or minimal fibrosis with marked type 1 inflammation (Il4ra∂/∂) after infection with S. mansoni were imaged using both probes for determination of signal enhancement. Schistosoma mansoni-infected wild-type mice developed chronic liver fibrosis.

RESULTS

The liver MR signal enhancement after either probe administration was significantly higher in S. mansoni-infected wild-type mice compared with naive animals. The S. mansoni-infected Il4ra∂/∂ mice presented with little liver signal enhancement after probe injection despite the presence of substantial inflammation. Schistosoma mansoni-infected Il10-/-Il12b-/-Il13ra2-/- mice presented with marked fibrosis, which correlated to increased signal enhancement after injection of either probe.

CONCLUSIONS

Both MR probes, EP-3533 and Gd-Hyd, were specific for fibrosis in this model of chronic liver disease regardless of the presence or severity of the underlying inflammation. These results, in addition to previous findings, show the potential application of both molecular MR probes for detection and quantification of fibrosis from various etiologies.

Quantitative, noninvasive MRI characterization of disease progression in a mouse model of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is an increasing cause of chronic liver disease characterized by steatosis, inflammation, and fibrosis which can lead to cirrhosis, hepatocellular carcinoma, and mortality. Quantitative, noninvasive methods for characterizing the pathophysiology of NASH at both the preclinical and clinical level are sorely needed. We report here a multiparametric magnetic resonance imaging (MRI) protocol with the fibrogenesis probe Gd-Hyd to characterize fibrotic disease activity and steatosis in a common mouse model of NASH. Mice were fed a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) to induce NASH with advanced fibrosis. Mice fed normal chow and CDAHFD underwent MRI after 2, 6, 10 and 14 weeks to measure liver T1, T2*, fat fraction, and dynamic T1-weighted Gd-Hyd enhanced imaging of the liver. Steatosis, inflammation, and fibrosis were then quantified by histology. NASH and fibrosis developed quickly in CDAHFD fed mice with strong correlation between morphometric steatosis quantification and liver fat estimated by MRI (r = 0.90). Sirius red histology and collagen quantification confirmed increasing fibrosis over time (r = 0.82). Though baseline T1 and T2* measurements did not correlate with fibrosis, Gd-Hyd signal enhancement provided a measure of the extent of active fibrotic disease progression and correlated strongly with lysyl oxidase expression. Gd-Hyd MRI accurately detects fibrogenesis in a mouse model of NASH with advanced fibrosis and can be combined with other MR measures, like fat imaging, to more accurately assess disease burden.

Enhanced effects of salidroside on erectile function and corpora cavernosa autophagy in a cavernous nerve injury rat model

We explored the efficacy and mechanisms of salidroside treatment for erectile dysfunction induced by bilateral cavernous nerve injury (BCNI). Forty male rats were divided into four groups as follows: sham (cavernous nerves exposed only) (S); BCNI (M); BCNI + rapamycin (M + rapamycin); and BCNI + salidroside (M + salidroside). Erectile function in the rats was measured by intracavernosal pressure. Penile tissue was harvested for transmission electron microscopy, immunohistochemistry, immunofluorescence, Masson's trichrome staining, haematoxylin-eosin staining, TdT-mediated dUTP Nick End Labeling and western blotting. The M group exhibited a decrease in erectile responses and increased apoptosis and fibrosis compared to these in the S group. Meanwhile, nerve content and the penile atrophy index were also decreased in the M group. Treatment with salidroside and rapamycin for 3 weeks partially restored erectile function and significantly attenuated corporal apoptosis, fibrosis, nerve content and penile atrophy in the M group. Moreover, the autophagy level was further enhanced in the M + salidroside group, which was the same as that in the positive observation group (M + rapamycin). Salidroside treatment not only improved erectile function in rats with BCNI, but also inhibited apoptosis and fibrosis and ameliorated the loss of nerve content and endothelial and corpus cavernosum smooth muscle cells by promoting protective autophagy.

Molecular MR Contrast Agents

Molecular magnetic resonance (MR) imaging utilizes molecular probes to provide added biochemical or cellular information to what can already be achieved with anatomical and functional MR imaging. This review provides an overview of molecular MR and focuses specifically on molecular MR contrast agents that provide contrast by shortening the T1 time. We describe the requirements for a successful molecular MR contrast agent and the challenges for clinical translation. The review highlights work from the last 5 years and places an emphasis on new contrast agents that have been validated in multiple preclinical models. Applications of molecular MR include imaging of inflammation, fibrosis, fibrogenesis, thromboembolic disease, and cancers. Molecular MR is positioned to move beyond detection of disease to the quantitative staging of disease and measurement of treatment response.

Molecular Magnetic Resonance Imaging of Fibrin Deposition in the Liver as an Indicator of Tissue Injury and Inflammation

RATIONALE AND OBJECTIVES

Liver inflammation is associated with nonalcoholic steatohepatitis and other pathologies, but noninvasive methods to assess liver inflammation are limited. Inflammation causes endothelial disruption and leakage of plasma proteins into the interstitial space and can result in extravascular coagulation with fibrin deposition. Here we assess the feasibility of using the established fibrin-specific magnetic resonance probe EP-2104R for the noninvasive imaging of fibrin as a marker of liver inflammation.

METHODS

Weekly 100 mg/kg diethylnitrosamine (DEN) dosing was used to generate liver fibrosis in male rats; control animals received vehicle. Magnetic resonance imaging at 1.5 T with EP-2104R, a matched non-fibrin-binding control linear peptide, or the collagen-specific probe EP-3533 was performed at 1 day or 7 days after the last DEN administration. Imaging data were compared with quantitative histological measures of fibrosis and inflammation.

RESULTS

After 4 or 5 DEN administrations, the liver becomes moderately fibrotic, and fibrosis is the same if the animal is killed 1 day (Ishak score, 3.62 ± 0.31) or 7 days (Ishak score, 3.82 ± 0.25) after the last DEN dose, but inflammation is significantly higher at 1 day compared with 7 days after the last DEN dose (histological activity index from 0-4, 3.54 ± 0.14 vs 1.61 ± 0.16, respectively; P < 0.0001). Peak EP-2104R signal enhancement was significantly higher in animals imaged at 1 day post-DEN compared with 7 days post-DEN or control rats (29.0% ± 3.2% vs 22.4% ± 2.0% vs 17.0% ± 0.2%, respectively; P = 0.017). Signal enhancement with EP-2104R was significantly higher than control linear peptide at 1 day post-DEN but not at 7 days post-DEN indicating specific fibrin binding during the inflammatory phase. Collagen molecular magnetic resonance with EP-3533 showed equivalent T1 change when imaging rats 1 day or 7 days post-DEN, consistent with equivalent fibrosis.

CONCLUSIONS

EP-2104R can specifically detect fibrin associated with inflammation in a rat model of liver inflammation and fibrosis.

Collagen-targeted molecular imaging in diffuse liver diseases

Liver fibrosis is a common pathway shared by all progressive chronic liver diseases (CLD) regardless of the underlying etiologies. With liver biopsy being the gold standard in assessing fibrosis degree, there is a large unmet clinical need to develop non-invasive imaging tools that can directly and repeatedly quantify fibrosis throughout the liver for a more accurate assessment of disease burden, progression, and treatment response. Type I collagen is a particularly attractive target for molecular imaging as its excessive deposition is specific to fibrosis, and it is present in concentrations suitable for many imaging modalities. Novel molecular MRI contrast agents designed to bind with collagen provide direct quantification of collagen deposition, which have been validated across animal species and liver injury models. Collagen-targeted molecular imaging probes hold great promise not only as a tool for initial staging and surveillance of fibrosis progression, but also as a marker of fibrosis regression in drug trials.

Advances in functional and molecular MRI technologies in chronic liver diseases

MRI has emerged as the most comprehensive non-invasive diagnostic tool for liver diseases. In recent years, the value of MRI in hepatology has been significantly enhanced by a wide range of contrast agents, both clinically available and under development, that add functional information to anatomically detailed morphological images, or increase the distinction between normal and pathological tissues by targeting molecular and cellular events. Several classes of contrast agents are available for contrast-enhanced hepatic MRI, including i) conventional non-specific extracellular fluid contrast agents for assessing tissue perfusion; ii) hepatobiliary-specific contrast agents that are taken up by functioning hepatocytes and excreted through the biliary system for evaluating hepatobiliary function; iii) superparamagnetic iron oxide particles that accumulate in Kupffer cells; and iv) novel molecular contrast agents that are biochemically targeted to specific molecular/cellular processes for staging liver diseases or detecting treatment responses. The use of different functional and molecular MRI methods enables the non-invasive assessment of disease burden, progression, and treatment response in a variety of liver diseases. A high diagnostic performance can be achieved with MRI by combining imaging biomarkers.

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.

Fibrotic Response to Neoadjuvant Therapy Predicts Survival in Pancreatic Cancer and Is Measurable with Collagen-Targeted Molecular MRI

PURPOSE

To evaluate the prognostic value of posttreatment fibrosis in human PDAC patients, and to compare a type I collagen targeted MRI probe, CM-101, to the standard contrast agent, Gd-DOTA, for their abilities to identify FOLFIRINOX-induced fibrosis in a murine model of PDAC.

EXPERIMENTAL DESIGN

Ninety-three chemoradiation-treated human PDAC samples were stained for fibrosis and outcomes evaluated. For imaging, C57BL/6 and FVB mice were orthotopically implanted with PDAC cells and FOLFIRINOX was administered. Mice were imaged with Gd-DOTA and CM-101.

RESULTS

In humans, post-chemoradiation PDAC tumor fibrosis was associated with longer overall survival (OS) and disease-free survival (DFS) on multivariable analysis (OS P = 0.028, DFS P = 0.047). CPA increased the prognostic accuracy of a multivariable logistic regression model comprised of previously established PDAC risk factors [AUC CPA (-) = 0.76, AUC CPA (+) = 0.82]. In multiple murine orthotopic PDAC models, FOLFIRINOX therapy reduced tumor weight (P < 0.05) and increased tumor fibrosis by collagen staining (P < 0.05). CM-101 MR signal was significantly increased in fibrotic tumor regions. CM-101 signal retention was also increased in the more fibrotic FOLFIRINOX-treated tumors compared with untreated controls (P = 0.027), consistent with selective probe binding to collagen. No treatment-related differences were observed with Gd-DOTA imaging.

CONCLUSIONS

In humans, post-chemoradiation tumor fibrosis is associated with OS and DFS. In mice, our MR findings indicate that translation of collagen molecular MRI with CM-101 to humans might provide a novel imaging technique to monitor fibrotic response to therapy to assist with prognostication and disease management.

Cross-sectional imaging for assessing intestinal fibrosis in Crohn's disease

More than 30% of patients with Crohn's disease (CD) develop fibrotic strictures in the bowel as the disease progresses. Excessive deposition of extracellular matrix components in the submucosa and smooth muscle hypertrophy or hyperplasia are the main features of fibrosis in CD. Cross-sectional imaging technology provides a wealth of information on the anatomy, histological composition, and physiological function of the bowel, allowing for a non-invasive and complete evaluation of associated abnormalities. This review summarizes recent advances in and the potential technologies of cross-sectional imaging for assessing intestinal fibrosis in CD, including ultrasound imaging, computed tomography, and magnetic resonance imaging.

Advanced MRI of Liver Fibrosis and Treatment Response in a Rat Model of Nonalcoholic Steatohepatitis

Background Liver biopsy is the reference standard to diagnose nonalcoholic steatohepatitis (NASH) but is invasive with potential complications. Purpose To evaluate molecular MRI with type 1 collagen-specific probe EP-3533 and allysine-targeted fibrogenesis probe Gd-Hyd, MR elastography, and native T1 to characterize fibrosis and to assess treatment response in a rat model of NASH. Materials and Methods MRI was performed prospectively (June-November 2018) in six groups of male Wistar rats (a) age- and (b) weight-matched animals received standard chow (n = 12 per group); (c) received choline-deficient, l-amino acid-defined, high-fat diet (CDAHFD) for 6 weeks or (d) 9 weeks (n = 8 per group); (e) were fed 6 weeks of CDAHFD and switched to standard chow for 3 weeks (n = 12); (f) were fed CDAHFD for 9 weeks with daily treatment of elafibranor beginning at week 6 (n = 14). Differences in imaging measurements and tissue analyses among groups were tested with one-way analysis of variance. The ability of each imaging measurement to stage fibrosis was quantified by using area under the receiver operating characteristic curve (AUC) with quantitative digital pathology (collagen proportionate area [CPA]) as reference standard. Optimal cutoff values for distinguishing advanced fibrosis were used to assess treatment response. Results AUC for distinguishing fibrotic (CPA >4.8%) from nonfibrotic (CPA ≤4.8%) livers was 0.95 (95% confidence interval [CI]: 0.91, 1.00) for EP-3533, followed by native T1, Gd-Hyd, and MR elastography with AUCs of 0.90 (95% CI: 0.83, 0.98), 0.84 (95% CI: 0.74, 0.95), and 0.65 (95% CI: 0.51, 0.79), respectively. AUCs for discriminating advanced fibrosis (CPA >10.3%) were 0.86 (95% CI: 0.76, 0.97), 0.96 (95% CI: 0.90, 1.01), 0.84 (95% CI: 0.70, 0.98), and 0.74 (95% CI: 0.63, 0.86) for EP-3533, Gd-Hyd, MR elastography, and native T1, respectively. Gd-Hyd MRI had the highest accuracy (24 of 26, 92%; 95% CI: 75%, 99%) in identifying responders and nonresponders in the treated groups compared with MR elastography (23 of 26, 88%; 95% CI: 70%, 98%), EP-3533 (20 of 26, 77%; 95% CI: 56%, 91%), and native T1 (14 of 26, 54%; 95% CI: 33%, 73%). Conclusion Collagen-targeted molecular MRI most accurately detected early onset of fibrosis, whereas the fibrogenesis probe Gd-Hyd proved most accurate for detecting treatment response. © RSNA, 2020 Online supplemental material is available for this article.

Molecular imaging of extracellular matrix proteins with targeted probes using magnetic resonance imaging

The extracellular matrix (ECM) consists of proteins and carbohydrates that supports different biological structures and processes such as tissue development, elasticity, and preservation of organ structure. Diseases involving inflammation, fibrosis, tumor invasion, and injury are all attributed to the transition of the ECM from homeostasis to remodeling, which can significantly change the biochemical and biomechanical features of ECM components. While contrast agents have played an indispensable role in facilitating clinical diagnosis of diseases using magnetic resonance imaging (MRI), there is a strong need to develop novel biomarker-targeted imaging probes for in vivo visualization of biological processes and pathological alterations at a cellular and molecular level, for both early diagnosis and monitoring drug treatment. Herein, we will first review the pathological accumulation and characterization of ECM proteins recognized as important molecular features of diseases. Developments in MRI probes targeting ECM proteins such as collagen, fibronectin, and elastin via conjugation of existing contrast agents to targeting moieties and their applications to various diseases, are also reviewed. We have also reviewed our progress in the development of collagen-targeted protein MRI contrast agent with significant improvement in relaxivity and metal binding specificity, and their applications in early detection of fibrosis and metastatic cancer. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging Biology-Inspired Nanomaterials > Peptide-Based Structures Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Early detection and staging of chronic liver diseases with a protein MRI contrast agent

Early diagnosis and noninvasive detection of liver fibrosis and its heterogeneity remain as major unmet medical needs for stopping further disease progression toward severe clinical consequences. Here we report a collagen type I targeting protein-based contrast agent (ProCA32.collagen1) with strong collagen I affinity. ProCA32.collagen1 possesses high relaxivities per particle (r₁ and r₂) at both 1.4 and 7.0 T, which enables the robust detection of early-stage (Ishak stage 3 of 6) liver fibrosis and nonalcoholic steatohepatitis (Ishak stage 1 of 6 or 1 A Mild) in animal models via dual contrast modes. ProCA32.collagen1 also demonstrates vasculature changes associated with intrahepatic angiogenesis and portal hypertension during late-stage fibrosis, and heterogeneity via serial molecular imaging. ProCA32.collagen1 mitigates metal toxicity due to lower dosage and strong resistance to transmetallation and unprecedented metal selectivity for Gd³⁺ over physiological metal ions with strong translational potential in facilitating effective treatment to halt further chronic liver disease progression.

Non-invasive early diagnosis of liver fibrosis is important to prevent disease progression and direct treatment strategies. Here the authors developed a collagen-targeting contrast agent for the detection of early stage fibrosis and non-alcoholic steatohepatitis by magnetic resonance and tested it in animal models.

Summary of Imaging in 2020: Visualizing the Future of Healthcare with MR Imaging

The Imaging in 2020 meeting convenes biannually to discuss innovations in medical imaging. The 2018 meeting, titled "Visualizing the Future of Healthcare with MR Imaging," sought to encourage discussions of the future goals of MRI research, feature important discoveries, and foster scientific discourse between scientists from a variety of fields of expertise. Here, we highlight presented research and resulting discussions of the meeting.

Molecular Probes for Imaging Fibrosis and Fibrogenesis

Fibrosis, or the accumulation of extracellular matrix molecules that make up scar tissue, is a common result of chronic tissue injury. Advances in the clinical management of fibrotic diseases have been hampered by the low sensitivity and specificity of noninvasive early diagnostic options, lack of surrogate end points for use in clinical trials, and a paucity of noninvasive tools to assess fibrotic disease activity longitudinally. Hence, the development of new methods to image fibrosis and fibrogenesis is a large unmet clinical need. Herein, an overview of recent and selected molecular probes for imaging of fibrosis and fibrogenesis by magnetic resonance imaging, positron emission tomography, and single photon emission computed tomography is provided.

Chemistry of MRI Contrast Agents: Current Challenges and New Frontiers

Tens of millions of contrast-enhanced magnetic resonance imaging (MRI) exams are performed annually around the world. The contrast agents, which improve diagnostic accuracy, are almost exclusively small, hydrophilic gadolinium(III) based chelates. In recent years concerns have arisen surrounding the long-term safety of these compounds, and this has spurred research into alternatives. There has also been a push to develop new molecularly targeted contrast agents or agents that can sense pathological changes in the local environment. This comprehensive review describes the state of the art of clinically approved contrast agents, their mechanism of action, and factors influencing their safety. From there we describe different mechanisms of generating MR image contrast such as relaxation, chemical exchange saturation transfer, and direct detection and the types of molecules that are effective for these purposes. Next we describe efforts to make safer contrast agents either by increasing relaxivity, increasing resistance to metal ion release, or by moving to gadolinium(III)-free alternatives. Finally we survey approaches to make contrast agents more specific for pathology either by direct biochemical targeting or by the design of responsive or activatable contrast agents.

Molecular imaging of fibrosis: recent advances and future directions

Fibrosis, the progressive accumulation of connective tissue that occurs in response to injury, causes irreparable organ damage and may result in organ failure. The few available antifibrotic treatments modify the rate of fibrosis progression, but there are no available treatments to reverse established fibrosis. Thus, more effective therapies are urgently needed. Molecular imaging is a promising biomedical methodology that enables noninvasive visualization of cellular and subcellular processes. It provides a unique means to monitor and quantify dysregulated molecular fibrotic pathways in a noninvasive manner. Molecular imaging could be used for early detection, disease staging, and prognostication, as well as for assessing disease activity and treatment response. As fibrotic diseases are often molecularly heterogeneous, molecular imaging of a specific pathway could be used for patient stratification and cohort enrichment with the goal of improving clinical trial design and feasibility and increasing the ability to detect a definitive outcome for new therapies. Here we review currently available molecular imaging probes for detecting fibrosis and fibrogenesis, the active formation of new fibrous tissue, and their application to models of fibrosis across organ systems and fibrotic processes. We provide our opinion as to the potential roles of molecular imaging in human fibrotic diseases.

Noninvasive quantification of fibrosis in skeletal and cardiac muscle in mdx mice using EP3533 enhanced magnetic resonance imaging

PURPOSE

Duchenne muscular dystrophy (DMD) is a genetic condition caused by mutations in the DMD gene leading to muscle degeneration, fatty replacement of muscle cells and fibrosis. A major obstacle to advancing therapeutic research into muscular dystrophies is development of sensitive, noninvasive outcome measures. To date, no validated method to noninvasively quantify fibrosis within skeletal muscle exists. EP3533 is a gadolinium-based MRI contrast agent with an affinity to collagen-1. The purpose of this study was to determine whether EP3533-enhanced MRI could quantify fibrosis in a murine model of DMD (mdx) in muscle.

METHODS

Mdx (n = 8) and control mice (BL10; n = 5) underwent contrast-enhanced MRI acquisitions with EP3533. T₁ mapping pre- and postcontrast was performed in skeletal and cardiac muscle. Post-MRI the tibialis anterior (TA) and gastrocnemius (GCN) muscles and the heart were removed for fibrosis quantification by means of Masson's trichrome staining and the hydroxyproline assay.

RESULTS

Significant differences in postcontrast R₁ were demonstrated between mdx and BL10 mice using EP3533 (cardiac P = 0.02, GCN P = 0.04, TA P = 0.04). Change in R₁ from baseline following EP3533 administration correlated strongly to hydroxyproline levels (GCN: r = 0.83, P = 0.001; TA: r = 0.73, P = 0.01).

CONCLUSIONS

This study provides evidence for the suitability of EP3533 in the quantification of muscular fibrosis in mdx mice and demonstrated that EP3533-derived measurements correlated strongly to ex vivo fibrosis measurement.

Multi-parametric T2 * magnetic resonance fingerprinting using variable echo times

The use of quantitative imaging biomarkers in the imaging of various disease states, including cancer and neurodegenerative disease, has increased in recent years. T₁ , T₂ , and T₂ * relaxation time constants have been shown to be affected by tissue structure or contrast infusion. Acquiring these biomarkers simultaneously in a multi-parametric acquisition could provide more robust detection of tissue changes in various disease states including neurodegeneration and cancer. Traditional magnetic resonance fingerprinting (MRF) has been shown to provide quick, quantitative mapping of T₁ and T₂ relaxation time constants. In this study, T₂ * relaxation is added to the MRF framework using variable echo times (TE). To demonstrate the feasibility of the method and compare incremental and golden angle spiral rotations, simulated phantom data was fit using the proposed method. Additionally, T₁ /T₂ /T₂ */δf MRF as well as conventional T₁ , T₂ , and T₂ * acquisitions were acquired in agar phantoms and the brains of three healthy volunteers. Golden angle spiral rotation was found to reduce inaccuracy resulting from off resonance effects. Strong correlations were found between conventional and MRF values in the T₁ , T₂ , and T₂ * relaxation time constants of the agar phantoms and healthy volunteers. In this study, T₂ * relaxation has been incorporated into the MRF framework by using variable echo times, while still fitting for T₁ and T₂ relaxation time constants. In addition to fitting these relaxation time constants, a novel method for fitting and correcting off resonance effects has been developed.

Plasmodium falciparum msp1 and msp2 genetic diversity and allele frequencies in parasites isolated from symptomatic malaria patients in Bobo-Dioulasso, Burkina Faso

Background

In Burkina Faso, malaria remains the overall leading cause of morbidity and mortality accounting for 35.12% of consultations, 40.83% of hospitalizations and 37.5% of deaths. Genotyping of malaria parasite populations remains an important tool to determine the types and number of parasite clones in an infection. The present study aimed to evaluate the merozoite surface protein 1 (msp1) and merozoite surface protein 2 (msp2) genetic diversity and allele frequencies in Bobo-Dioulasso, Burkina Faso.

Method

Dried blood spots (DBS) were collected at baseline from patients with uncomplicated malaria in urban health centers in Bobo-Dioulasso. Parasite DNA was extracted using chelex-100 and species were identified using nested PCR. Plamodium falciparum msp1 and msp2 genes were amplified by nested polymerase chain reaction (PCR) and PCR products were analyzed by electrophoresis on a 2.5% agarose gel. Alleles were categorized according to their molecular weight.

Results

A total of 228 blood samples were analyzed out of which 227 (99.9%) were confirmed as P. falciparum-positive and one sample classified as mixed infection for P. malaria and P. falciparum. In msp1, the K1 allelic family was predominant with 77.4% (162/209) followed respectively by the MAD20 allelic family with 41.3% and R033 allelic family with 36%. In msp2, the 3D7 allelic family was the most frequently detected with 93.1 % compared to FC27 with 41.3%. Twenty-one different alleles were observed in msp1 with 9 alleles for K1, 8 alleles for MAD20 and 4 alleles for R033. In msp2, 25 individual alleles were detected with 10 alleles for FC27 and 15 alleles for 3D7. The mean multiplicity of falciparum infection was 1.95 with respectively 1.8 (1.76–1.83) and 2.1 (2.03–2.16) for msp1 and msp2 (P = 0.01).

Conclusions

Our study showed high genetic diversity and allelic frequencies of msp1 and msp2 in Plasmodium falciparum isolates from symptomatic malaria patients in Bobo-Dioulasso.

Molecular magnetic resonance imaging accurately measures the antifibrotic effect of EDP-305, a novel farnesoid X receptor agonist

We examined a novel farnesoid X receptor agonist, EDP-305, for its antifibrotic effect in bile duct ligation (BDL) and choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) models of hepatic injury. We used molecular magnetic resonance imaging with the type 1 collagen-binding probe EP-3533 and the oxidized collagen-specific probe gadolinium hydrazide to noninvasively measure treatment response. BDL rats (n = 8 for each group) were treated with either low or high doses of EDP-305 starting on day 4 after BDL and were imaged on day 18. CDAHFD mice (n = 8 for each group) were treated starting at 6 weeks after the diet and were imaged at 12 weeks. Liver tissue was subjected to pathologic and morphometric scoring of fibrosis, hydroxyproline quantitation, and determination of fibrogenic messenger RNA expression. High-dose EDP-305 (30 mg/kg) reduced liver fibrosis in both the BDL and CDAHFD models as measured by collagen proportional area, hydroxyproline analysis, and fibrogenic gene expression (all P < 0.05). Magnetic resonance signal intensity with both EP-3533 in the BDL model and gadolinium hydrazide in the CDAHFD model was reduced with EDP-305 30 mg/kg treatment (P < 0.01). Histologically, EDP-305 30 mg/kg halted fibrosis progression in the CDAHFD model. Conclusion: EDP-305 reduced fibrosis progression in rat BDL and mouse CDAHFD models. Molecular imaging of collagen and oxidized collagen is sensitive to changes in fibrosis and could be used to noninvasively measure treatment response in clinical trials. (Hepatology Communications 2018;2:821-835).

Prolonged cenicriviroc therapy reduces hepatic fibrosis despite steatohepatitis in a diet-induced mouse model of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a progressive liver disease projected to become the leading cause of cirrhosis and liver transplantation in the next decade. Cenicriviroc (CVC), a dual chemokine receptor 2 and 5 antagonist, prevents macrophage trafficking and is under clinical investigation for the treatment of human NASH fibrosis. We assessed the efficacy and durability of short and prolonged CVC therapy in a diet‐induced mouse model of NASH, the choline deficient, L‐amino acid‐defined, high‐fat diet (CDAHFD) model. C57BL/6 mice received 4 or 14 weeks of standard chow or the CDAHFD. CVC (10 mg/kg/day and 30 mg/kg/day for 4 weeks and 20 mg/kg/day and 30 mg/kg/day for 14 weeks) was initiated simultaneously with the CDAHFD. At 4 and 14 weeks, livers were harvested for histology and flow cytometric analyses of intrahepatic immune cells. High‐dose CVC (30 mg/kg/day) therapy in CDAHFD mice for 4 or 14 weeks inhibited intrahepatic accumulation of Ly6C^high bone marrow‐derived macrophages. Prolonged CVC therapy (14 weeks) yielded no significant differences in the total intrahepatic macrophage populations among treatment groups but increased the frequency of intrahepatic anti‐inflammatory macrophages in the high‐dose CVC group. Despite ongoing steatohepatitis, there was significantly less fibrosis in CDAHFD mice receiving high‐dose CVC for 14 weeks based on histologic and molecular markers, mirroring observations in human NASH CVC trials. CVC also directly inhibited the profibrotic gene signature of transforming growth factor‐β‐stimulated primary mouse hepatic stellate cells in vitro. Conclusion: CVC is a novel therapeutic agent that is associated with reduced fibrosis despite ongoing steatohepatitis. Its ability to alter intrahepatic macrophage populations and inhibit profibrogenic genes in hepatic stellate cells in NASH livers may contribute to its observed antifibrotic effect. (Hepatology Communications 2018;2:529‐545)

CM-101: Type I Collagen-targeted MR Imaging Probe for Detection of Liver Fibrosis

Purpose To evaluate the biodistribution, metabolism, and pharmacokinetics of a new type I collagen-targeted magnetic resonance (MR) probe, CM-101, and to assess its ability to help quantify liver fibrosis in animal models. Materials and Methods Biodistribution, pharmacokinetics, and stability of CM-101 in rats were measured with mass spectrometry. Bile duct-ligated (BDL) and sham-treated rats were imaged 19 days after the procedure by using a 1.5-T clinical MR imaging unit. Mice were treated with carbon tetrachloride (CCl₄) or with vehicle two times a week for 10 weeks and were imaged with a 7.0-T preclinical MR imaging unit at baseline and 1 week after the last CCl₄ treatment. Animals were imaged before and after injection of 10 µmol/kg CM-101. Change in contrast-to-noise ratio (ΔCNR) between liver and muscle tissue after CM-101 injection was used to quantify liver fibrosis. Liver tissue was analyzed for Sirius Red staining and hydroxyproline content. The institutional subcommittee for research animal care approved all in vivo procedures. Results CM-101 demonstrated rapid blood clearance (half-life = 6.8 minutes ± 2.4) and predominately renal elimination in rats. Biodistribution showed low tissue gadolinium levels at 24 hours (<3.9% injected dose [ID]/g ± 0.6) and 10-fold lower levels at 14 days (<0.33% ID/g ± 12) after CM-101 injection with negligible accumulation in bone (0.07% ID/g ± 0.02 and 0.010% ID/g ± 0.004 at 1 and 14 days, respectively). ΔCNR was significantly (P < .001) higher in BDL rats (13.6 ± 3.2) than in sham-treated rats (5.7 ± 4.2) and in the CCl₄-treated mice (18.3 ± 6.5) compared with baseline values (5.2 ± 1.0). Conclusion CM-101 demonstrated fast blood clearance and whole-body elimination, negligible accumulation of gadolinium in bone or tissue, and robust detection of fibrosis in rat BDL and mouse CCl₄ models of liver fibrosis. ^© RSNA, 2017 Online supplemental material is available for this article.

Fibrosis imaging: Current concepts and future directions

Fibrosis plays an important role in many different pathologies. It results from tissue injury, chronic inflammation, autoimmune reactions and genetic alterations, and it is characterized by the excessive deposition of extracellular matrix components. Biopsies are routinely employed for fibrosis diagnosis, but they suffer from several drawbacks, including their invasive nature, sampling variability and limited spatial information. To overcome these limitations, multiple different imaging tools and technologies have been evaluated over the years, including X-ray imaging, computed tomography (CT), ultrasound (US), magnetic resonance imaging (MRI), positron emission tomography (PET) and single-photon emission computed tomography (SPECT). These modalities can provide anatomical, functional and molecular imaging information which is useful for fibrosis diagnosis and staging, and they may also hold potential for the longitudinal assessment of therapy responses. Here, we summarize the use of non-invasive imaging techniques for monitoring fibrosis in systemic autoimmune diseases, in parenchymal organs (such as liver, kidney, lung and heart), and in desmoplastic cancers. We also discuss how imaging biomarkers can be integrated in (pre-) clinical research to individualize and improve anti-fibrotic therapies.

Molecular MR imaging of fibrosis in a mouse model of pancreatic cancer

Fibrosis with excessive amounts of type I collagen is a hallmark of many solid tumours, and fibrosis is a promising target in cancer therapy, but tools for its non-invasive quantification are missing. Here we used magnetic resonance imaging with a gadolinium-based probe targeted to type I collagen (EP-3533) to image and quantify fibrosis in pancreatic ductal adenocarcinoma. An orthotopic syngeneic mouse model resulted in tumours with 2.3-fold higher collagen level compared to healthy pancreas. Animals were scanned at 4.7 T before, during and up to 60 min after i.v. injection of EP-3533, or of its non-binding isomer EP-3612. Ex-vivo quantification of gadolinium showed significantly higher uptake of EP-3533 compared to EP-3612 in tumours, but not in surrounding tissue (blood, muscle). Uptake of EP-3533 visualized in T1-weighted MRI correlated well with spatial distribution of collagen determined by second harmonic generation imaging. Differences in the tumour pharmacokinetic profiles of EP-3533 and EP-3612 were utilized to distinguish specific binding to tumour collagen from non-specific uptake. A model-free pharmacokinetic measurement based on area under the curve was identified as a robust imaging biomarker of fibrosis. Collagen-targeted molecular MRI with EP-3533 represents a new tool for non-invasive visualization and quantification of fibrosis in tumour tissue.

Evaluation of hepatic fibrosis: a review from the society of abdominal radiology disease focus panel

Hepatic fibrosis is potentially reversible; however early diagnosis is necessary for treatment in order to halt progression to cirrhosis and development of complications including portal hypertension and hepatocellular carcinoma. Morphologic signs of cirrhosis on ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) alone are unreliable and are seen with more advanced disease. Newer imaging techniques to diagnose liver fibrosis are reliable and accurate, and include magnetic resonance elastography and US elastography (one-dimensional transient elastography and point shear wave elastography or acoustic radiation force impulse imaging). Research is ongoing with multiple other techniques for the noninvasive diagnosis of hepatic fibrosis, including MRI with diffusion-weighted imaging, hepatobiliary contrast enhancement, and perfusion; CT using perfusion, fractional extracellular space techniques, and dual-energy, contrast-enhanced US, texture analysis in multiple modalities, quantitative mapping, and direct molecular imaging probes. Efforts to advance the noninvasive imaging assessment of hepatic fibrosis will facilitate earlier diagnosis and improve patient monitoring with the goal of preventing the progression to cirrhosis and its complications.

Molecular Magnetic Resonance Imaging of Lung Fibrogenesis with an Oxyamine-Based Probe

Fibrogenesis is the active production of extracellular matrix in response to tissue injury. In many chronic diseases persistent fibrogenesis results in the accumulation of scar tissue, which can lead to organ failure and death. However, no non-invasive technique exists to assess this key biological process. All tissue fibrogenesis results in the formation of allysine, which enables collagen cross-linking and leads to tissue stiffening and scar formation. We report herein a novel allysine-binding gadolinium chelate (GdOA), that can non-invasively detect and quantify the extent of fibrogenesis using magnetic resonance imaging (MRI). We demonstrate that GdOA signal enhancement correlates with the extent of the disease and is sensitive to a therapeutic response.

Optimization of a Collagen-Targeted PET Probe for Molecular Imaging of Pulmonary Fibrosis

There is a large unmet need for a simple, accurate, noninvasive, quantitative, and high-resolution imaging modality to detect lung fibrosis at early stage and to monitor disease progression. Overexpression of collagen is a hallmark of organ fibrosis. Here, we describe the optimization of a collagen-targeted PET probe for staging pulmonary fibrosis. Methods: Six peptides were synthesized, conjugated to a copper chelator, and radiolabeled with ⁶⁴Cu. The collagen affinity of each probe was measured in a plate-based assay. The pharmacokinetics and metabolic stability of the probes were studied in healthy rats. The capacity of these probes to detect and stage pulmonary fibrosis in vivo was assessed in a mouse model of bleomycin-induced fibrosis using PET imaging. Results: All probes exhibited affinities in the low micromolar range (1.6 μM < Kd < 14.6 μM) and had rapid blood clearance. The probes showed 2- to 8-fold-greater uptake in the lungs of bleomycin-treated mice than sham-treated mice, whereas the distribution in other organs was similar between bleomycin-treated and sham mice. The probe ⁶⁴Cu-CBP7 showed the highest uptake in fibrotic lungs and the highest target-to-background ratios. The superiority of ⁶⁴Cu-CBP7 was traced to a much higher metabolic stability compared with the other probes. The specificity of ⁶⁴Cu-CBP7 for collagen was confirmed by comparison with a nonbinding isomer. Conclusion:⁶⁴Cu-CBP7 is a promising candidate for in vivo imaging of pulmonary fibrosis.

Type I collagen-targeted PET probe for pulmonary fibrosis detection and staging in preclinical models

Pulmonary fibrosis is scarring of the lungs that can arise from radiation injury, drug toxicity, environmental or genetic causes, and for unknown reasons [idiopathic pulmonary fibrosis (IPF)]. Overexpression of collagen is a hallmark of organ fibrosis. We describe a peptide-based positron emission tomography (PET) probe (68Ga-CBP8) that targets collagen type I. We evaluated 68Ga-CBP8 in vivo in the bleomycin-induced mouse model of pulmonary fibrosis. 68Ga-CBP8 showed high specificity for pulmonary fibrosis and high target/background ratios in diseased animals. The lung PET signal and lung 68Ga-CBP8 uptake (quantified ex vivo) correlated linearly (r2 = 0.80) with the amount of lung collagen in mice with fibrosis. We further demonstrated that the 68Ga-CBP8 probe could be used to monitor response to treatment in a second mouse model of pulmonary fibrosis associated with vascular leak. Ex vivo analysis of lung tissue from patients with IPF supported the animal findings. These studies indicate that 68Ga-CBP8 is a promising candidate for noninvasive imaging of human pulmonary fibrosis.