Intravoxel incoherent motion diffusion-weighted imaging and dynamic contrast-enhanced MRI for predicting parametrial invasion in cervical cancer.

PURPOSE: This study aimed to assess the predictive efficacy of intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in parametrial invasion (PMI) in cervical cancer patients. METHODS: A total of 83 cervical cancer patients (32 PMI-positive and 51 PMI-negative) retrospectively underwent pretreatment IVIM-DWI and DCE-MRI scans. IVIM-DWI parameters included apparent diffusion coefficient (ADC), slow apparent diffusion coefficient (D), fast apparent diffusion coefficient (D*), and perfusion fraction (f). DCE-MRI parameters included volume transfer constant (Ktrans), flux rate constant (Kep), and fractional extravascular extracellular space volume (Ve). Logistic regression analyses were conducted to identify independent variables associated with PMI. Receiver operating characteristic curves were generated to assess the predictive performance of significant parameters. RESULTS: Multivariable analysis revealed that the MRI parameters D (odds ratio [OR]: 7.05; 95% CI 1.78-27.88; P = 0.005), D* (OR 6.58; 95% CI 1.49-29.10; P = 0.01), f (OR 5.12; 95% CI 1.23-21.37; P = 0.03), Ktrans (OR 4.60; 95% CI 1.19-17.81; P = 0.03), and Kep (OR 4.90; 95% CI 1.25-19.18; P = 0.02) were independent predictors of PMI in cervical cancer patients. The combined parameter incorporating these parameters demonstrated the highest performance in predicting PMI, yielding an area under the curve of 0.906, sensitivity of 84.4%, and specificity of 86.3%. CONCLUSION: The proposed combined parameter exhibited favorable performance in identifying PMI in cervical cancer patients.

Value of Non-Contrast-Enhanced Vessel Wall MR Imaging in Assessing Vascular Invasion of Retroperitoneal Tumors.

BACKGROUND: Due to their location and growth patterns, retroperitoneal tumors often involve the surrounding blood vessels. Clinical decisions on a proper treatment depend on the information on this condition. Evaluation of blood vessels using non-contrast-enhanced vessel wall MRI may provide noninvasive assessment of the extent of tumor invasion to assist clinical decision-making. PURPOSE: To investigate the performance and potential of non-contrast-enhanced vessel wall MRI in evaluating the degree of vessel wall invasion of retroperitoneal tumors. STUDY TYPE: Prospective. POPULATION: Thirty-seven participants (mean age: 60.59 ± 11.77 years, 59% male) with retroperitoneal tumors close to vessels based on their diagnostic computer tomography. FIELD STRENGTH/SEQUENCES: 3 T; vessel wall MRI sequences: two-dimensional T2-weighted MultiVane XD turbo spin-echo (2D-T2-MVXD-TSE) and three-dimensional T1-weighted motion sensitized driven equilibrium fat suppression turbo spin-echo (3D-T1-MSDE-TSE) sequences; conventional MRI sequences: T2-weighted fat suppression turbo spin-echo (T2-FS-TSE), T2-weighted turbo spin-echo (T2-TSE), modified Dixon T1-weighted fast field echo (T1-mDixon-FFE), and diffusion-weighted echo planar imaging (DWI-EPI) sequences. ASSESSMENT: All patients underwent preoperative imaging using both non-contrast conventional and vessel wall MRI sequences. Images obtained from conventional and vessel wall MRI sequences were evaluated independently by three junior radiologists (3 and 2 years of experience in reading MRI) and reviewed by one senior radiologist (25 years of experience in reading MRI) to assess the degree of vessel wall invasion. MRI were validated results from the clinical standard diagnosis based on surgical confirmation or histopathological reports. Interobserver agreement was determined based on the reports from three readers with similar years of experiences. Intraobserver variability was assessed based on categorizing and recategorizing the vessels of 37 patients 1 month apart. STATISTICAL TESTS: Intra-class correlation efficient (ICC), Chi-square test, McNemar test, area under the receiver-operating characteristic curve (AUC), Delong test, P < 0.05 was considered significant. RESULTS: The accuracy of vessel wall MRI (91.96%, 95% CI: 85.43-95.71; 103 of 112) in detecting the degree of vessel wall invasion was significantly higher than that of conventional MRI (75%, 95% CI: 66.24-82.10; 84 of 112). The interobserver variability or reproducibility in categorization of the degree of vascular wall invasion was good in evaluating images from conventional and vessel wall MRI sequences (ICC = 0.821, 95% CI: 0.765-0.867 and ICC = 0.881, 95% CI: 0.842-0.913, respectively). DATA CONCLUSION: Diagnosis of vessel wall invasion of retroperitoneal tumors and assessment of its severity can be improved by using non-contrast-enhanced vessel wall MRI. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 3.

Abnormal [18F]FDG uptake in liver and adipose tissue: a potential imaging biomarker for cancer-associated cachexia.

OBJECTIVES: This study aims to investigate and develop imaging biomarkers for the diagnosis of cancer-associated cachexia based on the organ and tissue-specific abnormal metabolisms measured by fluorine-18-fluorodeoxyglucose (18F-FDG) PET/CT. METHODS: FDG PET/CT data from 390 cancer patients were analyzed retrospectively. Patients were divided into a development cohort and a validation cohort. Cachexia was defined as weight loss > 5% in 6 months or BMI < 20 and weight loss > 2%. According to the above definitions, patients were divided into cachexia and non-cachexia groups. Results of the clinical laboratory tests for metabolic levels and organ and tissue-specific FDG uptake obtained from the cachexia and non-cachexia groups were compared statistically. Logistic regression analysis was performed to identify independent variables associated with cachexia in the development cohort for generating the regression model. The performance of the model was tested using the data from a validation cohort and evaluated by area under the receiver operating characteristic curve (AUC). RESULTS: Based on the data from the development cohort of 286 patients and a validation cohort of 104 patients, it is found that age, white blood cell count, peak standardized uptake value (SUV) of the liver, and minimum SUV of lean body mass of visceral fat and subcutaneous fat were independently associated with cachexia. The model incorporating these variables reached an AUC of 0.777 (95% confidence interval (CI): 0.721, 0.833) in the development cohort and an AUC of 0.729 (95% CI: 0.629, 0.829) in the validation cohort. CONCLUSION: Organ and tissue-specific abnormal glucose metabolism as measured by PET/CT can be used as a biomarker for cancer-associated cachexia. KEY POINTS: • Patients with cancer-associated cachexia have reduced FDG uptake in the liver and increased FDG uptake in visceral fat and subcutaneous fat. • FDG uptake of the liver, visceral fat, and subcutaneous fat can be independent risk factors for identifying cancer-associated cachexia. • Cancer-associated cachexia can be classified using the model that incorporates age, white blood cell count, FDG uptake of the liver, and visceral and subcutaneous fat can diagnose with an AUC of 0.729.

Reducing White Adipose Tissue Browning Using p38α MAPK Inhibitors Ameliorates Cancer-Associated Cachexia as Assessed by Magnetic Resonance Imaging.

BACKGROUND: Up to 80% of pancreatic cancer patients suffer from cachexia. White adipose tissue (WAT) browning caused by the tumorigenicity and progression aggravates the cancer-associated cachexia (CAC). Cancer-initiated changes in the protein-38 mitogen-activated protein kinases (p38 MAPK) pathway are likely involved in the development of CAC. METHODS: p38 MAPK inhibitors, VCP979 or SB203580, were used in the in vitro and in vivo models of pancreatic cancer cachexia. Expression of uncoupling protein 1 (UCP1) in the p38 MARK pathway and the properties and level of white adipocytes were analyzed and correlated to browning, followed by immunohistochemistry and Western blotting validations. Changes in the volume and fat fraction of WAT in animals were monitored by magnetic resonance imaging (MRI). RESULTS: The size of white adipocytes was increased after being treated with the p38 MAPK inhibitors, along with increase in the MRI-measured volume and fat fraction of WAT. Comparing two p38 MAPK inhibitors, the p38α subunit-specific inhibitor VCP979 had a better therapeutic effect than SB203580, which targets both p38α and ß subunits. CONCLUSIONS: Blockade of p38 MAPK reduced the WAT browning that contributes to CAC. Thus, p38 MARK inhibitors can potentially be used as a therapy for treating CAC. Non-invasive MRI can also be applied to assess the progression and treatment responses of CAC.

Assessment of Calf Skeletal Muscle in Male Type 2 Diabetes Mellitus Patients With Different Courses Using T1ρ Mapping.

CONTEXT: The current clinical methods for detecting skeletal muscle complications of type 2 diabetes mellitus (T2DM) are invasive and insensitive. There is an urgent need for noninvasive assessment of skeletal muscle microstructure changes during the disease progression and treatment to assist the clinical management. OBJECTIVE: This work aimed to investigate the T2DM caused changes in the fast-twitch tibialis anterior (TA) and slow-twitch soleus (SOL) skeletal muscles using T1ρ magnetic resonance imaging (MRI). METHODS: This cross-sectional study took place from December 2014 to December 2020 at Zhongda Hospital Southeast University. A total of 26 new-onset and 15 long-term T2DM patients were enrolled, with the addition of 20 young and 13 older healthy volunteers as age-matched controls. T1ρ relaxation times of SOL and TA muscles in different groups were measured. Parametric and nonparametric tests were used to analyze the relationship between the T1ρ values in SOL and TA muscles and the length of illness, level of fasting blood glucose, and status of homeostasis model assessment of insulin resistance (HOMA-IR). RESULTS: T1ρ relaxation times of SOL and TA muscles both of new-onset and long-term T2DM patients were significantly higher than those of the young (P < .01, P < .05) and older healthy controls (P < .05, P < .01). Positive correlations were observed between the T1ρ relaxation times of the TA or SOL and the duration of T2DM (R2 = 0.420, R2 = 0.326), the level of fasting blood glucose (R2 = 0.253, R2 = 0.071) and HOMA-IR (R2 = 0.232, R2 = 0.414). CONCLUSION: Quantitative MRI measurement of T1ρ provides a noninvasive tool to assess T2DM-induced changes in the skeletal muscles of T2DM patients.

Irisin induces white adipose tissue browning in mice as assessed by magnetic resonance imaging.

This study aimed to track and evaluate the effect of low-dose irisin on the browning of white adipose tissue (WAT) in mice using magnetic resonance imaging (MRI) noninvasively in vivo. Mature white adipocytes extracted from mice were cultured, induced and characterized before being treated by irisin. The volume and fat fraction of WAT were quantified using MRI in normal chow diet and high fat mice after injection of irisin. The browning of cultured white adipocytes and WAT in mice were validated by immunohistochemistry and western blotting for uncoupling protein 1 (UCP1) and deiodinase type II (DIO2). The serum indexes were examined with high fat diet after irisin intervention. UCP1 and DIO2 in adipocytes showed increases responding to the irisin treatment. The size of white adipocytes in mice receiving irisin intervention was reduced. MRI measured volumes and fat fraction of WAT were significantly lower after Irisin treatment. Blood glucose and cholesterol levels were reduced in high fat diet mice after irisin treatment. Irisin intervention exerted browning of WAT, resulting reduction of volume and fat fraction of WAT as measured by MRI. Furthermore, it improved the condition of mice with diet-induced obesity and related metabolic disorders.

Quantification of Fat Concentration and Vascular Response in Brown and White Adipose Tissue of Rats by Spectral CT Imaging.

OBJECTIVE: The purpose of the study was to non-invasively characterize and discriminate brown adipose tissue (BAT) from white adipose tissue (WAT) in rats using spectral computed tomography (CT) with histological validation. MATERIALS AND METHODS: A lipid-containing phantom (lipid fractions from 0% to 100%) was imaged with spectral CT. An in vivo, non-enhanced spectral CT scan was performed on 24 rats, and fat concentrations of BAT and WAT were measured. The rats were randomized to receive intraperitoneal treatment with norepinephrine (NE) (n = 12) or saline (n = 12). Non-enhanced and enhanced spectral CT scans were performed after treatment to measure the elevation of iodine in BAT and WAT. The BAT/aorta and WAT/aorta ratios were calculated and compared, after which isolated BAT and WAT samples were subjected to histological and uncoupling protein 1 (UCP1) analyses. RESULTS: The ex-vivo phantom study showed excellent linear fit between measured fat concentration and the known gravimetric reference standard (r² = 0.996). In vivo, BAT had significantly lower fat concentration than WAT (p < 0.001). Compared to the saline group, the iodine concentration of BAT increased significantly (p < 0.001) after injection of NE, while the iodine concentration of WAT only changed slightly. The BAT/aorta ratio also increased significantly after exposure to NE compared to the saline group (p < 0.001). Histological and UCP1 expression analyses supported the spectral CT imaging results. CONCLUSION: The study consolidates spectral CT as a new approach for non-invasive imaging of BAT and WAT. Quantitative analyses of BAT and WAT by spectral CT revealed different characteristics and pharmacologic activations in the two types of adipose tissue.

Noninvasive Identification of Renal Hypoxia in Experimental Myocardial Infarctions of Different Sizes by Using BOLD MR Imaging in a Mouse Model.

Purpose To test the feasibility of using blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging to measure alterations in renal oxygenation in a mouse model with experimental myocardial infarctions (MIs) of different sizes. Materials and Methods The study was approved by the local animal ethics committee. One hundred eighty-nine male C57BL/6 J mice were randomly subjected to MI surgery (with different locations of left anterior descending coronary artery occlusion) or sham surgery, defined as the exposure of the heart but no ligation. Mice with MI underwent late gadolinium enhancement imaging 1 day after occlusion to confirm infarct size. Mice were sorted into three groups: those with large MI (n = 48), those with small MI (n = 48), and those with sham operation (n = 36). Renal BOLD MR imaging was performed before and 1, 7, 14, 28, and 60 days after MI, and histologic analysis of renal hypoxia-inducible factor-1α (HIF-1α) and kidney injury molecule-1 (KIM-1) was performed to evaluate tissue hypoxia and kidney injury in subgroups imaged at each time point. The relationships between the BOLD R2* and HIF-1α expression and between HIF-1α and KIM-1 expression were assessed. Statistical analyses were performed with one-way analysis of variance or the Kruskal-Wallis test and Spearman correlation test. Results A significant elevation in R2* was detected in the MI groups compared with the sham group in the cortex (P < .001 for large MI vs sham group; P = .007 for small MI vs sham group) and medulla (P < .001 for large MI vs sham group; P = .003 for small MI vs sham group) on day 60, and R2* was higher in the large MI group than in the small MI group (P < .001). Renal HIF-1α expression was increased after MI and showed linear correlation with R2* in the cortex (R2 = 0.56) and medulla (R2 = 0.63). In addition, an increase in renal KIM-1 was observed in the MI groups compared with the sham group on day 60 (sham group, 53.9 × 103 arbitrary units [au] ± 35.2; large MI group, 389.3 × 103 au ± 99.8; and small MI group, 185.8 × 103 au ± 91.9; P < .001 for large MI group vs sham group; P = .037 for small MI group vs sham group), and renal KIM-1 showed a positive correlation with HIF-1α (R2 = 0.68). Conclusion The magnitude of renal hypoxia with MIs of different sizes can be noninvasively measured with BOLD MR imaging, and increased renal hypoxia is a potential risk factor for progressive tubulointerstitial injury in mouse kidneys. © RSNA, 2017 Online supplemental material is available for this article.

Noninvasive assessment of age, gender, and exercise effects on skeletal muscle: Initial experience with T1 ρ MRI of calf muscle.

PURPOSE: To prospectively investigate age- and gender-related changes in the fast-twitch (tibialis anterior, TA) and slow-twitch (soleus, SOL) skeletal muscle of healthy rats and volunteers and to compare the exercise-related difference in health volunteers with T1 ρ magnetic resonance imaging (MRI). MATERIALS AND METHODS: In all, 18 rats and 70 humans were involved in this study. For the animal study, T1 ρ relaxation times were measured in the TA and SOL rat muscle with a 3.0T MRI scanner and compared to histological data. For the human study, three groups (young, middle-aged, and elderly) of volunteers underwent T1 ρ MRI scans (3.0T) of their calves. To further differentiate the human scans, 18 volunteers were recruited, half of them (n = 9) routinely trained with high-intensity sports, while the other half (n = 9) with no physical training. Statistical analysis was performed via paired t-test, independent-sample t-test, and analysis of variance (ANOVA). Correlations between T1 ρ and age/gender/physical endurance were calculated. RESULTS: The average T1 ρ relaxation times of the TA and SOL of female rats were higher than that of male rats (P < 0.001). The T1 ρ relaxation time of TA was significantly lower compared to SOL (P < 0.001). A significant linear correlation was observed between T1 ρ and the type I slow-twitch fiber proportion (%) in SOL (R2 = 0.837, P < 0.001). Similarly, in human studies the average T1 ρ relaxation times of TA were significantly lower than SOL for all age groups (P < 0.001). The higher T1 ρ relaxation times of TA and SOL in the elderly volunteers (P < 0.001) and in the females (P < 0.05) indicated significant age- and gender-dependent differences. In high-intensity sports groups, the higher T1 ρ in SOL (P < 0.01) and lower in TA (P < 0.05) were observed compared with the control group. CONCLUSION: This study demonstrated that T1 ρ MRI can be used to display the differences in fast- and slow-twitch skeletal muscle as well as potentially age-, gender-, and exercise-related differences. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:61-70.

Transplanted Endothelial Progenitor Cells Improve Ischemia Muscle Regeneration in Mice by Diffusion Tensor MR Imaging.

Endothelial progenitor cells (EPCs) play an important role in repairing ischemia tissues. Diffusion tensor imaging (DTI) was applied to detect the architectural organization of skeletal muscle. This study investigated the feasibility and accuracy of using the DTI to evaluate effectiveness of EPCs treatment. Mouse bone marrow-derived EPCs were isolated, cultured, characterized, and transplanted to hindlimb ischemia mice model. DTI was performed on the hindlimb at postischemia time points. The edema regions of diffusion restriction (high signal in diffusion weighted imaging) were decreased in the ischemic muscle of EPCs treated mice after 14 days compared with the controls. These results from DTI show the lower apparent diffusion coefficient and eigenvalues (λ1, λ2, and λ3) and the higher fractional anisotropy and fiber counts of ischemic muscle on 7 and 14 days after EPCs treatment compared to the controls. There was a significant correlation between fiber counts calculated by DTI and survival fibers evaluated by histological section (r = 0.873, P < 0.01). Our study demonstrated that the time frame for muscle fiber regeneration after EPCs transplantation was significantly shortened in vivo. DTI could be a useful tool for noninvasive evaluation of muscle tissue damage and repair in animal models and patient with ischemic diseases.

Intervertebral disc regeneration using platelet­rich plasma­containing bone marrow­derived mesenchymal stem cells: A preliminary investigation.

Platelet­rich plasma (PRP) is a promising strategy for intervertebral disc degeneration (IDD). However, the short half­life of growth factors released from PRP cannot continuously stimulate the degenerated discs. Thus, the present study hypothesized that the combined use of PRP and bone marrow­derived mesenchymal stem cells (BMSCs) may repair the early degenerated discs in the long term for their synergistic reparative effect. In the present study, following the induction of early IDD by annular puncture in rabbits, PRP was prepared and mixed with BMSCs (PRP­BMSC group) for injection into the early degenerated discs. As controls, phosphate­buffered saline (PBS; PBS group) and PRP (PRP group) were similarly injected. Rabbits without any intervention served as a control group. At 8 weeks following treatment, histological changes of the injected discs were assessed. Magnetic resonance imaging (MRI) was used to detect the T2­weighted signal intensity of the targeted discs at weeks 1, 2 and 8 following treatment. Annular puncture resulted in disc narrowing and decreased T2­weighted signal intensity. At weeks 1 and 3, MRI examinations showed regenerative changes in the PRP­BMSC group and PRP group, whereas the PBS group exhibited a continuous degenerative process of the discs. At 8 weeks post­injection, the PRP­BMSCs induced a statistically significant restoration of discs, as shown by MRI (PRP­BMSCs, vs.PRP and PBS; P<0.05), which was also confirmed by histological evaluations. Thus, compared with PRP, the administration of PRP­containing BMSCs resulted in a superior regenerative effect on the early degenerated discs, which may be a promising therapeutic strategy for the restoration of early degenerated discs.

Bone Marrow Endothelial Progenitor Cell Transplantation After Ischemic Stroke: An Investigation Into Its Possible Mechanism.

AIMS: We tested the hypothesis that endothelial progenitor cell (EPC)-mediated functional recovery after stroke may be associated with the endothelial nitric oxide synthase (eNOS)/brain-derived neurotrophic factor (BDNF) signaling pathway. METHODS: Mice were infused with either EPCs or saline after being subjected to middle cerebral artery occlusion. The EPC-treated mice also received intravenous injections of either Nω-nitro-l-arginine methyl ester (L-NAME, the NOS inhibitor) or saline. RESULTS: The activation of eNOS and the expression of BDNF were significantly increased in ischemic brain of the EPC-treated mice, along with increased angiogenesis and neurogenesis. On diffusion tensor imaging (DTI), significant increases in fractional anisotropy and fiber count were observed in white matter, indicating axonal growth stimulated by EPCs. However, the EPC-treated mice that were received an L-NAME injection failed to exhibit the observed increases in angiogenesis, neurogenesis, and axonal growth. In addition, the neurons cocultured with EPCs in vitro exhibited the increased expression of BDNF and decreased apoptosis after oxygen-glucose deprivation compared with the control group. This EPC-induced protective effect was virtually absent in the L-NAME treatment group. CONCLUSION: The eNOS/BDNF pathway may be involved in the EPC-mediated functional recovery of stroke mice. DTI is feasible for dynamically tracking the orientation of axonal projections after EPC treatment.

Non-invasive monitoring of transplanted endothelial progenitor cells in diabetic ischemic stroke models.

Endogenous endothelial progenitor cells (EPCs) are functionally impaired in hyperglycemia through the p38 MAPK signaling pathway. However, the number and function of transplanted exogenous EPCs in diabetic animals remains unclear. The objectives of this study were to establish a non-invasive imaging strategy to monitor the homing of transplanted EPCs in diabetic stroke mice and to assess the effect of RWJ 67657, an inhibitor of p38 MAPK, on the homing ability of exogenous EPCs. Bone marrow-derived EPCs were labeled in vitro with a multi-functional nanoprobe modified with paramagnetic chelators and fluorophores before being infused into stroke mice. The signal of the nanoprobe reached its peak on day 5 in both magnetic resonance imaging and near-infrared fluorescence imaging after EPC transplantation in wild-type stroke models. The signal enhancement of diabetic stroke models was significantly lower than that of wild-type controls. However, the signal intensity of diabetic stroke models significantly increased after oral administration of RWJ 67657, indicating that more transplanted EPCs migrated to the ischemic brain. Furthermore, the increased exogenous EPCs induced remarkably greater angiogenesis after stroke. These results suggest that this dual-modal imaging strategy is feasible for non-invasively monitoring transplanted cells in vivo.

Image-guided pro-angiogenic therapy in diabetic stroke mouse models using a multi-modal nanoprobe.

PURPOSE: The efficacy of pro-angiogenic therapy is difficult to evaluate with current diagnostic modalities. The objectives were to develop a non-invasive imaging strategy to define the temporal characteristics of angiogenesis and to evaluate the response to pro-angiogenic therapy in diabetic stroke mouse models. METHODS: A home-made ανß3 integrin-targeted multi-modal nanoprobe was intravenously injected into mouse models at set time points after photothrombotic stroke. Magnetic resonance imaging (MRI) and near-infrared fluorescence (NIRF) imaging were carried out at 24 h post-injection. Bone marrow-derived endothelial progenitor cells (EPCs) were infused into the mouse models of ischemic stroke to stimulate angiogenesis. RESULTS: The peak signal intensity in the ischemic-angiogenic area of diabetic and wild-type mouse models was achieved on day 10, with significantly lower signal enhancement observed in the diabetic models. Although the signal intensity was significantly higher after EPC treatment in both models, the enhancement was less pronounced in the diabetic animals compared with the wild-type controls. Histological analysis revealed that the microvessel density and expression of ß3 integrin were correlated with the signal intensity assessed with MRI and NIRF imaging. CONCLUSIONS: The non-invasive imaging method could be used for early and accurate evaluation of the response to pro-angiogenic therapy in diabetic stroke models.

Renal lipids and oxygenation in diabetic mice: noninvasive quantification with MR imaging.

PURPOSE: To determine the relationship between renal lipid content and intrarenal oxygenation in diabetic nephropathy by using noninvasive chemical shift-selective (CSS) imaging and blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging. MATERIALS AND METHODS: The study was approved by the institutional Committee on Animal Research. Lipid and water phantoms for CSS imaging were made, and BOLD MR imaging phantoms from arterial and venous blood samples were collected from rats. CSS imaging and BOLD imaging were performed to measure lipid contents and T2* in phantoms and kidneys of diabetic gene (db) db/db mice and wild-type mice after exposure to nitrogen (four per group) and injection of furosemide (four per group). Results of MR imaging-measured lipid contents and oxygen tension were compared with known values in phantoms and reference standard from mice with histologic data. Statistical analysis was performed with independent sample and paired sample t tests and Pearson correlation test. RESULTS: Renal lipid content in db/db mice was significantly higher compared with that in control mice (9.40% ± 1.89 and 3.11% ± 0.57, respectively; P < .001). In addition, the lipid content in the cortex of db/db mice was significantly higher than that in medulla (12.73% ± 0.94 and 3.16% ± 0.50, respectively; P < .001). Correlation was significant between T2* measured with BOLD and oxygen tension in blood phantoms (r = 0.958; P < .001). Lower baseline T2* in diabetic kidney suggested lower oxygenation that reserved excess oxygen supply. Lower oxygenation in diabetic kidney cortex was observed after nitrogen exposure and furosemide injection. CONCLUSION: Noninvasive CSS imaging and MR imaging of db/db diabetic mice revealed the relationship between the renal lipid content and intrarenal oxygenation in diabetic kidney. Lipid accumulation in diabetic kidney compromises the oxygenation of the renal tissue and made it more susceptible to renal hypoxia. Online supplemental material is available for this article.

Comparison of brown and white adipose tissue fat fractions in ob, seipin, and Fsp27 gene knockout mice by chemical shift-selective imaging and (1)H-MR spectroscopy.

Brown adipose tissue (BAT) plays a key role in thermogenesis to protect the body from cold and obesity. White adipose tissue (WAT) stores excess energy in the form of triglycerides. To better understand the genetic effect on regulation of WAT and BAT, we investigated the fat fraction (FF) in two types of adipose tissues in ob/ob, human BSCL2/seipin gene knockout (SKO), Fsp27 gene knockout (Fsp27(-/-)), and wild-type (WT) mice in vivo using chemical shift selective imaging and (1)H-MR spectroscopy. We reported that the visceral fat volume in WAT was significantly larger in ob/ob mice, but visceral fat volumes were lower in SKO and Fsp27(-/-) mice compared with WT mice. BAT FF was significantly higher in ob/ob mice than the WT group and similar to that of WAT. In contrast, WAT FFs in SKO and Fsp27(-/-) mice were lower and similar to that of BAT. The adipocyte size of WAT in ob/ob mice and the BAT adipocyte size in ob/ob, SKO, and Fsp27 mice were significantly larger compared with WT mice. However, the WAT adipocyte size was significantly smaller in SKO mice than in WT mice. Positive correlations were observed between the adipocyte size and FFs of WAT and BAT. These results suggested that smaller adipocyte size correlates with lower FFs of WAT and BAT. In addition, the differences in FFs in WAT and BAT measured by MR methods in different mouse models were related to the different regulation effects of ob, seipin, or Fsp27 gene on developing WAT and BAT.

Non-invasive imaging of endothelial progenitor cells in tumor neovascularization using a novel dual-modality paramagnetic/near-infrared fluorescence probe.

OBJECTIVE: Bone-marrow derived endothelial progenitor cells (EPCs) play an important role in tumor neovasculature. Due to their tumor homing property, EPCs are regarded as promising targeted vectors for delivering therapeutic agents in cancer treatment. Consequently, non-invasive confirmation of targeted delivery via imaging is urgently needed. This study shows the development and application of a novel dual-modality probe for in vivo non-invasively tracking of the migration, homing and differentiation of EPCs. METHODS: The paramagnetic/near-infrared fluorescence probe Conjugate 1 labeled EPCs were systemically transplanted into mice bearing human breast MDA-MB-231 tumor xenografts. Magnetic resonance imaging (MRI) and near-infrared (NIR) fluorescence optical imaging were performed at different stages of tumor development. The homing of EPCs and the tumor neovascularization were further evaluated by immunofluorescence. RESULTS: Conjugate 1 labeled EPCs can be monitored in vivo by MRI and NIR fluorescence optical imaging without altering tumor growth for up to three weeks after the systemic transplantation. Histopathological examination confirmed that EPCs were recruited into the tumor bed and then incorporated into new vessels two weeks after the transplantation. Tumor size and microvessel density was not influenced by EPCs transplantation in the first three weeks. CONCLUSIONS: This preclinical study shows the feasibility of using a MRI and NIR fluorescence optical imaging detectable probe to non-invasively monitor transplanted EPCs and also provides strong evidence that EPCs are involved in the development of endothelial cells during the tumor neovascularization.

Involvement of epidermal growth factor receptor overexpression in the promotion of breast cancer brain metastasis.

BACKGROUND: Brain-metastatic breast cancer (BMBC) is increasing and poses a severe clinical problem because of the lack of effective treatments and because the underlying molecular mechanisms are largely unknown. Recent work has demonstrated that deregulation of epidermal growth factor receptor (EGFR) may correlate with BMBC progression. However, the exact contribution that EGFR makes to BMBC remains unclear. METHODS: The role of EGFR in BMBC was explored by serial analyses in a brain-trophic clone of human MDA-MB-231 breast carcinoma cells (231-BR cells). EGFR expression was inhibited by stable short-hairpin RNA transfection or by the kinase inhibitor erlotinib, and it was activated by heparin-binding epidermal growth factor-like growth factor (HB-EGF). Cell growth and invasion activities also were analyzed in vitro and in vivo. RESULTS: EGFR inhibition or activation strongly affected 231-BR cell migration/invasion activities as assessed by an adhesion assay, a wound-healing assay, a Boyden chamber invasion assay, and cytoskeleton staining. Also, EGFR inhibition significantly decreased brain metastases of 231-BR cells in vivo. Surprisingly, changes to EGFR expression affected cell proliferation activities less significantly as determined by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, an anchorage-independent growth assay, and cell cycle analysis. Immunoblot analysis suggested that EGFR drives cells' invasiveness capability mainly through phosphoinositide 3-kinase/protein kinase B and phospholipase C γ downstream pathways. In addition, EGFR was involved less in proliferation because of the insensitivity of the downstream mitogen-activated protein kinase pathway. CONCLUSIONS: The current results indicated that EGFR plays more important roles in cell migration and invasion to the brain than in cell proliferation progression on 231-BR cells, providing new evidence of the potential value of EGFR inhibition in treating BMBC.

Quantification of liver fat in mice: comparing dual-echo Dixon imaging, chemical shift imaging, and 1H-MR spectroscopy.

We evaluated dual-echo Dixon in-phase and out-of-phase (IP-OP), chemical shift imaging (CSI), and (1)H MRS (hydrogen MR spectroscopy) in estimating fat content (FC) in phantoms and in livers of mice. Phantoms were made according to the volume percentage of fat ranging from 0% to 100%. The three MR methods were performed to measure FC in phantoms and in livers of obese leptin-deficient (ob/ob), human BSCL2/seipin gene knockout (SKO), and wild-type (WT) mice. The results were compared with known FC in phantoms and to a reference standard from mice by histological semiautomatic vacuole segmentation (HIS-S) procedure and liver lipid (LL) chemical analysis. In phantoms, CSI underestimated FC from 50% to 100%, to a lesser extent than IP-OP. In vivo, liver FC in ob/ob and SKO mice measured by the three MR methods were all significantly higher than that in WT mice. Liver FC measured by IP-OP were significantly lower than that measured by CSI and MRS, with no significant difference between CSI and MRS. CSI and MRS showed a linear correlation with LL analysis and with each other. IP-OP underestimated FC, whereas CSI and MRS were more accurate for quantifying FC in both phantoms and liver. CSI and MRS have the potential to replace HIS-S and LL analysis in longitudinal studies.