Comparison of Gadolinium-BOPTA and Ferucarbotran-Enhanced Three-Dimensional T1-Weighted Dynamic Liver Magnetic Resonance Imaging in the Same Patient

The effects of iron oxide incorporation on the chondrogenic potential of three human cell types

Non-invasive monitoring of living cells in vivo provides an important tool in the development of cell-based therapies in cartilage tissue engineering. High-resolution magnetic resonance imaging (MRI) has been used to monitor target cell populations in vivo. However, the side-effects on cell function of the labelling reagents, such as superparamagnetic iron oxide (SPIO), are still unclear. This study investigated the effect of SPIO particles on the chondrogenic differentiation of human bone marrow stromal cells (HBMSCs), neonatal and adult chondrocytes in vitro. Cells were labelled with SPIO for 24 h and chondrogenesis induced in serum-free medium including TGFβ3. For labelled/unlabelled cells, viability, morphology and proliferation were determined using CellTracker™ Green and PicoGreen dsDNA assays. The expression of SOX9, COL2A1 and ACAN was investigated using qRT-PCR after 2, 7 and 14 days. The results showed that viability was unaffected in all of the cells but cell morphology changed towards a 'stretched' phenotype following SPIO uptake. Cell proliferation was reduced only for labelled neonatal chondrocytes. SOX9 and COL2A1 expression decreased at day 2 but not at days 7 and 14 for labelled HBMSCs and adult chondrocytes; ACAN expression was unaffected. In contrast, SOX9 and COL2A1 expression were unaffected in labelled neonatal chondrocytes but a decrease in ACAN expression was seen at day 14. The results suggest that downregulation of chondrogenic genes associated with SPIO labelling is temporary and target cell-dependent. Resovist® can be used to label HBMSCs or mature chondrocytes for MR imaging of cells for cartilage tissue engineering.

Focal nodular hyperplasia or focal nodular hyperplasia-like lesions of the liver: a special emphasis on diagnosis

BACKGROUND AND AIM

Focal nodular hyperplasia (FNH) and FNH-like lesions are hypervascular masses that can mimic hepatocellular carcinoma (HCC). We have investigated the clinical, radiological and pathological features of FNH and FNH-like lesions of the liver, with particular focus on the aspect of diagnosis.

METHODS

A total of 84 patients, 77 with pathologically-proven FNH and seven with FNH-like lesions of the liver, were analyzed retrospectively.

RESULTS

Of the 84 patients, seven had underlying liver cirrhosis, including two with Budd-Chiari syndrome and one with cardiac cirrhosis. These cases were therefore classified as having FNH-like lesions. Two of the remaining 77 patients without underlying liver cirrhosis were positive for hepatitis B surface antigen. Seven of 50 (14.0%) patients evaluated by four-phase computed tomography (CT) showed portal or delayed washout, and three of 28 (10.7%) patients analyzed by three-phase CT showed washout on the portal phase. Collectively, three of nine (33.3%) patients with risk factors for HCC could have been wrongly diagnosed with HCC based on the non-invasive diagnostic criteria for HCC. A central scar was observed in 30 patients (35.7%) radiologically. Among 62 patients who underwent percutaneous needle biopsy, four patients (6.5%) were misdiagnosed as having HCC and two patients (3.2%) had inconclusive results by a first needle biopsy.

CONCLUSIONS

The presence of a hepatic lesion with arterial hypervascularity and/or portal/delayed washout is not necessarily diagnostic of HCC, particularly in patients without risk factors for HCC. These radiological findings can also occur in cirrhotic patients with FNH-like lesions, including those with hepatic outflow obstruction.

Functional investigations on human mesenchymal stem cells exposed to magnetic fields and labeled with clinically approved iron nanoparticles

Background

For clinical applications of mesenchymal stem cells (MSCs), labeling and tracking is crucial to evaluate cell distribution and homing. Magnetic resonance imaging (MRI) has been successfully established detecting MSCs labeled with superparamagnetic particles of iron oxide (SPIO). Despite initial reports that labeling of MSCs with SPIO is safe without affecting the MSC's biology, recent studies report on influences of SPIO-labeling on metabolism and function of MSCs. Exposition of cells and tissues to high magnetic fields is the functional principle of MRI. In this study we established innovative labeling protocols for human MSCs using clinically established SPIO in combination with magnetic fields and investigated on functional effects (migration assays, quantification of colony forming units, analyses of gene and protein expression and analyses on the proliferation capacity, the viability and the differentiation potential) of magnetic fields on unlabeled and labeled human MSCs. To evaluate the imaging properties, quantification of the total iron load per cell (TIL), electron microscopy, and MRI at 3.0 T were performed.

Results

Human MSCs labeled with SPIO permanently exposed to magnetic fields arranged and grew according to the magnetic flux lines. Exposure of MSCs to magnetic fields after labeling with SPIO significantly enhanced the TIL compared to SPIO labeled MSCs without exposure to magnetic fields resulting in optimized imaging properties (detection limit: 1,000 MSCs). Concerning the TIL and the imaging properties, immediate exposition to magnetic fields after labeling was superior to exposition after 24 h. On functional level, exposition to magnetic fields inhibited the ability of colony formation of labeled MSCs and led to an enhanced expression of lipoprotein lipase and peroxisome proliferator-activated receptor-γ in labeled MSCs under adipogenic differentiation, and to a reduced expression of alkaline phosphatase in unlabeled MSCs under osteogenic differentiation as detected by qRT-PCR. Moreover, microarray analyses revealed that exposition of labeled MSCs to magnetic fields led to an up regulation of CD93 mRNA and cadherin 7 mRNA and to a down regulation of Zinc finger FYVE domain mRNA. Exposition of unlabeled MSCs to magnetic fields led to an up regulation of CD93 mRNA, lipocalin 6 mRNA, sialic acid acetylesterase mRNA, and olfactory receptor mRNA and to a down regulation of ubiquilin 1 mRNA. No influence of the exposition to magnetic fields could be observed on the migration capacity, the viability, the proliferation rate and the chondrogenic differentiation capacity of labeled or unlabeled MSCs.

Conclusions

In our study an innovative labeling protocol for tracking MSCs by MRI using SPIO in combination with magnetic fields was established. Both, SPIO and the static magnetic field were identified as independent factors which affect the functional biology of human MSCs. Further in vivo investigations are needed to elucidate the molecular mechanisms of the interaction of magnetic fields with stem cell biology.

The Use of Clinically Approved Small Particles of Iron Oxide (SPIO) for Labeling of Mesenchymal Stem Cells Aggravates Clinical Symptoms in Experimental Autoimmune Encephalomyelitis and Influences Their In Vivo Distribution

Multiple sclerosis (MS) is an inflammatory and demyelinating disease of the central nervous system (CNS). Mesenchymal stem cells (MSC) have been shown to ameliorate symptoms in experimental autoimmune encephalomyelitis (EAE), a model of MS. Using cloned MSC labeled with clinically approved small particles of iron oxide (SPIO) for treatment of EAE we analyzed the tissue localization of transferred cells. Treatment with unlabeled MSC led to disease amelioration compared to controls. In contrast, treatment with SPIO-labeled MSC lead to increase in disease severity. Treatment with SPIO alone did not alter disease course. After transplantation labeled and nonlabeled MSC were detected in the CNS and the liver with significantly more SPIO-labeled cells present in the CNS. Iron deposition was present in the group treated with SPIO-labeled MSC, indicating that in vivo the initially cell surface-bound iron detached from the MSC. These results could be of great importance for imaging of patients in the clinical setting, indicating that in vivo application of SPIO-labeled MSC needs to be performed with caution because the cell-derived exposure of iron can lead to disease aggravation.

Preclinical safety evaluation of Gd-EOB-DTPA (Primovist)

OBJECTIVES

Gadoxetic acid [gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid (Gd-EOB-DTPA); Primovist] is a liver specific contrast agent for magnetic resonance imaging. For risk assessment of the single diagnostic use the toxicity of this compound was assessed.

MATERIALS AND METHODS

Studies into acute, repeated-dose, reproductive and developmental toxicity, and local tolerance, contact sensitizing, and genotoxic potential were performed.

RESULTS

Lethality was observed after a single intravenous administration at doses 2 orders of magnitude higher than the clinical dose. The no observed adverse effect levels after repeated administration markedly exceeds the single diagnostic dose in humans and no unexpected organ toxicity was observed. No indications of reproductive and developmental toxicity, potential contact allergenic, and genotoxic effects were observed. Gd-EOB-DTPA was well tolerated after intravenous administration.

CONCLUSIONS

Gd-EOB-DTPA was well tolerated with high safety margins between the single diagnostic dose and the doses showing adverse effects in animal studies.

Advances in magnetic resonance (2007)

Advances in clinical magnetic resonance (MR) are discussed in this review in the context of publications from Investigative Radiology during 2006 and 2007. The articles relevant to this topic, published during this 2 year time period, are considered as organized by anatomic region. An additional final focus of discussion is in regards to those studies involving MR contrast media.

Model-based analysis of Gd-BOPTA-induced MR signal intensity changes in cirrhotic rat livers

OBJECTIVE

To quantify the hepatic transport of the hepatobiliary contrast agent gadobenate dimeglumine (Gd-BOPTA) in rats with biliary cirrhosis of various severity degrees from magnetic resonance (MR) signal intensities using a population pharmacokinetic approach.

MATERIALS AND METHODS

MR signal intensity was recorded during the Gd-BOPTA perfusion of normal and cirrhotic isolated rat livers. Similar experiments were conducted with Gd-labeled Gd-BOPTA to quantify Gd-BOPTA content in liver, bile, and perfusate. All experimental data were analyzed together according to a population pharmacokinetic approach.

RESULTS

A 6-compartment model developed from the radioactivity data adequately fit all MRI data when 4 image parameters were added to describe the relationship between the amount of contrast agent and the signal intensity. The model showed that entry of Gd-BOPTA into hepatocytes was decreased in cirrhotic livers when compared to normal livers.

CONCLUSIONS

Although the MR signal intensity is similar in normal and cirrhotic livers, the population pharmacokinetic approach developed in this study shows a decreased entry of Gd-BOPTA into cirrhotic hepatocytes.

Transferrin Receptor Upregulation: In Vitro Labeling of Rat Mesenchymal Stem Cells with Superparamagnetic Iron Oxide

PURPOSE

To prospectively evaluate the influence of superparamagnetic iron oxide (SPIO) or ultrasmall SPIO (USPIO) particles on the surface epitope pattern of adult mesenchymal stem cells (MSCs) by regulating the expression of transferrin receptor and to prospectively evaluate the influence of transfection agents (TAs) on the uptake of SPIO or USPIO particles in MSCs.

MATERIALS AND METHODS

The study was approved by the institutional animal care committee of the University of Tübingen. MSCs were isolated from the bone marrow of four rats. To obtain highly homogeneous MSC populations, MSCs from one rat were single-cell cloned. One MSC clone was characterized and selected for the labeling experiments. The MSCs, which were characterized with flow cytometry and in vitro differentiation, were labeled with 200 microg/mL SPIO or USPIO or with 60 microg/mL SPIO or USPIO in combination with TAs. Aggregations of labeled cells were accommodated inside a defined volume in an agar gel matrix. Magnetic resonance (MR) imaging was performed to measure SPIO- or USPIO-induced signal voids. Quantification of cellular total iron load (TIL) (intracellular iron plus iron coating the cellular surface), determination of cellular viability, and electron microscopy were also performed.

RESULTS

Labeling of MSCs with SPIO or USPIO was feasible without affecting cell viability (91.1%-94.7%) or differentiation potential. For MR imaging, SPIO plus a TA was most effective, depicting 5000 cells with an average TIL of 76.5 pg per cell. SPIO or USPIO particles in combination with TAs coated the cellular surface but were not incorporated into cells. In nontransfected cells, SPIO or USPIO was taken up. MSCs labeled with SPIO or USPIO but without a TA showed enhanced expression of transferrin receptor, in contrary to both MSCs labeled with SPIO or USPIO and a TA and control cells.

CONCLUSION

SPIO or USPIO labeling without TAs has an influence on gene expression of MSCs upregulating transferrin receptor. Furthermore, SPIO labeling with a TA will coat the cellular surface.

Evaluation of a Novel Time-Efficient Protocol for Gadobenate Dimeglumine (Gd-BOPTA)-Enhanced Liver Magnetic Resonance Imaging

OBJECTIVE

We sought to evaluate gadobenate dimeglumine for the detection and characterization of focal liver lesions in the unenhanced and already pre-enhanced liver.

MATERIALS AND METHODS

Sixty patients were evaluated prospectively. Unenhanced T1-weighted gradient echo (T1wGRE) and T2-weighted turbo spin echo (T2wTSE) images were acquired followed by contrast-enhanced T1wGRE images during the dynamic, equilibrium, and delayed phases after the bolus injection of 0.05 mmol/kg gadobenate dimeglumine. An identical series of dynamic images was then acquired after the delayed scan following a second 0.05 mmol/kg bolus of gadobenate dimeglumine. Images were evaluated randomly in 2 sessions by 3 independent blinded readers. Evaluated images in the first session comprised the unenhanced images, the first or second set of dynamic images, and the delayed images. The second session included the unenhanced images, the dynamic images not yet evaluated in the first session, and the delayed images. The 2 reading sessions were compared for lesion characterization and diagnosis, and kappa (kappa) values for interobserver agreement were determined. Quantitative evaluation of lesion contrast enhancement was also performed.

RESULTS

The enhancement behavior in the second dynamic series was similar to that in the first series, although pre-enhancement of the normal liver resulted in reduced lesion-liver contrast-to-noise ratios and the visualization of some lesions only on arterial phase images. Typical imaging features for the lesions included in the study were visualized clearly in both series. Strong agreement (kappa=0.56-0.89; all evaluations) between the 2 images sets was noted by all readers for differentiation of benign from malignant lesions and for definition of specific diagnosis, and between readers for diagnoses established based on images acquired in the unenhanced and pre-enhanced liver.

CONCLUSION

Dynamic imaging in the hepatobiliary phase gives similar information as dynamic imaging of the unenhanced liver. This might prove advantageous for screening protocols involving same session imaging of primary extrahepatic tumors and liver.

Multishot diffusion-weighted PROPELLER magnetic resonance imaging of the abdomen

OBJECTIVE

The objective of this study was to evaluate the feasibility of using multishot PROPELLER for diffusion-weighted imaging (DWI) of the abdomen.

MATERIALS AND METHODS

Diffusion-weighted abdominal imaging was performed in 9 healthy volunteers and 3 patients using both single-shot DW-SE-EPI and multishot DW-PROPELLER (BLADE sequence). We compared ADC measurements in phantoms, liver and pancreatic tissues and performed qualitative comparisons of the diffusion-weighted images and ADC maps provided by these 2 techniques.

RESULTS

DW-PROPELLER significantly improved image quality (P < 0.05) with reduced geometric distortion and artifact. The ADC values of phantoms and abdominal organs measured by DW-PROPELLER were generally greater than those measured by single-shot DW-SE-EPI. The ADC values measured by both DWI techniques were significantly different for liver tissues but not for pancreatic tissues (P < 0.05). Preliminary patient studies demonstrated clearly distinguished lesion areas from surrounding normal liver tissues in the DW-PROPELLER images. DW-PROPELLER offers the potential for high-resolution DWI of the abdomen.

CONCLUSIONS

The multishot DW-PROPELLER sequence is a promising technique for DWI of abdominal organs. Future clinical studies will evaluate the use of DW-PROPELLER technique for abdominal oncologic imaging applications.

Advances in Magnetic Resonance (2006)

Advances in the field of magnetic resonance (MR) as it pertains to clinical diagnostic radiology are examined in this review on the basis of publications in Investigative Radiology over the past 2 years (2005-2006). The articles published during that timeframe are discussed, organizationally wise, by anatomic region with an additional focus on studies involving MR contrast media.

Relaxivity of Gadopentetate Dimeglumine (Magnevist), Gadobutrol (Gadovist), and Gadobenate Dimeglumine (MultiHance) in Human Blood Plasma at 0.2, 1.5, and 3 Tesla

OBJECTIVES

We sought to determine the relaxivity and accurate relaxation rates of Gd-DTPA, Gd-BT-DO3A, and Gd-BOPTA at 0.2, 1.5, and 3 T in human blood plasma.

MATERIALS AND METHODS

Contrast media concentrations between 0.01 and 16 mM in human plasma were used for relaxation measurements. The R1 and R2 relaxation rates and r1 and r2 relaxivities were determined.

RESULTS

Gd-BOPTA produced the highest relaxation rates and relaxivities at all field strengths. The r1 and r2 values for Gd-BOPTA were 107-131% and 91-244% higher than for Gd-DTPA, respectively, and 72-98% and 82-166% higher than for Gd-BT-DO3A. Higher field strengths resulted in lower values of R1, R2, and r1 for all contrast agents tested and of r2 for Gd-DTPA and Gd-BT-DO3A. A linear dependence of R1 and R2 on concentration was found for Gd-DTPA and Gd-BT-DO3A and a nonlinear dependence for Gd-BOPTA for concentrations larger than 1 mM. The r1 and r2 relaxivity of Gd-BOPTA increased with decreasing concentration.

CONCLUSIONS

Gd-BOPTA demonstrates the highest longitudinal r1 at all field strengths, which is ascribable to weak protein interaction. The R2/R1 ratio increases at higher field strength only for Gd-BOPTA, hence very short echo times are required for Gd-BOPTA to benefit from the higher longitudinal relaxivity.