Gadolinium and nephrogenic systemic fibrosis: association or causation

A Heart Rate-Dependent Protocol of "One-Stop" Computed Tomography Angiography of Coronary Combined with Pulmonary Arteries Reduces the Dosages of Contrast Agent

Background:

The personalized, heart rate-dependent computed tomography angiography (CTA) protocol can reduce the use of contrast medium (CM) and the radiation dose. This is especially beneficial for patients with CTA of coronary combined with pulmonary arteries.

Purpose:

To evaluate the feasibility of low CM in one-stop coronary and pulmonary arterial CTA tailored by patients’ heart rate.

Material and Methods:

94 patients set to undergo CTA of coronary combined with pulmonary arteries with one-stop scans. Patients were prospectively randomized into two groups: For group A (n = 47), the timing of the scans was determined according to the patient’s HR using 30 mL CM; For group B (n = 47), in which the routine bolus tracking was applied by setting the ascending aortic threshold of 80 HU with 70 mL CM, scans were performed simultaneously.

Results:

Compared with group B, group A had slightly higher computed tomography (CT) value and image quality of pulmonary artery (CT value: group A 484.7HU; group B 457.9HU; t = 2.446, P = .016; image quality: χ2 = 8.292, P = .016), but in coronary artery wasn’t statistically different between two groups(image quality: χ2 = 2.516, P = .642).

Conclusion:

The heart rate-dependent CM injection protocol can greatly reduce the use of CM, simplify the work-flow, and may obtain comparable or even better image quality compared with the routine bolus tracking.

Nano-confinement-driven enhanced magnetic relaxivity of SPIONs for targeted tumor bioimaging

Superparamagnetic iron oxide nanoparticles (SPIONs) are highly biocompatible and have a versatile synthetic technique based on coprecipitation, reduction-precipitation, and hydrothermal methods, where Fe³⁺ and Fe²⁺ react in aqueous solutions; both these ions are present in our body and have clear metabolic pathways; therefore, they have attracted extensive research interest and development in the field of diagnostic imaging and therapy. However, most SPION-based clinical diagnostic contrast agents are discontinued due to severe pain, low transverse magnetic relaxivity range of 80-180 mM^-1 s^-1, shorter circulation half-life, and lack of disease specificity. Therefore, in this study, we engineered a bone cancer-targeted hybrid nanoconstruct (HNC) with a high transverse magnetic relaxivity of 625 mM^-1 s^-1, which was significantly higher than that of clinical contrast agents. The engineered HNC is peripherally decorated with a bone-seeking agent, alendronic acid-conjugated phospholipid, exhibiting a hydrodynamic size of 80 nm with a negative surface potential, -35 mV. The interior skeleton of the HNC is composed of biodegradable and biocompatible poly(l-lactic-co-glycolic acid) (PLGA), in which 5 nm SPIONs are confined. We have successfully tuned the distance between the confined SPIONs from 0.5 to 4 nm, as revealed by transmission electron microscopy (TEM) images and magnetic resonance image (MRI) phantoms. This cluster confinement dramatically enhances magnetic relaxivity possibly due to the increase in net local magnetization due to proximal field inhomogeneity. In an in vitro examination, 80% of HNC is found to bind with hydroxyapatite (HAp), which when characterized by TEM shows a painting of SPIONs over a HAp crystal. HNC is found to accumulate in mouse osteosarcoma tumor (K7M2 tumor model); both MRI and histological examination of the tumor show the potential of HNC as targeting agents for diagnosis of tumor in the bone.

Synthesis and In Vitro Characterization of Fe3+-Doped Layered Double Hydroxide Nanorings as a Potential Imageable Drug Delivery System

Highly dispersed Fe3+-doped layered double hydroxide (LDH-Fe) nanorings were obtained by a simple coprecipitation-acid etching approach. The morphology, structure, magnetic resonance imaging (MRI) performance in vitro, drug loading and releasing, Fe3+ leakage, and cytotoxicity of the as-prepared LDH-Fe nanorings were characterized. The LDH-Fe nanorings showed good water dispersity and a well-crystallized structure. The DLS average size of nanoparticles was measured to be 94.5 nm. Moreover, the MRI tests showed a favourable T₁-weighted MRI performance of the LDH-Fe nanoring with r₁ values of 0.54 and 1.68, and low r₂/r₁ ratios of 10.1 and 6.3, pre- and after calcination, respectively. The nanoparticles also showed high model drug (ibuprofen) loading capacities, low Fe3+ leakage, and negligible cytotoxicity. All these results demonstrate the potential of LDH-Fe nanorings as an imageable drug delivery system.

Gadolinium-Induced Fibrosis

Gadolinium-based contrast agents (GBCAs), once believed to be safe for patients with renal disease, have been strongly associated with nephrogenic systemic fibrosis (NSF), a severe systemic fibrosing disorder that predominantly afflicts individuals with advanced renal dysfunction. We provide a historical perspective on the appearance and disappearance of NSF, including its initial recognition as a discrete clinical entity, its association with GBCA exposure, and the data supporting a causative relationship between GBCA exposure and NSF. On the basis of this body of evidence, we propose that the name gadolinium-induced fibrosis (GIF) more accurately reflects the totality of knowledge regarding this disease. Use of high-risk GBCAs, such as formulated gadodiamide, should be avoided in patients with renal disease. Restriction of GBCA use in this population has almost completely eradicated new cases of this debilitating condition. Emerging antifibrotic therapies may be useful for patients who suffer from GIF.

Pathophysiology of gadolinium-associated systemic fibrosis

Systemic fibrosis from gadolinium-based magnetic resonance imaging contrast is a scourge for the afflicted. Although gadolinium-associated systemic fibrosis is a rare condition, the threat of litigation has vastly altered clinical practice. Most theories concerning the etiology of the fibrosis are grounded in case reports rather than experiment. This has led to the widely accepted conjecture that the relative affinity of certain contrast agents for the gadolinium ion inversely correlates with the risk of succumbing to the disease. How gadolinium-containing contrast agents trigger widespread and site-specific systemic fibrosis and how chronicity is maintained are largely unknown. This review highlights experimentally-derived information from our laboratory and others that pertain to our understanding of the pathophysiology of gadolinium-associated systemic fibrosis.

Multiple sclerosis lesion formation and early evolution revisited: A weekly high-resolution magnetic resonance imaging study

BACKGROUND

Several magnetic resonance imaging (MRI) studies investigated the evolution of multiple sclerosis (MS) lesions to understand the pathophysiological mechanisms leading to blood-brain barrier breakdown and lesion formation. Only a few assessed the early natural history of MS lesions using short-interval longitudinal MRI.

OBJECTIVE

The purpose of this study was to characterize MS lesion occurrence and early evolution on high-resolution MRI acquired at weekly intervals.

METHODS

Active lesions were characterized on 3D fluid attenuation inversion recovery (FLAIR) and gadolinium-enhanced 3D T1-weighted MRI performed weekly (seven weeks) on five untreated patients with relapsing-remitting MS (RRMS).

RESULTS

Active lesions (n=212) were detected in all patients. All showed contrast-enhancement on at least one time-point. Most new lesions (83.5%) were visible on FLAIR and post-contrast T1-weighted images at first detection; 11.2% showed activity on FLAIR images, one or more weeks before the appearance of contrast-enhancement; 12.5% enhanced before being apparent on FLAIR.

CONCLUSION

Blood brain barrier disruption is a constant step in the natural history of active MS lesions, but does not always constitute the initial event. These findings are consistent with the existence of a subpopulation of lesions with an 'inside-out' genesis, where neurodegenerative processes might precede microglial activation, and a subsequent adaptive immune response.

Integrin-mediated signaling contributes to gadolinium-containing-particle-promoted cell survival and G₁ to S phase cell cycle transition by enhancing focal adhesion formation

We previously reported that Gd-containing particles formed under physiological conditions act as active entities to enhance cell survival and promote S phase entry via activation of both mitogen-activated protein kinase/extracellular-signal-regulated protein kinase (ERK) and phosphatidylinositol 3-kinase/Akt signaling pathways. However, how they transduce the extracellular signal inside the cell remains unclear. The present study demonstrates that Gd-containing particles can alleviate serum-deprivation-induced cell death and promote G₁ to S phase cell cycle progression by enhancing cell adhesion to the extracellular matrix. As an indicator of adhesion, the vinculin distribution was detected by confocal laser scanning microscopy. The control cells exhibited fewer and less typical focal adhesions. After treatment with Gd-containing particles, a large number of vinculin-containing focal adhesions were maintained. In the presence of integrin antagonists, the percentage of S phase entry induced by Gd-containing particles was decreased and the enhancement of cell viability was also attenuated, along with a decrease in both cyclin D expression and ERK phosphorylation. In summary, the present results suggest that the integrin-mediated signaling pathway plays an important role in cell survival and G₁ to S phase transition promoted by Gd-containing particles by enhancing focal adhesion formation. The results presented here provide novel evidence to advance knowledge leading to further understanding of the mechanisms of both cell proliferation and cell survival promoted by Gd and may be helpful for developing effective measures to prevent or treat nephrogenic systemic fibrosis.

Preoperative staging of renal cell carcinoma using magnetic resonance imaging: comparison with pathological staging

We have retrospectively assessed the accuracy of our MRI protocol on 1.0-T MRI system for preoperative staging of renal cell carcinoma using the 2002 TNM staging system and pathological staging as the gold standard. Medical records of 48 patients (mean age, 56.28 years) with 57 renal tumors were reviewed: 52 malignant renal tumors were found; most of the patients were staged T1N0M0. In our study, κ test revealed excellent agreement between all three classes of the TNM staging system.

Gadolinium-promoted precipitation of calcium phosphate is associated with profibrotic activation of RAW 264.7 macrophages

Gadolinium-based contrast agents are now being linked to nephrogenic systemic fibrosis (NSF). The exact mechanism by which gadolinium species act in the pathogenesis of NSF is not fully understood. In this study, we evaluated the effect of gadolinium chloride (GdCl(3)) on the precipitation of calcium phosphate, and examined the role of the gadolinium-containing precipitates in the profibrotic activation of macrophages. In a free-drift system, the induction time was markedly reduced with increasing concentration of GdCl(3), accompanied by alterations of morphology and composition of the precipitates. In complete cell culture medium, the addition of GdCl(3) resulted in formation of particles around 200-300 nm. In an in vitro cellular model with RAW 264.7 macrophages, GdCl(3) increased the production of TGF-beta1 and IL-6 via the activation of PKC and ERK signaling pathway. Our findings demonstrate that GdCl(3) promotes calcium phosphate precipitation and induces profibrotic activation of macrophages.

Induction of the expression of profibrotic cytokines and growth factors in normal human peripheral blood monocytes by gadolinium contrast agents

OBJECTIVE

Nephrogenic systemic fibrosis (NSF) is a severe fibrosing disorder occurring in patients with renal insufficiency. The majority of patients with this disorder have documented exposure to magnetic resonance imaging contrast agents containing Gd. The purpose of this study was to examine the effects of gadolinium diethylenetriaminepentaacetic acid bismethylamide (Gd[DTPA-BMA]; Omniscan) as compared with Gd-DTPA and GdCl3 on the expression and production of cytokines and growth factors by normal human peripheral blood monocytes in vitro and to examine whether conditioned media from Gd-exposed peripheral blood monocytes could induce a profibrotic phenotype in dermal fibroblasts.

METHODS

Normal human peripheral blood monocytes isolated by Ficoll-Hypaque gradient centrifugation and plastic adherence were incubated with various concentrations of Gd[DTPA-BMA], Gd-DTPA, or GdCl3. Gene expression of interleukins 4, 6, and 13, interferon-gamma, tumor necrosis factor alpha, transforming growth factor beta, connective tissue growth factor, and vascular endothelial growth factor were assessed by real-time polymerase chain reaction (PCR) analysis. Production and secretion of cytokines and growth factors by Gd compound-exposed monocytes was quantified by enzyme-linked immunosorbent assay proteome multiplex arrays. The effects of conditioned media from the Gd compound-exposed monocytes on the phenotype of normal human dermal fibroblasts were examined by real-time PCR and Western blotting.

RESULTS

The 3 Gd-containing compounds stimulated the expression and production of numerous cytokines and growth factors by normal human peripheral blood monocytes. Conditioned media from these cells induced a profibrotic phenotype in normal human dermal fibroblasts.

CONCLUSION

The 3 Gd-containing compounds studied induce potent cellular responses in normal human peripheral blood monocytes, which may participate in the development of tissue fibrosis in NSF.

[Nephrogenic systemic fibrosis]

Nephrogenic systemic fibrosis is a highly debilitating and emotionally depressing disorder. So far, it has exclusively occurred in patients suffering from acute or chronic renal failure. Most patients had been exposed to gadolinium- based contrast agents. Early symptoms include pain, swelling and pruritus, predominantly of the extremities. Fibrosis of the skin and other organs develops in the further course of the disease. The diagnosis is made based on the synopsis of medical history, clinical and dermatohistological findings. To avoid the application of gadolinium-based contrast agents in patients with highly impaired renal function is the best measure to prevent the disease. An effective therapy has not yet been established. Possible therapies, which have been successful in individual cases, comprise, among others, a quick restoration of renal function, physiotherapy, and extracorporeal photopheresis.

Contrast Media in Urogenital Radiology

Background

Contrast media are widely used in urogenital radiology. The ideal contrast agent should be totally inert, causing no interactions with organism, and with a rapid and complete excretion. Adverse reactions could occur after using any type of contrast media. Contrast enhanced procedures are performed with increasing frequency and the patients population is progressively older and with multiple co-morbid conditions, thus contrast media toxicity is becoming a serious problem. Contrast media-induced nephropathy (CIN) is considered an important cause of hospital-acquired renal failure. The administration of gadolinium-based contrast agents has been recently associated with the development of a serious adverse reaction, potentially lethal in patients with renal insufficiency, named nephrogenic systemic fibrosis (NSF).

Methods

Literature review on contrast media in urogenital radiology, CIN, NSF.

Conclusions

Since 1996, the Contrast Media Safety Committee of the European Society of Urogenital Radiology (ESUR) has released its guidelines regarding safety about the use of contrast media. CIN, and the emerging NSF, are topics of increasing interest for urologists, radiologists, nephrologists, dermatologists and all the clinicians. Contrast media have progressively become safer in the last years. Even if rare, some adverse reactions still occurr up to now. CIN and its prevention remain an issue under debate. In the past, whenever a patient required a contrast-enhanced imaging study, the trend was to select magnetic resonance imaging with gadolinium-based contrast agents in order to avoid the well-known CIN of iodinated-based contrast agents. The awareness of NFS is changing the contrast–enhanced imaging in patients with renal failure. At present we have to investigate NSF etiopathogenesis, in order to prevent and eventually to cure it. The understanding of the risk factors for both CIN and NSF is an emerging need, the adoption of all preventive measures to reduce the risks remain a mandatory issue.

Blood oxygen level-dependent MR imaging of the kidneys

Oxygenation status plays a major role in renal physiology and pathophysiology, and thus has attracted considerable attention in recent years. While much of the early work and a significant amount of present work is based on invasive methods or ex vivo analysis, and is therefore restricted to animal models, blood oxygen level-dependent (BOLD) MR imaging has been shown to extend these findings to human beings. BOLD MR imaging is most useful in monitoring effects of physiologic or pharmacologic maneuvers. Several teams around the world have demonstrated reproducible data and have illustrated several useful applications. Studies supporting the use of renal BOLD MR imaging in characterizing disease with prognostic value have also been reported. This article provides an overview of current state-of-the art of renal BOLD MR imaging.

MRI for identification of progression in brain tumors: from morphology to function

For monitoring of brain tumors, it is crucial to identify progression or treatment failure early during follow-up to change treatment schemes and, thereby, optimize patient outcome. In the past years, several areas within the field of magnetic resonance (MR) have seen considerable advances: modern contrast media, advanced morphologic approaches and several functional techniques, for example, in the visualization of tumor perfusion or tumor cell metabolism. This review presents these recent advances by introducing the different techniques and outlining their benefit for identification of progression in brain tumors, with a focus on gliomas, metastases and meningiomas. After radiotherapy, MR spectroscopy helps to more accurately discriminate between radiation necrosis and glioma progression. In low-grade gliomas, perfusion MR techniques enable a more sensitive detection of anaplastic transformation than conventional MRI. Modern contrast media, as well as diffusion tensor imaging, allow for an improved tumor delineation and assessment of tumor extension. We will also highlight the biological background of these techniques, their applicability and current limitations. In conclusion, modern MRI techniques have been developed that are on the doorstep to be integrated in clinical routine.

Epidemiology and diagnosis of peripheral arterial disease in patients with chronic kidney disease

Chronic kidney disease (CKD) and peripheral arterial disease (PAD) are common and frequently coexist. Among subjects with CKD, arterial disease may be due to atherosclerosis, medial arterial calcification (MAC), or both conditions concomitantly. It is important for clinicians to recognize both conditions because each identifies individuals at higher risk of cardiovascular disease events, and because the presence of MAC complicates interpretation of the ankle brachial index, the most commonly used diagnostic test for artherosclerotic PAD. To that end, we review the epidemiology and diagnosis of atherosclerotic PAD and medical arterial calcification in patients with CKD.

Magnetic resonance urography in children

Magnetic resonance (MR) urography is a powerful tool that fuses anatomic information with functional data in a single test without the use of ionizing radiation. This article provides an overview of the technical aspects of MR urography and common clinical applications, such as the evaluation of hydronephrosis, reflux nephropathy, and renal dysplasia.

Effects of cardiotonic steroids on dermal collagen synthesis and wound healing

We previously reported that cardiotonic steroids stimulate collagen synthesis by cardiac fibroblasts in a process that involves signaling through the Na-K-ATPase pathway (Elkareh et al. Hypertension 49: 215-224, 2007). In this study, we examined the effect of cardiotonic steroids on dermal fibroblasts collagen synthesis and on wound healing. Increased collagen expression by human dermal fibroblasts was noted in response to the cardiotonic steroid marinobufagenin in a dose- and time-dependent fashion. An eightfold increase in collagen synthesis was noted when cells were exposed to 10 nM marinobufagenin for 24 h (P < 0.01). Similar increases in proline incorporation were seen following treatment with digoxin, ouabain, and marinobufagenin (10 nM x 24 h, all results P < 0.01 vs. control). The coadministration of the Src inhibitor PP2 or N-acetylcysteine completely prevented collagen stimulation by marinobufagenin. Next, we examined the effect of digoxin, ouabain, and marinobufagenin on the rate of wound closure in an in vitro model where human dermal fibroblasts cultures were wounded with a pipette tip and monitored by digital microscopy. Finally, we administered digoxin in an in vivo wound healing model. Olive oil was chosen as the digoxin carrier because of a favorable partition coefficient observed for labeled digoxin with saline. This application significantly accelerated in vivo wound healing in rats wounded with an 8-mm biopsy cut. Increased collagen accumulation was noted 9 days after wounding (both P < 0.01). The data suggest that cardiotonic steroids induce increases in collagen synthesis by dermal fibroblasts, as could potentially be exploited to accelerate wound healing.

Synthesis of multimeric MR contrast agents for cellular imaging

We have prepared a series of molecular multimeric MR contrast agents for cell labeling that are easy to synthesize, relatively low molecular weight, and biocompatible. The relaxivities of the agents range from 17 to 85 mM(-1) s(-1). Cellular uptake is concentration dependent and viability is excellent. MR images of cell pellets reveal a marked increase in observed signal intensity.