Cytotoxicity of iodinated and gadolinium-based contrast agents in renal tubular cells at angiographic concentrations: in vitro study

Inflammatory response toward a Mg-based metallic biomaterial implanted in a rat femur fracture model

The immune system plays an important role in fracture healing, by modulating the pro-inflammatory and anti-inflammatory responses occurring instantly upon injury. An imbalance in these responses can lead to adverse outcomes, such as non-union of fractures. Implants are used to support and stabilize complex fractures. Biodegradable metallic implants offer the potential to avoid a second surgery for implant removal, unlike non-degradable implants. However, considering our dynamic immune system it is important to conduct in-depth studies on the immune response to these implants in living systems. In this study, we investigated the immune response to Mg and Mg-10Gd in vivo in a rat femur fracture model with external fixation. In vivo imaging using liposomal formulations was used to monitor the fluorescence-related inflammation over time. We combine ex vivo methods with our in vivo study to evaluate and understand the systemic and local effects of the implants on the immune response. We observed no significant local or systemic effects in the Mg-10Gd implanted group compared to the SHAM and Mg implanted groups over time. Our findings suggest that Mg-10Gd is a more compatible implant material than Mg, with no adverse effects observed in the early phase of fracture healing during our 4-week study. STATEMENT OF SIGNIFICANCE: Degradable metallic implants in form of Mg and Mg-10Gd intramedullary pins were assessed in a rat femur fracture model, alongside a non-implanted SHAM group with special respect to the potential to induce an inflammatory response. This pre-clinical study combines innovative non-invasive in vivo imaging techniques associated with multimodal, ex vivo cellular and molecular analytics. The study contributes to the development and evaluation of degradable biometals and their clinical application potential. The study results indicate that Mg-10Gd did not exhibit any significant harmful effects compared to the SHAM and Mg groups.

Decoration of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) with N-oxides increases the T1 relaxivity of Gd-complexes

High complex stability and longitudinal relaxivity of Gd-based contrast agents are important requirements for magnetic resonance imaging (MRI) because they ensure patient safety and contribute to measurement sensitivity. Charged and zwitterionic Gd3+-complexes of the well-known chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) provide an excellent basis for the development of safe and sensitive contrast agents. In this report, we describe the synthesis of DOTA-NOx, a DOTA derivative with four N-oxide functionalities via "click" functionalization of the tetraazide DOTAZA. The resulting complexes Gd-DOTA-NOx and Eu-DOTA-NOx are stable compounds in aqueous solution. NMR-spectroscopic characterization revealed a high excess of the twisted square antiprismatic (TSAP) coordination geometry over square antiprismatic (SAP). The longitudinal relaxivity of Gd-DOTA-NOx was found to be r1=7.7 mm-1 s-1 (1.41 T, 37 °C), an unusually high value for DOTA complexes of comparable weight. We attribute this high relaxivity to the steric influence and an ordering effect on outer sphere water molecules surrounding the complex generated by the strongly hydrated N-oxide groups. Moreover, Gd-DOTA-NOx was found to be stable against transchelation with high excess of EDTA (200 eq) over a period of 36 h, and it has a similar in vitro cell toxicity as clinically used DOTA-based GBCAs.

Toxicity Mechanisms of Gadolinium and Gadolinium-Based Contrast Agents-A Review

Gadolinium-based contrast agents (GBCAs) have been used for more than 30 years to improve magnetic resonance imaging, a crucial tool for medical diagnosis and treatment monitoring across multiple clinical settings. Studies have shown that exposure to GBCAs is associated with gadolinium release and tissue deposition that may cause short- and long-term toxicity in several organs, including the kidney, the main excretion organ of most GBCAs. Considering the increasing prevalence of chronic kidney disease worldwide and that most of the complications following GBCA exposure are associated with renal dysfunction, the mechanisms underlying GBCA toxicity, especially renal toxicity, are particularly important. A better understanding of the gadolinium mechanisms of toxicity may contribute to clarify the safety and/or potential risks associated with the use of GBCAs. In this work, a review of the recent literature concerning gadolinium and GBCA mechanisms of toxicity was performed.

Effect of gadopentetate dimeglumine on bone growth in zebrafish caudal fins

Compared with MR plain scanning, gadolinium (Gd)-enhanced MR scanning can provide more diagnostic information. Gadopentetate dimeglumine is generally used as an MR enhancement contrast agent in some countries. It is a member of linear Gd-based contrast agents (GBCAs) which are considered more likely to release free Gd ions (Gd³⁺) than macrocyclic GBCAs. Gd³⁺ is one of the most effective known calcium antagonists, and can compete with calcium ions (Ca²⁺) in Ca²⁺-related biological reactions. In this study, animal models of tissue regeneration were established by cutting the caudal fins of zebrafish, and the models were exposed with gadopentetate dimeglumine solution for different immersion times of 1, 3, and 5 min. Three GBCA exposures per week were performed in the first 3 weeks of the follow-up time. Morphological parameters such as regenerative area (RA), bone density, bone thickness and regenerative bone volume (RBV) were quantified using a camera and synchrotron radiation micro CT. RA decreased as total Gd intake increased in both the female group (ρ = -0.784, P < 0.0001) and the male group (ρ = -0.471, P = 0.011). The bone density of the regenerated bone increased after Gd exposure in the treated groups. The morphology of the regenerated bone from the treated groups became shorter and thicker. Our results showed that gadopentetate dimeglumine had osteogenic toxicity in zebrafish.

Assessment of genetic damage induced by gadolinium-based radiocontrast agents

BACKGROUND

Today, although gadolinium based contrast agents have been frequently used in the field of medicine, there is limited data available whether gadolinium based agents affect the genome.

AIM

The present study aimed to investigate the genotoxic and cytotoxic potentials of gadoteric acid and gadoversetamide used as gadolinium-based contrast agents for magnetic resonance (MR) imaging.

MATERIAL AND METHODS

The cytokinesis-block micronucleus assay was applied to human peripheral blood lymphocytes to assess the genotoxicity measured as micronucleus (MN), nucleoplasmic bridge (NPBs) and nuclear bud (NBUDs) frequencies. Furthermore, cytokinesis-block proliferation index (CBPI) was calculated to determine cytostasis. Lymphocytes were treated with gadoteric acid at concentrations of 1.0, 2.5, 5.0, and 25 mM and with gadoversetamide at concentrations of 0.25, 1.0, 2.5, and 5.0 mM for 48 h.

RESULTS

Gadoteric acid did not cause significant increase in MN, NBPs and NBUDs frequencies and CBPI values at any concentration. Gadoversetamide induced significantly increase MN formation at concentration of 2.5 mM, NBP formation at concentrations of 1.0 and 2.5 mM, and NBUD formation at concentrations of 0.25, 1.0 and 2.5 mM. Additionally, gadoversetamide exposure resulted in statistically significant decrease in CBPI values compared to the control at concentrations of 2.5 and 5.0 mM. In addition, CBPI levels in response to concentrations of gadoversetamide was negatively and significantly associated with concentration.

CONCLUSION

These findings show that gadoteric acid does not have genotoxic or cytotoxic potential, while gadoversetamide might have both genotoxic and cytotoxic potential on human peripheral blood lymphocytes. As a comparison, gadoversetamide was found more genotoxic and cytotoxic.

Cellular and molecular pathways underlying the nephrotoxicity of gadolinium

Mounting evidence on the short- and long-term adverse effects associated with gadolinium [Gd (III)]-based contrast agents used in magnetic resonance imaging have emerged in the past three decades. Safety issues arise from the release of Gd (III) from chelates and its deposition in tissues, which is exacerbated in patients with renal disease, since the kidney is the major excretion organ of most of these agents. This study aimed at unveiling the cellular and molecular mechanisms of nephrotoxicity of Gd (III), using an in vitro model of human proximal tubular cells (HK-2 cell line). Cell viability declined in a concentration- and time-dependent manner after exposure to GdCl3·6H2O. The estimated inhibitory concentrations (ICs) eliciting 1 to 50% of cell death, after 24 h of exposure, ranged from 3.4 to 340.5 µM. At toxic concentrations, exposure to Gd (III) led to disruption of the oxidative status, mitochondrial dysfunction, cell death by apoptosis, switching to necrosis at higher levels, and autophagic activation. Disturbance of the lipid metabolism was already observed at low-toxicity ICs, with accumulation of lipid droplets, and upregulation of genes related to both lipogenesis and lipolysis. Gd (III)-exposure, even at the subtoxic IC01, increased the expression of modulators of various signaling pathways involved in the development and progression of renal disease, including inflammation, hypoxia and fibrosis. Our results give new insights into the mechanisms underlying the nephrotoxic potential of Gd (III) and highlight the need to further clarify the risks versus benefits of the Gd (III)-based contrast agents currently in use.

Use of Intravenous Gadolinium-based Contrast Media in Patients with Kidney Disease and the Risk of Nephrogenic Systemic Fibrosis: Radiology In Training

A 66-year-old male patient with end-stage chronic kidney disease undergoing maintenance dialysis and with a history of group I intravenous gadolinium-based contrast media (GBCM) administration presented with clinical and pathologic findings consistent with nephrogenic systemic fibrosis. A summary of the evidence and recommendations for use of intravenous GBCM in patients with kidney disease is presented. © RSNA, 2021.

Assessment of Gadobutrol Safety in Combination with Ionizing Radiation Using a Preclinical MRI-Guided Radiotherapy Model

MR-linac technology enhances the precision of therapeutic radiation by clarifying the tumor-normal tissue interface and provides the potential for adaptive treatment planning. Accurate delineation of tumors on diagnostic magnetic resonance imaging (MRI) frequently requires gadolinium-based contrast agents (GBCAs). Despite generally being considered safe, previous literature suggests that GBCAs are capable of contrast-induced acute kidney injury (AKI). It is unclear if the risk for AKI is enhanced when GBCAs are administered concurrently with ionizing radiotherapy. During irradiation, gadolinium may be liberated from its chelator which may induce AKI. The goal of this work was to determine if radiation combined with GBCAs increased the incidence of AKI. Using a preclinical MRI-guided irradiation system, where MRI acquisitions and radiation delivery are performed in rapid succession, tumor-bearing mice with normal kidney function were injected with GBCA and treated with 2, 8 or 18 Gy irradiation. Renal function was assessed on days three and seven postirradiation to assess for AKI. No clinically relevant changes in blood urea nitrogen and creatinine were observed in any combination of GBCA and radiation dose. From these data, we conclude that GBCA in combination with radiation does not increase the risk for AKI in mice. Additional investigation of multiple doses of GBCA administered concurrently with irradiation is warranted to evaluate the risk of chronic kidney injury.

Effects of gadolinium-based magnetic resonance imaging contrast media on red blood cells and K562 cancer cells

BACKGROUND

Gadolinium-based contrast media (GBCM) are commonly used in diagnostic magnetic resonance imaging (MRI) in clinical applications. The objective of this study is to evaluate the antioxidant properties and effects on red blood cells (RBCs) and K562 cancer cells of three GBCMs (i.e.; gadoterate meglumine, gadopentetate dimeglumine, and gadobenate dimeglumine) inin vitro levels.

METHODS

For determiningin vitro antioxidant properties, the di (phenyl)-(2,4,6-trinitrophenyl) iminoazanium (DPPH) and ferric reducing ability of plasma (FRAP) assay were used. For determining effect on red blood cells, hemolysis, morphology and reactive oxygen species (ROS) were used. For determining effect on K562 cancer cells, cytotoxicity and ROS were used. The GBCM -exposed cells were compared to corresponding non-exposed control groups at various harvest times.

RESULTS

The results show no changes occurring in the DPPH data. However, there were significant increases based on FRAP data in three GBCMs compared to the corresponding control at all concentrations. The ROS, morphology, and percentage of hemolysis in red blood cells indicated that no change had occurred in three GBCMs-exposed red blood cells compared to the corresponding non-exposed control groups at all harvest times. The percentage of cell viability in K562 cancer cells showed decreases in gadoterate meglumine- and gadobenate dimeglumine- in a concentration dependent manner, but did not show same in gadopentetate dimeglumine-exposed K562 cancer cells. The percentage of ROS in K562 cancer cells indicated that no change in three GBCMs-exposed cells had occurred when compared to the corresponding non-exposed control groups at all harvest times.

CONCLUSION

These findings suggests thatin vitro antioxidant properties exhibited by those three GBCMs depends on their concentration and species of radical in testing assay. There were no toxic effects from those GBCMs when red blood cells were exposed in an in vitro condition. In addition, some of those GBCMs could induce cell death in cancer cells.

Use of Intravenous Gadolinium-based Contrast Media in Patients with Kidney Disease: Consensus Statements from the American College of Radiology and the National Kidney Foundation

Inaugural consensus statements were developed and endorsed by the American College of Radiology (ACR) and the National Kidney Foundation to improve and standardize the care of patients with kidney disease who have indication(s) to receive ACR-designated group II or group III intravenous gadolinium-based contrast media (GBCM). The risk of nephrogenic systemic fibrosis (NSF) from group II GBCM in patients with advanced kidney disease is thought to be very low (zero events following 4931 administrations to patients with estimated glomerular filtration rate [eGFR] <30 mL/min per 1.73 m²; upper bounds of the 95% confidence intervals: 0.07% overall, 0.2% for stage 5D chronic kidney disease [CKD], 0.5% for stage 5 CKD and no dialysis). No unconfounded cases of NSF have been reported for the only available group III GBCM (gadoxetate disodium). Depending on the clinical indication, the potential harms of delaying or withholding group II or group III GBCM for an MRI in a patient with acute kidney injury or eGFR less than 30 mL/min per 1.73 m² should be balanced against and may outweigh the risk of NSF. Dialysis initiation or alteration is likely unnecessary based on group II or group III GBCM administration. This article is a simultaneous joint publication in Radiology and Kidney Medicine. The articles are identical except for stylistic changes in keeping with each journal's style. Either version may be used in citing this article.

Use of Intravenous Gadolinium-Based Contrast Media in Patients With Kidney Disease: Consensus Statements from the American College of Radiology and the National Kidney Foundation

Inaugural consensus statements were developed and endorsed by the American College of Radiology (ACR) and National Kidney Foundation to improve and standardize the care of patients with kidney disease who have indication(s) to receive ACR-designated group II or group III intravenous gadolinium-based contrast media (GBCM). The risk of nephrogenic systemic fibrosis (NSF) from group II GBCM in patients with advanced kidney disease is thought to be very low (zero events following 4931 administrations to patients with estimated glomerular filtration rate [eGFR] <30 mL/min per 1.73 m²; upper bounds of the 95% confidence intervals: 0.07% overall, 0.2% for stage 5D chronic kidney disease [CKD], 0.5% for stage 5 CKD and no dialysis). No unconfounded cases of NSF have been reported for the only available group III GBCM (gadoxetate disodium). Depending on the clinical indication, the potential harms of delaying or withholding group II or group III GBCM for an MRI in a patient with acute kidney injury or eGFR less than 30 mL/min per 1.73 m² should be balanced against and may outweigh the risk of NSF. Dialysis initiation or alteration is likely unnecessary based on group II or group III GBCM administration.

MRI demonstration of gadolinium deposition in bone after monthly triple-dose gadopentetate dimeglumine and correlation with frequency of hypophosphatemia

OBJECTIVES

We retrospectively analyzed data of the BECOME trial to investigate whether serial administration of triple-dose (3-dose) gadopentetate dimeglumine would result in the development of T1 signal-to-noise (S/N) changes in the cranial diploic space and whether S/N changes correlated with on-study hypophosphatemia.

METHODS

Signal intensity analysis was performed on the first year's data of the BECOME trial using 3-dose Gd (14 months, maximum number of doses, 39, mean: 36). Routine blood and urine tests were obtained each month for safety monitoring. Linear mixed regression modeling with random intercept was used to analyze monthly signal-to-noise ratio (S/N = Bone/Air) using an ROI of the diploic space created from T2W images and overlaid on T1FS (T1 fat-saturated) images. Incidence of phosphate abnormalities was analyzed using the general estimation equation; correlation of phosphate and S/N change was achieved with type 3 test of fixed effects.

RESULTS

Cranial diploic space T1FS S/N increased over 14 months: S/N = 0.039 mean monthly increase (S.E. 0.008; p < 0.0001). Subjects with consistently normal phosphate levels (n = 32) experienced more of a S/N increase than patients with at least one episode of hypophosphatemia (n = 35) (0.057 vs. 0.023, respectively, p = 0.037). Those with moderate hypophosphatemia demonstrated no significant S/N increase.

CONCLUSION

Monthly administration of 3-dose gadopentetate dimeglumine is associated with development of increased S/N on T1FS imaging in the cranial diploic space, suggesting Gd retention in bone. Our data suggests MRI could be used as a noninvasive method of tracking Gd retention in bone, which was more pronounced in patients with normal phosphate levels.

Peptide-Based Soft Hydrogels Modified with Gadolinium Complexes as MRI Contrast Agents

Poly-aromatic peptide sequences are able to self-assemble into a variety of supramolecular aggregates such as fibers, hydrogels, and tree-like multi-branched nanostructures. Due to their biocompatible nature, these peptide nanostructures have been proposed for several applications in biology and nanomedicine (tissue engineering, drug delivery, bioimaging, and fabrication of biosensors). Here we report the synthesis, the structural characterization and the relaxometric behavior of two novel supramolecular diagnostic agents for magnetic resonance imaging (MRI) technique. These diagnostic agents are obtained for self-assembly of DTPA(Gd)-PEG8-(FY)3 or DOTA(Gd)-PEG8-(FY)3 peptide conjugates, in which the Gd-complexes are linked at the N-terminus of the PEG8-(FY)3 polymer peptide. This latter was previously found able to form self-supporting and stable soft hydrogels at a concentration of 1.0% wt. Analogously, also DTPA(Gd)-PEG8-(FY)3 and DOTA(Gd)-PEG8-(FY)3 exhibit the trend to gelificate at the same range of concentration. Moreover, the structural characterization points out that peptide (FY)3 moiety keeps its capability to arrange into β-sheet structures with an antiparallel orientation of the β-strands. The high relaxivity value of these nanostructures (~12 mM⁻¹·s⁻¹ at 20 MHz) and the very low in vitro cytotoxicity suggest their potential application as supramolecular diagnostic agents for MRI.

Renal Safety of Intravenous Gadolinium-enhanced MRI in Patients Following Liver Transplantation

BACKGROUND

Intravenous contrast-enhanced imaging is invaluable in diagnosing pathology following liver transplantation. Given the potential risk of contrast nephropathy associated with iodinated computed tomography contrast, alternate contrast modalities need to be examined, especially in the setting of renal insufficiency. The purpose of this study was to examine the renal safety of MRI with gadolinium following liver transplantation.

METHODS

The study involved a retrospective analysis of 549 cases of abdominal MRI with low-dose gadobenate dimeglumine in liver transplant recipients at a single center. For each case, serum creatinine values before and after the MRI were compared. In addition, cases were analyzed for the development of nephrogenic systemic fibrosis.

RESULTS

Pre-MRI creatinine values ranged from 0.32 to 6.57 mg/dL (median, 1.28 g/dL), with 191 cases having values ≥1.5 mg/dL (median, 1.86 g/dL). A comparison of the pre- and post-MRI creatinine values showed no significant difference, including those patients with pre-MRI values ≥1.5 mg/dL (mean change of -0.04 [95% confidence interval, -0.07 to -0.01; P = 0.004]). No cases of nephrogenic systemic fibrosis were noted.

CONCLUSIONS

Our findings suggest that, irrespective of baseline renal function, MRI with gadobenate dimeglumine is a nonnephrotoxic imaging modality in liver transplant recipients. Importantly, this intravenous contrast-enhanced imaging modality can be considered in those posttransplant patients who have a contraindication to computed tomography contrast due to renal insufficiency.

Periprocedural Concerns in the Patient with Renal Disease

Treating patients with kidney disease can be both a difficult and a complex process. Understanding how to care for patients who have kidney disease is essential for lowering perioperative as well as periprocedural morbidity and mortality. The primary aim in renal evaluation and care is to control and mitigate factors that may result in acute kidney injury (AKI) and/or cause further decline in renal function. It is essential for the foot and ankle specialist to recognize patients who are predisposed to developing or already have impairment of renal function.

Exposure of Macrophages to Low-Dose Gadolinium-Based Contrast Medium: Impact on Oxidative Stress and Cytokines Production

The toxicity of gadolinium-based contrast agents (GBCAs) has drawn a lot of attention. Nephrogenic systemic fibrosis (NSF), a lethal disease related to the use of GBCAs, is still not understood. Recently, gadolinium retention is found in brain tissues after repeated use of GBCAs in magnetic resonance imaging (MRI). However, most of the works investigating the toxicity of GBCAs are focusing on its high-concentration (0.5–10 mM) part, which is not reflective of the physiological conditions in human beings. Macrophages play a regulatory role in immune responses and are responsible for the fibrosis process. Their role in gadolinium retention and the pathogenesis of NSF, however, has seldom been investigated. This study aimed to evaluate the immune response generated by macrophages (RAW 264.7) exposing to low levels of GBCAs. The incubation concentration of GBCAs, including Omniscan®, Primovist®, Magnevist®, and Gadovist®, is proportional to the level of gadolinium uptake when detected via inductively coupled plasma mass spectrometry (ICP-MS) and imaged by MRI, whereas Primovist® treatment groups have highest gadolinium uptake among all of the tested concentrations. Low-concentration (2.5 μmol/L) Gd chloride or GBCAs exposure promoted the reactive production of oxygen species (ROS), nitrate/nitrite, prostaglandin E2 (PGE2), and suppressed the potential of mitochondrial membrane. There was higher ROS, nitrate/nitrite, and PGE2 production in the Primovist®, Omniscan®, and Magnevist® groups compared to the Gadovist® group. In face of lipopolysaccharide (LPS) stimulation, Primovist®, Omniscan®, and Magnevist® groups exhibited elevated nitrite/nitrate and suppressed IL-1β secretion and IL-6 and IL-10 secretion. Moreover, upon LPS stimulation, there is decreased TNF-α secretion 4 hours after Primovist® or Omiscan® exposure but the TNF-α secretion increased at 24 hours. Our data suggest that there is upregulated inflammation even in the presence of low levels of GBCAs, even similar to the physiological condition in murine macrophage. Further investigation of GBCAs on the human macrophage or in vivo animal study may clarify the role of macrophage on the pathogenesis of NSF and other GBCAs-related disease.

The potential toxic impact of different gadolinium-based contrast agents combined with 7-T MRI on isolated human lymphocytes

Background

To investigate a potentially amplifying genotoxic or cytotoxic effect of different gadolinium-based contrast agents (GBCAs) in combination with ultra-high-field 7-T magnetic resonance imaging (MRI) exposure in separated human peripheral blood lymphocytes.

Methods

This in vitro study was approved by the local ethics committee and written informed consent was obtained from all participants. Isolated lymphocytes from twelve healthy donors were incubated with gadobutrol, gadoterate meglumine, gadodiamide, gadopentetate dimeglumine, or gadoxetate either alone or combined with 7-T MRI (1 h). Deoxyribonucleic acid (DNA) double-strand breaks were assessed 15 min after MRI exposure by automated γH2AX foci quantification. Cytotoxicity was determined at later endpoints by Annexin V/propidium iodide apoptosis assay (24 h) and [³H]-thymidine proliferation test (72 h). As a reference, lymphocytes from four different donors were exposed analogously to iodinated contrast agents (iomeprol, iopromide) in combination with computed tomography.

Results

Baseline γH2AX levels (0.08 ± 0.02 foci/cell) were not significantly (p between 0.135 and 1.000) enhanced after administration of GBCAs regardless of MRI exposure. In contrast to the two investigated macrocyclic GBCAs, lymphocytes exposed to the three linear GBCAs showed a dose-dependent increase in apoptosis (maximum 186% of unexposed control, p < 0.001) and reduced proliferation rate (minimum 0.7% of unexposed control, p < 0.001). However, additional 7-T MRI co-exposure did not alter GBCA-induced cytotoxicity.

Conclusions

Exposure of lymphocytes to different GBCAs did not reveal significant induction of γH2AX foci, and enhanced cytotoxicity was only observed in lymphocytes treated with the linear GBCAs used in this study, independent of additional 7-T MRI co-exposure.

Electronic supplementary material

The online version of this article (10.1186/s41747-018-0069-y) contains supplementary material, which is available to authorized users.

Cationic Substitutions in Hydroxyapatite: Current Status of the Derived Biofunctional Effects and Their In Vitro Interrogation Methods

High-performance bioceramics are required for preventing failure and prolonging the life-time of bone grafting scaffolds and osseous implants. The proper identification and development of materials with extended functionalities addressing socio-economic needs and health problems constitute important and critical steps at the heart of clinical research. Recent findings in the realm of ion-substituted hydroxyapatite (HA) could pave the road towards significant developments in biomedicine, with an emphasis on a new generation of orthopaedic and dentistry applications, since such bioceramics are able to mimic the structural, compositional and mechanical properties of the bone mineral phase. In fact, the fascinating ability of the HA crystalline lattice to allow for the substitution of calcium ions with a plethora of cationic species has been widely explored in the recent period, with consequent modifications of its physical and chemical features, as well as its functional mechanical and in vitro and in vivo biological performance. A comprehensive inventory of the progresses achieved so far is both opportune and of paramount importance, in order to not only gather and summarize information, but to also allow fellow researchers to compare with ease and filter the best solutions for the cation substitution of HA-based materials and enable the development of multi-functional biomedical designs. The review surveys preparation and synthesis methods, pinpoints all the explored cation dopants, and discloses the full application range of substituted HA. Special attention is dedicated to the antimicrobial efficiency spectrum and cytotoxic trade-off concentration values for various cell lines, highlighting new prophylactic routes for the prevention of implant failure. Importantly, the current in vitro biological tests (widely employed to unveil the biological performance of HA-based materials), and their ability to mimic the in vivo biological interactions, are also critically assessed. Future perspectives are discussed, and a series of recommendations are underlined.

Iodixanol versus iopromide in patients with renal insufficiency undergoing coronary angiography with or without PCI

BACKGROUND

The use of contrast agents during coronary angiography can result in contrast-induced nephropathy (CIN), particularly in patients with renal dysfunction. On the contrary, different contrast agents can induce different degree of changes in cardiac function. The objective of our meta-analysis was to compare the clinical safety of iso-osmolar contrast medium iodixanol to low-osmolar contrast medium iopromide in patients with renal insufficiency undergoing coronary angiography with or without percutaneous coronary intervention (PCI).

METHODS

We searched Medline, Embase, Cochrane Library, and reference lists to identify randomized controlled trials that compared iodixanol to iopromide with the incidence of CIN as an endpoint in renal impaired patients undergoing coronary angiography. Outcome measures were the incidence of CIN, absolute peak serum creatinine (Scr) increase from baseline and a composite of cardiovascular adverse events.

RESULTS

A total of 8 trials with 3532 patients were pooled; 1759 patients received iodixanol and 1773 patients received iopromide. There was no significant difference in the incidence of CIN (summary odds ratio [OR] 0.50, 95% confidence interval [CI] 0.19-1.35, P = .17) and peak Scr increase (mean difference -0.01 mg/dL, 95% CI -0.08 to 0.05, P = .69) when iodixanol was compared with iopromide. But iodixanol was associated with a statistically significant reduction in cardiovascular adverse events when compared with iopromide (OR 0.47, 95% CI 0.30-0.73, P = .0009).

CONCLUSIONS

Analysis of pooled data from 8 randomized controlled trials of iodixanol against iopromide in patients with renal insufficiency undergoing coronary angiography with or without PCI showed that iodixanol nonsignificantly reduced the incidence of CIN, but was associated with a significantly reduced risk of cardiovascular adverse events when compared with iopromide.

Extent of simultaneous radiation dose and iodine reduction at stable image quality in computed tomography of the chest: A systematic approach using automated tube voltage adaption and iterative reconstructions

BACKGROUND

Aim of this study was to systematically combine tube voltage adaptation and iterative reconstructions for reduction of iodine and radiation dose.

METHODS

Settings for the study protocol were evaluated in ex-ante trials to provide image quality that is comparable to a reference protocol at 120 kV with tube current modulation. Consecutive patients were randomized to undergo computed tomography (CT) of the chest using the study protocol (n = 62) or reference protocol (n = 50). Objective and subjective image quality was assessed and compared.

RESULTS

Tube voltage was decreased to 100 kV in 47 patients and to 80 kV in 15 patients in the study group. The iodine dosage (16.1 vs 10.5 g) and the effective radiation dose (3.6 vs 2.5 mSv) were significantly decreased in the study group (both P < .001). Contrast-to-noise ratio was comparable in the pulmonary trunk and increased in the aorta (P < .01). Subjective image quality was comparable without statistically significance.

CONCLUSIONS

Simultaneous reductions in iodine dosage and radiation dose by one-third are feasible for CT of the chest.

Serum Neutrophil Gelatinase-Associated Lipocalin and Urinary Kidney Injury Molecule-1 as Potential Biomarkers of Subclinical Nephrotoxicity After Gadolinium-Based and Iodinated-Based Contrast Media Exposure in Pediatric Patients with Normal Kidney Function

Background

New renal biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) show promise in early diagnosis of contrast media induced acute kidney injury (CI-AKI). The purpose of our study was to compare the subclinical nephrotoxicity (a condition without changes in standard renal biomarkers) of gadolinium-based contrast media (Gd-DTPA, gadopentetate dimeglumine) and iodinated-based contrast media (iopromide) in pediatric patients with normal kidney function.

Material/Methods

The first group (n=58) of patients included in the study were undergoing angiography with iopromide, and the second group (n=65) were undergoing magnetic resonance (MR) angiography/urography with Gd-DTPA administration. The concentrations of NGAL and KIM-1 were measured four times in the urine (pre-contrast, then at four hours, 24 hours, and 48 hours after contrast administration), and serum NGAL was measured at 0 (baseline), 24 hours, and 48 hours after contrast exposure.

Results

After 24 hours, serum NGAL increase of ≥25% was noticed in 32.6% of the patients in the iopromide group and in 25.45% of the patients in the gadolinium group, with significantly higher average percent of this increase in first group (62.23% vs. 36.44%, p=0.002). In the Gd-DTPA group, we observed a statistically significant increase in urinary KIM-1 24 hours after the procedure. Normalized urinary KIM-1, 24 hours after contrast exposure, was a better predictive factor for CI-AKI than other biomarkers (AUC 0.757, cut off 214 pg/mg, sensitivity 83.3%, specificity 54.2%, p=0.035).

Conclusions

In children with normal renal function, exposure to iodinated-based and gadolinium-based media might lead to subclinical nephrotoxicity, which could be detected using serum NGAL and urinary KIM-1.

Self-assembly of Gd3+/SDS/HEPES complex and curcumin entrapment for enhanced stability, fluorescence image in cellular system

At present, strategies to disperse hydrophobic molecules in water without altering their chemical structures include conventional surfactant-based micellar and vesicular systems, encapsulation into water dispersible polymeric nanoparticles, and loading onto the surface of various metal nanoparticles. Here, we report a simple and low cost platform to incorporate hydrophobic molecules into a stable water dispersible nanostructure that can significantly increase the stability of the encapsulated materials. The platform is based on the incorporation of hydrophobic molecules into the self-assembled complex of gadolinium ion (Gd³⁺), sodium dodecyl sulfate (SDS), and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) called GdSH. After being incorporated, the two model hydrophobic dyes, curcumin and curcumin borondifluoride show approximately 50% and 30% improved stability, respectively. Investigation of the self-assembled 10-14 multilayered 60nm spheres with inter-layer distances of 4.25nm indicates coordination of SDS and HEPES with Gd³⁺. Incorporation of the hydrophobic molecules into the multilayered spheres results in reduction of the interlayer distance of the multilayer spheres to 4.17nm, suggesting enhanced packing of the hydrophobic chain of SDS and HEPES around the Gd³⁺. The incorporation of the two curcuminoids into the self-assembled complex also causes an increase in fluorescence quantum yield of the two dyes, thus suggesting spatial confinement of the packed dye molecules. The better cellular uptake of the nanoparticles is responsible for the expected enhancement in fluorescence image of the encapsulated materials.

Contrast-induced acute kidney injury: A review of practical points

Contrast-induced acute kidney injury (CI-AKI) is one of the most common causes of AKI in clinical practice. CI-AKI has been found to be strongly associated with morbidity and mortality of the patients. Furthermore, CI-AKI may not be always reversible and it may be associated with the development of chronic kidney disease. Pathophysiology of CI-AKI is not exactly understood and there is no consensus on the preventive strategies. CI-AKI is an active research area thus clinicians should be updated periodically about this topic. In this review, we aimed to discuss the indications of contrast-enhanced imaging, types of contrast media and their impact on nephrotoxicity, major pathophysiological mechanisms, risk factors and preventive strategies of CI-AKI and alternative non-contrast-enhanced imaging methods.

Incidence and Risk Factors for Gadolinium-Based Contrast Agent Immediate Reactions

Since their clinical introduction in 1988, gadolinium-based contrast agents (GBCAs) have demonstrated an excellent safety profile with a reported acute adverse reaction rate ranging from 0.01% to 2%. By comparison, the acute adverse reaction rate of low osmolar nonionic computed tomography contrast agents (CTCs) ranges from 0.7% to 3.1%. Many of the risk factors associated with CTC reactions (drug allergies, asthma, atopy, prior contrast reaction) also point toward an increased incidence of acute adverse events to GBCAs. With CTCs, an increased adverse event rate was associated with ionic preparations and high osmolality. In response to concerns for nephrogenic systemic fibrosis, GBCAs are now selected for their augmented chemical stability. These agents possess some combination of macrocyclic chelates or ionic preparations. With their improved chemical stability, these agents also possess higher osmolality and the increased potential to elicit an acute adverse reaction. In light of these concerns, researchers are now focusing greater efforts on reexamining acute adverse reactions to GBCAs and whether there is an increased association with certain agents. In addition to hypersensitivity reactions, this article will also discuss contrast extravasations, safety of GBCAs for pregnant and nursing patients, and the potential nephrotoxic effects of GBCAs.

Biological effects induced by Gadolinium nanoparticles on Lymphocyte A20 cell line

Gadolinium nanoparticles (GdNPs) are potential agents for MRI of lymph nodes. The aim of this study was to evaluate the in vitro effects of 1 μM, 2.5 μM and 5 μM of GdDOTA⊂CS-TPP/HA and GdDOTP⊂CS-TPP/HA NPs on A20 lymphocyte cells exposed for 6 and 24 hours. The total cellular biomass (SRB), lactate dehydrogenase activity (LDH) and oxidative stress parameters, such as reactive oxygen species generation (ROS), reduced glutathione (GSH), malondialdehyde (MDA) and advanced oxidation protein products (AOPP) were analyzed by spectrophotometric and fluorimetric methods. After cells exposure to 1 μM, 2.5 μM and 5 μM of GdDOTP⊂CS-TPP/HA NPs their viability decreased in a time- and dose-dependent manner, whereas for GdDOTA⊂CS-TPP/HA no significant changes were noticed. Both NPs formulations in doses of 1 μM, 2.5 μM, 5 μM did not affect the plasma membrane at each time point tested. The levels of ROS, MDA and AOPP increased proportionally with the concentration and exposure time. GSH concentration decreased significantly for all doses of both NPs tested. Taken together our data suggest that, GdDOTP⊂CS-TPP/HA and GdDOTA⊂CS-TPP/HA NPs induced oxidative stress in A20 lymphocyte cells which was counteracted by the cells antioxidant defense system to a certain extend.

Gadolinium-based contrast agent toxicity: a review of known and proposed mechanisms

Gadolinium chelates are widely used as contrast media for magnetic resonance imaging. The approved gadolinium-based contrast agents (GBCAs) have historically been considered safe and well tolerated when used at recommended dosing levels. However, for nearly a decade, an association between GBCA administration and the development of nephrogenic systemic fibrosis (NSF) has been recognized in patients with severe renal impairment. This has led to modifications in clinical practices aimed at reducing the potential and incidence of NSF development. Newer reports have emerged regarding the accumulation of gadolinium in various tissues of patients who do not have renal impairment, including bone, brain, and kidneys. Despite the observations of gadolinium accumulation in tissues regardless of renal function, very limited clinical data regarding the potential for and mechanisms of toxicity is available. This significant gap in knowledge warrants retrospective cohort study efforts, as well as prospective studies that involve gadolinium ion (Gd(3+)) testing in patients exposed to GBCA. This review examines the potential biochemical and molecular basis of gadolinium toxicity, possible clinical significance of gadolinium tissue retention and accumulation, and methods that can limit gadolinium body burden.

Renal safety of intravenous gadolinium-enhanced magnetic resonance imaging in patients awaiting liver transplantation

Renal dysfunction in cirrhosis carries a high morbidity and mortality. Given the potential risk of contrast-induced nephropathy associated with iodinated intravenous contrast used in computed tomography (CT), alternate contrast modalities for abdominal imaging in liver transplant candidates need to be examined. The purpose of this study was to examine the renal safety of magnetic resonance imaging (MRI) with gadolinium in patients awaiting liver transplantation. The study involved a retrospective analysis of 352 patients of abdominal MRI with low-dose gadobenate dimeglumine (MultiHance) (0.05 mmol/kg) in patients with cirrhosis and without renal replacement therapy at a single center during the period from 2007 to 2013. For each case, serum creatinine before and within a few days after the MRI were compared. In addition, the patients were analyzed for the development of nephrogenic systemic fibrosis (NSF), a reported complication of gadolinium in chronic kidney disease. The pre-MRI serum creatinine values ranged from 0.36 to 4.86 mg/dL, with 70 patients (20%) having values ≥ 1.5 mg/dL. A comparison of the pre- and post-MRI serum creatinine values did not demonstrate a clinically significant difference (mean change = 0.017 mg/dL; P = 0.38), including those patients with a pre-MRI serum creatinine ≥ 1.5 mg/dL. In addition, no cases of NSF were noted. In conclusion, our findings suggest that MRI with low-dose gadobenate dimeglumine (MultiHance) is a nonnephrotoxic imaging modality in liver transplant candidates, and its use can be cautiously expanded to liver transplant candidates with concomitant renal insufficiency.

Lack of nephrotoxicity of gadopentetate dimeglumine-enhanced non-vascular MRI and MRI without contrast agent in patients at high-risk for acute kidney injury

Background

Gadolinium chelates (GCs) have been traditionally considered as non-nephrotoxic magnetic resonance imaging (MRI) contrast materials. However, it has been suggested in some recent articles that GCs may have a nephrotoxic potential, but most of these reports are retrospective. However, the evaluated contrast agents, their doses, and the tests used to determine the kidney function were not consistent across studies. We aimed to investigate the effect of magnetic field and an MRI contrast agent, gadopentetate dimeglumine (GD), on renal functions in patients at high risk for acute kidney injury (AKI).

Material/Methods

We designed a prospective case-control study with 2 age- and sex-matched groups of patients at high-risk for AKI (n=72 for each group). Patients in Group 1 received a fixed dose of (0.2 mmol/kg) GD-enhanced non-vascular MRI and patients in Group 2 received MRI without GD. Before the MRI and at 6, 24, 72, and 168 hours after the MRI, biochemical tests, estimated glomerular filtration rate (eGFR), albumin/creatinine ratio in spot urine, and early AKI biomarkers (cystatin C, N-Acetyl-Glucosaminidase [NAG], Neutrophil gelatinase-associated lipocalin [NGAL]) were measured.

Results

Serum creatinine, albumin/creatinine ratio, and eGFR were not different between Group 1 and 2 (p>0.05). There were no significant changes in renal function tests and AKI biomarkers (Δ_{serum creatinine}, Δ_{albumin/creatinine ratio}, Δ_GFR, Δ_{cystatin C}, Δ_NAG, and Δ_NGAL) for either groups 6, 24, 72, and 168 hours after the procedures (p>0.05).

Conclusions

MRI without contrast agent and non-vascular contrast-enhanced (GD, 0.2 mmol/kg) MRI are not nephrotoxic procedures for patients at high risk for AKI.

Microstructure, mechanical and corrosion properties of Mg-Dy-Gd-Zr alloys for medical applications

In previous investigations, a Mg-10Dy (wt.%) alloy with a good combination of corrosion resistance and cytocompatibility showed great potential for use as a biodegradable implant material. However, the mechanical properties of Mg-10Dy alloy are not satisfactory. In order to allow the tailoring of mechanical properties required for various medical applications, four Mg-10(Dy+Gd)-0.2Zr (wt.%) alloys were investigated with respect to microstructure, mechanical and corrosion properties. With the increase in Gd content, the number of second-phase particles increased in the as-cast alloys, and the age-hardening response increased at 200°C. The yield strength increased, while the ductility reduced, especially for peak-aged alloys with the addition of Gd. Additionally, with increasing Gd content, the corrosion rate increased in the as-cast condition owing to the galvanic effect, but all the alloys had a similar corrosion rate (~0.5 mm year(-1)) in solution-treated and aged condition.

Linearity and shift invariance for quantitative magnetic particle imaging

Magnetic Particle Imaging (MPI) is a promising tracer imaging modality that employs a kidney-safe contrast agent and does not use ionizing radiation. MPI already shows high contrast and sensitivity in small animal imaging, with great potential for many clinical applications, including angiography, cancer detection, inflammation imaging, and treatment monitoring. Currently, almost all clinically relevant imaging techniques can be modeled as systems with linearity and shift invariance (LSI), characteristics crucial for quantification and diagnostic utility. In theory, MPI has been proven to be LSI. However, in practice, high-pass filters designed to remove unavoidable direct feedthrough interference also remove information crucial to ensuring LSI in MPI scans. In this work, we present a complete theoretical and experimental description of the image artifacts from filtering. We then propose and validate a robust algorithm to completely restore the lost information for the x-space MPI method. We provide the theoretical, simulated, and experimental proof that our algorithm indeed restores the LSI properties of MPI.

Time- and dose-dependent cytotoxicities of ioxitalamate and indigocarmine in human nucleus pulposus cells

BACKGROUND CONTEXT

Ioxitalamate (Telebrix 300) is an ionic iodinated contrast medium commonly used for discography or percutaneous endoscopic lumbar discectomy (PELD), though it has side effects such as anaphylactic shock and renal toxicity. Indigocarmine is an organic compound dye with a distinctive blue color that is commonly used during PELD to stain the acidic, degenerated nucleus pulposus (NP). Although ioxitalamate and indigocarmine are widely used in spinal surgery, there have been no reports on their effects on NP cells. We studied the toxicities of both ioxitalamate and indigocarmine to NP cells.

PURPOSE

To determine the toxicities of both ioxitalamate and indigocarmine to NP cells in vitro.

STUDY DESIGN

In vitro, controlled study of the toxicities of both ioxitalamate and indigocarmine to human NP cells.

METHODS

Nucleus pulposus cells were obtained via discectomy from lumbar disc patients and isolated. Nucleus pulposus cells were cultured in three-dimensional (3D) alginate beads with 0.001, 0.1, 10, and 100 mg/mL ioxitalamate, 0.00001, 0.001, 0.1, and 10 mg/mL indigocarmine, or a mixture of both for 1, 2, or 3 days. The living cells were analyzed with trypan blue staining. Fluorescence Activated Cell Sorting analysis using Annexin V and propidium iodide and 3D alginate bead immunostaining was performed to identify live, apoptotic, and necrotic cells.

RESULTS

Ioxitalamate, indigocarmine, and their combination induced statistically significant NP cell injury that was both time- and dose dependent (p<.05). Also, at the same concentration, ioxitalamate was more cytotoxic than was indigocarmine or the combination (p<.05). All three treatments also showed dose-dependent cytotoxicity according to flow cytometry and immunostaining.

CONCLUSIONS

Ioxitalamate and indigocarmine are toxic to human NP cells in vitro in a time- and dose-dependent manner. We assume that ioxitalamate and indigocarmine may have similar effects in patients undergoing discography and PELD. Thus, we suggest that ioxitalamate and indigocarmine should be used carefully at low concentrations.

Does the MRI or MRI contrast medium gadopentetate dimeglumine change the oxidant and antioxidant status in humans?

BACKGROUND

It has become evident that gadolinium-based contrast agents (GBCA) may have nephrotoxic potential. Oxidative stress is one of the most important pathways in the pathogenesis of iodinated contrast-induced nephropathy.

PURPOSE

To investigate the effects of static magnetic fields and gadopentetate dimeglumine (Magnevist(®)) on oxidant/antioxidant status via measurement of total antioxidant capacity (TAC), total oxidant status (TOS), and serum malondialdehide (MDA).

MATERIAL AND METHODS

Two age- and sex-matched groups of patients not under oxidative stress conditions that underwent magnetic resonance imaging (MRI) were recruited to this study. While contrast-enhanced (Magnevist(®), 0.2 mmol/kg) MRI was performed in group 1, MRI without GBCA was performed in group 2. Fasting blood glucose, C-reactive protein, serum creatinine, liver enzymes, uric acid, and lipid parameters were examined in all patients. Peripheral venous blood samples in order to determine TAC, TOS, and MDA were collected before and 6, 24, and 72 h after the MRI procedures. The TOS:TAC ratio was used as the oxidative stress index (OSI). Patients were followed up to 72 h.

RESULTS

There were no significant changes in serum TAC, TOS, and MDA levels (Δ(serum TAC), Δ(serum TOS), and Δ(MDA)) in either group 6, 24, or 72 h after the procedures (P > 0.05). Furthermore, OSI did not change after the procedures in either group (P > 0.05).

CONCLUSION

Magnetic field and gadopentetate dimeglumine (Magnevist(®)) do not change the oxidant or antioxidant status at a dose of 0.2 mmol/kg.

Designed polyelectrolyte shell on magnetite nanocore for dilution-resistant biocompatible magnetic fluids

Magnetite nanoparticles (MNPs) coated with poly(acrylic acid-co-maleic acid) polyelectrolyte (PAM) have been prepared with the aim of improving colloidal stability of core-shell nanoparticles for biomedical applications and enhancing the durability of the coating shells. FTIR-ATR measurements reveal two types of interaction of PAM with MNPs: hydrogen bonding and inner-sphere metal-carboxylate complex formation. The mechanism of the latter is ligand exchange between uncharged -OH groups of the surface and -COO(-) anionic moieties of the polyelectrolyte as revealed by adsorption and electrokinetic experiments. The aqueous dispersion of PAM@MNP particles (magnetic fluids - MFs) tolerates physiological salt concentration at composition corresponding to the plateau of the high-affinity adsorption isotherm. The plateau is reached at small amount of added PAM and at low concentration of nonadsorbed PAM, making PAM highly efficient for coating MNPs. The adsorbed PAM layer is not desorbed during dilution. The performance of the PAM shell is superior to that of poly(acrylic acid) (PAA), often used in biocompatible MFs. This is explained by the different adsorption mechanisms; metal-carboxylate cannot form in the case of PAA. Molecular-level understanding of the protective shell formation on MNPs presented here improves fundamentally the colloidal techniques used in core-shell nanoparticle production for nanotechnology applications.

Prophylactic 0.9% saline hydration inhibited high-dose gadodiamide-induced nephropathy in rats

High doses of gadolinium-based contrast media are reported to induce deterioration of renal function. We assessed whether prophylactic 0.9% saline hydration inhibits high-dose gadodiamide-induced renal damage in rats. Twelve Sprague-Dawley rats were randomly divided into two groups, which are given gadodiamide (5 mmol/kg) with (hydration group) or without (control group) 0.9% saline hydration. The saline (4 mL/kg) was infused as a bolus into the peritoneum every 4 h, starting 12 h before and continuing for 12 h after the gadodiamide injection. Urine was collected to calculate creatinine clearance (Ccr) 24 h before and 48 h after the gadodiamide injection. The kidneys were harvested and stained for pathologic analysis. High-dose gadodiamide induced acute kidney injury as shown by decreased Ccr and renal histology with tubular cell injuries 48 h postinjection in both the groups. However, the extent of Ccr reduction was significantly (p = 0.02) less in the hydrated rats (-15% in the hydration group vs. -39% in the control group). Renal tubular cell injuries characterized by vacuolization, loss of brush borders, sloughing of tubular cells into the lumen, and flattening of the tubular epithelium were less frequently seen in the hydration group; only vacuolization (p = 0.01) and epithelial sloughing (p = 0.02) of the proximal tubules differed significantly between the two groups. We conclude that prophylactic 0.9% saline hydration significantly inhibited high-dose gadodiamide-induced nephropathy.

MRI study of subconjunctival and intravitreal injections

Previous magnetic resonance imaging (MRI) studies to investigate the routes of penetration and barriers in ocular delivery have provided insights into the mechanisms of transscleral and intraocular drug delivery. The objective of the present study was to investigate ocular penetration and clearance after subconjunctival and intravitreal injections using a contrast agent at concentrations higher than those in the previous studies. This high concentration approach was hypothesized to allow the visualization of the contrast agent in the eye that could not be achieved previously. Subconjunctival and intravitreal injections of contrast agent Magnevist, a model hydrophililc probe, were performed in rabbits, and the distribution and clearance of the probe after the injections were examined by MRI. After subconjunctival injection in vivo, significant contrast agent penetration into the anterior chamber was observed but not into the vitreous. A clearance pathway of the hydrophilic probe from the subconjunctival depot to the regions near the periocular fat behind the eye was found. After intravitreal injection in vivo, the contrast agent was observed in the anterior chamber, optic nerve, and tissues surrounding the eye during clearance. MRI continues to provide insights into the transport barriers and clearance pathways of hydrophilic molecules in ocular delivery.

Effects of short- and long-term hypercholesterolemia on contrast-induced acute kidney injury

BACKGROUND

Whether hypercholesterolemia is a risk factor for contrast-induced acute kidney injury (CI-AKI) remains unclear. In the present study, the effects of short- and long-term dietary hypercholesterolemia on contrast media-induced nephrotoxicity were evaluated.

METHODS

Rats were fed either a normal rodent diet (N) or high-cholesterol diet (H). At the end of 2 and 8 weeks, 8 rats from each diet group were given a tail vein injection of either iohexol (group NC and group HC) or vehicle (group N and group H). Blood lipids, renal function and renal hemodynamics were evaluated 1 day after contrast media administration. Renal and urinary prostaglandin E(2) (PGE(2)) and thromboxane B(2) (TXB(2)) were detected by radioimmunoassay. Renal nitric oxide and malondialdehyde (MDA) were measured by the Griess reaction and thiobarbituric acid method, respectively.

RESULTS

Contrast media administration increased serum creatinine levels and induced severe renal tubular necrosis in rats fed the high-cholesterol diet for 8 weeks but not in rats fed the normal diet or high-cholesterol diet for 2 weeks. The renal and urinary PGE(2) and TXB(2) levels increased significantly in rats in group H and group HC at the end of 8 weeks. Renal nitric oxide production decreased, and MDA levels increased markedly in group HC and group H at the end of 8 weeks.

CONCLUSIONS

We conclude that long-term hypercholesterolemia appeared to be a risk factor for CI-AKI, which might be associated with disorders in intrarenal prostaglandins and abnormalities in renal nitric oxide system induced by lipid peroxidation.

Diamagnetically trapped arrays of living cells above micromagnets

Cell arrays are of foremost importance for many applications in pharmaceutical research or fundamental biology. Although arraying techniques have been widely investigated for adherent cells, organization of cells in suspension has been rarely considered. The arraying of non-adherent cells using the diamagnetic repulsive force is presented. A planar arrangement of Jurkat cells is achieved at the microscale above high quality microfabricated permanent magnets with remanent magnetization of J(r)≈ 1 T, in the presence of a paramagnetic contrast agent. The cytotoxicity of three Gd based contrast agents, Gd-DOTA, Gd-BOPTA and Gd-HP-DO3A, is studied. Among them, Gd-HP-DO3A appears to be the most biocompatible toward Jurkat cells. In close agreement with analytical simulations, diamagnetically 'suspended' cells have been successfully arrayed above square and honeycomb-like micromagnet arrays, which act as a "diamagnetophobic" surface. Living cell trapping is achieved in a simple manner using concentrations of Gd-HP-DO3A as low as 1.5 mM.

The effects of the iodinated X-ray contrast media iodixanol, iohexol, iopromide, and ioversol on the rat kidney epithelial cell line NRK 52-E

Nephrotoxicity, associated with the administration of iodinated X-ray contrast media (ICM), continues to be a major side effect in a significant number of vulnerable patients undergoing diagnostic X-ray imaging procedures. The molecular mechanisms underlying these adverse effects on the kidneys are unclear despite several decades of investigation. Side effects are more common after exposure to high-osmolar compared with low-osmolar ICM, suggesting that osmolality may be an important physical-chemical property related to nephrotoxicity. This investigation in cultured NRK 52-E cells, a cell line of renal origin, compares the in vitro toxicity of the iso-osmolal ICM iodixanol with the low-osmolal ICM iohexol, iopromide, and ioversol. The cellular toxicity was evaluated with the trypan blue exclusion assay, the MTT assay, and incidences of cell death. A qualitative assessment of vacuolation of the cultured NRK 52-E cells was taken as a measure of intracellular uptake of ICM. A difference in cell death incidence was observed between the iso-osmolal iodixanol and the low-osmolal iohexol, iopromide, and ioversol contrast media, with the iso-osmolal iodixanol having the least effect in each of the in vitro systems tested. The osmolality of the contrast media appeared to be the major cause for the observed in vitro toxicity.

Risk of acute kidney injury after exposure to gadolinium-based contrast in patients with renal impairment

OBJECTIVES

Gadolinium-based contrast media (Gd-CM) are reported to induce acute kidney injury (AKI) in a high-risk population group at the usual dose for magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) examinations. We assessed gadolinium-induced nephropathy in patients with renal impairment who underwent MRI or MRA examinations, and evaluated the risk factors.

MATERIALS AND METHODS

In this retrospective study, 238 patients with baseline renal impairment, who received MRI or MRA examinations with Gd-CM, were recruited. After all other AKI causes-liver decompensation, severe heart failure, all kinds of shock, and severe sepsis-and patients on dialysis were excluded, 158 patients were enrolled. AKI was defined as a decrease in glomerular filtration rate (GFR) >10% of baseline data within 3 days after administration of Gd-CM. Regression analysis was used to find independent risk factors for gadolinium-induced AKI (Gd-AKI).

RESULTS

Twenty-six of the 158 patients (16.5%) developed Gd-AKI. There were no significant differences in gender, age, or baseline GFR between those who did and who did not develop AKI. Comorbid coronary artery disease, liver cirrhosis, diabetes mellitus, and hypertension were not significantly associated with the development of Gd-AKI. However, sepsis was an independent risk factor for Gd-AKI after multivariate regression analysis (adjusted odds ratio: 4.417; 95% confidence interval: 1.671-11.676, p = 0.03).

CONCLUSIONS

It is potential AKI after administration of Gd-CM under sepsis condition at the dose for MRI and MRA examinations in patients with renal impairment. It is important to identify high-risk patients and closely monitor renal function after administration of Gd-CM.

Effects of magnetic resonance imaging contrast agents on human umbilical vein endothelial cells and evaluation of magnetic resonance imaging contrast media-triggered transforming growth factor-beta induction in dermal fibroblasts (HSF) as a model for nephrogenic systemic fibrosis

RATIONALE AND OBJECTIVES

The objective of this study was to evaluate effects of 6 commercially available magnetic resonance contrast media (CM) on human umbilical vein endothelial cells (HUVEC) and the induction of transforming growth factor-beta (TGF-β) in dermal fibroblasts (HSF) as a possible model for the pathogenesis of nephrogenic systemic fibrosis.

METHODS

HUVECs were incubated with 10× and 20× of the molar standard blood concentration achieved with CM applications for magnetic resonance imaging examinations (10× and 20× concentration) for 24 hours using gadolinium-based CM Gadovist, Magnevist, Multihance, and Omniscan, as well as Teslascan (Manganese-based), and Resovist (Iron-based). Proliferation kinetics (PK), colony formation, and viability assays were performed. Additionally, human dermal fibroblasts (HSF) were incubated for 24 hours with 1× and 20× concentration in all 6 CM, and TGF-β levels were assessed directly after the incubation period as well as on days 3 and 8 postincubation.

RESULTS

HUVEC PK data show similar gains in cell numbers for all 6 CM in both concentration groups over the 17-day assessment period. Only cells incubated with Omniscan and Teslascan differed from the other groups on days 3 and 7 postincubation (P < 0.05). After day 7, a cell regain occurred in the Omniscan and Teslascan groups reaching the numbers of the other groups in sequel. Differences in colony formation were consistent with PK results with a statistically significant reduction in clonogenic activity for Teslascan and Omniscan in HUVEC cells, P < 0.05. No reduction in viability was seen for all groups and conditions. TGF-β expression of HSF cells incubated with 1× concentration and all CM did not differ significantly from control cells for any point in time investigated. At 20× concentration directly after incubation, TGF-β was significantly reduced for the Teslascan and Resovist group as 3 compared with control and all other CM groups, P < 0.05. On day 3 postincubation, only Resovist-incubated HSF cells showed a significant reduction of TGF-β (1.614, standard deviations: 89) as compared with the control group (2.883, standard deviations: 30) and the other CM. TGF-β was slightly reduced for all CM groups 8 days after incubation (not statistically significant, P > 0.05).

CONCLUSIONS

After 24 hours of incubation with Omniscan and Teslascan (10× and 20× concentration), considerable short-term antiproliferative effects in HUVECs were observed. HSF cells (20× concentration) showed a reduction of TGF-β for Resovist and Teslascan directly after incubation, whereas TGF-β levels in HSF cells were slightly reduced for all CM 8 days after incubation. Therefore, TGF-β-mediated proliferative effects on fibroblasts or on collagen synthesis potentially leading to nephrogenic systemic fibrosis may mainly be triggered by tissue monocytes and macrophages in the peripheral blood instead of dermal fibroblasts.

Triggering of suicidal erythrocyte death by radiocontrast agents

BACKGROUND

According to in vitro observations, gadolinium-containing magnetic resonance (MRT) contrast agents stimulate suicidal cell death or apoptosis. Similar to nucleated cells, erythrocytes may undergo suicidal death or eryptosis, characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine (PS) exposure at the erythrocyte surface. Eryptosis is triggered by increased cytosolic Ca2+-activity. This study explored whether gadolinium-containing MRT contrast agents stimulate eryptosis.

MATERIALS AND METHODS

Annexin V-binding reflecting PS exposure and forward scatter reflecting cell volume were determined in erythrocytes within freshly drawn blood from patients (8female symbol, 3male symbol, 29-72 years) prior to and 10 min after administration of gadoterate meglumine (0.1 mmol kg(-1) b.w. Dotarem; six patients) or gadobenate dimeglumine (0.05 mmol kg(-1) bw Multi Hance; five patients). In a separate series, eryptosis was determined prior to and following in vitro incubation of erythrocytes from 16 blood donors for 4 h with gadoterate meglumine (5 mM Dotarem) or gadobenate dimeglumine (5 mM Multi Hance). Finally, eryptosis and Fluo3 fluorescence reflecting cytosolic Ca2+ were determined in vitro following exposure to Gd3+. Data were analysed using paired t-test or anova with Tukey's test as post-test.

RESULTS

The MRT contrast agents such as gadoterate meglumine (Dotarem) and gadobenate dimeglumine (Multi Hance) significantly increased the percentage of eryptotic cells. Moreover, in vitro exposure to gadoterate meglumine (5 mM), gadobenate dimeglumine (5 mM) or Gd3+ (1.9 microM) stimulated eryptosis in vitro. The effect of Gd3+ was paralleled by increase in cytosolic Ca2+-activity.

CONCLUSIONS

MRT contrast agents may stimulate suicidal erythrocyte death or eryptosis in vitro and in vivo.

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.