Nathalie Fretellier

T1-Weighted Hypersignal in the Deep Cerebellar Nuclei After Repeated Administrations of Gadolinium-Based Contrast Agents in Healthy Rats: Difference Between Linear and Macrocyclic Agents.

ObjectivesTo prospectively compare in healthy rats the effect of multiple injections of macrocyclic (gadoterate meglumine) and linear (gadodiamide) gadolinium-based contrast agents (GBCAs) on T1-weighted signal intensity in the deep cerebellar nuclei (DCN), including the dentate nucleus. Materials and MethodsHealthy rats (n = 7/group) received 20 intravenous injections of 0.6 mmol of gadolinium (Gd) per kilogram (4 injections per week during 5 weeks) of gadodiamide, gadoterate meglumine, or hyperosmolar saline (control group). Brain T1-weighted magnetic resonance imaging was performed before and once a week during the 5 weeks of injections and during 5 additional weeks (treatment-free period). Gadolinium concentrations were measured with inductively coupled plasma mass spectrometry in plasma and brain. Blinded qualitative and quantitative evaluations of the T1 signal intensity in DCN were performed, as well as a statistical analysis on quantitative data. ResultsA significant and persistent T1 signal hyperintensity in DCN was observed only in gadodiamide-treated rats. The DCN-to-cerebellar cortex signal ratio was significantly increased from the 12th injection of gadodiamide (1.070 ± 0.024) compared to the gadoterate meglumine group (1.000 ± 0.033; P < 0.001) and control group (1.019 ± 0.022; P < 0.001) and did not significantly decrease during the treatment-free period. Total Gd concentrations in the gadodiamide group were significantly higher in the cerebellum (3.66 ± 0.91 nmol/g) compared with the gadoterate meglumine (0.26 ± 0.12 nmol/g; P < 0.05) and control (0.06 ± 0.10 nmol/g; P < 0.05) groups. ConclusionsRepeated administrations of the linear GBCA gadodiamide to healthy rats are associated with progressive and persistent T1 signal hyperintensity in the DCN, with Gd deposition in the cerebellum in contrast with the macrocyclic GBCA gadoterate meglumine for which no effect was observed.

Comparative in vivo dissociation of gadolinium chelates in renally impaired rats: a relaxometry study.

Purpose:Investigation of dissociated versus chelated gadolinium (Gd) in plasma, skin, and bone of rats with impaired renal function after administration of ionic macrocyclic (gadoterate or Dotarem) or nonionic linear (gadodiamide or Omniscan) Gd chelates. Materials and Methods:Subtotally nephrectomized Wistar rats were subjected to receive daily injections of 2.5 mmol/kg of Omniscan, gadodiamide without excess ligand caldiamide, Dotarem, or saline (n = 7–10 rats/group) for 5 consecutive days. The Gd concentration was measured by inductively coupled plasma mass spectrometer in skin, femur epiphysis, and plasma on completion of the study (day 11), and dissociated Gd3+ was measured in the plasma at day 11 (liquid chromatography inductively coupled plasma mass spectrometry). The r1 relaxivity constant was measured in skin (at day 4 and day 11) and bone (day 11) to investigate the dissociated or chelated form of Gd found in tissue samples. Clinical and skin histopathologic studies were performed. Results:Subtotal nephrectomy decreased creatinine clearance by 60%. No macroscopic skin lesions were observed in the Dotarem and Omniscan groups in contrast with the gadodiamide group (2 rats survived the study period and 4 of 10 rats showed skin ulcerations and scabs). Skin histopathologic lesions were in the range gadodiamide > Omniscan > Dotarem (similar to control rats). At day 11, the skin Gd concentration was lower in the Dotarem group (161.0 ± 85.5 nmol/g) as compared with the Omniscan (490.5 ± 223.2 nmol/g) and gadodiamide groups (mean value, 776.1 nmol/g; n = 2 survivors). The total Gd concentration in the femur was significantly higher in the Omniscan group than in the Dotarem group. At day 11, the dissociated Gd3+ concentration in plasma was below the limit of detection in the Dotarem group and was 1.5 ± 0.7 &mgr;mol/L in the Omniscan group corresponding to 62% ± 15% of the total Gd concentration. The dissociated Gd3+ concentration was 1.1 &mgr;mol/L in gadodiamide rats (n = 2 survivors). In the skin, the in vivo r1 relaxivity value increased from 4.8 ± 0.7 mM−1s−1 at day 4 to 10.5 ± 3.9 mM−1s−1 at day 11 in the Omniscan group, P < 0.05 (in vitro r1 in skin, 3.5 mM−1s−1) and gadodiamide group, whereas no significant change was observed in the Dotarem group (2.8 ± 0.2 and 4.9 ± 2.8 mM−1s−1 at day 4 and 11, respectively, NS) (in vitro value in the skin, 3.2 mM−1s−1). In the femur, the in vivo r1 relaxivity was higher in the Omniscan group (8.9 ± 2.1 mM−1s−1) (in vitro relaxivity, 4.5 mM−1s−1) and gadodiamide group (8.8 mM−1s−1, n = 2 survivors) than in the Dotarem group (3.8 mM−1s−1, n = 1 rat with measurable r1, since for 7 rats, 1/T1 − 1/T1(diamagnetic) <10% of 1/T1(diamagnetic) because of low Gd concentration) (in vitro relaxivity value in the femur matrix, 3.1 mM−1s−1). Conclusions:Unlike Dotarem, Omniscan and gadodiamide induced histologic skin lesions. At day 11, a higher Gd concentration was found in both skin and femur of Omniscan- and gadodiamide-treated rats than in Dotarem-treated rats. Relaxometry results indicate gradual in vivo dechelation and release of dissociated Gd3+ in a soluble form in renally impaired rats receiving Omniscan and gadodiamide, whereas Dotarem remained stable over the study period.

Clinical, biological, and skin histopathologic effects of ionic macrocyclic and nonionic linear gadolinium chelates in a rat model of nephrogenic systemic fibrosis.

Objective:The purpose of this study was to compare the clinical, pathologic, and biochemical effects of repeated administrations of ionic macrocyclic or nonionic linear gadolinium chelates (GC) in rats with impaired renal function. Material and Methods:Rats submitted to subtotal nephrectomy were allocated to single injections of 2.5 mmol/kg of gadodiamide (nonionic linear chelate), nonformulated gadodiamide (ie, without the free ligand caldiamide), gadoterate (ionic macrocyclic chelate), or saline for 5 consecutive days. Blinded semi-quantitative histopathologic and immunohistochemical examinations of the skin were performed, as well as clinical, hematological, and biochemical follow-up. Rats were killed at day 11. Long-term (up to day 32) follow-up of rats was also performed in an auxiliary study. Results:Epidermal lesions (ulcerations and scabs) were found in 4 of the 10 rats treated with nonformulated gadodiamide. Two rats survived the study period. Inflammatory signs were observed in this group. No clinical, hematological, or biochemical signs were observed in the saline and gadoterate- or gadodiamide-treated groups. Plasma fibroblast growth factor-23 levels were significantly higher in the gadodiamide group than in the gadoterate group (day 11). Decreased plasma transferrin-bound iron levels were measured in the nonformulated gadodiamide group. Histologic lesions were in the range: nonformulated gadodiamide (superficial epidermal lesions, inflammation, necrosis, and increased cellularity in papillary dermis) > gadodiamide (small superficial epidermal lesions and signs of degradation of collagen fibers in the dermis) > gadoterate (very few pathologic lesions, similar to control rats). Conclusions:Repeated administration of the nonionic linear GC gadodiamide to renally impaired rats is associated with more severe histologic lesions and higher FGF-23 plasma levels than the macrocyclic GC gadoterate.

Hyperphosphataemia sensitizes renally impaired rats to the profibrotic effects of gadodiamide

Hyperphosphataemia is common in patients with nephrogenic systemic fibrosis (NSF). NSF has been linked to administration of gadolinium (Gd) chelates (GCs) and elevated serum phosphate levels accelerate the release of Gd from linear, non‐ionic GCs but not macrocyclic GCs. Hence, we determined whether hyperphosphataemia is a cofactor or risk factor for NSF by investigating the role of hyperphosphataemia in renally impaired rats.

Gadolinium contrast agent associated stimulation of human fibroblast collagen production.

Objectives:Nephrogenic systemic fibrosis occurs in patients with poor renal function who receive gadolinium-based contrast agents (Gd-CAs). Several reports suggest that this is more likely to occur with the less stable forms of Gd chelates, suggesting a release of cytotoxic free Gd ions from these. There is evidence that Gd can stimulate human fibroblast proliferation but the evidence is less clear concerning the production of collagen by these cells. Our aim was to assess effects of Gd chelates on human skin cell activity and collagen production. Materials and Methods:Keratinocytes and fibroblasts were cultured with 3 Gd chelates (Gd-EDTA, Omniscan [nonionic linear Gd-CA], and Dotarem [ionic macrocyclic Gd-CA]) for up to 7 days, and cell viability and collagen production were assessed using the colorimetric assays of MTT (3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyltetrazolium bromide) and Sirius Red, respectively. The uptake of Gd by cultured fibroblasts was also undertaken using the techniques of inductively coupled plasma mass spectrometry and relaxometry. Results:Our data show that Gd-EDTA and Omniscan significantly stimulated both fibroblast and keratinocyte viability and fibroblast (but not keratinocyte) collagen production. In contrast, Dotarem had little, if any, effect on these cultured cells. The Omniscan-induced increase in fibroblast collagen was around 40% over 7 days—a similar increase to that seen for cell viability, suggesting that collagen production was secondary to an initial stimulatory effect on fibroblast viability. Studies of the uptake of Gd by the cultured fibroblasts showed that these took up Gd when cultured with Omniscan for 7 days, and our study also suggests that some of this Gd was in a free dissociated form. Conclusions:We conclude that these results support a simple nephrogenic systemic fibrosis causative role of low-stability nonionic linear Gd-CA inducing dermal collagen via the release of dissociated Gd which enters fibroblasts and stimulates their activity and associated collagen production.

Nephrogenic Systemic Fibrosis-Like Effects of Magnetic Resonance Imaging Contrast Agents in Rats with Adenine-Induced Renal Failure

Nephrogenic systemic fibrosis (NSF) is a scleroderma-like disease associated with prior administration of certain gadolinium chelates (GCs). NSF occurs in patients with severe renal failure. The purpose of this study was to set up a rat model of GC-associated NSF to elucidate the mechanism of this devastating disease. Firstly, after characterization of the model, male Wistar rats received a 0.75% adenine-enriched diet for 8, 14, or 16 days to obtain various degrees of renal failure. Rats received five consecutive daily iv injections of saline or gadodiamide (2.5 mmol/kg/day). Secondly, the safety profile and in vivo propensity to dissociate of all categories of marketed GCs (gadoterate, gadobutrol, gadobenate, gadopentetate, and gadodiamide) were compared in rats receiving adenine-enriched diet for 16 days. Serial skin biopsies were performed for blinded histopathological study. Total Gd concentration in tissues was measured by Inductively Coupled Plasma Mass Spectrometry. Relaxometry was used to evaluate the presence of dissociated Gd in skin and bone. Gadodiamide-induced high mortality and skin lesions (dermal fibrosis, calcification, and inflammation) were related to adenine diet duration. No skin lesions were observed with other molecules. Unlike macrocyclic GCs, gadodiamide, gadopentetate, and gadobenate gradually increased the r(1) relaxivity value, consistent with in vivo dissociation and release of soluble Gd (or, in the case of gadobenate, the consequence of protein binding). Gadodiamide-induced cutaneous and systemic toxicity depended on baseline renal function. We demonstrate in vivo dissociation of linear GCs, gadodiamide, and gadopentetate, whereas macrocyclic agents remained stable over the study period.

Total gadolinium tissue deposition and skin structural findings following the administration of structurally different gadolinium chelates in healthy and ovariectomized female rats

OBJECTIVE To assess the retention of gadolinium (Gd) in skin, liver, and bone following gadodiamide or gadoteric acid administration. METHODS Gd was measured in skin, liver and femur bone in female rats 10 weeks after administration of 17.5 mmol Gd/kg over 5 days of Gd agents. Rat skin microscopy, energy filtering transmission electron microscopy and elemental analysis were performed, and repeated after receiving the same dosage of gadodiamide in rats with osteoporosis induced with bilateral ovariectomy (OVX). The OVX was performed 60 days after the last injection of gadodiamide and animals sacrificed 3 weeks later. RESULTS Gd concentration was 180-fold higher in the skin, 25-fold higher in the femur, and 30-fold higher in the liver in rats received gadodiamide than rats received gadoteric acid. The retention of Gd in the skin with gadodiamide was associated with an increase in dermal cellularity, and Gd encrustation of collagen fibers and deposition inside the fibroblasts and other cells. No differences in Gd concentration in liver, skin, and femur were observed between rats receiving gadodiamide with or without OVX. CONCLUSIONS Gd tissue retention with gadodiamide was higher than gadoteric acid. Tissues Gd deposition did not alter following gadodiamide administration to ovariectomized rats.

Moderate Renal Failure Accentuates T1 Signal Enhancement in the Deep Cerebellar Nuclei of Gadodiamide-treated Rats

Objectives The purpose of this preclinical study was to investigate whether moderate chronic kidney disease is a factor in potentiating gadolinium (Gd) uptake in the brain. Materials and Methods A comparative study was performed on renally impaired (subtotal nephrectomy) rats versus rats with normal renal function. The animals received 4 daily injections of 0.6 mmol Gd/kg a week for 5 weeks (cumulative dose of 12 mmol Gd/kg) of gadodiamide or saline solution. The MR signal enhancement in the deep cerebellar nuclei was monitored by weekly magnetic resonance imaging examinations. One week after the final injection, the total Gd concentration was determined by inductively coupled plasma mass spectrometry in different regions of the brain including the cerebellum, plasma, cerebrospinal fluid, parietal bone, and femur. Results After the administration of gadodiamide, the subtotal nephrectomy group presented a significantly higher T1 signal enhancement in the deep cerebellar nuclei and a major increase in the total Gd concentration in all the studied structures, compared with the normal renal function group receiving the same linear Gd-based contrast agent. Those potentiated animals also showed a pronounced hypersignal in the choroid plexus, still persistent 6 days after the last injection, whereas low concentration of Gd was found in the cerebrospinal fluid (<0.05 &mgr;mol/L) at this time point. Plasma Gd concentration was then around 1 &mgr;mol/L. Interestingly, plasma Gd was predominantly in a dissociated and soluble form (around 90% of total Gd). Total Gd concentrations in the brain, cerebellum, plasma, and bones correlated with creatinine clearance in both the gadodiamide-treated groups. Conclusions Renal insufficiency in rats potentiates Gd uptake in the cerebellum, brain, and bones.

Analytical interference in serum iron determination reveals iron versus gadolinium transmetallation with linear gadolinium-based contrast agents.

ObjectivesThe purposes of this study were to evaluate the risk for analytical interference with gadolinium-based contrast agents (GBCAs) for the colorimetric measurement of serum iron (Fe3+) and to investigate the mechanisms involved. Materials and MethodsRat serum was spiked with several concentrations of all molecular categories of GBCAs, ligands, or “free” soluble gadolinium (Gd3+). Serum iron concentration was determined by 2 different colorimetric methods at pH 4.0 (with a Vitros DT60 analyzer or a Cobas Integra 400 analyzer). Secondly, the cause of interference was investigated by (a) adding free soluble Gd3+ or Mn2+ to serum in the presence of gadobenic acid or gadodiamide and (b) electrospray ionization mass spectrometry. ResultsSpurious decrease in serum Fe3+ concentration was observed with all linear GBCAs (only with the Vitros DT60 technique occurring at pH 4.0) but not with macrocyclic GBCAs or with free soluble Gd3+. Spurious hyposideremia was also observed with the free ligands present in the pharmaceutical solutions of the linear GBCAs gadopentetic acid and gadodiamide (ie, diethylene triamine pentaacetic acid and calcium-diethylene triamine pentaacetic acid bismethylamide, respectively), suggesting the formation of Fe-ligand chelate.Gadobenic acid-induced interference was blocked in a concentration-dependent fashion by adding a free soluble Gd3+ salt. Conversely, Mn2+, which has a lower affinity than Gd3+ and Fe3+ for the ligand of gadobenic acid (ie, benzyloxypropionic diethylenetriamine tetraacetic acid), was less effective (interference was only partially blocked), suggesting an Fe3+ versus Gd3+ transmetallation phenomenon at pH 4.0. Similar results were observed with gadodiamide. Mass spectrometry detected the formation of Fe-ligand with all linear GBCAs tested in the presence of Fe3+ and the disappearance of Fe-ligand after the addition of free soluble Gd3+. No Fe-ligand chelate was found in the case of the macrocyclic GBCA gadoteric acid. ConclusionsMacrocyclic GBCAs induced no interference with colorimetric methods for iron determination, whereas negative interference was observed with linear GBCAs using a Vitros DT60 analyzer. This interference of linear GBCAs seems to be caused by the excess of ligand and/or an Fe3+ versus Gd3+ transmetallation phenomenon.