99mTc-MAG3 scintigraphy for the longitudinal follow-up of kidney function in a mouse model of renal ischemia-reperfusion injury

Development and autoregulation of kidney function in children: a retrospective study using 99mTc-MAG3 renography

BACKGROUND

Both the development of kidney function in healthy children and autoregulation ability of kidney function in patients with asymmetric kidneys are important in clinical diagnosis and treatment of kidney-related diseases, but there are however only limited studies. This study aimed to investigate development of kidney function in normal children with healthy symmetric kidneys and autoregulation of the healthy kidney compensating the functional loss of a diseased one in children with asymmetric kidneys.

METHODS

Two hundred thirty-seven children (156 male, 81 female) from 0 to 20y (average 4.6y ± 5.1) undergoing ^99mTc-MAG3 renography were included, comprising 134 with healthy symmetrically functioning kidneys and 103 with asymmetric kidneys. Clearance was calculated from kidney uptakes at 1-2 min. A developmental model between MAG3 clearance (CL) and patient age in normal group was identified (CL = 84.39Age^0.395 ml/min, r = 0.957, p < 0.001). The clearance autoregulation rate in abnormal group with asymmetric kidneys was defined as the ratio of the measured MAG3 clearance and the normal value predicted from the renal developmental model of normal group.

RESULTS

No significant difference of MAG3 clearance (p = 0.723) was found between independent abnormal group and normal group. The autoregulation rate of kidney clearance in abnormal group was 94.2% on average, and no significant differences were found between two age groups (p = 0.49), male and female (p = 0.39), and left kidney and right kidney (p = 0.92) but two different grades of asymmetric kidneys (p = 0.02).

CONCLUSIONS

The healthy kidney of two asymmetric kidneys can automatically regulate total kidney function up to 94% of two symmetric kidneys in normal children.

Toxicity of a combined therapy using the mTOR-inhibitor everolimus and PRRT with [177Lu]Lu-DOTA-TATE in Lewis rats

PURPOSE

Peptide receptor radionuclide therapy (PRRT) with [177Lu]Lu-DOTA0,TYR3-octreotate ([177Lu]Lu-DOTA-TATE) and the mechanistic target of rapamycin (mTOR) inhibitor everolimus are both approved for the treatment of neuroendocrine tumours (NET). However, tumour progression is still frequent, and treatment strategies need further improvement. One possible approach could be to combine different therapy options. In this study, we investigated the toxicity of a combined treatment with everolimus and [177Lu]Lu-DOTA-TATE in female Lewis rats.

METHODS

Animals received 200 MBq of [177Lu]Lu-DOTA-TATE once and/or 5 mg/kg body weight everolimus or placebo weekly for 16 weeks and were divided into four groups (group 1, placebo; group 2, everolimus; group 3, placebo + [177Lu]Lu-DOTA-TATE; group 4, everolimus + [177Lu]Lu-DOTA-TATE). Blood levels of creatinine and blood urea nitrogen (BUN) were assessed weekly to monitor nephrotoxicity, and a full blood count was performed at the time of euthanasia to monitor myelotoxicity. Additionally, renal function was analysed by sequential [99mTc]Tc-mercaptoacetyltriglycine ([99mTc]Tc-MAG3) scintigraphies. Histopathological examination was performed in all the kidneys using a standardized renal damage score (RDS).

RESULTS

Rats receiving everolimus showed a significantly lower increase in creatinine levels than those receiving placebo. Everolimus therapy reduced white blood count significantly, which was not observed for [177Lu]Lu-DOTA-TATE. Functional renal scintigraphies using [99mTc]Tc-MAG3 showed a compromised initial tracer uptake after PRRT and slower but still preserved excretion after everolimus. Histology showed no significant RDS differences between groups.

CONCLUSION

Renal scintigraphy is a highly sensitive tool for the detection of renal function impairment after a combination of everolimus and PRRT. Additional treatment with everolimus does not increase renal and haematological toxicity of PRRT with [177Lu]Lu-DOTA-TATE.

Effects of flexible ureteroscopy on kidney: A prospective clinical trial

OBJECTIVE

To investigate the effects of flexible ureteroscopy (F-URS) on the operated side of a kidney by assessing the renal damage markers, urine neutrophil gelatinase-related lipocalin (NGAL) and serum cystatin-C (Cys-C), and overall kidney function with the measurements of standard serum creatinine and urine albumin and protein levels.

MATERIAL AND METHODS

A total of 30 patients who underwent F-URS for treatment of upper urinary stone disease were prospectively evaluated. Preoperative serum urea, creatinine, and Cys-C levels were noted. Levels of urine albumin, protein, creatinine, and NGAL in spot urine samples from the operated side of a kidney obtained through the access sheath preoperatively and through the ureteral catheter 1 and 24 hours postoperatively were also measured. Preoperative and postoperative parameter levels were statistically compared.

RESULTS

The patients' mean age was 46.6±15.9 years. The mean operative and fluoroscopy times were 90.67±32.5 and 3.15±1.43 minutes, respectively. The urine creatinine, albumin, protein, albumin/creatinine, and protein/creatinine levels were similar in preoperative and postoperative periods. Postoperative serum urea, creatinine, and Cys-C levels and urine NGAL and NGAL/creatinine levels were not also found with remarkable changes from the baseline levels.

CONCLUSION

F-URS is a safe therapeutic intervention in the treatment of urolithiasis, especially regarding renal damage, and functional outcomes.

Scintigraphic evaluation of renoprotective effects of coenzyme Q10 in a rat renal ischemia-reperfusion injury

PURPOSE

Renal ischemia-reperfusion injury (RIRI) may occur secondary to several reasons leading to renal failure. Coenzyme-Q10 (CoQ10) is a well-known antioxidant. However, the effects CoQ10 against RIRI have not been evaluated. Our aim was to evaluate protective effects of CoQ10 to renal ischemia-reperfusion by biochemical, immunohistochemical and scintigraphic findings.

METHODS

Thirty Wistar-albino rats were randomly separated into groups of 10; Group Sham; Group ischemia-reperfusion (IR) had left renal pedicle clamping; Group CoQ10+IR had IR and CoQ10. Twenty-four hours later after reperfusion, scintigraphy was performed and after that, rats were sacrificed. To demonstrate effects of RIRI, serum urea and creatinine levels and tissue levels oxidative stress markers were evaluated. Both kidneys were subjected to histopathological evaluation and to confirm RIRI-induced immunohistochemical aspects of apoptosis, terminal-deoxynucleotidyl-transferase mediated-deoxyuridine-triphosphate-nick-end-labeling assay and caspase-3 were assessed.

RESULTS

Tissue oxidative stress, histopathologic changes, apoptosis scores and quantitative scintigraphic parameters were significantly higher in Group IR compared with Group Sham. Although tissue oxidative stress levels and histopathologic changes were not significant, quantitative scintigraphic parameters of contralateral kidney of Group IR were significantly increased. Compared with Group IR, Group CoQ10+IR presented decreased tissue oxidative stress levels; decreased scores of histopathology and apoptosis; and decreased quantitative scintigraphic parameters with increased split renal function in ischemic kidney.

CONCLUSIONS

Our results suggest that other than its antioxidant properties, CoQ10 shows antiperoxidative, antiapoptotic and antiinflammatory potential in protecting renal functioning of ischemic kidney. Furthermore, our results show that renal scintigraphy is a feasible method to detect early changes in renal functioning after RIRI.

Non-Invasive Imaging Methodologies for Assessment of Radiation Damage to Bone Marrow and Kidneys from Peptide Receptor Radionuclide Therapy

BACKGROUND/AIMS

Peptide receptor radionuclide therapy (PRRT) is becoming clinical routine for management of neuroendocrine tumours. The number of PRRT cycles is correlated with treatment effect but theoretically limited by off-target radiation damage to kidneys and bone marrow. New imaging biomarkers for assessment of PRRT tissue damage would enable evaluation of novel renal and bone marrow protective agents, as well as personalised PRRT treatment regiments.

METHODS

Mice treated with [177Lu]Lu-DOTA-TATE PRRT or vehicle were examined at baseline and following treatment with [18F]fluorothymidine (FLT) positron emission tomography (PET) and technetium-99m-mercapto-acetyl-tri-glycine ([99mTc]Tc-Mag3) single-photon emission tomography (SPECT) to assess dynamic changes in bone marrow proliferation and renal function, respectively.

RESULTS

Bone marrow proliferation as assessed by [18F]FLT was decreased 2 days after PRRT treatment, but not vehicle, compared to baseline (target-to-background ratio [TBRmax] baseline:1.69 ± 0.29 vs. TBRmax PRRT: 0.91 ± 0.02, p < 0.01). Renal function as assessed by [99mTc]Tc-Mag3 SPECT was similarly decreased 2 days following PRRT compared to vehicle (fractional uptake rate [FUR] vehicle: 0.030 ± 0.014 s-1 vs. FUR PRRT: 0.0051 ± 0.0028 s-1, p < 0.01).

CONCLUSION

[18F]FLT PET and [99mTc]Tc-Mag3 SPECT are promising techniques for assessing bone marrow and renal injury from [177Lu]Lu-DOTA-TATE PRRT and may potentially improve patient management by allowing evaluation of protective interventions as well as enabling personalised PRRT treatments.

Nephroprotective effects of enalapril after [177Lu]-DOTATATE therapy using serial renal scintigraphies in a murine model of radiation-induced nephropathy

Background

Radiation-induced nephropathy is still dose limiting in radionuclide therapy of neuroendocrine tumors. We investigated the nephroprotective potential of the angiotensine converting enzyme inhibiting drug enalpril after [177Lu]-DOTATATE therapy in a murine model of radiation-induced nephropathy by renal scintigraphy.

At first, the appropriate therapy activity to induce nephropathy was identified. Baseline scintigraphy (n = 12) entailed 12-min dynamic acquisitions after injection of 25 MBq [99mTc]-MAG3, which was followed by radionuclide therapy at four escalating activities of [177Lu]-DOTATATE: group (Gp) 1: 10 MBq; Gp 2: 20 MBq; Gp 3: 40 MBq; Gp 4: 65 MBq. Follow-up [99mTc]-MAG3 scintigraphy was carried out at days 9, 23, 44, and 65. The treatment activity for the intervention arm was selected on the basis of histological examination and declining renal function. In the second part, daily administration by gavage of 10 mg/kg/d enalapril or water (control group) was initiated on the day of radionuclide therapy. Follow-up scintigraphy was carried out at days 9, 23, 44, 65, and 86. We also created a non-therapy control group to detect therapy-independent changes of renal function over time. For all scintigraphies, mean renogram curves were analyzed and the “fractional uptake rate” (FUR; %I.D./min ± SEM) of the tracer by the kidneys was calculated as an index of renal clearance.

Results

At day 65 of follow-up, no significant change in the FUR relative to baseline (11.0 ± 0.3) was evident in radionuclide therapy groups 1 (11.2 ± 0.5) and 2 (10.1 ± 0.6), but FUR was significantly reduced in groups 3 (8.93 ± 0.6, p < 0.05) and 4 (6.0 ± 0.8, p < 0.01); we chose 40 MBq [177Lu]-DOTATATE (Gp 3) for the intervention study. Here, at the last day of follow-up (day 86), FUR was unaltered in enalapril-treated mice (11.8 ± 0.5) relative to the baseline group (12.4 ± 0.3) and non-therapy group (11.9 ± 0.8), whereas FUR in the control group had undergone a significant decline (9.3 ± 0.5; p < 0.01). Histological examination revealed prevention of kidney damage by enalapril treatment.

Conclusions

Treatment with enalapril is effective for nephroprotection during radionuclide therapy with [177Lu]-DOTATATE in mice. Although these results are only limitedly transferable to human studies, enalapril might serve as a promising drug in the mitigation of nephropathy following treatment with [177Lu]-DOTATATE.

Electronic supplementary material

The online version of this article (doi:10.1186/s13550-016-0219-2) contains supplementary material, which is available to authorized users.

Imaging technologies for monitoring the safety, efficacy and mechanisms of action of cell-based regenerative medicine therapies in models of kidney disease

The incidence of end stage kidney disease is rising annually and it is now a global public health problem. Current treatment options are dialysis or renal transplantation, which apart from their significant drawbacks in terms of increased morbidity and mortality, are placing an increasing economic burden on society. Cell-based Regenerative Medicine Therapies (RMTs) have shown great promise in rodent models of kidney disease, but clinical translation is hampered due to the lack of adequate safety and efficacy data. Furthermore, the mechanisms whereby the cell-based RMTs ameliorate injury are ill-defined. For instance, it is not always clear if the cells directly replace damaged renal tissue, or whether paracrine effects are more important. Knowledge of the mechanisms responsible for the beneficial effects of cell therapies is crucial because it could lead to the development of safer and more effective RMTs in the future. To address these questions, novel in vivo imaging strategies are needed to monitor the biodistribution of cell-based RMTs and evaluate their beneficial effects on host tissues and organs, as well as any potential adverse effects. In this review we will discuss how state-of-the-art imaging modalities, including bioluminescence, magnetic resonance, nuclear imaging, ultrasound and an emerging imaging technology called multispectral optoacoustic tomography, can be used in combination with various imaging probes to track the fate and biodistribution of cell-based RMTs in rodent models of kidney disease, and evaluate their effect on renal function.

Initial Preclinical Evaluation of 18F-Fluorodeoxysorbitol PET as a Novel Functional Renal Imaging Agent

Accurate assessment of kidney function plays an essential role for optimal clinical decision making in a variety of diseases. The major intrinsic advantages of PET are superior spatial and temporal resolutions for quantitative tomographic renal imaging. 2-deoxy-2-¹⁸F-fluorodeoxysorbitol (¹⁸F-FDS) is an analog of sorbitol that is reported to be freely filtered at the renal glomerulus without reabsorption at the tubule. Furthermore, it can be synthesized via simple reduction of widely available ¹⁸F-FDG. We tested the feasibility of ¹⁸F-FDS renal PET imaging in rats.

METHODS

The systemic and renal distribution of ¹⁸F-FDS were determined by dynamic 35-min PET imaging (15 frames × 8 s, 26 frames × 30 s, 20 frames × 60 s) with a dedicated small-animal PET system and postmortem tissue counting in healthy rats. Distribution of coinjected ^99mTc-diethylenetriaminepentaacetic acid (DTPA) was also estimated as a reference. Plasma binding and in vivo stability of ¹⁸F-FDS were determined.

RESULTS

In vivo PET imaging visualized rapid excretion of the administrated ¹⁸F-FDS from both kidneys, with minimal tracer accumulation in other organs. Initial cortical tracer uptake followed by visualization of the collecting system could be observed with high contrast. Split-function renography curves were successfully obtained in healthy rats (the time of maximal concentration [T_max] right [R] = 2.8 ± 1.2 min, T_max left [L] = 2.9 ± 1.5 min, the time of half maximal concentration [T_1/2max] R = 8.8 ± 3.7 min, T_1/2max L = 11.1 ± 4.9 min). Postmortem tissue counting of ¹⁸F-FDS confirmed the high kidney extraction (kidney activities at 10, 30, and 60 min after tracer injection [percentage injected dose per gram]: 1.8 ± 0.7, 1.2 ± 0.1, and 0.5 ± 0.2, respectively) in a degree comparable to ^99mTc-DTPA (2.5 ± 1.0, 1.5 ± 0.2, and 0.8 ± 0.3, respectively). Plasma protein binding of ¹⁸F-FDS was low (<0.1%), and metabolic transformation was not detected in serum and urine.

CONCLUSION

In rat experiments, ¹⁸F-FDS demonstrated high kidney extraction and excretion, low plasma protein binding, and high metabolic stability as preferable properties for renal imaging. These preliminary results warrant further confirmatory studies in large animal models and clinical studies as a novel functional renal imaging agent, given the advantages of PET technology and broad tracer availability.

X-ray phase-contrast tomography of renal ischemia-reperfusion damage

Purpose

The aim of the study was to investigate microstructural changes occurring in unilateral renal ischemia-reperfusion injury in a murine animal model using synchrotron radiation.

Material and Methods

The effects of renal ischemia-reperfusion were investigated in a murine animal model of unilateral ischemia. Kidney samples were harvested on day 18. Grating-Based Phase-Contrast Imaging (GB-PCI) of the paraffin-embedded kidney samples was performed at a Synchrotron Radiation Facility (beam energy of 19 keV). To obtain phase information, a two-grating Talbot interferometer was used applying the phase stepping technique. The imaging system provided an effective pixel size of 7.5 µm. The resulting attenuation and differential phase projections were tomographically reconstructed using filtered back-projection. Semi-automated segmentation and volumetry and correlation to histopathology were performed.

Results

GB-PCI provided good discrimination of the cortex, outer and inner medulla in non-ischemic control kidneys. Post-ischemic kidneys showed a reduced compartmental differentiation, particularly of the outer stripe of the outer medulla, which could not be differentiated from the inner stripe. Compared to the contralateral kidney, after ischemia a volume loss was detected, while the inner medulla mainly retained its volume (ratio 0.94). Post-ischemic kidneys exhibited severe tissue damage as evidenced by tubular atrophy and dilatation, moderate inflammatory infiltration, loss of brush borders and tubular protein cylinders.

Conclusion

In conclusion GB-PCI with synchrotron radiation allows for non-destructive microstructural assessment of parenchymal kidney disease and vessel architecture. If translation to lab-based approaches generates sufficient density resolution, and with a time-optimized image analysis protocol, GB-PCI may ultimately serve as a non-invasive, non-enhanced alternative for imaging of pathological changes of the kidney.

Decompression of Inflammatory Edema along with Endothelial Cell Therapy Expedites Regeneration after Renal Ischemia-Reperfusion Injury

Increased pressure due to postischemic edema aggravates renal ischemia-reperfusion injury (IRI). Prophylactic surgical decompression using microcapsulotomy improves kidney dysfunction after IRI. Supportive cell therapy in combination with microcapsulotomy might act synergistically protecting kidney function against IRI. The effects of therapeutic endothelial cell application alone and in combination with microcapsulotomy were investigated in a xenogenic murine model of 45-min warm renal ischemia. Renal function and perfusion were determined before as well as 2 and 18 days postischemia by 99mTc-MAG3 imaging and laser Doppler. Histological analysis included H&E stains and immunohistology for endothelial marker MECA-32, cell proliferation marker Ki-67, and macrophage marker F4/80. Histomorphological changes were quantified using a tubular injury score. Ischemia of 45 min led to severe tissue damage and a significant decrease in renal function and perfusion. Microcapsulotomy and cell therapy alone had no significant effect on renal function, while only surgical decompression significantly increased blood flow in ischemic kidneys. However, the combination of both microcapsulotomy and cell therapy significantly improved kidney function and perfusion. Combination therapy significantly reduced morphological injury of ischemic kidneys as determined by a tubular injury score and MECA-32 staining. Macrophage infiltration evidenced by F4/80 staining was significantly reduced. The Ki-67 proliferation index was increased, suggesting a regenerative environment. While microcapsulotomy and cell therapy alone have limited effect on renal recovery after IRI, combination therapy showed synergistic improvement of renal function, perfusion, and structural damage. Microcapsulotomy may create a permissive environment for cell therapy to work.