Diffusion tensor imaging MRI of sickle cell kidney disease: initial results and comparison with iron deposition

Advances of Iron and Ferroptosis in Diabetic Kidney Disease

Diabetes mellitus presents a significant threat to human health because it disrupts energy metabolism and gives rise to various complications, including diabetic kidney disease (DKD). Metabolic adaptations occurring in the kidney in response to diabetes contribute to the pathogenesis of DKD. Iron metabolism and ferroptosis, a recently defined form of cell death resulting from iron-dependent excessive accumulation of lipid peroxides, have emerged as crucial players in the progression of DKD. In this comprehensive review, we highlight the profound impact of adaptive and maladaptive responses regulating iron metabolism on the progression of kidney damage in diabetes. We summarize the current understanding of iron homeostasis and ferroptosis in DKD. Finally, we propose that precise manipulation of iron metabolism and ferroptosis may serve as potential strategies for kidney management in diabetes.

Emerging Therapies and Advances in Sickle Cell Disease with a Focus on Renal Manifestations

The underlying mechanisms of disease in sickle cell disease (SCD) contribute to a multifaceted nephropathy, commonly manifested as albuminuria. In severe SCD genotypes ( e.g. , Hemoglobin SS [HbSS]), albuminuria and CKD are major predictors of mortality in this population. Therefore, the monitoring and management of renal function is an intrinsic part of comprehensive care in SCD. Management of nephropathy in SCD can be accomplished with SCD-directed therapies and/or CKD-directed therapies. In the past 5 years, novel disease-modifying and palliative therapies have been approved in SCD to target aspects of the disease, such as anemia, inflammation, and vasculopathy. Along with conventional hydroxyurea and chronic transfusion, l -glutamine, crizanlizumab, and voxelotor have all been shown to mitigate some adverse effect of SCD, and their effect on nephropathy is being investigated. CKD-directed therapies such as renin-angiotensin-aldosterone system blockers have long been used in SCD nephropathy; however, more complete long-term studies on benefits are needed. Given the effect of renal disease on survival, further assessment of the mechanisms and efficacy of these SCD-directed or CKD-directed therapeutic agents is essential.

Diffusion-weighted magnetic resonance imaging in rat kidney using two-dimensional navigated, interleaved echo-planar imaging at 7.0 T

The purpose of this study was to investigate the feasibility of two-dimensional (2D) navigated, interleaved multishot echo-planar imaging (EPI) to enhance kidney diffusion-weighted imaging (DWI) in rats at 7.0 T. Fully sampled interleaved four-shot EPI with 2D navigators was tailored for kidney DWI (Sprague-Dawley rats, n = 7) on a 7.0-T small bore preclinical scanner. The image quality of four-shot EPI was compared with T₂ -weighted rapid acquisition with relaxation enhancement (RARE) (reference) and single-shot EPI (ss-EPI) without and with parallel imaging (PI). The contrast-to-noise ratio (CNR) was examined to assess the image quality for the EPI approaches. The Dice similarity coefficient and the Hausdorff distance were used for evaluation of image distortion. Mean diffusivity (MD) and fractional anisotropy (FA) were calculated for renal cortex and medulla for all DWI approaches. The corticomedullary difference of MD and FA were assessed by Wilcoxon signed-rank test. Four-shot EPI showed the highest CNR among the three EPI variants and lowest geometric distortion versus T₂ -weighted RARE (mean Dice: 0.77 for ss-EPI without PI, 0.88 for ss-EPI with twofold undersampling, and 0.92 for four-shot EPI). The FA map derived from four-shot EPI clearly identified a highly anisotropic region corresponding to the inner stripe of the outer medulla. Four-shot EPI successfully discerned differences in both MD and FA between renal cortex and medulla. In conclusion, 2D navigated, interleaved multishot EPI facilitates high-quality rat kidney DWI with clearly depicted intralayer and interlayer structure and substantially reduced image distortion. This approach enables the anatomic integrity of DWI-MRI in small rodents and has the potential to benefit the characterization of renal microstructure in preclinical studies.

Multiparametric MRI analysis for the evaluation of renal function in patients with hyperuricemia: a preliminary study

Background

To investigate the renal dysfunction in patients with hyperuricemia by employing a multiparametric MRI protocol, consisting of quantitative water molecule diffusion, microstructure, microscopic perfusion, and oxygenation measurements in kidneys.

Materials and methods

A total of 48 patients with hyperuricemia (HU) and 22 age-matched healthy control subjects (HC) were enrolled in the study. For each participant, three different functional magnetic resonance imaging (fMRI) sequences were acquired and analyzed, including intravoxel incoherent motion imaging (IVIM), diffusion tensor imaging (DTI), and blood-oxygen-level-dependent MRI (BOLD). Thereafter, an independent two-sample t-test was applied to discover the significant differences of MRI indices between the hyperuricemia (HU) and HC groups, and the specific potential biomarkers between two subgroups of HU group (asymptomatic hyperuricemia group (AH) and gouty arthritis group (GA)). Further, multivariate logistic regression analyses were performed to classify the AH from the GA group using the MRI indices with significant between-group differences. The receiver operating characteristic (ROC) curve was plotted, and the area under the ROC curve (AUC) was calculated to assess the performance of each MR index for differentiation between the AH and GA groups.

Results

Ten parametric values of the HU group were significantly lower than those of the HC group among the 14 fMRI parameters (P < 0.05). The cortical D, D^*, and f values and medullary D and R2^*values had significant differences between the AH and GA groups (P < 0.05). Combining the cortical D and f values and medullary R2* value gave the best diagnostic efficacy, yielding an AUC, sensitivity, and specificity of 0.967 ± 0.022, 91.67%, and 95.83%, respectively.

Conclusions

A multiparametric MR analysis plays an important role in the evaluation of renal dysfunction in hyperuricemia from multiple perspectives. It could be a promising method for noninvasive detection and identification of the early-stage renal damage induced by hyperuricemia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12880-021-00675-4.

Diffusion Tensor Imaging in early prediction of renal fibrosis in patients with renal disease: Functional and histopathological correlations

AIM

Renal fibrosis (RF) is a well-known marker of chronic kidney disease (CKD) progression. However, renal biopsy is an available tool for evaluation of RF, non-invasive tools are needed not only to detect but also to monitor the progression of fibrosis. The aim of this study is to evaluate the role of diffusion tensor imaging (DTI) in the assessment of renal dysfunction and RF in patients with renal disease.

METHODS

Fifty-six patients with renal disorders and 22 healthy controls were recruited. All participants underwent DTI. Renal biopsy was performed for all patients. Mean renal medullary and cortical fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were compared between patients and healthy controls and correlated to serum creatinine (SCr), estimated glomerular filtration rate (eGFR), 24-h urinary protein (24h-UPRO) and renal histopathological scores.

RESULTS

Cortical FA values were significantly higher (P = .001), while cortical ADC values were significantly lower in the patients' group (P = .002). Cortical FA values positively correlated to SCr (P = .006) and negatively correlated to eGFR (P = .03), while cortical ADC negatively correlated to percentage of sclerotic glomeruli, atrophic tubules and interstitial fibrosis (P = .001 for all variables). Medullary ADC negatively correlated to tubular atrophy (P = .02). The diagnostic performance of DTI for detecting RF was supported by ROC curve. Multiple linear regression analysis revealed that the mean cortex ADC was significantly decreased by 0.199 mg/dL for patients with >50% glomerulosclerosis in renal biopsy.

CONCLUSION

DTI appears to represent a valuable tool for the non-invasive assessment of renal dysfunction and renal fibrosis.

Combined application of DTI and BOLD-MRI in the assessment of renal injury with hyperuricemia

OBJECTIVE

To explore the value of combined diffusion tensor imaging (DTI) and blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) in detecting early renal alterations in patients with hyperuricemia.

MATERIALS AND METHODS

Seventy-one individuals were enrolled in this study and divided into three groups according to their serum uric acid (SUA) level and clinical symptoms: healthy controls (HC, n = 23), asymptomatic hyperuricemia (AH, n = 22) and gouty arthritis (GA, n = 26). All patients underwent both DTI and BOLD-MRI examination. Renal cortical and medullary ADC, FA and R2* values were calculated, respectively, and compared among the three groups. Correlations between ADC, FA and R2* with estimated glomerular filtration rate (eGFR) and SUA in hyperuricemia were evaluated, respectively.

RESULT

In the renal cortex, the ADC, FA and R2* values of the AH and GA groups were significantly lower than those of the HC groups (p < 0.05). In the renal medulla, the ADC and FA values in AH and GA patients were significantly lower than those in healthy controls (p < 0.05). The R2* value of the GA group significantly decreased, compared to that of the AH and HC groups (p < 0.05). SUA was negatively correlated with cortical ADC, FA and R2* values (p < 0.05) as well as with medullary ADC and FA values. No significant correlation was discovered between the eGFR and ADC, FA and R2* values.

CONCLUSION

The combined evaluation of DTI and BOLD might provide a sensitive and non-invasive approach for detection of renal microstructural alterations and oxygen metabolism abnormality in hyperuricemia.

Intravoxel incoherent motion imaging of the kidney: The application in patients with hyperuricemia

BACKGROUND

Hyperuricemia is an independent risk factor for onset and progression of kidney disease. However, there remains a lack of a reliable and noninvasive biomarker to identify and monitor the changes of renal function in patients with hyperuricemia.

PURPOSE

To assess the utility of intravoxel incoherent motion (IVIM) parameters in identifying the early changes of renal function in patients with hyperuricemia.

STUDY TYPE

Retrospective case-control study.

POPULATION

Eighty-four male participants, including asymptomatic hyperuricemia (AH, 27 cases), gouty arthritis (GA, 31 cases), and 26 age-matched healthy controls.

FIELD STRENGTH/SEQUENCE

3.0T; intravoxel incoherent motion (IVIM).

ASSESSMENT

Differences in the IVIM parameters among the three groups were assessed. Pure molecular diffusion (D value); perfusion-related diffusion (D* value); pseudodiffusion fraction (f value); apparent diffusion coefficient (ADC value); estimated glomerular filtration rate (eGFR). Also, they were correlated with eGFR.

STATISTICAL TESTS

Bonferroni test, Tamhane's T₂ method, and Pearson correlation analysis.

RESULTS

The D values in renal cortex and medulla significantly decreased from the control, AH to GA groups (P < 0.05). The GA patients had a significantly lower cortical f value than the controls and AH patients (P < 0.05). The medullary f values in the AH and GA patients were significantly lower than that in the controls (P < 0.05). Also, the cortical and medullary ADC values had similar results across the three groups (P < 0.05), except for the comparison between the AH and GA groups (P = 0.668, P = 0.111, respectively). No significant correlation was found between any IVIM parameters with eGFR.

DATA CONCLUSION

IVIM imaging may be helpful for detecting the early changes of renal function induced by hyperuricemia. The D value could be the most sensitive IVIM-derived parameter in the assessment of renal function in patients with hyperuricemia in this study.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2020;51:833-840.

Urine biomarkers of chronic kidney damage and renal functional decline in childhood-onset systemic lupus erythematosus

OBJECTIVES

To delineate urine biomarkers that reflect kidney structural damage and predict renal functional decline in pediatric lupus nephritis (LN).

METHODS

In this prospective study, we evaluated kidney biopsies and urine samples of 89 patients with pediatric LN. Urinary levels of 10 biomarkers [adiponectin, ceruloplasmin, kidney injury molecule-1, monocyte chemotactic protein-1, neutrophil gelatinase-associated lipocalin, osteopontin, transforming growth factor-ß (TGFß), vitamin-D binding protein, liver fatty acid binding protein (LFABP), and transferrin] were measured. Regression analysis was used to identify individual and combinations of biomarkers that determine LN damage status [NIH-chronicity index (NIH-CI) score ≤ 1 vs. ≥ 2] both individually and in combination, and biomarker levels were compared for patients with vs. without renal functional decline, i.e., a 20% reduction of the glomerular filtration rate (GFR) within 12 months of a kidney biopsy.

RESULTS

Adiponectin, LFABP, and osteopontin levels differed significantly with select histological damage features considered in the NIH-CI. The GFR was associated with NIH-CI scores [Pearson correlation coefficient (r) = - 0.49; p < 0.0001] but not proteinuria (r = 0.20; p > 0.05). Similar to the GFR [area under the ROC curve (AUC) = 0.72; p < 0.01], combinations of osteopontin and adiponectin levels showed moderate accuracy [AUC = 0.75; p = 0.003] in discriminating patients by LN damage status. Renal functional decline occurred more commonly with continuously higher levels of the biomarkers, especially of TGFß, transferrin, and LFABP.

CONCLUSION

In combination, urinary levels of adiponectin and osteopontin predict chronic LN damage with similar accuracy as the GFR. Ongoing LN activity as reflected by high levels of LN activity biomarkers heralds renal functional decline.

KEY MESSAGES

• Levels of osteopontin and adiponectin measured at the time of kidney biopsy are good predictors of histological damage with lupus nephritis. • Only about 20% of children with substantial kidney damage from lupus nephritis will have an abnormally low urine creatinine clearance. • Continuously high levels of biomarkers reflecting lupus nephritis activity are risk factors of declining renal function.