Percutaneous revascularization for ischemic nephropathy: the past, present, and future

Associations between non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio and hyperuricemia: a cross-sectional study

BACKGROUND AND OBJECTIVE

The value of the non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) assessment in the context of metabolic abnormalities is growing in importance. Nevertheless, the relationship between NHHR and hyperuricemia (HUA) is unknown. This study seeks to investigate the relationship between NHHR and HUA.

METHODS

The data derived from the 2017-2020 National Health and Nutrition Examination Survey (NHANES) included 7,876 adult participants. The multivariable logistic regression model, subgroup analysis and smooth fitting curve were utilized in order to investigate the association between NHHR and HUA.

RESULTS

In the fully adjusted model 3, NHHR was significantly associated with HUA. Specifically, participants in the highest quartile of NHHR had 1.95 times higher odds of HUA prevalence compared to those in the lowest quartile [2.95 (2.39, 3.64), P < 0.0001]. Although the overall trend suggested a positive association, further analysis using smooth fitting curves and threshold effect analysis indicated that this association was nonlinear, with an inflection point at 5.8. The positive association persisted across different HUA definitions and after removing outliers. Subgroup analysis showed significant interactions between NHHR and HUA in different races and diabetes statuses. The odds of HUA prevalence were higher among non-diabetic participants [1.40 (1.32, 1.49), P < 0.0001] compared to diabetic participants [1.18 (1.06, 1.32), P = 0.0031]. Mexican Americans had the lowest odds of HUA prevalence [1.09 (0.92, 1.27), P = 0.2413] compared to other races.

CONCLUSIONS

There is a significant positive association between NHHR and HUA, indicating that NHHR may serve as a potential risk assessment maker for HUA, although further prospective studies are needed for validation.

A case of successful revascularization and renal recovery after 6 days of renal artery occlusion

A 72-year-old man with peripheral arterial disease, an atrophic left kidney, and prior right renal chimney stent as part of a complex endovascular abdominal aortic aneurysm repair presented to our emergency department with right flank pain and anuria resulting from right artery occlusion. His serum creatinine on admission was 7.5 mg/dL. Computed tomography angiography 6 days after the onset of his symptoms revealed complete occlusion of the right renal artery stent. Percutaneous thrombectomy was performed restored renal blood flow. The urine flow started the following day, and his serum creatinine decreased to 3.5 mg/dL 7 days after discharge.

Kidney Intrinsic Mechanisms as Novel Targets in Renovascular Hypertension

Almost a hundred years have passed since obstruction of the renal artery has been recognized to raise blood pressure. By now chronic renovascular disease (RVD) due to renal artery stenosis is recognized as a major source of renovascular hypertension and renal disease. In some patients, RVD unaccompanied by noteworthy renal dysfunction or blood pressure elevation may be incidentally identified during peripheral angiography. Nevertheless, in others, RVD might present as a progressive disease associated with diffuse atherosclerosis, leading to loss of renal function, renovascular hypertension, hemodynamic compromise, and a magnified risk for cardiovascular morbidity and mortality. Atherosclerotic RVD leads to renal atrophy, inflammation, and hypoxia but represents a potentially treatable cause of chronic renal failure because until severe fibrosis sets in the ischemic kidney, it retains a robust potential for vascular and tubular regeneration. This remarkable recovery capacity of the kidney begs for early diagnosis and treatment. However, accumulating evidence from both animal studies and randomized clinical trials has convincingly established the inadequate efficacy of renal artery revascularization to fully restore renal function or blood pressure control and has illuminated the potential of therapies targeted to the ischemic renal parenchyma to instigate renal regeneration. Some of the injurious mechanisms identified as potential therapeutic targets included oxidative stress, microvascular disease, inflammation, mitochondrial injury, and cellular senescence. This review recapitulates the intrinsic mechanisms that orchestrate renal damage and recovery in RVD and can be harnessed to introduce remedial opportunities.

Temporal trends in hypertension related end stage renal disease mortality rates: an analysis of gender, race/ethnicity, and geographic disparities in the United States

Background

According to one USA Renal Data System report, 57% of end-stage renal disease (ESRD) cases are attributed to hypertensive and diabetic nephropathy. Yet, trends in hypertension related ESRD mortality rates in adults ≥ 35 years of age have not been studied.

Objectives

The aim of this retrospective study was to analyze the different trends hypertension related ESRD death rates among adults in the United States.

Methods

Death records from the CDC (Centers for Disease Control and Prevention Wide-Ranging OnLine Data for Epidemiologic Research) database were analyzed from 1999 to 2020 for hypertension related ESRD mortality in adults ≥ 35 years of age. Age-Adjusted mortality rates (AAMRs) per 100,000 persons and annual percent change (APC) were calculated and stratified by year, sex, race/ethnicity, place of death, and geographic location.

Results

Hypertension-related ESRD caused a total of 721,511 deaths among adults (aged ≥ 35 years) between 1999 and 2020. The overall AAMR for hypertension related ESRD deaths in adults was 9.70 in 1999 and increased all the way up to 43.7 in 2020 (APC: 9.02; 95% CI: 8.19-11.04). Men had consistently higher AAMRs than woman during the analyzed years from 1999 (AAMR men: 10.8 vs women: 9) to 2020 (AAMR men: 52.2 vs women: 37.2). Overall AAMRs were highest in Non-Hispanic (NH) Black or African American patients (45.7), followed by NH American Indian or Alaska Natives (24.7), Hispanic or Latinos (23.4), NH Asian or Pacific Islanders (19.3), and NH White patients (15.4). Region-wise analysis also showed significant variations in AAMRs (overall AAMR: West 21.2; South: 21; Midwest: 18.3; Northeast: 14.2). Metropolitan areas had slightly higher AAMRs (19.1) than nonmetropolitan areas (19). States with AAMRs in 90th percentile: District of Columbia, Oklahoma, Mississippi, Tennessee, Texas, and South Carolina, had roughly double rates compared to states in 10th percentile.

Conclusions

Overall hypertension related ESRD AAMRs among adults were seen to increase in almost all stratified data. The groups associated with the highest death rates were NH Black or African Americans, men, and populations in the West and metropolitan areas of the United States. Strategies and policies targeting these at-risk groups are required to control the rising hypertension related ESRD mortality.

Progressive abdominal pain in a 63-year-old man

50%-60% of patients with chronic mesenteric ischemia suffer from concomitant cardiovascular disease. We therefore suggest an extensive diagnostic screening to detect coronary artery and peripheral arterial disease in these patients.

Heart Disease and Stroke Statistics-2021 Update: A Report From the American Heart Association

BACKGROUND

The American Heart Association, in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, diet, and weight) and health factors (cholesterol, blood pressure, and glucose control) that contribute to cardiovascular health. The Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease, heart failure, valvular disease, venous disease, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The American Heart Association, through its Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States to provide the most current information available in the annual Statistical Update. The 2021 Statistical Update is the product of a full year's worth of effort by dedicated volunteer clinicians and scientists, committed government professionals, and American Heart Association staff members. This year's edition includes data on the monitoring and benefits of cardiovascular health in the population, an enhanced focus on social determinants of health, adverse pregnancy outcomes, vascular contributions to brain health, the global burden of cardiovascular disease, and further evidence-based approaches to changing behaviors related to cardiovascular disease.

RESULTS

Each of the 27 chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policy makers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

Estimation of Intraglomerular Pressure Using Invasive Renal Arterial Pressure and Flow Velocity Measurements in Humans

Significance Statement

Increased intraglomerular pressure is an important contributor to the pathogenesis and progression of CKD in patients with hypertension and diabetes. This study used an adapted Windkessel model to estimate overall renal arterial resistance, arterial compliance, and intraglomerular pressure based on intrarenal pressure and flow velocity measurements in patients undergoing angiography. The mean intraglomerular pressure was consistent with values in non-human primates. It decreased following hyperemia with efferent exceeding afferent dilatation and had significant positive correlation with perfusion pressure and diabetes. The current model and its derived parameters provide a new research technique to assess the renal hemodynamic effects of therapeutic interventions.

Background

Glomerular hyperfiltration resulting from an elevated intraglomerular pressure (Pglom) is an important cause of CKD, but there is no feasible method to directly assess Pglom in humans. We developed a model to estimate Pglom in patients from combined renal arterial pressure and flow measurements.

Methods

We performed hemodynamic measurements in 34 patients undergoing renal or cardiac angiography under baseline conditions and during hyperemia induced by intrarenal dopamine infusion (30 μg/kg). For each participant during baseline and hyperemia, we fitted an adapted three-element Windkessel model that consisted of characteristic impedance, compliance, afferent resistance, and Pglom.

Results

We successfully analyzed data from 28 (82%) patients. Median age was 58 years (IQR, 52–65), median eGFR was 95 ml/min per 1.73 m2 (IQR, 74–100) using the CKD-EPI formula, 30% had microalbuminuria, and 32% had diabetes. The model showed a mean Pglom of 48.0 mm Hg (SD=10.1) at baseline. Under hyperemia, flow increased by 88% (95% CI, 68% to 111%). This resulted in a 165% (95% CI, 79% to 294%) increase in afferent compliance and a 13.1-mm Hg (95% CI, 10.0 to 16.3) decrease in Pglom. In multiple linear regression analysis, diabetes (coefficient, 10.1; 95% CI, 5.1 to 15.1), BMI (0.99 per kg/m2; 95% CI, 0.38 to 1.59), and renal perfusion pressure (0.42 per mm Hg; 95% CI, 0.25 to 0.59) were significantly positively associated with baseline Pglom.

Conclusions

We constructed a model on the basis of proximal renal arterial pressure and flow velocity measurements that provides an overall estimate of glomerular pressure and afferent and efferent resistance in humans. The model provides a novel research technique to evaluate the hemodynamics of CKD on the basis of direct pressure and flow measurements.

Clinical Trial registry name and registration number

Functional HEmodynamics in patients with and without Renal Artery stenosis (HERA), NL40795.018.12 at the Dutch national trial registry (toetsingonline.nl).

How should we define appropriate patients for percutaneous transluminal renal angioplasty treatment?

Renovascular hypertension (RVH) is one of the most common causes of secondary hypertension and can result in resistant hypertension. RVH is associated with an increased risk for progressive decline in renal function, cardiac destabilization syndromes including "flash" pulmonary edema, recurrent congestive heart failure, and cerebrocardiovascular disease. The most common cause of renal artery stenosis (RAS) is atherosclerotic lesions, followed by fibromuscular dysplasia. The endovascular technique of percutaneous transluminal renal angioplasty (PTRA) with or without stenting is one of the standard treatments for RAS. Randomized controlled trials comparing medical therapy with PTRA to medical therapy alone have failed to show a benefit of PTRA; however, the subjects of these randomized clinical trials were limited to atherosclerotic RAS patients, and patients with the most severe RAS, who would be more likely to benefit from PTRA, might not have been enrolled in these trials. This review compares international guidelines related to PTRA, reevaluates the effects of PTRA treatment on blood pressure and renal and cardiac function, discusses strategies for the management of RVH patients, and identifies factors that may predict which patients are most likely to benefit from PTRA.

Estimation of Intraglomerular Pressure Using Invasive Renal Arterial Pressure and Flow Velocity Measurements in Humans

BACKGROUND

Glomerular hyperfiltration resulting from an elevated intraglomerular pressure (Pglom) is an important cause of CKD, but there is no feasible method to directly assess Pglom in humans. We developed a model to estimate Pglom in patients from combined renal arterial pressure and flow measurements.

METHODS

We performed hemodynamic measurements in 34 patients undergoing renal or cardiac angiography under baseline conditions and during hyperemia induced by intrarenal dopamine infusion (30 μg/kg). For each participant during baseline and hyperemia, we fitted an adapted three-element Windkessel model that consisted of characteristic impedance, compliance, afferent resistance, and Pglom.

RESULTS

We successfully analyzed data from 28 (82%) patients. Median age was 58 years (IQR, 52-65), median eGFR was 95 ml/min per 1.73 m² (IQR, 74-100) using the CKD-EPI formula, 30% had microalbuminuria, and 32% had diabetes. The model showed a mean Pglom of 48.0 mm Hg (SD=10.1) at baseline. Under hyperemia, flow increased by 88% (95% CI, 68% to 111%). This resulted in a 165% (95% CI, 79% to 294%) increase in afferent compliance and a 13.1-mm Hg (95% CI, 10.0 to 16.3) decrease in Pglom. In multiple linear regression analysis, diabetes (coefficient, 10.1; 95% CI, 5.1 to 15.1), BMI (0.99 per kg/m²; 95% CI, 0.38 to 1.59), and renal perfusion pressure (0.42 per mm Hg; 95% CI, 0.25 to 0.59) were significantly positively associated with baseline Pglom.

CONCLUSIONS

We constructed a model on the basis of proximal renal arterial pressure and flow velocity measurements that provides an overall estimate of glomerular pressure and afferent and efferent resistance in humans. The model provides a novel research technique to evaluate the hemodynamics of CKD on the basis of direct pressure and flow measurements.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Functional HEmodynamics in patients with and without Renal Artery stenosis (HERA), NL40795.018.12 at the Dutch national trial registry (toetsingonline.nl).

Impact of Percutaneous Revascularization on Left Ventricular Mass and Its Relationship to Outcome in Hypertensive Patients With Renal Artery Stenosis

BACKGROUND

We investigated the effects of percutaneous transluminal renal angioplasty on left ventricular (LV) mass, and the impact of LV mass reduction on outcomes.

METHODS

A total of 144 hypertensive patients with renal artery stenosis (RAS) (mean age 69 years; 22.2% fibromuscular dysplasia (FMD)) who underwent angioplasty were included. Echocardiography was performed at baseline and after 1 year, and patients were thereafter followed up for a median of 5.6 years for primary composite outcomes.

RESULTS

In both the FMD and atherosclerotic stenosis (ARAS) groups, LV mass decreased after angioplasty, but the decrease in LV mass index (-15.4 ± 18.3% vs. -0.8 ± 27.8%, P < 0.01) as well as the regression rate of LV hypertrophy was greater in FMD. Multiple logistic regression analysis indicated that FMD (odds ratio (OR) 2.94, P < 0.01), severe RAS (≥90%) (OR 2.94, P < 0.05), and higher LV mass index at baseline (OR 2.94 for 1 SD increase, P < 0.001) were independent predictors of LV mass index decrease of at least 20%. The primary composite outcomes occurred in 45 patients (31.3%). In FMD, lower LV mass index after 1 year (hazard ratio 2.81 for 1 SD increase, P < 0.05) or regression of LV mass (hazard ratio 0.75 for 5% decrease, P = 0.054) showed a tendency to be associated with better outcomes; however, these associations were not found in ARAS.

CONCLUSIONS

Hypertensive patients with ARAS have less regression of LV mass in response to angioplasty than those with FMD, and LV mass regression is less useful as a surrogate marker of outcomes especially in ARAS.

Renal Artery Stenosis As Etiology of Recurrent Flash Pulmonary Edema and Role of Imaging in Timely Diagnosis and Management

Renal hypoperfusion from renal artery stenosis (RAS) activates the renin-angiotensin system, which in turn causes volume overload and hypertension. Atherosclerosis and fibromuscular dysplasia are the most common causes of renal artery stenosis. Recurrent flash pulmonary edema, also known as Pickering syndrome, is commonly associated with bilateral renal artery stenosis. There should be a high index of clinical suspicion for renal artery stenosis in the setting of recurrent flash pulmonary edema and severe hypertension in patients with atherosclerotic disease. Duplex ultrasonography is commonly recommended as the best initial test for the detection of renal artery stenosis. Computed tomography (CT) angiography (CTA) or magnetic resonance (MR) angiography (MRA) are useful diagnostic imaging studies for the detection of renal artery stenosis in patients where duplex ultrasonography is difficult. If duplex ultrasound, CTA, and MRA are indeterminate or pose a risk of significant renal impairment, renal angiography is useful for a definitive diagnosis of RAS. The focus of medical management for RAS relies on controlling renovascular hypertension and aggressive lifestyle modification with control of atherosclerotic disease risk factors. The restoration of renal artery patency by revascularization in the setting of RAS due to atherosclerosis may help in the management of hypertension and minimize renal dysfunction.

Novel therapeutic strategies for renovascular disease

PURPOSE OF REVIEW

Renovascular disease (RVD) remains an important cause of hypertension and renal dysfunction. Given the failure of renal revascularization to provide consistent clinical benefit in the Cardiovascular Outcomes for Renal Artery Lesions trial among others, further research has underscored the need for mechanistically targeted interventions to improve renal outcomes in patients in RVD. This review discusses novel therapeutic approaches for RVD in the post-Cardiovascular Outcomes for Renal Artery Lesions era.

RECENT FINDINGS

Emerging evidence indicates that renal inflammation, microvascular remodeling, and mitochondrial damage accelerate progression of renal injury and are important determinants of the response to revascularization. Experimental studies have identified interventions capable of ameliorating renal inflammation (e.g., cytokine inhibitors, mesenchymal stem cells), microvascular remodeling (proangiogenic interventions), and mitochondrial injury (mito-protective drugs), alone or combined with renal revascularization, to preserve the structure and function of the poststenotic kidney. Recent prospective pilot studies in patients with atherosclerotic RVD demonstrate the safety and feasibility of some of such interventions to protect the kidney.

SUMMARY

Experimental studies and pilot clinical trials suggest that therapies targeting renal inflammation, microvascular remodeling, and mitochondrial damage have the potential to preserve the structure and function of the stenotic kidney. Further studies in larger cohorts are needed to confirm their renoprotective effects and clinical role in human RVD.

Consensus-based technical recommendations for clinical translation of renal BOLD MRI

Harmonization of acquisition and analysis protocols is an important step in the validation of BOLD MRI as a renal biomarker. This harmonization initiative provides technical recommendations based on a consensus report with the aim to move towards standardized protocols that facilitate clinical translation and comparison of data across sites. We used a recently published systematic review paper, which included a detailed summary of renal BOLD MRI technical parameters and areas of investigation in its supplementary material, as the starting point in developing the survey questionnaires for seeking consensus. Survey data were collected via the Delphi consensus process from 24 researchers on renal BOLD MRI exam preparation, data acquisition, data analysis, and interpretation. Consensus was defined as ≥ 75% unanimity in response. Among 31 survey questions, 14 achieved consensus resolution, 12 showed clear respondent preference (65-74% agreement), and 5 showed equal (50/50%) split in opinion among respondents. Recommendations for subject preparation, data acquisition, processing and reporting are given based on the survey results and review of the literature. These technical recommendations are aimed towards increased inter-site harmonization, a first step towards standardization of renal BOLD MRI protocols across sites. We expect this to be an iterative process updated dynamically based on progress in the field.

Renovascular Hypertension

Renovascular disease (RVD) is a major cause of secondary hypertension. Atherosclerotic renal artery stenosis is the most common type of RVD followed by fibromuscular dysplasia. It has long been recognized as the prototype of angiotensin-dependent hypertension. However, the mechanisms underlying the physiopathology of hypertensive occlusive vascular renal disease are complex and distinction between the different causes of RVD should be made. Recognition of these distinct types of RVD with different degrees of renal occlusive disease is important for management. The greatest challenge is to individualize and implement the best approach for each patient in the setting of widely different comorbidities.

Consensus-based technical recommendations for clinical translation of renal BOLD MRI

Harmonization of acquisition and analysis protocols is an important step in the validation of BOLD MRI as a renal biomarker. This harmonization initiative provides technical recommendations based on a consensus report with the aim to move towards standardized protocols that facilitate clinical translation and comparison of data across sites. We used a recently published systematic review paper, which included a detailed summary of renal BOLD MRI technical parameters and areas of investigation in its supplementary material, as the starting point in developing the survey questionnaires for seeking consensus. Survey data were collected via the Delphi consensus process from 24 researchers on renal BOLD MRI exam preparation, data acquisition, data analysis, and interpretation. Consensus was defined as ≥ 75% unanimity in response. Among 31 survey questions, 14 achieved consensus resolution, 12 showed clear respondent preference (65-74% agreement), and 5 showed equal (50/50%) split in opinion among respondents. Recommendations for subject preparation, data acquisition, processing and reporting are given based on the survey results and review of the literature. These technical recommendations are aimed towards increased inter-site harmonization, a first step towards standardization of renal BOLD MRI protocols across sites. We expect this to be an iterative process updated dynamically based on progress in the field.

Urinary mitochondrial DNA copy number identifies renal mitochondrial injury in renovascular hypertensive patients undergoing renal revascularization: A Pilot Study

AIMS

Patients with renovascular hypertension (RVH) exhibit elevated urinary mtDNA copy numbers, considered to constitute surrogate markers of renal mitochondrial injury. The modest success of percutaneous transluminal renal angioplasty (PTRA) in restoring renal function in RVH has been postulated to be partly attributable to acute reperfusion injury. We hypothesized that mitoprotection during revascularization would ameliorate PTRA-induced renal mitochondrial injury, reflected in elevated urinary mtDNA copy numbers and improve blood pressure and functional outcomes 3 months later.

METHODS

We prospectively measured urinary copy number of the mtDNA genes COX3 and ND1 using qPCR in RVH patients before and 24 hrs after PTRA, performed during IV infusion of vehicle (n = 8) or the mitoprotective drug elamipretide (ELAM, 0.05 mg/kg/h, n = 6). Five healthy volunteers (HV) served as controls. Urinary mtDNA levels were also assessed in RVH and normal pigs (n = 7 each), in which renal mitochondrial structure and density were studied ex-vivo.

RESULTS

Baseline urinary mtDNA levels were elevated in all RVH patients vs HV and directly correlated with serum creatinine levels. An increase in urinary mtDNA 24 hours after PTRA was blunted in PTRA+ELAM vs PTRA+Placebo. Furthermore, 3-months after PTRA, systolic blood pressure decreased and estimated glomerular filtration rate increased only in ELAM-treated subjects. In RVH pigs, mitochondrial damage was observed using electron microscopy in tubular cells and elevated urinary mtDNA levels correlated inversely with renal mitochondrial density.

CONCLUSIONS

PTRA leads to an acute rise in urinary mtDNA, reflecting renal mitochondrial injury that in turn inhibits renal recovery. Mitoprotection might minimize PTRA-associated mitochondrial injury and improve renal outcomes after revascularization.

OSTIAL VERSUS TRUNCAL RENAL ARTERY STENOSIS: PREDICTOR OF LARGE ARTERY ATHEROSCLEROSIS SEVERITY AND HIGHER MORTALITY

The aim of this study was to determine arterial stiffness and the effect of stenting in patients with renal artery stenosis. We hypothesized that ostial renal artery stenosis is not only a marker of more pronounced atherosclerosis of large arteries, but is also a predictor of higher cardiovascular mortality. We enrolled 33 patients with renal artery stenosis refractory to pharmacological treatment and divided them according to the renal artery stenosis location, ostial and truncal (23 vs. 10 patients). We analyzed patient survival at five-year follow up. After the intervention and at six-month follow up, there was a significant decrease in blood pressure values, as well as in pulse wave velocity (PWV) and augmentation index. PWV was significantly lower in patients with truncal renal artery stenosis and these patients were significantly younger. Twelve patients with ostial and one patient with truncal renal artery stenosis (52% vs. 10%, p<0.001) died from cardiovascular events. Our study is the first to confirm the predictive role of PWV and arterial stiffness in patients with renal artery stenosis, especially ostial one, and to emphasize its ability of detecting future higher incidence of cardiovascular events.

A translational model of chronic kidney disease in swine

Animal models of chronic kidney disease (CKD) are critical for understanding its pathophysiology and for therapeutic development. The cardiovascular and renal anatomy and physiology of the pig are virtually identical to humans. This study aimed to develop a novel translational model of CKD that mimics the pathological features of CKD in humans. CKD was induced in seven domestic pigs by bilateral renal artery stenosis and diet-induced dyslipidemia. Animals were observed for a total of 14 wk. Renal hemodynamics and function were quantified in vivo using multi-detector CT after 6, 10, and 14 wk of CKD. Urine and blood were collected at each time-point, and blood pressure was continuously measured (telemetry). After completion of in vivo studies, pigs were euthanized, kidneys were removed, and microvascular (MV) architecture (μCT), markers of renal injury, inflammation, and fibrosis were evaluated ex vivo. Additional pigs were used as controls ( n = 7). Renal blood flow and glomerular filtration were reduced by 50% in CKD, accompanied by hypertension and elevated plasma creatinine, albumin-to-creatinine ratio and increased urinary KIM-1 and NGAL, suggesting renal injury. Furthermore, 14 wk of CKD resulted in cortical and medullary MV remodeling and loss, inflammation, glomerulosclerosis, tubular atrophy, and tubule-interstitial fibrosis compared with controls. The current study characterizes a novel model of CKD that mimics several of the pathological features observed in human CKD, irrespective of the etiology. Current approaches only slow rather than halt CKD progression, and this novel model may offer a suitable platform for the development of new treatments in a translational fashion.

The association between high-density lipoproteins and estimated glomerular filtration rate in patients without severe kidney disease

PURPOSE

Several studies investigated the association between the estimated glomerular filtration rate (eGFR) and the concentration of high-density lipoproteins (HDL) in patients without severely damaged kidney function. As results of those studies were inconclusive and contradictory, we wanted to investigate this association in multiple cardiovascular disease (CVD) risk patients without severe kidney disease or renal failure.

METHODS

We enrolled a cohort of 187 patients with intermediate and high CVD risk without severe renal disease. We grouped them based on their eGFR into: group 1 (≥ 30 < 60 ml/min/1.73 m²), group 2 (≥ 60 < 90 ml/min/1.73 m²) and group 3 (≥ 90 ml/min/1.73 m²). We analyzed the difference between their HDL levels and assessed the association of HDL and eGFR in three regression models with the following predictors: model 1 (age and gender), model 2 (model 1 plus smoking status, hs-CRP and diabetes mellitus) and model 3 (model 2 plus excessive weight and obesity, hypertension, hypercholesterolemia, hypertriglyceridemia, family history of CVD and medications they used).

RESULTS

Patients with the lowest eGFR had the lowest HDL values (P = 0.013). In multiple linear regression, HDL was an independent predictor of eGFR (β = 0.189, P = 0.025) which was also shown in multinomial regression for all three models: model 1 [odds ratio (OR) 0.05; 95% confidence interval (CI) 0.007-0.331; P = 0.002], model 2 (OR 0.052; 95% CI 0.006-0.428; P = 0.006) and model 3 (OR 0.2; 95% CI 0.001-0.309; P = 0.005).

CONCLUSIONS

Low HDL is an independent predictor of lower eGFR in intermediate and high CVD risk patients without severe kidney disease. In such patients, low HDL could be one of the early indicators of renal failure.

VEGF therapy for the kidney: emerging strategies

Renovascular disease (RVD), which is prevalent in the elderly, significantly increases cardiovascular risk and can progressively deteriorate renal function. The loss of renal function in patients with RVD is associated with a progressive dysfunction, damage, and loss of renal microvessels, which can be combined with decreased renal bioavailability of vascular endothelial growth factor (VEGF) and a defective vascular repair and proliferation. This association has been the impetus for recent efforts that have focused on developing methods to stop the progression of renal injury by protecting the renal microvasculature. This mini-review focuses on recent studies supporting potential applications of VEGF therapy for the kidney and discusses underlying mechanisms of renoprotection.

Current Concepts in the Treatment of Renovascular Hypertension

Renovascular disease (RVD) remains a major cause of secondary and treatment-resistant hypertension. Most cases are related either to fibromuscular or atherosclerotic lesions, but a variety of other causes including arterial dissection, stent occlusion, and embolic disease can produce the same syndrome. Recent studies emphasize the kidney's tolerance to moderate flow reduction during antihypertensive drug therapy and the relative safety of medical therapy to control blood pressure. Several prospective trials in moderate RVD fail to identify major benefits from endovascular revascularization for moderate atherosclerotic disease. However, high-risk and progressive renovascular syndromes are recognized to be relatively refractory to medical therapy only and respond better to combining renal revascularization with ongoing medical therapy. Clinicians caring for complex hypertension should be familiar with pathogenic pathways, imaging techniques, and a rational approach to managing renovascular hypertension in the current era.

Renal artery stenting for atherosclerotic renal artery stenosis identified in patients with coronary artery disease: Does captopril renal scintigraphy predict outcomes?

The authors evaluated the effectiveness of percutaneous renal revascularization (PRR) with stenting for the treatment of atherosclerotic renal artery stenosis (ARAS) in patients with coronary artery disease and the usefulness of captopril renal scintigraphy for predicting clinical outcomes after PRR. Sixty-four consecutive patients, referred for evaluation of suspected ARAS, after coronary angiography, underwent baseline captopril renal scintigraphy followed by renal angiography. Forty-four patients (68.7%) were diagnosed with a significant ARAS≥ 60% and were treated with PRR plus medical therapy. Twenty-four months after PRR, 86.4% and 73.3% of patients showed a hypertension and renal benefit, respectively. Captopril renal scintigraphy positivity had moderate sensitivity and high specificity in predicting a hypertension and renal benefit. In patients with ARAS≥ 70%, the sensitivity and specificity were 100% for both a hypertension and renal benefit.PRR for ARAS conferred a substantial benefit in patients with a high coronary artery disease burden. Captopril renal scintigraphy was highly accurate in predicting clinical outcomes.

Systemic biopolymer-delivered vascular endothelial growth factor promotes therapeutic angiogenesis in experimental renovascular disease

We recently developed a therapeutic biopolymer composed of an elastin-like polypeptide (ELP) fused to vascular endothelial growth factor (VEGF) and showed long-term renoprotective effects in experimental renovascular disease after a single intra-renal administration. Here, we sought to determine the specificity, safety, efficacy, and mechanisms of renoprotection of ELP-VEGF after systemic therapy in renovascular disease. We tested whether kidney selectivity of the ELP carrier would reduce off-target binding of VEGF in other organs. In vivo bio-distribution after systemic administration of ELP-VEGF in swine was determined in kidneys, liver, spleen, and heart. Stenotic-kidney renal blood flow and glomerular filtration rate were quantified in vivo using multi-detector computed tomography (CT) after six weeks of renovascular disease, then treated with a single intravenous dose of ELP-VEGF or placebo and observed for four weeks. CT studies were then repeated and the pigs euthanized. Ex vivo studies quantified renal microvascular density (micro-CT) and fibrosis. Kidneys, liver, spleen, and heart were excised to quantify the expression of angiogenic mediators and markers of progenitor cells. ELP-VEGF accumulated predominantly in the kidney and stimulated renal blood flow, glomerular filtration rate, improved cortical microvascular density, and renal fibrosis, and was accompanied by enhanced renal expression of VEGF, downstream mediators of VEGF signaling, and markers of progenitor cells compared to placebo. Expression of angiogenic factors in liver, spleen, and heart were not different compared to placebo-control. Thus, ELP efficiently directs VEGF to the kidney after systemic administration and induces long-term renoprotection without off-target effects, supporting the feasibility and safety of renal therapeutic angiogenesis via systemic administration of a novel kidney-specific bioengineered compound.

Association between renal function and outcomes after percutaneous transluminal renal angioplasty in hypertensive patients with renal artery stenosis

OBJECTIVE

We investigated the impact of renal function on outcomes after percutaneous transluminal angioplasty.

METHODS

A total of 139 hypertensive patients with atherosclerotic renal artery stenosis (mean age, 70 years, 80.6% men) who underwent renal percutaneous transluminal angioplasty were included. Renal function was evaluated on the basis of estimated glomerular filtration rate (eGFR) and albuminuria/proteinuria, and classified into three categories according to eGFR (≥45, 30-44, and <30 ml/min/1.73 m) and albuminuria/proteinuria [normal-to-mild: albumin/creatinine ratio (ACR) less than 3.0, protein/creatinine ratio (PCR) less than 15; moderate: ACR 3.0-30.0, PCR 15-50; severe: ACR > 30.0, PCR > 50 mg/mmol].

RESULTS

During a median follow-up of 5.4 years, 36.0% of patients developed the primary composite end point, including cardiovascular and renal outcomes. In multivariate Cox regression analysis, eGFR less than 30 (hazard ratio 3.47, P < 0.01) as well as severe albuminuria/proteinuria (hazard ratio 2.63, P < 0.05) was an independent predictor of worse outcome. In the subgroup without events within 1 year after angioplasty (n = 117), the outcome differed among the three renal functional categories at 1 year based on eGFR (log-rank χ = 16.28, P < 0.001) as well as on albuminuria/proteinuria (log-rank χ = 8.30, P < 0.05). At 1 year, 24 patients (20.1%) showed at least 20% decrease in eGFR, and their outcome was worse than that in those with at least 20% increase (n = 23) (hazard ratio 3.50, P < 0.05). Multiple logistic regression analysis indicated that pretreatment moderate-to-severe albuminuria/proteinuria was an independent predictor of at least 20% eGFR decrease (odds ratio 2.82, P < 0.05).

CONCLUSION

Impaired renal function, and in particular, a poor response of eGFR to angioplasty, is associated with worse outcome. Therapeutic effectiveness of renal angioplasty seems to be limited in patients with albuminuria/proteinuria.

Noninvasive Identification of Renal Hypoxia in Experimental Myocardial Infarctions of Different Sizes by Using BOLD MR Imaging in a Mouse Model

Purpose To test the feasibility of using blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging to measure alterations in renal oxygenation in a mouse model with experimental myocardial infarctions (MIs) of different sizes. Materials and Methods The study was approved by the local animal ethics committee. One hundred eighty-nine male C57BL/6 J mice were randomly subjected to MI surgery (with different locations of left anterior descending coronary artery occlusion) or sham surgery, defined as the exposure of the heart but no ligation. Mice with MI underwent late gadolinium enhancement imaging 1 day after occlusion to confirm infarct size. Mice were sorted into three groups: those with large MI (n = 48), those with small MI (n = 48), and those with sham operation (n = 36). Renal BOLD MR imaging was performed before and 1, 7, 14, 28, and 60 days after MI, and histologic analysis of renal hypoxia-inducible factor-1α (HIF-1α) and kidney injury molecule-1 (KIM-1) was performed to evaluate tissue hypoxia and kidney injury in subgroups imaged at each time point. The relationships between the BOLD R2* and HIF-1α expression and between HIF-1α and KIM-1 expression were assessed. Statistical analyses were performed with one-way analysis of variance or the Kruskal-Wallis test and Spearman correlation test. Results A significant elevation in R2* was detected in the MI groups compared with the sham group in the cortex (P < .001 for large MI vs sham group; P = .007 for small MI vs sham group) and medulla (P < .001 for large MI vs sham group; P = .003 for small MI vs sham group) on day 60, and R2* was higher in the large MI group than in the small MI group (P < .001). Renal HIF-1α expression was increased after MI and showed linear correlation with R2* in the cortex (R² = 0.56) and medulla (R² = 0.63). In addition, an increase in renal KIM-1 was observed in the MI groups compared with the sham group on day 60 (sham group, 53.9 × 10³ arbitrary units [au] ± 35.2; large MI group, 389.3 × 10³ au ± 99.8; and small MI group, 185.8 × 10³ au ± 91.9; P < .001 for large MI group vs sham group; P = .037 for small MI group vs sham group), and renal KIM-1 showed a positive correlation with HIF-1α (R² = 0.68). Conclusion The magnitude of renal hypoxia with MIs of different sizes can be noninvasively measured with BOLD MR imaging, and increased renal hypoxia is a potential risk factor for progressive tubulointerstitial injury in mouse kidneys. ^© RSNA, 2017 Online supplemental material is available for this article.

Renal Arterial Disease and Hypertension

Renal artery disease produces a spectrum of progressive clinical manifestations ranging from minor degrees of hypertension to circulatory congestion and kidney failure. Moderate reductions in renal blood flow do not induce tissue hypoxia or damage, making medical therapy for renovascular hypertension feasible. Several prospective trials indicate that optimized medical therapy using agents that block the renin-angiotensin system should be the initial management. Evidence of progressive disease and/or treatment failure should allow recognition of high-risk subsets that benefit from renal revascularization. Severe reductions in kidney blood flow ultimately activate inflammatory pathways that do not reverse with restoring blood flow alone.

Renovascular hypertension: Effects of mesenchymal stem cells in the contralateral hypertensive kidney in rats

Mesenchymal stem cells (MSC) induced neovascularization and improved renal morphology of the stenotic kidney in 2 kidneys-1 clip (2K-1C) model of renovascular hypertension. The present study evaluated the effects of MSC in the contralateral hypertensive kidney. Three weeks after left renal artery occlusion, MSC were injected into the tail vein of the 2K-1C rats. Renal function and morphology were analyzed in both kidneys. Labeled MSC were found in stenotic and contralateral kidneys. Hypertensive 2K-1C animals presented increased circulating levels of Angiotensin II (Ang II) and renin. MSC prevented the progressive increase of blood pressure and reduced circulating Ang II and renin levels. Stenotic kidney showed reduced renal plasma flow (RPF) and glomerular filtration rate (GFR), whereas the contralateral kidney had a tendency (p > 0.5) of reduction in GFR in spite of unchanged RPF. MSC treatment caused an improvement in GFR with no effect of on RPF in the stenotic kidney. Contralateral kidney showed increased diuresis and natriuresis that were even higher in MSC-treated animals, indicating that cell treatment improved the capacity of the contralateral kidney to excrete sodium. Contralateral kidney expressed higher levels of inflammatory cytokines (IL-6, TNF-α) and signs of fibrosis, which were attenuated by MSC treatment. MSC treatment improved the stenotic kidney function, and it was also beneficial to the contralateral hypertensive kidney because it improved the morphology and preserved its capacity to excrete sodium.

Vascular Endothelial Growth Factor and Podocyte Protection in Chronic Hypoxia: Effects of Endothelin-A Receptor Antagonism

BACKGROUND

Podocytes are major components of the filtration barrier and a renal source of vascular endothelial growth factor (VEGF). Chronic renovascular disease (RVD) progressively degrades the renal function, accompanied by podocyte damage and a progressive reduction in VEGF. We showed that the endothelin (ET) pathway contributes to this pathological process and ET-A (but not ET-B) receptor antagonism protects the kidney in RVD. We hypothesize that ET-A-induced renoprotection is largely driven by the protection of podocyte integrity and function.

METHODS

To mimic the renal environment of chronic RVD, human podocytes were incubated under chronic hypoxia for 96 h and divided in untreated or treated with an ET-A or ET-B receptor antagonist. Cells were quantified after 96 h. Cell homogenates and media were obtained after 1, 24 and 96 h to quantify production of VEGF, anti-VEGF soluble receptor s-Flt1, and the expression of apoptotic mediators. A separate set of similar experiments was performed after addition of a VEGF-neutralizing antibody (VEGF-NA).

RESULTS

Hypoxia decreased podocyte number, which was exacerbated by ET-B but improved after ET-A antagonism. Production of VEGF was preserved by ET-A antagonism, whereas s-Flt1 increased in hypoxic cells after ET-B antagonism only, accompanied by a greater expression of pro-apoptotic mediators. On the other hand, treatment with VEGF-NA diminished ET-A-induced protection of podocytes.

CONCLUSION

ET-A antagonism preserves podocyte viability and integrity under chronic hypoxia, whereas ET-B antagonism exacerbates podocyte dysfunction and death. Enhanced bioavailability of VEGF after ET-A antagonism could be a pivotal mechanism of podocyte protection that significantly contributes to ET-A receptor blockade-induced renal recovery in chronic RVD.

Changes in inflammatory biomarkers after renal revascularization in atherosclerotic renal artery stenosis

BACKGROUND

Atherosclerotic renal artery stenosis (ARAS) activates oxidative stress and chronic inflammatory injury. Contrast imaging and endovascular stenting pose potential hazards for acute kidney injury, particularly when superimposed upon reduced kidney perfusion.

METHODS

We measured sequential early and long-term changes in circulating inflammatory and injury biomarkers in 12 ARAS subjects subjected to computed tomography imaging and stent revascularization compared with essential hypertensive (EH) subjects of similar age under fixed sodium intake and medication regimens in a clinical research unit.

RESULTS

NGAL, TIMP-2, IGFBP7, MCP-1 and TNF-α all were elevated before intervention. Post-stenotic kidney volume, perfusion, blood flow and glomerular filtration rate (GFR) were lower in ARAS than in EH subjects. TIMP-2 and IGFBP7 fell briefly, then rose over 18 h after contrast imaging and stent deployment. Circulating NGAL decreased and remained lower for 27 h. These biomarkers in ARAS returned to baseline after 3 months, while kidney volume, perfusion, blood flow and GFR increased, but remained lower than EH.

CONCLUSIONS

These divergent patterns of inflammatory signals are consistent with cell cycle arrest (TIMP-2, IGFBP7) and relative protection from acute kidney injury after imaging and stenting. Sustained basal elevation of circulating and renal venous inflammatory biomarkers support ongoing, possibly episodic, renal stress in ARAS that limits toxicity from stent revascularization.

Renal Therapeutic Angiogenesis Using a Bioengineered Polymer-Stabilized Vascular Endothelial Growth Factor Construct

Renovascular disease (RVD) induces renal microvascular (MV) rarefaction that drives progressive kidney injury. In previous studies, we showed that renal vascular endothelial growth factor (VEGF) therapy attenuated MV damage, but did not resolve renal injury at practical clinical doses. To increase the bioavailability of VEGF, we developed a biopolymer-stabilized elastin-like polypeptide (ELP)-VEGF fusion protein and determined its in vivo potential for therapeutic renal angiogenesis in RVD using an established swine model of chronic RVD. We measured single-kidney blood flow (RBF) and GFR and established the degree of renal damage after 6 weeks of RVD. Pigs then received a single stenotic kidney infusion of ELP-VEGF (100 μg/kg), a matching concentration of unconjugated VEGF (18.65 μg/kg), ELP alone (100 μg/kg), or placebo. Analysis of organ distribution showed high renal binding of ELP-VEGF 4 hours after stenotic kidney infusion. Therapeutic efficacy was determined 4 weeks after infusion. ELP-VEGF therapy improved renal protein expression attenuated in RVD, restoring expression levels of VEGF, VEGF receptor Flk-1, and downstream angiogenic mediators, including phosphorylated Akt and angiopoietin-1 and -2. This effect was accompanied by restored MV density, attenuated fibrogenic activity, and improvements in RBF and GFR greater than those observed with placebo, ELP alone, or unconjugated VEGF. In summary, we demonstrated the feasibility of a novel therapy to curtail renal injury. Recovery of the stenotic kidney in RVD after ELP-VEGF therapy may be driven by restoration of renal angiogenic signaling and attenuated fibrogenic activity, which ameliorates MV rarefaction and improves renal function.

Diabetic Kidney Disease: A Syndrome Rather Than a Single Disease

The term "diabetic kidney" has recently been proposed to encompass the various lesions, involving all kidney structures that characterize protean kidney damage in patients with diabetes. While glomerular diseases may follow the stepwise progression that was described several decades ago, the tenet that proteinuria identifies diabetic nephropathy is disputed today and should be limited to glomerular lesions. Improvements in glycemic control may have contributed to a decrease in the prevalence of glomerular lesions, initially described as hallmarks of diabetic nephropathy, and revealed other types of renal damage, mainly related to vasculature and interstitium, and these types usually present with little or no proteinuria. Whilst glomerular damage is the hallmark of microvascular lesions, ischemic nephropathies, renal infarction, and cholesterol emboli syndrome are the result of macrovascular involvement, and the presence of underlying renal damage sets the stage for acute infections and drug-induced kidney injuries. Impairment of the phagocytic response can cause severe and unusual forms of acute and chronic pyelonephritis. It is thus concluded that screening for albuminuria, which is useful for detecting "glomerular diabetic nephropathy", does not identify all potential nephropathies in diabetes patients. As diabetes is a risk factor for all forms of kidney disease, diagnosis in diabetic patients should include the same combination of biochemical, clinical, and imaging tests as employed in non-diabetic subjects, but with the specific consideration that chronic kidney disease (CKD) may develop more rapidly and severely in diabetic patients.

Paradigm Shifts in Atherosclerotic Renovascular Disease: Where Are We Now?

Results of recent clinical trials and experimental studies indicate that whereas atherosclerotic renovascular disease can accelerate both systemic hypertension and tissue injury in the poststenotic kidney, restoring vessel patency alone is insufficient to recover kidney function for most subjects. Kidney injury in atherosclerotic renovascular disease reflects complex interactions among vascular rarefication, oxidative stress injury, and recruitment of inflammatory cellular elements that ultimately produce fibrosis. Classic paradigms for simply restoring blood flow are shifting to implementation of therapy targeting mitochondria and cell-based functions to allow regeneration of vascular, glomerular, and tubular structures sufficient to recover, or at least stabilize, renal function. These developments offer exciting possibilities of repair and regeneration of kidney tissue that may limit progressive CKD in atherosclerotic renovascular disease and may apply to other conditions in which inflammatory injury is a major common pathway.

From the 1990s to CORAL (Cardiovascular Outcomes in Renal Atherosclerotic Lesions) trial results and beyond: does stenting have a role in ischemic nephropathy?

The prevalence of atherosclerotic renal artery stenosis is high, ∼7% in individuals older than 65 years and ∼50% in patients with diffuse arterial disease, and it is increasingly frequent in an aging population. About 10% to 15% of atherosclerotic renal artery stenosis cases lead to the development of resistant hypertension and/or ischemic nephropathy. The management of ischemic nephropathy may include medical therapy and/or revascularization. In the past, revascularization required surgical bypass or endarterectomy, accompanied by the morbidity and mortality associated with a major surgical procedure. During the last few decades, less invasive endovascular procedures such as percutaneous transluminal renal artery angioplasty with stent placement have become available. At the same time, new antihypertensive and cardiovascular drugs have been developed, which may preclude revascularization, at least in some cases. The indications of each of these therapeutic options have changed over time. This review offers a temporal perspective on the course of technical and scientific advances and the accompanying change in clinical practice for the treatment of ischemic nephropathy. The latest randomized clinical trials, including the CORAL (Cardiovascular Outcomes in Renal Atherosclerotic Lesions) trial, the largest on the subject, as well as a meta-analysis of these studies, have indicated that the best approach is medical therapy alone. There is evidence that revascularization brings no additional benefit, at least in low-risk and stable atherosclerotic renal artery stenosis. High-risk patients, especially those with recurrent flash pulmonary edema, could benefit from percutaneous transluminal renal artery angioplasty and stent placement, but there is no definitive evidence and the treatment choice should take into account the risks and potential benefits of the procedure.

[Ischemic renal disease and renal artery stenosis]

Severe renal artery stenosis may cause renovascular hypertension; in case of bilateral narrowing or in a stenotic solitary or transplant kidney, renal insufficiency (ischemic renal disease) or rarely pulmonary flash edema may occur. In most cases arteriosclerotic disease is the underlying cause; less prevalent are the various manifestations of fibromuscular disease. Renal artery stenosis may be treated by revasularization, using either percutaneous (balloon angioplasty, stenting) or rarely open surgical procedures, both with excellent primary patency rates. However, randomized trials of renal artery angioplasty or stenting in patients with arteriosclerotic lesions have failed to demonstrate a longer-term benefit with regard to hypertension control and renal dysfunction over medical management alone. Careful patient selection is essential to maximize the potential benefit (e.g., in patients with refractory hypertension, progressive renal failure or recurrent pulmonary flash edema).

Chronic blockade of endothelin A and B receptors using macitentan in experimental renovascular disease

BACKGROUND

Emerging research has identified the endothelin (ET)-1 pathway as a potential target for novel renoprotective therapies. We recently showed that selective ET-A receptor antagonism in chronic renovascular disease (RVD) improves renal function and reduces renal injury. Although ET-A and -B have opposing roles, in some clinical situations they may induce similar effects. Thus, we hypothesized that simultaneous blockade of the ET-A and -B receptors would protect the kidney during RVD.

METHODS

Unilateral RVD was induced in pigs. After 6 weeks, single-kidney function was quantified in vivo using multi-detector computer tomography. Pigs were subsequently divided into untreated (RVD, n = 7) or daily-treated with the dual ET-A/B receptor antagonist macitentan (RVD + macitentan, n = 6) for 4 weeks. At 10 weeks, in vivo studies were repeated, then pigs were euthanized and ex vivo studies performed in the stenotic kidney to quantify inflammation, fibrosis, microvascular density and remodeling.

RESULTS

Four weeks of macitentan therapy modestly improved renal blood flow (29%, P = 0.06 versus pre-treatment) and showed protective effects on the renal parenchyma by attenuating inflammation and glomerulosclerosis, reducing apoptosis and tubular casts and improving albuminuria and cortical microvessel density. No overt adverse effects were observed.

CONCLUSION

Possibly by inducing a pro-survival renal microenvironment, macitentan increased renal microvascular density, promoted cell survival and decreased injury, which in turn improved stenotic kidney hemodynamics in our model. Our results further support the safety of using macitentan in patients with concomitant chronic renal disease and supported the feasibility of a new strategy that may preserve the stenotic kidney in RVD.

Endothelin-a receptor antagonism after renal angioplasty enhances renal recovery in renovascular disease

Percutaneous transluminal renal angioplasty/stenting (PTRAS) is frequently used to treat renal artery stenosis and renovascular disease (RVD); however, renal function is restored in less than one half of the cases. This study was designed to test a novel intervention that could refine PTRAS and enhance renal recovery in RVD. Renal function was quantified in pigs after 6 weeks of chronic RVD (induced by unilateral renal artery stenosis), established renal damage, and hypertension. Pigs with RVD then underwent PTRAS and were randomized into three groups: placebo (RVD+PTRAS), chronic endothelin-A receptor (ET-A) blockade (RVD+PTRAS+ET-A), and chronic dual ET-A/B blockade (RVD+PTRAS+ET-A/B) for 4 weeks. Renal function was again evaluated after treatments, and then, ex vivo studies were performed on the stented kidney. PTRAS resolved renal stenosis, attenuated hypertension, and improved renal function but did not resolve renal microvascular rarefaction, remodeling, or renal fibrosis. ET-A blocker therapy after PTRAS significantly improved hypertension, microvascular rarefaction, and renal injury and led to greater recovery of renal function. Conversely, combined ET-A/B blockade therapy blunted the therapeutic effects of PTRAS alone or PTRAS followed by ET-A blockade. These data suggest that ET-A receptor blockade therapy could serve as a coadjuvant intervention to enhance the outcomes of PTRAS in RVD. These results also suggest that ET-B receptors are important for renal function in RVD and may contribute to recovery after PTRAS. Using clinically available compounds and techniques, our results could contribute to both refinement and design of new therapeutic strategies in chronic RVD.

Clinical problems in renovascular disease and the role of nuclear medicine

Although renovascular disease remains defined as a stenosis of the main renal artery or its proximal branches (renal artery stenosis [RAS]), its clinical overview has changed dramatically over the last 15-20 years and its management is more controversial than ever before. The clinical problems, not only diagnosis and treatment but also the relative contribution of different pathophysiological mechanisms involved in the progression of kidney disease, have shifted dramatically. This presentation aims to emphasize the paradigm change revisiting the (recent) past focused on renovascular hypertension (RVH) to the current context of preservation or recovery of threatened renal function in patients with progressive atherosclerotic renovascular disease until its last stage of irreversible "ischemic nephropathy." In the past, the foreground was occupied by RVH, a very rare disease, where the activation of the renin-angiotensin-aldosterone system (RAAS) was supposed to play the major, if not only, role in RVH issues. The retrospective RVH diagnosis was established either on the improvement or, more rarely, on the cure of hypertension after revascularization by, most often, a percutaneous transluminal renal angioplasty with or without a stent placement. At this time, captoptril radionuclide renography was an efficient diagnostic tool, because it was a functional (angiotensin-converting enzyme inhibition), noninvasive test aiming to evidence both the RAAS activation and the lateralization (or asymmetry) of renin secretion by the kidney affected by a "hemodynamically significant" RAS. At present, even if captoptril radionuclide renography could be looked upon as the most efficient (and cost effective in selected high-risk patients) noninvasive, functional test to predict the improvement of hypertension after RAS correction, its clinical usefulness is questioned as the randomized, prospective trials failed to demonstrate any significant benefits (either on blood pressure control or on renal function protection) of the revascularization over current antihypertensive therapy. Today many patients with RVH remain undetected for years because they are treated successfully and at low expense with these new blockers of RAAS. In addition to its well-known role in hemodynamics, angiotensin II promotes activations of profibrogenic and inflammatory factors and cells and stimulates reactive oxygen species generation. The "atherosclerotic milieu" itself plays a role in the loss of renal microvessels and defective angiogenesis. After an "adaptative" phase, ischemia eventually develops and induces hypoxia, the substratum of ischemic nephropathy. Because blood oxygen level-dependent MRI may provide an index of oxygen content in vivo, it may be useful to predict renal function outcome after percutaneous transluminal renal angioplasty. New PET tracers, dedicated to assess RAAS receptors, inflammatory cell infiltrates, angiogenesis, and apoptose, would be tested in this context of atherosclerotic renovascular disease.

Management of atherosclerotic renovascular disease after Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL)

Many patients with occlusive atherosclerotic renovascular disease (ARVD) may be managed effectively with medical therapy for several years without endovascular stenting, as demonstrated by randomized, prospective trials including the Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial, the Angioplasty and Stenting for Renal Artery Lesions (ASTRAL) trial and the Stent Placement and Blood Pressure and Lipid-Lowering for the Prevention of Progression of Renal Dysfunction Caused by Atherosclerotic Ostial Stenosis of the Renal Artery (STAR) and ASTRAL. These trials share the limitation of excluding subsets of patients with high-risk clinical presentations, including episodic pulmonary edema and rapidly progressing renal failure and hypertension. Although hemodynamically significant, ARVD can reduce renal blood flow and glomerular filtration rate; adaptive mechanisms preserve both cortical and medullary oxygenation over a wide range of vascular occlusion. Progression of ARVD to severe vascular compromise eventually produces cortical hypoxia, however, associated with active inflammatory cytokine release and cellular infiltration of the renal parenchyma. In such cases ARVD produces a loss of glomerular filtration rate that no longer is reversible simply by restoring vessel patency with technically successful renal revascularization. Each of these trials reported adverse renal functional outcomes ranging between 16 and 22% over periods of 2-5 years of follow-up. Blood pressure control and medication adjustment may become more difficult with declining renal function and may prevent the use of angiotensin receptor blocker and angiotensin-converting enzyme inhibitors. The objective of this review is to evaluate the current management of ARVD for clinical nephrologists in the context of recent randomized clinical trials and experimental research.

Blood oxygen level-dependent (BOLD) MRI analysis in atherosclerotic renal artery stenosis

PURPOSE OF REVIEW

Blood oxygen level-dependent MRI (BOLD MRI) is a noninvasive technique for evaluating kidney tissue oxygenation that requires no contrast exposure, with the potential to allow functional assessment in patients with atherosclerotic renal artery stenosis. Normal cortical-to-medulla oxygenation gradients are preserved in many patients treated for several years with medical antihypertensive therapy without restoring renal blood flow. The current review is of particular interest as new methods have been applied to the analyses of BOLD MRI, opening the perspective of its wider utilization in clinical practice.

RECENT FINDINGS

Recent findings show that more severe vascular compromise ultimately overwhelms renal adaptive changes, leading to overt cortical hypoxia and expansion of medullary hypoxic zones. 'Fractional kidney hypoxia' method of analysis, developed as an alternative method of BOLD MRI analysis, avoids the assumption of discrete cortical and medullary values and decreases the bias related to operator selection of regions of interests.

SUMMARY

We believe that thoughtful application and analysis of BOLD MRI can provide critical insights into changes in renal function prior to the onset of irreversible renal injury and may identify patients most likely to gain from measures to reverse or repair disorders of tissue oxygenation.

Renovascular hypertension: is there still a role for stent revascularization?

PURPOSE OF REVIEW

Management of renovascular hypertension remains controversial and problematic, in part, due to failure of prospective trials to demonstrate added benefit to revascularization.

RECENT FINDINGS

Effective drug therapy often can achieve satisfactory blood pressure control, although concerns persist of the potential for progressive, delayed loss of kidney function beyond a stenotic lesion. Recent studies highlight benefits of renal artery stenting in subsets of patients including those with recurrent pulmonary edema and those intolerant to blockade of the renin-angiotensin system. Occasional patients with recent deterioration in renal function recover sufficient glomerular filtration rate after stenting to avoid requirements for renal replacement therapy. Emerging paradigms from both clinical and experimental studies suggest that hypoxic injury within the kidney activates inflammatory injury pathways and microvascular rarification that may not recover after technically successful revascularization alone. Initial data suggest that additional measures to repair the kidney, including the use of cell-based therapy, may offer the potential to recover kidney function in advanced renovascular disease.

SUMMARY

Specific patient groups benefit from renal revascularization. Nephrologists will increasingly be asked to manage complex renovascular patients, different from those in randomized trials, that require intensely individualized management.

Sildenafil ameliorates oxidative stress and DNA damage in the stenotic kidneys in mice with renovascular hypertension

Background

Oxidative stress and DNA damage have been implicated in the pathogenesis of renovascular hypertension induced by renal artery stenosis in the two-kidney, one-clip (2K1C) Goldblatt model. Considering our previous report indicating that the chronic blockade of phosphodiesterase 5 with sildenafil (Viagra®) has marked beneficial effects on oxidative stress and DNA damage, we tested the hypothesis that sildenafil could also protect the stenotic kidneys of 2K1C hypertensive mice against oxidative stress and genotoxicity.

Methods

The experiments were performed with C57BL6 mice subjected to renovascular hypertension by left renal artery clipping. Two weeks after clipping, the mice were treated with sildenafil (40 mg/kg/day for 2 weeks, 2K1C-sildenafil group) or the vehicle (2K1C). These mice were compared with control mice not subjected to renal artery clipping (Sham). After hemodynamic measurements, the stenotic kidneys were assessed using flow cytometry to evaluate cell viability and the comet assay to evaluate DNA damage. Measurements of intracellular superoxide anions and hydrogen peroxide levels as well as nitric oxide bioavailability were also obtained.

Results

Sildenafil treatment significantly reduced mean arterial pressure (15%), heart rate (8%), intrarenal angiotensin II (50%) and renal atrophy (36%). In addition, it caused a remarkable decrease of reactive oxygen species production. On the other hand, sildenafil increased nitric oxide levels relative to those in the nontreated 2K1C mice. Sildenafil treatment also significantly reduced the high level of kidney DNA damage that is a characteristic of renovascular hypertensive mice.

Conclusions

Our data reveal that sildenafil has a protective effect on the stenotic kidneys of 2K1C mice, suggesting a new use of phosphodiesterase 5 inhibitors for protection against the DNA damage observed in the hypoperfused kidneys of individuals with renovascular hypertension. Further translational research is necessary to delineate the mechanisms involved in the prevention of renal stenosis in the clinical setting.

Attending rounds: a patient with accelerated hypertension and an atrophic kidney

This case represents an individual with accelerating hypertension and declining kidney function associated with atherosclerotic renal artery stenosis. Key features include loss of GFR (reaching stage V CKD) during intensified antihypertensive drug therapy including agents that block the renin-angiotensin system and failure to appreciate the extent to which moderate renal artery stenosis was affecting his better kidney. Interpretation of duplex ultrasound studies was complicated by a discrepancy between near-normal peak systolic velocities and markedly abnormal segmental arterial waveforms. It was essential to recognize that both kidneys were abnormal and focus on recovery of perfusion to the better of these kidneys. Successful revascularization of one kidney allowed major improvement in GFR and BP control.

Association of high-density lipoprotein cholesterol with the estimated glomerular filtration rate in a community-based population

Background

Reduced kidney function is independently associated with low high-density lipoprotein cholesterol (HDL-C) levels in patients with end-stage renal disease (ESRD), those on hemodialysis, and those with stage 3–5 chronic kidney disease (CKD). However, epidemiological data investigating the relationship between HDL-C levels and kidney function in the general population with roughly normal kidney function are limited, and the results are also inconsistent. The aim of this study was to evaluate the relationship between HDL-C levels and the estimated glomerular filtration rate (eGFR) in a community-based population in China.

Methods

This was a community-based cross-sectional survey. In total, 4925 participants (age range, 18–96 years; mean, 51.30±11.98 years) were recruited during routine health status examinations. A questionnaire was used to ascertain age, smoking status, and the history of hypertension and diabetes mellitus for each participant. We measured the body mass index, waist circumference, systolic and diastolic blood pressure, and fasting glucose, total cholesterol, triglyceride, HDL-C, low-density lipoprotein cholesterol, uric acid, and serum creatinine level of each participant. eGFR was evaluated using the Chinese modified Modification of Diet in Renal Disease equation.

Results

The HDL-C level was higher in the first quartile (lowest quartile) of eGFR than in the fourth quartile (the highest quartile). Additionally, HDL-C levels decreased as eGFR decreased. Pearson’s correlation analysis revealed that HDL-C levels were associated with eGFR (r=0.16). After adjustment for some confounders, HDL-C was independently associated with all quartiles of eGFR in the participants.

Conclusions

HDL-C was independently associated with kidney function in a community-dwelling general population. The association between low HDL-C levels and a decreased eGFR gradually strengthened as eGFR declined.