Extrarenal atherosclerotic disease blunts renal recovery in patients with renovascular hypertension

Emergent players in renovascular disease

Renovascular disease (RVD) remains a common etiology of secondary hypertension. Recent clinical trials revealed unsatisfactory therapeutic outcomes of renal revascularization, leading to extensive investigation to unravel key pathophysiological mechanisms underlying irreversible functional loss and structural damage in the chronically ischemic kidney. Research studies identified complex interactions among various players, including inflammation, fibrosis, mitochondrial injury, cellular senescence, and microvascular remodeling. This interplay resulted in a shift of our understanding of RVD from a mere hemodynamic disorder to a pro-inflammatory and pro-fibrotic pathology strongly influenced by systemic diseases like metabolic syndrome (MetS), hypertension, diabetes mellitus, and hyperlipidemia. Novel diagnostic approaches have been tested for early detection and follow-up of RVD progression, using new imaging techniques and biochemical markers of renal injury and dysfunction. Therapies targeting some of the pathological pathways governing the development of RVD have shown promising results in animal models, and a few have moved from bench to clinical research. This review summarizes evolving understanding in chronic ischemic kidney injury.

Cell-based regenerative medicine for renovascular disease

Renal artery stenosis (RAS) elicits the development of hypertension and post-stenotic kidney damage, which may become irresponsive to restoration of arterial patency. Rather than mere losses of blood flow or oxygen supply, irreversible intrarenal microvascular rarefaction, tubular injury, and interstitial fibrosis are now attributed to intrinsic pathways activated within the kidney, focusing attention on the kidney parenchyma as a therapeutic target. Several regenerative approaches involving the delivery of reparative cells or products have achieved kidney repair in experimental models of RAS and the delivery of mesenchymal stem/stromal cells (MSCs) has already been translated to human subjects with RAS with promising results. The ongoing development of innovative approaches in kidney disease awaits application, validation, and acceptance as routine clinical treatment to avert kidney damage in RAS.

Design of a clinical risk calculator for major clinical outcomes in patients with atherosclerotic renovascular disease

BACKGROUND

Risk stratification in atherosclerotic renovascular disease (ARVD) can influence treatment decisions and facilitate patient selection for revascularization. In this study, we aim to use variables with the best predictive value to design a risk calculator that can assist clinicians with risk stratification and outcome prediction.

METHODS

Patients with a radiological diagnosis of ARVD referred to our tertiary renal centre were recruited into this prospective cohort study between 1986 and 2014. Primary clinical endpoints included: death, progression to end-stage kidney disease and cardiovascular events (CVE). A stepwise regression model was used to select variables with the most significant hazard ratio for each clinical endpoint. The risk calculator was designed using Hypertext Markup Language. Survival and CVE-free survival were estimated at 1, 5 and 10 years.

RESULTS

In total, 872 patients were recruited into the Salford ARVD study with a median follow-up period of 54.9 months (interquartile range 20.2-96.0). Only models predicting death and CVE showed good performance (C-index >0.80). Survival probabilities obtained from the risk calculator show that most patients with ARVD have reduced long-term survival. Revascularization improved outcomes in patients with higher baseline estimated glomerular filtration rate and lower proteinuria but not in those with co-existing comorbidities and higher levels of baseline proteinuria.

CONCLUSIONS

Although this risk calculator requires further independent validation in other ARVD cohorts, this study shows that a small number of easily obtained variables can help predict clinical outcomes and encourage a patient-specific therapeutic approach.

Association of systolic blood pressure and pulse pressure with microalbuminuria in treatment-naïve hypertensive patients

INTRODUCTION

To investigate the association between blood pressure components and microalbuminuria (MAU) in newly diagnosed and treatment-naïve hypertensive patients.

MATERIAL AND METHODS

A total of 1858 newly diagnosed and treatment-naïve hypertensive patients were enrolled. Based on 24 h urine albumin concentration, all patients were divided into MAU and normo-albuminuria groups. The associations between blood pressure (BP) components, namely systolic/diastolic BP (SBP/DBP) and pulse pressure (PP) and MAU, as well as the sensitivity and specificity of each BP component in predicting MAU, were evaluated.

RESULTS

Compared to the normo-albuminuria group, patients in the MAU group were older and had significantly higher SBP and PP (p < 0.05). Serum levels of fasting blood glucose, total protein and creatinine were significantly higher in the MAU group (p < 0.05). 24-hour urine albumin excretion was significantly higher in the MAU group than the normo-albuminuria group (182.5 ±156.5 mg vs. 17.6 ±7.1 mg, p < 0.001). Logistic regression analyses revealed that SBP and PP were significantly associated with MAU, with an odds ratio (OR) of 1.010 (95% confidence interval (CI): 1.005-1.016, p < 0.001) in SBP and OR of 1.009 (95% CI: 1.003-1.015, p = 0.003) in PP. The receiver operating characteristic curve showed that the area under the curve for SBP to predict MAU was 0.541 ±0.013, and PP was 0.536 ±0.013. The difference in predicting MAU by SBP or PP was non-significant.

CONCLUSIONS

In newly diagnosed and treatment-naïve hypertensive patients, increased SBP and PP were independently associated with MAU.

Impact of Serum Uric Acid Levels on Outcomes following Renal Artery Revascularization in Patients with Renovascular Disease

BACKGROUND

Percutaneous transluminal renal angioplasty (PTRA) improves blood pressure (BP) and renal function only in selected patients with atherosclerotic renovascular disease (ARVD). Hyperuricemia is associated with elevated risk for hypertension and chronic renal disease, but its role in renovascular hypertension is unclear. We hypothesized that hyperuricemia negatively impacts renal and BP outcomes among patients with ARVD undergoing PTRA.

METHODS

This retrospective, observational cohort study included 94 patients with ARVD and preserved systolic cardiac function, who underwent PTRA at Mayo Clinic, Rochester, Minnesota. Renal, BP, and mortality outcomes were compared among patients according to their serum uric acid (SUA) levels. Multivariate analysis was used to determine significant predictors of renal, BP, and mortality outcomes after PTRA.

RESULTS

Compared to patients with normal basal SUA levels (≤5.7 mg/dl), patients with very high SUA (≥8.7 mg/dl) had lower baseline estimated glomerular filtration rate (eGFR), more extensive use of antihypertensive and diuretic drugs, increased baseline systolic blood pressure (SBP), and elevated left ventricular mass index. After PTRA, multiple logistic regression analysis showed that, compared to normal SUA, very high SUA was associated with decreased odds ratio (OR) of change in eGFR (adjusted OR=0.90; 95% confidence interval [CI], 0.86-0.95), but not of change in SBP. In multivariate linear analysis SUA independently predicted delta urine protein/creatinine ratio (β: 26.0; 95% confidence interval, 13.9 to 38.1).

CONCLUSION

Severe hyperuricemia in patients with AVRD may have a negative impact on outcomes of renal revascularization.

Related factors for worsening renal function following percutaneous transluminal renal angioplasty (PTRA) in patients with atherosclerotic renal artery stenosis

PURPOSE

To identify candidates for PTRA in terms of the preservation of renal function, we herein evaluated factors that caused worsening renal function (WRF) after PTRA.

METHODS

We evaluated 92 patients with atherosclerotic renal artery stenosis (mean age 70.7 ± 8.4 years). WRF was defined as a ≥0.3 mg/dL increase in creatinine levels after PTRA compared to before PTRA.

RESULTS

A total of 92 patients exhibited non-WRF 83 (90.2%), WRF 9 (9.8%). Significant differences were observed in serum creatinine levels between two groups both before (non-WRF 1.34 ± 0.49 versus WRF 1.70 ± 0.68 mg/dL, p = 0.0462) and after PTRA (non-WRF 1.31 ± 0.43 versus WRF 2.42 ± 1.12 mg/dL, p < 0.0001). Patients with WRF had higher comorbidity rate of diabetes mellitus (DM) (non-WRF 31.3% versus WRF 66.7%, p = 0.0345) and proteinuria (non-WRF 27.7% versus WRF 66.7%, p = 0.0169), and had higher systolic blood pressure (non-WRF 143.6 ± 18.7 versus WRF 157.1 ± 19.9 mmHg, p = 0.0436), higher plasma B-type natriuretic peptide (BNP) levels, and larger left atrial and left ventricular end-diastolic dimensions before PTRA. Patients with WRF had a higher rate of taking diuretics (non-WRF 27.7% versus WRF 66.7%, p = 0.0169) after PTRA. Multiple logistic regression analysis revealed that comorbidity of DM was an independent related factor for WRF (comorbidity of DM, yes: OR 31.0, 95% CI 2.44-1024.62, p = 0.0055).

CONCLUSIONS

Comorbidity of DM, coexisting of proteinuria, high creatinine level, high blood pressure, high BNP levels, and large left atrial and ventricular dimensions were related to WRF after PTRA in patients with atherosclerotic renal artery stenosis.

Intra-renal delivery of mesenchymal stem cells attenuates myocardial injury after reversal of hypertension in porcine renovascular disease

Introduction

Percutaneous transluminal renal angioplasty (PTRA) fails to fully improve cardiac injury and dysfunction in patients with renovascular hypertension (RVH). Mesenchymal stem cells (MSCs) restore renal function, but their potential for attenuating cardiac injury after reversal of RVH has not been explored. We hypothesized that replenishment of MSCs during PTRA would improve cardiac function and oxygenation, and decrease myocardial injury in porcine RVH.

Methods

Pigs were studied after 16 weeks of RVH, RVH treated 4 weeks earlier with PTRA with or without adjunct intra-renal delivery of MSC (10^6 cells), and controls. Cardiac structure, function (fast-computed tomography (CT)), and myocardial oxygenation (Blood-Oxygen-Level-Dependent- magnetic resonance imaging) were assessed in-vivo. Myocardial microvascular density (micro-CT) and myocardial injury were evaluated ex-vivo. Kidney venous and systemic blood levels of inflammatory markers were measured and their renal release calculated.

Results

PTRA normalized blood pressure, yet stenotic-kidney glomerular filtration rate, similarly blunted in RVH and RVH + PTRA, normalized only in PTRA + MSC-treated pigs. PTRA attenuated left ventricular remodeling, whereas myocardial oxygenation, subendocardial microvascular density, and diastolic function remained decreased in RVH + PTRA, but normalized in RVH + PTRA-MSC. Circulating isoprostane levels and renal release of inflammatory cytokines increased in RVH and RVH + PTRA, but normalized in RVH + PTRA-MSC, as did myocardial oxidative stress, inflammation, collagen deposition, and fibrosis.

Conclusions

Intra-renal MSC delivery during PTRA preserved stenotic-kidney function, reduced systemic oxidative stress and inflammation, and thereby improved cardiac function, oxygenation, and myocardial injury four weeks after revascularization, suggesting a therapeutic potential for adjunctive MSC delivery to preserve cardiac function and structure after reversal of experimental RVH.

Intrarenal Delivery of Mesenchymal Stem Cells and Endothelial Progenitor Cells Attenuates Hypertensive Cardiomyopathy in Experimental Renovascular Hypertension

Renovascular hypertension (RVH) leads to left ventricular (LV) hypertrophy and diastolic dysfunction, associated with increased cardiovascular mortality. Intrarenal delivery of endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs) improves kidney function in porcine RVH, and the potent anti-inflammatory properties of MSCs may serve to blunt inflammatory mediators in the cardiorenal axis. However, their relative efficacy in attenuating cardiac injury and dysfunction remains unknown. This study tested the hypothesis that the cardioprotective effect of EPCs and MSCs delivered into the stenotic kidney in experimental RVH are comparable. Pigs (n = 7 per group) were studied after 10 weeks of RVH or control untreated or treated with a single intrarenal infusion of autologous EPCs or MSCs 4 weeks earlier. Cardiac and renal function (fast CT) and stenotic kidney release of inflammatory mediators (ELISA) were assessed in vivo, and myocardial inflammation, remodeling, and fibrosis ex vivo. After 10 weeks of RVH, blood pressure was not altered in cell-treated groups, yet stenotic kidney glomerular filtration rate (GFR), blunted in RVH, improved in RVH + EPC, and normalized in RVH + MSCs. Stenotic kidney release of monocyte chemoattractant protein (MCP)-1 and its myocardial expression were elevated in RVH + EPC, but normalized only in RVH + MSC pigs. RVH-induced LV hypertrophy was normalized in both EPC- and MSC-treated pigs, while diastolic function (E/A ratio) was restored to normal levels exclusively in RVH + MSCs. RVH-induced myocardial fibrosis and collagen deposition decreased in RVH + EPCs but further decreased in RVH + MSC-treated pigs. Intrarenal delivery of EPCs or MSCs attenuates RVH-induced myocardial injury, yet MSCs restore diastolic function more effectively than EPCs, possibly by greater improvement in renal function or reduction of MCP-1 release from the stenotic kidney. These observations suggest a therapeutic potential for EPCs and MSCs in preserving the myocardium in chronic experimental RVH.

Experimental coronary artery stenosis accelerates kidney damage in renovascular hypertensive swine

The impact of coronary artery stenosis (CAS) to renal injury is unknown. Here we tested whether the existence of CAS, regardless of concurrent atherosclerosis, would induce kidney injury and magnify its susceptibility to damage from co-existing hypertension (HT). Pigs (7 each) were assigned to Sham, left-circumflex CAS, renovascular HT, and CAS plus HT groups. Cardiac and non-stenotic kidney functions, circulating and renal inflammatory and oxidative markers, and renal and microvascular remodeling, were assessed 10 weeks later. Myocardial perfusion declined distal to CAS. Systemic levels of PGF2-α isoprostane, a marker of oxidative stress, increased in CAS and CAS plus HT, while single-kidney blood flow responses to acetylcholine were significantly blunted only in CAS plus HT compared to sham, HT, and CAS, indicating renovascular endothelial dysfunction. Tissue expression of inflammatory and oxidative markers were elevated in the CAS pig kidney, and further magnified in CAS plus HT, whereas angiogenic factor expression was decreased. Bendavia, a mitochondria-targeted peptide, decreased oxidative stress and improved renal function and structure in CAS. Furthermore, CAS and HT synergistically amplified glomerulosclerosis and renal fibrosis. Thus, mild myocardial ischemia, independent of systemic atherosclerosis, induced renal injury, possibly mediated by increased oxidative stress. Superimposed HT aggravates renal inflammation and endothelial dysfunction caused by CAS, and synergistically promotes kidney fibrosis, providing impetus to preserve cardiac integrity in order to protect the kidney.