Role of the microvascular endothelium in progressive renal disease

Interventions for renal artery stenosis: Appraisal of novel physiological insights and procedural techniques to improve clinical outcome

Randomized clinical trials failed to show additional benefit of renal artery stenting on top of medical therapy. Instead of writing an obituary on renal artery stenting, we try to explain these disappointing results. A transstenotic pressure gradient is needed to reduce renal perfusion and to activate the renin-angiotensin-aldosterone system. In only a minority of patients included in trials, a transstenotic pressure gradient is measured and reported. Like the coronary circulation, integration of physiological lesion assessment will allow to avoid stenting of non-significant lesions and select those patients that are most likely to benefit from renal artery stenting. Renal artery interventions are associated with peri-procedural complications. Contemporary techniques, including radial artery access, no-touch technique to engage the renal ostium and the use of embolic protection devices, will minimize procedural risk. Combining optimal patient selection and meticulous technique might lead to a netto clinical benefit when renal artery stenting is added to optimal medical therapy.

Proteinuria and risk of ocular motor cranial nerve palsy: a nationwide population-based study

Understanding the association between dipstick-detected proteinuria and oculomotor cranial nerve palsy (CNP) could have significant implications for understanding the mechanism of CNP development and for developing preventive strategies against CNP development in patients with proteinuria. This study aimed to determine the relationship between dipstick-determined proteinuria and ocular motor CNP using National Sample Cohort (NSC) database from Korea's National Health Insurance Service (NHIS). A nationwide population-based cohort study was conducted using data from the NSC database of Korea's NHIS. These data were collected from 2009 to 2018. A one-year time lag was established to prevent a situation in which the causal link was inverted. Participants aged 20 years or more who were diagnosed with proteinuria in 2009 were included. Individuals with specific pre-existing CNP, missing data, and those who were newly diagnosed with CNP or who died within one year of being tested were excluded. The study population was classified into six groups according to the degree of proteinuria (negative, trace, or between 1 + and 4 +) based on the urine dipstick test. A Cox proportional hazard regression analysis was performed to determine the linkage between the degree of proteinuria and ocular motor CNP. A total of 5,807 (0.14% of subjects) with ocular motor CNP were assigned to the ocular motor CNP group and 4,047,205 subjects were assigned to the control group. After full adjustment of comorbidities, hazard ratios (HRs) for 1 + , 2 + , 3 + and 4 + proteinuria groups were 1.449 (95% confidence interval [CI] 1.244-1.687), 2.081 (1.707-2.538), 1.96 (1.322-2.904), and 3.011 (1.507-6.014), respectively, for developing ocular motor CNP compared to the proteinuria-negative group. In subgroup analysis, the HR of patients with proteinuria for the development of ocular motor CNP was higher in the younger age group (less than 40 years) (P = 0.0242) and the group with DM (P = 0.04). Our population-based cohort study demonstrated a significant association between proteinuria and the incidence of CNP, suggesting that urine protein level could be a new clinical marker for predicting the development of CNP.

Fibrosis in Chronic Kidney Disease: Pathophysiology and Therapeutic Targets

Chronic kidney disease (CKD) is a slowly progressive condition characterized by decreased kidney function, tubular injury, oxidative stress, and inflammation. CKD is a leading global health burden that is asymptomatic in early stages but can ultimately cause kidney failure. Its etiology is complex and involves dysregulated signaling pathways that lead to fibrosis. Transforming growth factor (TGF)-β is a central mediator in promoting transdifferentiation of polarized renal tubular epithelial cells into mesenchymal cells, resulting in irreversible kidney injury. While current therapies are limited, the search for more effective diagnostic and treatment modalities is intensive. Although biopsy with histology is the most accurate method of diagnosis and staging, imaging techniques such as diffusion-weighted magnetic resonance imaging and shear wave elastography ultrasound are less invasive ways to stage fibrosis. Current therapies such as renin-angiotensin blockers, mineralocorticoid receptor antagonists, and sodium/glucose cotransporter 2 inhibitors aim to delay progression. Newer antifibrotic agents that suppress the downstream inflammatory mediators involved in the fibrotic process are in clinical trials, and potential therapeutic targets that interfere with TGF-β signaling are being explored. Small interfering RNAs and stem cell-based therapeutics are also being evaluated. Further research and clinical studies are necessary in order to avoid dialysis and kidney transplantation.

Capillary rarefaction: a missing link in renal and cardiovascular disease?

Patients with chronic kidney disease (CKD) have an increased risk for cardiovascular morbidity and mortality. Capillary rarefaction may be both one of the causes as well as a consequence of CKD and cardiovascular disease. We reviewed the published literature on human biopsy studies and conclude that renal capillary rarefaction occurs independently of the cause of renal function decline. Moreover, glomerular hypertrophy may be an early sign of generalized endothelial dysfunction, while peritubular capillary loss occurs in advanced renal disease. Recent studies with non-invasive measurements show that capillary rarefaction is detected systemically (e.g., in the skin) in individuals with albuminuria, as sign of early CKD and/or generalized endothelial dysfunction. Decreased capillary density is found in omental fat, muscle and heart biopsies of patients with advanced CKD as well as in skin, fat, muscle, brain and heart biopsies of individuals with cardiovascular risk factors. No biopsy studies have yet been performed on capillary rarefaction in individuals with early CKD. At present it is unknown whether individuals with CKD and cardiovascular disease merely share the same risk factors for capillary rarefaction, or whether there is a causal relationship between rarefaction in renal and systemic capillaries. Further studies on renal and systemic capillary rarefaction, including their temporal relationship and underlying mechanisms are needed. This review stresses the importance of preserving and maintaining capillary integrity and homeostasis in the prevention and management of renal and cardiovascular disease.

Post-ischemic inactivation of HIF prolyl hydroxylases in endothelium promotes maladaptive kidney repair by inducing glycolysis

Ischemic acute kidney injury (AKI) is common in hospitalized patients and increases the risk for chronic kidney disease (CKD). Impaired endothelial cell (EC) functions are thought to contribute in AKI to CKD transition, but the underlying mechanisms remain unclear. Here, we identify a critical role for endothelial oxygen sensing prolyl hydroxylase domain (PHD) enzymes 1-3 in regulating post-ischemic kidney repair. In renal endothelium, we observed compartment-specific differences in the expression of the three PHD isoforms in both mice and humans. We found that post-ischemic concurrent inactivation of endothelial PHD1, PHD2, and PHD3 but not PHD2 alone promoted maladaptive kidney repair characterized by exacerbated tissue injury, fibrosis, and inflammation. Single-cell RNA-seq analysis of the post-ischemic endothelial PHD1, PHD2 and PHD3 deficient (PHDTiEC) kidney revealed an endothelial glycolytic transcriptional signature, also observed in human kidneys with severe AKI. This metabolic program was coupled to upregulation of the SLC16A3 gene encoding the lactate exporter monocarboxylate transporter 4 (MCT4). Strikingly, treatment with the MCT4 inhibitor syrosingopine restored adaptive kidney repair in PHDTiEC mice. Mechanistically, MCT4 inhibition suppressed pro-inflammatory EC activation reducing monocyte-endothelial cell interaction. Our findings suggest avenues for halting AKI to CKD transition based on selectively targeting the endothelial hypoxia-driven glycolysis/MCT4 axis.

Macular Microvascular Perfusion Status in Hypertensive Patients with Chronic Kidney Disease

To compare retinal microvascular perfusion between the eyes of hypertensive patients with and without chronic kidney disease (CKD), the vessel density (VD) and fractal dimension (FD) of the superficial (SVP) and deep retinal vascular plexus (DVP) were analyzed on 6 × 6 mm fovea-centered optical coherence tomography angiography (OCTA) images of patients with hypertension. The retina was divided into an inner ring (IR) and outer ring (OR) according to the Early Treatment of Diabetic Retinopathy Study grid. The glomerular filtration rate (GFR) was determined and CKD was diagnosed (GFR < 60 mL/min/1.73 m2). Ninety-six eyes from 52 patients with hypertension were included in this analysis. Twenty patients (n = 37 eyes) were diagnosed with CKD. The mean age was 69 ± 11.7 years and 60.4 ± 9.2 years in the CKD group and in the control group, respectively. The univariate model revealed a significant difference in VD between patients without and with CKD in the superficial IR (0.36 ± 0.03 vs. 0.34 ± 0.04, p = 0.03), the superficial OR (0.35 ± 0.02 vs. 0.33 ± 0.04, p = 0.02), the deep OR (0.24 ± 0.01 vs. 0.23 ± 0.02, p = 0.003), and the FD in the SVP (1.87 ± 0.01 vs. 1.86 ± 0.02, p = 0.02) and DVP (1.83 ± 0.01 vs. 1.82 ± 0.01, p = 0.006). After adjusting for age and sex, these differences did not remain statistically significant. Similar results were observed for the FD in the SVP and DVP. In our cohort, patients with hypertension and CKD did not differ from patients without CKD in regard to microvascular perfusion status in the macular area as assessed using OCTA.

Tubular injury in diabetic kidney disease: molecular mechanisms and potential therapeutic perspectives

Diabetic kidney disease (DKD) is a chronic complication of diabetes and the leading cause of end-stage renal disease (ESRD) worldwide. Currently, there are limited therapeutic drugs available for DKD. While previous research has primarily focused on glomerular injury, recent studies have increasingly emphasized the role of renal tubular injury in the pathogenesis of DKD. Various factors, including hyperglycemia, lipid accumulation, oxidative stress, hypoxia, RAAS, ER stress, inflammation, EMT and programmed cell death, have been shown to induce renal tubular injury and contribute to the progression of DKD. Additionally, traditional hypoglycemic drugs, anti-inflammation therapies, anti-senescence therapies, mineralocorticoid receptor antagonists, and stem cell therapies have demonstrated their potential to alleviate renal tubular injury in DKD. This review will provide insights into the latest research on the mechanisms and treatments of renal tubular injury in DKD.

Beraprost and Overall Survival in Cats with Chronic Kidney Disease

BACKGROUND

Overall survival is the most important outcome for treatment response in feline chronic kidney disease (CKD). Beraprost has been shown to reduce the kidney function decline in cats with International Renal Interest Society (IRIS) stage 2 and 3 CKD. However, the association with prolonged survival has not yet been examined.

OBJECTIVE

To assess the relationship between beraprost and overall survival in cats with CKD in real clinical practice.

ANIMALS

Client-owned cats with IRIS stage 3 CKD (n = 134) were evaluated between 2017 and 2020.

METHODS

A retrospective cohort study based on data from electronic medical records of one hospital.

RESULTS

The cohort was divided into "beraprost therapy" and "no beraprost therapy" groups, and survival analyses revealed that overall survival was significantly longer in the beraprost therapy group, using Kaplan-Meier curves (p = 0.004). However, baseline phosphate is known to be an important prognostic indicator and was not well balanced between the two groups. Therefore, a subcohort of 97 cats was selected (those having baseline phosphate <6.0 mg/dL) that allowed for this parameter to be balanced between groups. The survival data in this subcohort were consistent with those of the overall study cohort.

CONCLUSIONS

In feline patients with CKD, beraprost therapy is associated with better overall survival.

Effect of Low Protein Diet Supplemented with Ketoanalogs on Endothelial Function and Protein-Bound Uremic Toxins in Patients with Chronic Kidney Disease

Studies have demonstrated that a low-protein diet supplemented with ketoanalogs (KAs) could significantly retard progression of renal function in patients with chronic kidney disease (CKD) stages 3-5. However, its effects on endothelial function and serum levels of protein-bound uremic toxins remain elusive. Therefore, this study explored whether a low-protein diet (LPD) supplemented with KAs affects kidney function, endothelial function, and serum uremic toxin levels in a CKD-based cohort. In this retrospective cohort, we enrolled 22 stable CKD stage 3b-4 patients on LPD (0.6-0.8 g/day). Patients were categorized into control (LPD only) and study groups (LPD + KAs 6 tab/day). Serum biochemistry, total/free indoxyl sulfate (TIS/FIS), total/free p-cresyl sulfate (TPCS/FPCS), and flow-mediated dilation (FMD) were measured before and after 6 months of KA supplementation. Before the trial, there were no significant differences in kidney function, FMD, or uremic toxin levels between the control and study groups. When compared with the control group, the paired t-test showed a significant decrease in TIS and FIS (all p < 0.05) and a significant increase in FMD, eGFR, and bicarbonate (all p < 0.05). In multivariate regression analysis, an increase in FMD (p < 0.001) and a decrease in FPCS (p = 0.012) and TIS (p < 0.001) remained persistent findings when adjusted for age, systolic blood pressure (SBP), sodium, albumin, and diastolic blood pressure (DBP). LPD supplemented with KAs significantly preserves kidney function and provides additional benefits on endothelial function and protein-bound uremic toxins in patients with CKD.

CKD, Brain Atrophy, and White Matter Lesion Volume: The Japan Prospective Studies Collaboration for Aging and Dementia

Rationale & Objective

Chronic kidney disease, defined by albuminuria and/or reduced estimated glomerular filtration rate (eGFR), has been reported to be associated with brain atrophy and/or higher white matter lesion volume (WMLV), but there are few large-scale population-based studies assessing this issue. This study aimed to examine the associations between the urinary albumin-creatinine ratio (UACR) and eGFR levels and brain atrophy and WMLV in a large-scale community-dwelling older population of Japanese.

Study Design

Population-based cross-sectional study.

Setting & Participants

A total of 8,630 dementia-free community-dwelling Japanese aged greater than or equal to 65 years underwent brain magnetic resonance imaging scanning and screening examination of health status in 2016-2018.

Exposures

UACR and eGFR levels.

Outcomes

The total brain volume (TBV)-to-intracranial volume (ICV) ratio (TBV/ICV), the regional brain volume-to-TBV ratio, and the WMLV-to-ICV ratio (WMLV/ICV).

Analytical Approach

The associations of UACR and eGFR levels with the TBV/ICV, the regional brain volume-to-TBV ratio, and the WMLV/ICV were assessed by using an analysis of covariance.

Results

Higher UACR levels were significantly associated with lower TBV/ICV and higher geometric mean values of the WMLV/ICV (P for trend = 0.009 and <0.001, respectively). Lower eGFR levels were significantly associated with lower TBV/ICV, but not clearly associated with WMLV/ICV. In addition, higher UACR levels, but not lower eGFR, were significantly associated with lower temporal cortex volume-to-TBV ratio and lower hippocampal volume-to-TBV ratio.

Limitations

Cross-sectional study, misclassification of UACR or eGFR levels, generalizability to other ethnicities and younger populations, and residual confounding factors.

Conclusions

The present study demonstrated that higher UACR was associated with brain atrophy, especially in the temporal cortex and hippocampus, and with increased WMLV. These findings suggest that chronic kidney disease is involved in the progression of morphologic brain changes associated with cognitive impairment.

Association between Kidney Function and the Burden of Cerebral Small Vessel Disease: An Updated Meta-Analysis and Systematic Review

INTRODUCTION

Due to anatomical and functional similarities in microvascular beds, the brain and kidney share distinctive susceptibilities to vascular injury and common risk factors of small vessel disease. The aim of this updated meta-analysis is to explore the association between kidney function and the burden of cerebral small vessel disease (CSVD).

METHODS

PubMed, EMBASE, and Cochrane Library were systematically searched for observational studies that explored the association between the indicators of kidney function and CSVD neuroimaging markers. The highest-adjusted risk estimates and their 95% confidence intervals (CIs) were aggregated using random-effect models.

RESULTS

Twelve longitudinal studies and 51 cross-sectional studies with 57,030 subjects met the inclusion criteria of systematic review, of which 52 were included in quantitative synthesis. According to the pooled results, we found that low estimated glomerular filtration rate (eGFR <60 mL/min/1.73 m2) was associated with cerebral microbleeds (odds ratio (OR) = 1.55, 95% CI = 1.26-1.90), white matter hyperintensities (OR = 1.40, 95% CI = 1.05-1.86), and lacunar infarctions (OR = 1.50, 95% CI = 1.18-1.92), but not with severe perivascular spaces (OR = 1.20, 95% CI = 0.77-1.88). Likewise, patients with proteinuria (OR = 1.75, 95% CI = 1.47-2.09) or elevated serum cystatin C (OR = 1.51, 95% CI = 1.25-1.83) also had an increased risk of CSVD.

CONCLUSION

The association between kidney function and CSVD has been comprehensively updated through this study, that kidney insufficiency manifested as low eGFR, proteinuria, and elevated serum cystatin C was independently associated with CSVD burden.

Noninvasive evaluation of IgA nephropathy fibrosis using Doppler ultrasound

In this study, we aimed to explore the clinical value of routine color ultrasound parameters in the evaluation of tubular atrophy and interstitial fibrosis (TA/IF) in IgA nephropathy (IgAN). We enrolled 725 patients with IgAN who underwent renal biopsy at the First Affiliated Hospital of Anhui Medical University between January 2019 and May 2022. Examinations were performed to measure the routine ultrasound renal parameters and renal biopsy was done within next three days. Univariate and multivariate analyses were used to determine the correlates and the independent predictors of TA/IF. Simultaneously, a nomogram based on risk indicators was created to predict TA/IF. Univariate and multivariate analyses showed that sex (p < 0.001, OR = 2.538, 95%CI: 1.739–3.734), renal length (p < 0.001, OR = 0.927, 95%CI: 0.905–0.95), resistive index of main renal artery (p = 0.037, OR = 1.891, 95%CI: 1.027–3.426), peak systolic velocity of segmental renal artery (p = 0.58, OR = 0.975, 95%CI: 0.399–0.841), and cortex echogenicity (p < 0.001, OR = 3.448, 95%CI: 2.382–5.018) were independent predictors of TA/IF in IgAN nomograms, with a good C-index of 0.765 (95%CI = 0.727–0.803). Analyses of the calibration charts show that nomograms have good performance and clinical applicability. In our study, renal color ultrasound parameters correlated well with TA/IF in IgAN. By establishing a conventional color ultrasound prediction model, we can accurately gauge the extent of TA/IF in patients with IgAN for clinical applications.

Extracellular CIRP induces acute kidney injury via endothelial TREM-1

Introduction: Acute kidney injury is associated with elevated serum levels of extracellular cold-inducible RNA-binding protein (eCIRP), a damage-associated molecular pattern released during ischemia/reperfusion injury, hemorrhagic shock, and sepsis. It is unknown if circulating eCIRP and eCIRP-induced activation of receptor triggering receptor expressed on myeloid cells-1 (TREM-1), expressed on endothelial cells, play an important role in the pathogenesis of AKI.

Methods: Male B6 wild-type (WT) and TREM-1^−/− mice were subjected to intravenous injection of recombinant murine (rm) CIRP. Serum, urine, and renal tissue were collected 6 h later for analysis. Additionally, primary human renal glomerular endothelial cells (HRGEC) were stimulated in vitro with rmCIRP after pretreatment with M3, a novel inhibitory peptide of TREM-1, or vehicle. Supernatants and cells were collected 20 h after stimulation.

Results: After injection with rmCIRP, WT mice had a significant increase in serum levels of BUN, creatinine, and NGAL compared to control. Additionally, NGAL was significantly increased in the urine of rmCIRP-injected mice, suggesting that circulating eCIRP can directly induce AKI. The levels of TREM-1 mRNA in the kidneys, as well as soluble (s) TREM-1 released into the serum and urine, were significantly increased in rmCIRP-injected mice. TREM-1^−/− mice injected with rmCIRP had attenuated AKI, indicated by significantly decreased serum BUN, creatinine, and NGAL, and renal mRNA expression of NGAL and KIM-1 compared to WT mice. TREM-1^−/− mice also had attenuated endothelial activation, with decreased mRNA and protein expression of ICAM-1 in renal tissue. HRGEC stimulated with rmCIRP in vitro had significant increases in cytokine production and sTREM-1 release, which was attenuated in cells treated with M3.

Conclusion: Activation of renal TREM-1 with circulating eCIRP is sufficient to cause AKI. Elevated levels of eCIRP may be critical for the development of AKI under conditions such as ischemia/reperfusion injury, hemorrhagic shock, and sepsis. Mice deficient in the TREM-1 receptor have attenuated AKI and reduced endothelial cell activation after injection of rmCIRP. TREM-1 inhibition with M3 attenuates HRGEC activation after eCIRP stimulation. Targeting eCIRP activation of TREM-1 may provide a novel and effective treatment for AKI.

Association of retinal fractal dimension and vessel tortuosity with impaired renal function among healthy Chinese adults

Purpose

This study investigated the association of retinal fractal dimension (FD) and blood vessel tortuosity (BVT) with renal function [assessed by estimated glomerular filtrate rate (eGFR)] in healthy Chinese adults using swept-source optical coherence tomographic angiography (SS-OCTA).

Materials and methods

This cross-sectional study was conducted among ocular treatment–naïve healthy participants from Guangzhou, China. FD and BVT in the superficial capillary plexus and deep capillary plexus were measured by SS-OCTA with a 3 × 3 macula model. eGFR was calculated using the Xiangya equation, and impaired renal function (IRF) was defined as eGFR = 90 mL/min/1.73 m2. Linear regression was performed to evaluate the relationships between SS-OCTA metrics and renal function.

Results

A total of 729 participants with a mean age of 57.6 ± 9.1 years were included in the final analysis. Compared to participants with normal renal function, those with IRF had lower FD both in the superficial capillary plexus (1.658 ± 0.029 vs. 1.666 ± 0.024, p = 0.001) and deep capillary plexus (1.741 ± 0.016 vs. 1.746 ± 0.016, p = 0.0003), while the deep BVT was larger in participants with IRF than those with normal renal function (1.007 ± 0.002 vs. 1.006 ± 0.002, p = 0.028). The superficial FD was linearly and positively associated with eGFR after adjusting for confounders (β = 0.2257; 95% CI 0.0829–0.3685; p = 0.002), while BVT was not associated with eGFR (all p ≥ 0.05).

Conclusion

The patients with IRF had lower FD and larger BVT than those with normal renal function. The superficial FD decreased linearly with renal function deterioration. Our study suggests that the retinal microvasculature can represent a useful indicator of subclinical renal microvascular abnormalities and serve as a useful non-invasive assessment to predict and monitor the progression of renal function.

Interaction effect of blood glucose and pressure on the risk of chronic kidney disease: a population-based prospective cohort study

OBJECTIVE

To evaluate the interaction effect of blood glucose and blood pressure on the risk of chronic kidney disease (CKD).

METHODS

31,165 subjects were selected without CKD at baseline and had completed the first follow-up from "Jinchang cohort". Cox regression model and restricted cubic splines functions were used to evaluate the effects of blood glucose or pressure on the incidence of CKD and dose-response relationship after adjusting for confounding covariates. Synergic effect was assessed by the multiplicative or additive interaction scale.

RESULTS

Among 31,165 subjects, 1307 new-onset CKD were observed during 68905.78 person-years follow-up, and the incidence density was 18.97 per 1000 person-years. The risk of CKD gradually increased with the increase of blood pressure in diabetes, pre-diabetes and normal groups (P_trend < 0.05). And, the risk was greatest when SBP/DBP reached ≥150/≥110 mmHg in three groups, and HRs (95% CI) were 1.610 (1.070-2.422), 2.142 (1.396-3.288) and 2.455 (1.941-3.106), respectively. Additionally, among hypertension, pre-hypertension and normal groups, the risk of CKD increased by 16.0%, 14.3% and 25.2% for each 1 mmol/L of FPG. When FPG level was more than 9.0 mmol/L, the risk was greatest and adjusted HRs (95% CI) were 2.856 (2.176-3.748), 2.979 (1.828-4.854) and 7.520 (4.517-12.519). Furthermore, the risk was highest when hypertension was accompanied by diabetes (HR = 4.915, 95% CI: 3.923-6.157). This analysis supported a less than multiplicative effect (HR = 0.634, 95% CI: 0.417-0.964) for the interaction term of diabetes and hypertension, while there was no additive interaction towards CKD in all interaction term.

CONCLUSIONS

Blood glucose and pressure were independent risk factors in incidence of CKD, but there was only a negative multiplicative interaction between hypertension and diabetes, but no additive interaction effect between them.

Comparison of the Surgical Resection and Infarct 5/6 Nephrectomy Rat Models of Chronic Kidney Disease

The 5/6 nephrectomy rat remnant kidney model is commonly employed to study chronic kidney disease (CKD). This model requires removal of one whole kidney and two-thirds of the other. The two most common ways of producing the remnant kidney are surgical resection of poles, known as the polectomy (Pol) model, or ligation of upper and lower renal arterial branches, resulting in pole infarction (Inf). These models have much in common, but also major phenotypic differences, and thus respectively model unique aspects of human CKD. The purpose of this review is to summarize phenotypic similarities and differences between these two models and their relation to human CKD, while emphasizing their vascular phenotype. In this article we review studies that have evaluated arterial blood pressure, the renin-angiotensin-aldosterone-system (RAAS), autoregulation, nitric oxide, single nephron physiology, angiogenic and anti-angiogenic factors, and capillary rarefaction in these two models. Phenotypic similarities: both models spontaneously develop hallmarks of human CKD including uremia, fibrosis, capillary rarefaction, and progressive renal function decline. They both undergo whole-organ hypertrophy, hyperfiltration of functional nephrons, reduced renal expression of angiogenic factor VEGF, increased renal expression of the anti-angiogenic thrombospondin-1, impaired renal autoregulation, and abnormal vascular nitric oxide physiology. Key phenotypic differences: the Inf model develops rapid-onset, moderate-to-severe systemic hypertension, and the Pol model early normotension followed by mild-to-moderate hypertension. The Inf rat has a markedly more active renin-angiotensin-aldosterone-system. Comparison of these two models facilitates understanding of how they can be utilized for studying CKD pathophysiology (e.g., RAAS dependent or independent pathology).

Prognostic Effect of Underlying Chronic Kidney Disease and Renal Replacement Therapy on the Outcome of Patients after Out-of-Hospital Cardiac Arrest: A Nationwide Observational Study

Background and Objectives: This study assessed the prognostic value of underlying chronic kidney disease (CKD) and renal replacement therapy (RRT) on the clinical outcomes from out-of-hospital cardiac arrest (OHCA). Materials and Methods: This retrospective study was conducted utilizing the population-based OHCA data of South Korea between 2008 and 2018. Adult (>18 years) OHCA patients with a medical cause of cardiac arrest were included and classified into three categories based on the underlying CKD and RRT: (1) non-CKD group; (2) CKD without RRT group; and (3) CKD with RRT group. A total of 13,682 eligible patients were included (non-CKD, 9863; CKD without RRT, 1778; CKD with RRT, 2041). From the three comparison subgroups, data with propensity score matching were extracted. The influence of CKD and RRT on patient outcomes was assessed using propensity score matching and multivariate logistic regression analyses. The primary outcome was survival at hospital discharge and the secondary outcome was a good neurological outcome at hospital discharge. Results: The two CKD groups (CKD without RRT and CKD with RRT) showed no significant difference in survival at hospital discharge compared with the non-CKD group (CKD without RRT vs. non-CKD, p > 0.05; CKD with RRT vs. non-CKD, p > 0.05). The non-CKD group had a higher chance of having good neurological outcomes than the CKD groups (non-CKD vs. CKD without RRT, p < 0.05; non-CKD vs. CKD with RRT, p < 0.05) whereas there was no significant difference between the two CKD groups (CKD without RRT vs. CKD with RRT, p > 0.05). Conclusions: Compared with patients without CKD, the underlying cause of CKD—regardless of RRT—may be linked to poor neurological outcomes. Underlying CKD and RRT had no effect on the survival at hospital discharge.

Chemokine (C-C Motif) Ligand 8 and Tubulo-Interstitial Injury in Chronic Kidney Disease

Kidney fibrosis has been accepted to be a common pathological outcome of chronic kidney disease (CKD). We aimed to examine serum levels and tissue expression of chemokine (C-C motif) ligand 8 (CCL8) in patients with CKD and to investigate their association with kidney fibrosis in CKD model. Serum levels and tissue expression of CCL8 significantly increased with advancing CKD stage, proteinuria level, and pathologic deterioration. In Western blot analysis of primary cultured human tubular epithelial cells after induction of fibrosis with rTGF-β, CCL8 was upregulated by rTGF-β treatment and the simultaneous treatment with anti-CCL8 mAb mitigated the rTGF-β-induced an increase in fibronectin and a decrease E-cadherin and BCL-2 protein levels. The antiapoptotic effect of the anti-CCL8 mAb was also demonstrated by Annexin V/propidium iodide staining assay. In qRT-PCR analysis, mRNA expression levels of the markers for fibrosis and apoptosis showed similar expression patterns to those observed by western blotting. The immunohistochemical analysis revealed CCL8 and fibrosis- and apoptosis-related markers significantly increased in the unilateral ureteral obstruction model, which agrees with our in vitro findings. In conclusion, CCL8 pathway is associated with increased risk of kidney fibrosis and that CCL8 blockade can ameliorate kidney fibrosis and apoptosis.

BM-MSC-derived small extracellular vesicles (sEV) from trained animals presented nephroprotective potential in unilateralureteral obstruction model

Background:

The efficacy of bone marrow mesenchymal stromal cells (BM-MSC) and its extracellular vesicles has been demonstrated for a broad spectrum of indications, including kidney diseases. However, BM-MSC donor characteristics and their potential are not usually considered. Therefore, the present work aims to evaluate the nephroprotective capacity of sEV secreted by BM-MSC from trained rats inunilateral ureteral obstruction (UUO) model.

Methods:

BM-MSC was characterized by their differentiation potential and immunophenotypic markers. The sEV were isolated by ultracentrifugation and characterized by nanoparticle tracking analysis and western blot. Its miRNA cargo was examined by quantitative PCR analysis for miR-26a, 126a, and 296. Wistar rats were submitted to UUO procedure and concomitantly treated with sEV secreted by BM-MSC from the untrained andtrained rats. The kidney tissue from all groups was evaluated for fibrosis mediators (transforming growth factor beta1 and collagen), CD34-angiogenesis marker, and hypoxia-inducible factor 1 alpha (HIF-1α).

Results:

Treadmill training stimulated in BM-MSC the production of sEV loaded with pro-angiogenic miR-296. The treatment with this sEVin UUO-rats was able to attenuate collagen accumulation and increase CD34 and HIF-1α in the kidney tissue when compared to untrained ones. Tubular proximal cells under hypoxia and exposed to BM-MSC sEV demonstrate accumulation in HIF-1α and NFR-2 (nuclear factor erythroid 2-related factor 2), possibly to mediate the response to hypoxia and oxidative stress, under these conditions.

Conclusion:

The BM-MSC sEV from trained animals presented an increased nephroprotective potential compared to untrained vesicles by carrying 296-angiomiR and contributing to angiogenesis in UUO model.

Polygenic Risk Scores for Kidney Function and Their Associations with Circulating Proteome, and Incident Kidney Diseases

BACKGROUND

Genome-wide association studies (GWAS) have revealed numerous loci for kidney function (eGFR). The relationship between polygenic predictors of eGFR, risk of incident adverse kidney outcomes, and the plasma proteome is not known.

METHODS

We developed a genome-wide polygenic risk score (PRS) for eGFR by applying the LDpred algorithm to summary statistics generated from a multiethnic meta-analysis of CKDGen Consortium GWAS ( n =765,348) and UK Biobank GWAS (90% of the cohort; n =451,508), followed by best-parameter selection using the remaining 10% of UK Biobank data ( n =45,158). We then tested the association of the PRS in the Atherosclerosis Risk in Communities (ARIC) study ( n =8866) with incident CKD, ESKD, kidney failure, and AKI. We also examined associations between the PRS and 4877 plasma proteins measured at middle age and older adulthood and evaluated mediation of PRS associations by eGFR.

RESULTS

The developed PRS showed a significant association with all outcomes. Hazard ratios per 1 SD lower PRS ranged from 1.06 (95% CI, 1.01 to 1.11) to 1.33 (95% CI, 1.28 to 1.37). The PRS was significantly associated with 132 proteins at both time points. The strongest associations were with cystatin C, collagen α -1(XV) chain, and desmocollin-2. Most proteins were higher at lower kidney function, except for five proteins, including testican-2. Most correlations of the genetic PRS with proteins were mediated by eGFR.

CONCLUSIONS

A PRS for eGFR is now sufficiently strong to capture risk for a spectrum of incident kidney diseases and broadly influences the plasma proteome, primarily mediated by eGFR.

High salt exacerbates acute kidney injury by disturbing the activation of CD5L/apoptosis inhibitor of macrophage (AIM) protein

The influence of excess salt intake on acute kidney injury (AKI) has not been examined precisely except for some clinical data, unlike in chronic kidney disease. Here, we addressed the influence of high salt (HS) on AKI and its underlying mechanisms in terms of the activity of circulating apoptosis inhibitor of macrophage (AIM, also called CD5L) protein, a facilitator of AKI repair. HS loading in mice subjected to ischemia/reperfusion (IR) resulted in high mortality with advanced renal tubular obstruction and marked exacerbation in biomarkers of proximal renal tubular damage. This AKI exacerbation appeared to be caused mainly by the reduced AIM dissociation from IgM pentamer in serum, as IgM-free AIM is indispensable for the removal of intratubular debris to facilitate AKI repair. Injection of recombinant AIM (rAIM) ameliorated the AKI induced by IR/HS, dramatically improving the tubular damage and mouse survival. The repair of lethal AKI by AIM was dependent on AIM/ kidney injury molecule-1 (KIM-1) axis, as rAIM injection was not effective in KIM-1 deficient mice. Our results demonstrate that the inhibition of AIM dissociation from IgM is an important reason for the exacerbation of AKI by HS, that AIM is a strong therapeutic tool for severe AKI.

Hypoxia-induced thyroid hormone receptor expression regulates cell-cycle progression in renal tubule epithelial cells

Hypoxia occurs in the kidneys of chronic kidney disease (CKD) patients, inducing interstitial fibrosis and tubule cell death. Renal tubule cell death is an important determinant of mortality in CKD. We focused on the regulation of cell-cycle-mediated protein expression to prevent cell death under chronic hypoxia in the kidneys of CKD patients. Paraffin-embedded kidney sections from patients with CKD (diabetes nephropathy, nephrosclerosis, or IgA nephropathy) were analyzed for the expression of hypoxia-inducible factor (HIF), thyroid hormone receptor (TR) β, or p21 and levels of interstitial fibrosis. Human renal proximal tubule cells were exposed to hypoxia and analyzed for the expression of HIF, TRβ, or p21 and the cell-cycle stage. TRβ expression was enhanced early on when fibrosis was not fully developed in the tubule cells of CKD patients. HIF1α bound to the TRβ promoter and directly induced its transcription. Further, HIF1α expression induced the expression of TRβ and inhibited cell-cycle progression. In the early stage of kidney injury, TRβ might act as a guardian to prepare and organize cell-cycle proliferation and prevent cell death. While the molecular mechanism that regulates the expression of cell-cycle regulators in renal tubule cells remains controversial, TRβ has strong potential as a new therapeutic target.

Retinopathy and Risk of Kidney Disease in Persons With Diabetes

Rationale & Objective

Retinopathy and chronic kidney disease (CKD) are typically considered microvascular complications of diabetes, and cardiovascular and cerebrovascular diseases are considered macrovascular complications; however, all may share common pathological mechanisms. This study quantified the association of retinopathy with risk of kidney disease and compared with the association with cardiovascular disease in persons with diabetes.

Study Design

Retrospective cohort study.

Setting & Participants

1,759 participants in the ARIC study who had diabetes at visit 4 and underwent retinal examination at visit 3.

Exposure

Retinopathy.

Outcome

Prevalent CKD (estimated glomerular filtration rate [eGFR] < 60 mL/min/1.73 m²), prevalent albuminuria (urinary albumin-creatinine ratio [UACR] > 30 mg/g), incident CKD, incident end-stage kidney disease (ESKD), incident coronary heart disease (CHD), and incident stroke.

Analytical Approach

The cross-sectional association of retinopathy with prevalent CKD and albuminuria was assessed by logistic regression. The associations between retinopathy, incident CKD, incident ESKD, incident CHD, and incident stroke were examined using Cox proportional hazards models. Seemingly unrelated regression was used to compare the strength of association between retinopathy and outcomes.

Results

During the median follow-up period of 14.2 years, 723 participants developed CKD, and there were 109 ESKD events, 399 CHD events, and 196 stroke events. Compared with the participants without retinopathy, participants with retinopathy were more likely to have reduced eGFR (OR, 1.56 [95% CI, 1.09-2.23]) and UACR > 30 mg/g (OR, 1.61 [95% CI, 1.24-2.10]). Retinopathy was associated with risk of incident CKD (HR, 1.22 [95% CI, 1.02-1.46]), ESKD (HR, 1.69 [95% CI, 1.11-2.58]), CHD (HR, 1.46 [95% CI, 1.15-1.84]), and stroke (HR, 1.43 [95% CI, 1.03-1.97]). A stronger relationship was found between retinopathy and CHD when compared with retinopathy and CKD (P = 0.03); all other associations were similar.

Limitations

Retinal examination and kidney measurements were taken at different visits.

Conclusions

The presence of retinopathy was associated with higher prevalence of kidney disease and higher risk of incident CKD, ESKD, and CHD. These results may suggest that a similar mechanism underlies the development of retinopathy and other adverse outcomes in diabetes.

LTBP4 affects renal fibrosis by influencing angiogenesis and altering mitochondrial structure

Transforming growth factor beta (TGFβ) signalling regulates extracellular matrix accumulation known to be essential for the pathogenesis of renal fibrosis; latent transforming growth factor beta binding protein 4 (LTBP4) is an important regulator of TGFβ activity. To date, the regulation of LTBP4 in renal fibrosis remains unknown. Herein, we report that LTBP4 is upregulated in patients with chronic kidney disease and fibrotic mice kidneys created by unilateral ureteral obstruction (UUO). Mice lacking the short LTBP4 isoform (Ltbp4S-/-) exhibited aggravated tubular interstitial fibrosis (TIF) after UUO, indicating that LTBP4 potentially protects against TIF. Transcriptomic analysis of human proximal tubule cells overexpressing LTBP4 revealed that LTBP4 influences angiogenic pathways; moreover, these cells preserved better mitochondrial respiratory functions and expressed higher vascular endothelial growth factor A (VEGFA) compared to wild-type cells under hypoxia. Results of the tube formation assay revealed that additional LTBP4 in human umbilical vein endothelial cell supernatant stimulates angiogenesis with upregulated vascular endothelial growth factor receptors (VEGFRs). In vivo, aberrant angiogenesis, abnormal mitochondrial morphology and enhanced oxidative stress were observed in Ltbp4S-/- mice after UUO. These results reveal novel molecular functions of LTBP4 stimulating angiogenesis and potentially impacting mitochondrial structure and function. Collectively, our findings indicate that LTBP4 protects against disease progression and may be of therapeutic use in renal fibrosis.

Εndothelial and microvascular function in CKD: Evaluation methods and associations with outcomes

BACKGROUND

Cardiovascular disease is the major cause of morbidity and mortality in patients with chronic kidney disease (CKD). Endothelial dysfunction, the hallmark of atherosclerosis, is suggested to be involved pathogenetically in cardiovascular and renal disease progression in these patients.

METHODS

This is a narrative review presenting the techniques and markers used for assessment of microvascular and endothelial function in patients with CKD and discussing findings of the relevant studies on the associations of endothelial dysfunction with co-morbid conditions and outcomes in this population.

RESULTS

Venous Occlusion Plethysmography was the first method to evaluate microvascular function; subsequently, several relevant techniques have been developed and used in patients with CKD, including brachial Flow-Mediated Dilatation, and more recently, Near-Infrared Spectroscopy and Laser Speckle Contrast Analysis. Furthermore, several circulating biomarkers are commonly used in clinical research. Studies assessing endothelial function using the above techniques and biomarkers suggest that endothelial dysfunction occurs early in CKD and contributes to the target organ damage, cardiovascular events, death and progression towards end-stage kidney disease.

CONCLUSIONS

Older and newer functional methods and several biomarkers have assessed endothelial dysfunction in CKD; accumulated evidence supports an association of endothelial dysfunction with outcomes. Future research with new, non-invasive and easily applicable methods could further delineate the role of endothelial dysfunction on cardiovascular and renal disease progression in patients with CKD.

Difference in risk factors of silent brain infarction between paroxysmal and persistent atrial fibrillation

•

Differences in risk factors for SBI between paroxysmal and persistent AF was studied.

•

NVAF patients (119 paroxysmal, 71 persistent) underwent brain MRI, TTE, and TEE.

•

DM and CKD, which represents microvascular disease, predicted SBI in paroxysmal AF.

•

There was no obvious therapeutic target for SBI after progression to persistent NVAF.

•

Intervention for DM and CKD from paroxysmal NVAF may prevent SBI and future stroke.

Background

Although silent brain infarction is an independent risk factor for subsequent symptomatic stroke and dementia in patients with nonvalvular atrial fibrillation, little is known regarding differences in risk factors for silent brain infarction between patients with paroxysmal and persistent nonvalvular atrial fibrillation.

Methods

This study population consisted of 190 neurologically asymptomatic patients (mean age, 64 ± 11 years) with nonvalvular atrial fibrillation (119 paroxysmal, 71 persistent) who were scheduled for catheter ablation. All patients underwent brain magnetic resonance imaging to screen for silent brain infarction prior to ablation. Transthoracic and transesophageal echocardiography was performed to screen for left atrial abnormalities (left atrial enlargement, spontaneous echo contrast, or left atrial appendage emptying velocity) and complex plaques in the aortic arch.

Results

Silent brain infarction was detected in 50 patients (26%) [26 patients (22%) in paroxysmal vs. 24 patients (34%) in persistent, p = 0.09]. Multiple logistic regression analysis indicated that age and diabetes mellitus or chronic kidney disease (estimated glomerular filtration rate < 60 mL/min/1.73 m²) were associated with silent brain infarction in patients with paroxysmal nonvalvular atrial fibrillation (p < 0.05), whereas no modifiable risk factors of silent brain infarction were observed in patients with persistent nonvalvular atrial fibrillation.

Conclusions

These findings suggest that intensive intervention for diabetes mellitus and renal impairment from the paroxysmal stage or ablation therapy at the time of paroxysmal stage to prevent progression to persistent nonvalvular atrial fibrillation may prevent silent brain infarction and consequently reduce the risk of future symptomatic stroke.

A combined morphometric approach to feature mouse kidney vasculature

Physiological kidney function is closely related to the state of the vascular network. Disorders, such as capillary rarefaction, predispose to chronic kidney disease (CKD). In this context, deepening of the methodologies for studying the renal vascular network can be of basic importance. To meet this need, numerous animal models and, in parallel, several methods have been developed. In this work we propose a protocol to accurately feature kidney vasculature in mouse, however, the same protocol is suitable to be applied also to other animal models. The approach is multiparametric and mainly based on micro-computed tomography (μCT) technique. Micro-ct allows to study in detail the vascular network of any organ by exploiting the possibility to perfuse the sample with a contrast agent. The proposed protocol provides a fast and reliable method to extract quantitative information from the μCT scan by using only the basic functions of the software supplied by the scanner without any additional analysis. Through iterative cropping of the scanned ROI and calculation of a sample-specific threshold we calculated that the average volume of a female BALB/c kidney of eighth weeks is 147.8 mm³ (5.4%). We also pointed out that the average volume of the vascular network is 4.9% (0.3%). In parallel we performed traditional histological and immunofluorescence techniques to integrate the information gained via μCT and to frame them in the tissue context. Vessel count on histological sections showed a different density in the different regions of the organ parenchyma, in detail, vessel density in the cortex was 19.03 ± 2.51 vessels/ROI while in the medulla it was 10.6 ± 1.7 vessels/ROI and 5.4 ± 1.3 vessels/ROI in the outer and inner medulla, respectively. We then studied vessel distribution in the renal parenchyma which showed that the 55% of vascular component is included in the cortex, the 30% in the outer medulla and the 15% in the inner medulla. Collectively, we propose an integrated approach that can be particularly useful in the preclinical setting to characterize the vasculature of any organ accurately and rapidly.

Renal artery stenosis

Renal artery stenosis is the most common secondary cause of hypertension and predominantly caused by atherosclerosis. In suspected patients, a non-invasive diagnosis with ultrasound is preferred. Asymptomatic, incidentally found RAS does not require revascularization. In symptomatic patients requiring revascularization, renal artery stenting is the preferred therapy. Selecting appropriate patients for revascularization requires careful consideration of lesion severity and is optimized with a multidisciplinary team. All patients with atherosclerotic RAS should be treated with guideline-directed medical therapy, including hypertension control, diabetes control, statins, antiplatelet therapy, smoking cessation and encouraging activity.

Acute Kidney Injury, Microvascular Rarefaction, and Estimated Glomerular Filtration Rate in Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

Animal studies suggest that microvascular rarefaction is a key factor in the acute kidney disease to CKD transition. Hence, delayed graft function appears as a unique human model of AKI to further explore the role of microvascular rarefaction in kidney transplant recipients. Here, we assessed whether delayed graft function is associated with peritubular capillary loss and evaluated the association between this loss and long-term kidney graft function.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This observational, retrospective cohort study included 61 participants who experienced delayed graft function and 130 who had immediate graft function. We used linear regression models to evaluate associations between delayed graft function and peritubular capillary density expressed as the percentage of efficient cortical area occupied by peritubular capillaries in pre- and post-transplant graft biopsies. eGFRs 1 and 3 years post-transplant were secondary outcomes.

RESULTS

Post-transplant biopsies were performed at a median of 113 days (interquartile range, 101-128) after transplantation. Peritubular capillary density went from 15.4% to 11.5% in patients with delayed graft function (median change, -3.7%; interquartile range, -6.6% to -0.8%) and from 19.7% to 15.1% in those with immediate graft function (median change, -4.5%; interquartile range, -8.0% to -0.8%). Although the unadjusted change in peritubular capillary density was similar between patients with and without delayed graft function, delayed graft function was associated with more peritubular capillary loss in the multivariable analysis (adjusted difference in change, -2.9%; 95% confidence interval, -4.0 to -1.8). Pretransplant peritubular capillary density and change in peritubular capillary density were associated with eGFR 1 and 3 years post-transplantation.

CONCLUSIONS

Perioperative AKI is associated with lower density in peritubular capillaries before transplantation and with loss of peritubular capillaries following transplantation. Lower peritubular capillary density is linked to lower long-term eGFR.

Cortical perfusion as assessed with contrast-enhanced ultrasound is lower in patients with chronic kidney disease than in healthy subjects but increases under low salt conditions

Background

Disturbances in renal microcirculation play an important role in the pathophysiology of chronic kidney disease (CKD), but the lack of easy accessible techniques hampers our understanding of the regulation of the renal microcirculation in humans. We assessed whether contrast-enhanced ultrasound (CEUS) can identify differences in cortical perfusion and alterations induced by different dietary salt intakes in CKD patients and controls.

Methods

Participants underwent CEUS twice: once after 5 days of high-salt (HS) intake, and again after 5 days of low salt (LS) diet. Sonovue® (0.015 mL/kg/min) was perfused as contrast agent and four consecutive destruction–reperfusion sequences were analysed per visit. The primary outcome measure was the (change in) mean perfusion index (PI) of the renal cortex.

Results

Forty healthy volunteers (mean age ± standard deviation 50 ± 8 years) and 18 CKD Stages 2–4 patients [aged 55 ± 11 years, estimated glomerular filtration rate (eGFR) 54 ± 28 mL/min/1.73 m2] were included and underwent CEUS without side effects. Under HS conditions, cortical PI was significantly lower in CKD patients [1618 ± 1352 versus 3176 ± 2278 arbitrary units (a.u) in controls, P = 0.034]. Under LS, renal PI increased in CKD patients (with +1098 to 2716 ± 1540 a.u., P = 0.048), whereas PI remained stable in controls. In the continuous analysis, PI correlated with eGFR (Spearman’s r = 0.54, P = 0.005) but not with age, sex, blood pressure or aldosterone levels.

Conclusions

CEUS identified important reductions in cortical micro-perfusion in patients with moderate CKD. Lowering salt intake increased perfusion in CKD patients, but not in controls, underlining the benefits of an LS diet in CKD patients. Whether a low PI is an early sign of kidney damage and predicts renal function decline needs further study.

Microvascular disease in chronic kidney disease: the base of the iceberg in cardiovascular comorbidity

Chronic kidney disease (CKD) is a relentlessly progressive disease with a very high mortality mainly due to cardiovascular complications. Endothelial dysfunction is well documented in CKD and permanent loss of endothelial homeostasis leads to progressive organ damage. Most of the vast endothelial surface area is part of the microcirculation, but most research in CKD-related cardiovascular disease (CVD) has been devoted to macrovascular complications. We have reviewed all publications evaluating structure and function of the microcirculation in humans with CKD and animals with experimental CKD. Microvascular rarefaction, defined as a loss of perfused microvessels resulting in a significant decrease in microvascular density, is a quintessential finding in these studies. The median microvascular density was reduced by 29% in skeletal muscle and 24% in the heart in animal models of CKD and by 32% in human biopsy, autopsy and imaging studies. CKD induces rarefaction due to the loss of coherent vessel systems distal to the level of smaller arterioles, generating a typical heterogeneous pattern with avascular patches, resulting in a dysfunctional endothelium with diminished perfusion, shunting and tissue hypoxia. Endothelial cell apoptosis, hypertension, multiple metabolic, endocrine and immune disturbances of the uremic milieu and specifically, a dysregulated angiogenesis, all contribute to the multifactorial pathogenesis. By setting the stage for the development of tissue fibrosis and end organ failure, microvascular rarefaction is a principal pathogenic factor in the development of severe organ dysfunction in CKD patients, especially CVD, cerebrovascular dysfunction, muscular atrophy, cachexia, and progression of kidney disease. Treatment strategies for microvascular disease are urgently needed.

Intensive BP Control and eGFR Declines: Are These Events Due to Hemodynamic Effects and Are Changes Reversible?

PURPOSE OF REVIEW

Acute declines in estimated glomerular filtration rate (eGFR) are often observed during intensive blood pressure (BP) lowering. This review focuses on identifying the various mechanisms of eGFR decline associated with intensive BP lowering and evaluates the evidence linking BP control with kidney and cardiovascular (CV) outcomes.

RECENT FINDINGS

In 2017, the American College of Cardiology and the American Heart Association (ACC/AHA) began recommending treatment of all individuals to a BP target of < 130/80 mmHg. Since then, multiple post hoc analyses of BP trials have associated intensive BP lowering with acute declines in kidney function and acute kidney injury; whether these represent reversible changes in the kidney is still debated. There is ample evidence that intensive BP lowering is associated with declines in eGFR. The clinical implications of these events remain unclear. Individualizing the risks and benefits of intensive BP therapy continues to be warranted.

Aberrant Differentiation of Human Pluripotent Stem Cell-Derived Kidney Precursor Cells inside Mouse Vascularized Bioreactors

BACKGROUND

Numerous studies have documented the in vitro differentiation of human pluripotent stem cells (hPSCs) into kidney cells. Fewer studies have followed the fates of such kidney precursor cells (KPCs) inside animals, a more life-like setting. Here, we tested the hypothesis that implanting hPSC-derived KPCs into an in vivo milieu surgically engineered to be highly vascular would enhance their maturation into kidney tissues.

METHODS

3D printed chambers containing KPCs were implanted into the thighs of adult immunodeficient mice. In some chambers, an arterial and venous flow-through (AVFT) was surgically fashioned. After 3 weeks and 3 months, implants were studied by histology, using qualitative and quantitative methods.

RESULTS

After 3 weeks, chambers containing AVFTs were richer in small vessels than contralateral chambers without AVFTs. Glomeruli with capillary loops and diverse types of tubules were detected in all chambers. At 3 months, chambers contained only rudimentary tubules and glomeruli that appeared avascular. In chambers with AVFTs, prominent areas of muscle-like cells were also detected near tubules and the abnormal tissues immunostained for transforming growth factor β1. These features have similarities to renal dysplasia, a typical histological signature of human congenital kidney malformations.

CONCLUSIONS

This study urges a note of caution regarding the in vivo fates of hPSC-derived kidney precursors, with pathological differentiation appearing to follow a period of increased vascularity.

Alk1 haploinsufficiency causes glomerular dysfunction and microalbuminuria in diabetic mice

Endothelial dysfunction has been shown to play an important role in the pathogenesis of glomerular damage during diabetic kidney disease (DKD). As such, a better understanding of the molecular mechanisms involved in glomerular endothelial dysfunctions could provide novel therapeutic strategies for the prevention of DKD. We have previously shown that Alk1/BMP9 signaling plays an important function to maintain vascular integrity in diabetic animals. As such, we evaluated the effects of Alk1 suppression on glomerular endothelial function in diabetic mice. In the present study, we used mice with conditional heterozygote deletion of Alk1 in the endothelium (Alk1ΔEC) to evaluate the role of Alk1 on kidney function during STZ-induced diabetes. DKD was investigated in diabetic control and Alk1ΔEC mice euthanized eight weeks after the onset of diabetes. We showed that Alk1 expression is reduced in the glomeruli of human DKD patients. While renal function was not altered in Alk1ΔEC non-diabetic mice, we showed that Alk1 haploinsufficiency in the glomerular endothelium leads to microalbuminuria, thickening of the glomerular basement membrane, glomerular apoptosis and podocyte loss in diabetic mice. These data suggest that Alk1 is important for the proper function of glomerular endothelial cells and that decreased Alk1 combined with chronic hyperglycemia can impair renal function.

Evaluation of profibrotic gene transcription in renal tissues from cats with naturally occurring chronic kidney disease

BACKGROUND

Increased gene transcription of hypoxia-induced mediators of fibrosis in renal tissue has been identified in experimentally induced, ischemic chronic kidney disease (CKD).

OBJECTIVE

To characterize hypoxia-induced profibrotic pathways in naturally occurring CKD in cats.

ANIMALS

Twelve client-owned cats with CKD and 8 healthy control cats.

METHODS

In this prospective, cross-sectional study, bilateral renal tissue samples were assessed histologically for inflammation, tubular atrophy, and fibrosis, and by reverse transcription-quantitative PCR for characterization of transcript levels of hypoxia-inducible factor-1α (HIF1A), matrix metalloproteinases-2 (MMP2), -7 (MMP7), and -9 (MMP9), tissue inhibitor of metalloproteinase-1 (TIMP1), transforming growth factor-β1 (TGFB1), and vascular endothelial growth factor-A (VEGFA). Linear mixed models were used to compare gene transcription between diseased and healthy kidneys, and to examine the association between transcript levels and serum creatinine concentration for all cats, and between transcript levels and histologic scores of diseased kidneys.

RESULTS

Kidneys from cats with CKD had significantly higher transcript levels of HIF1A, MMP2, MMP7, MMP9, TIMP1, and TGFB1 (all P < .001), and lower levels of VEGFA (P = .006) than those from control cats. Transcript levels of MMP7 (P = .05) and TIMP1 (P = .005) were positively associated with serum creatinine in cats with CKD, but not in control cats. In diseased kidneys, transcript levels of MMP2 (P = .002), MMP7 (P = .02), and TIMP1 (P = .02) were positively, whereas those of VEGFA (P = .003) were negatively, associated with histologic score severity.

CONCLUSION AND CLINICAL SIGNIFICANCE

Evaluation of the expression of the corresponding proteins in larger populations could identify therapeutic targets and/or biomarkers of tubulointerstitial fibrosis in cats.

Open microfluidic coculture reveals paracrine signaling from human kidney epithelial cells promotes kidney specificity of endothelial cells

Endothelial cells (ECs) from different human organs possess organ-specific characteristics that support specific tissue regeneration and organ development. EC specificity is identified by both intrinsic and extrinsic cues, among which the parenchyma and organ-specific microenvironment are critical contributors. These extrinsic cues are, however, largely lost during ex vivo cultures. Outstanding challenges remain to understand and reestablish EC organ specificity for in vitro studies to recapitulate human organ-specific physiology. Here, we designed an open microfluidic platform to study the role of human kidney tubular epithelial cells in supporting EC specificity. The platform consists of two independent cell culture regions segregated with a half wall; culture media are added to connect the two culture regions at a desired time point, and signaling molecules can travel across the half wall (paracrine signaling). Specifically, we report that in the microscale coculture device, primary human kidney proximal tubule epithelial cells (HPTECs) rescued primary human kidney peritubular microvascular EC (HKMEC) monolayer integrity and fenestra formation and that HPTECs upregulated key HKMEC kidney-specific genes (hepatocyte nuclear factor 1 homeobox B, adherens junctions-associated protein 1, and potassium voltage-gated channel subfamily J member 16) and endothelial activation genes (vascular cell adhesion molecule-1, matrix metalloproteinase-7, and matrix metalloproteinase-10) in coculture. Coculturing with HPTECs also promoted kidney-specific genotype expression in human umbilical vein ECs and human pluripotent stem cell-derived ECs. Compared with culture in HPTEC conditioned media, coculture of ECs with HPTECs showed increased upregulation of kidney-specific genes, suggesting potential bidirectional paracrine signaling. Importantly, our device is compatible with standard pipettes, incubators, and imaging readouts and could also be easily adapted to study cell signaling between other rare or sensitive cells.

Regression of Peritubular Capillaries Coincides with Angiogenesis and Renal Cyst Growth in Experimental Polycystic Kidney Disease

Background/Aim

The natural history of the renal microvasculature changes in PKD is not known. The aim of this study was to test the hypothesis that angiogenesis is coupled with kidney cyst expansion, and the loss of peritubular capillary networks precedes the onset of interstitial fibrosis.

Methods

The renal microvasculature (RECA-1 and CD34) was evaluated in groups of Lewis polycystic kidney (LPK) rats and juvenile cystic kidney (jck) mice during the early, mid and late stage of disease. In addition, LPK rats and jck mice received sirolimus to determine if the reduction in renal cyst growth is in part mediated by the suppression of angiogenesis.

Results

In LPK rats, the loss of peritubular capillaries occurred in early-stage disease and paralleled cyst formation whereas in jck mice it was delayed to the mid stage. In both models, vasa recta were displaced by growing cysts and regressed in LPK rats with disease progression but lengthened in jck mice. Cortical and medullary capillary neoangiogenesis occurred during the early stage in both models and persisted with progression. Treatment with sirolimus reduced cyst enlargement but did not alter the progression of renal microvasculature changes in either model.

Conclusion

Regression of peritubular capillaries and disruption of vasa recta occur in parallel with angiogenesis and the progressive enlargement of kidney cysts. These data suggest that the regrowth of peritubular capillaries together with inhibition of angiogenesis are potential strategies to be considered in the treatment of PKD.

Effects of endothelial progenitor cells transplantation on hyperlipidemia associated kidney damage in ApoE knockout mouse model

Background

Hyperlipidaemia causes kidney damage over the long term. We investigated the effect of the administration of endothelial progenitor cells (EPCs) on the progression of kidney damage in a mouse model of hyperlipidaemia.

Methods

Apolipoprotein E-knockout (ApoE^−/−) mice were treated with a high-cholesterol diet after spleen resection. Twenty-four weeks later, the mice were divided into two groups and intravenously injected with PBS or EPCs. Six weeks later, the recruitment of EPCs to the kidney was monitored by immunofluorescence. The lipid, endothelial cell, and collagen contents in the kidney were evaluated by specific immunostaining. The protein expression levels of transforming growth factor-β (TGF-β), Smad2/3, and phospho-Smad3 (p-smad3) were detected by western blot analysis.

Results

ApoE^−/− mice treated with a high-fat diet demonstrated glomerular lipid deposition, enlargement of the glomerular mesangial matrix, endothelial cell enlargement accompanied by vacuolar degeneration and an area of interstitial collagen in the kidney. Six weeks after EPC treatment, only a few EPCs were detected in the kidney tissues of ApoE^−/− mice, mainly in the kidney interstitial area. No significant differences in TGF-β, p-smad3 or smad2/3 expression were found between the PBS group and the EPC treatment group (TGF-β expression, PBS group: 1.06 ± 0.09, EPC treatment group: 1.09 ± 0.17, P = 0.787; p-smad3/smad2/3 expression: PBS group: 1.11 ± 0.41, EPC treatment group: 1.05 ± 0.33, P = 0.861).

Conclusions

Our findings demonstrate that hyperlipidaemia causes basement membrane thickening, glomerulosclerosis and the vascular degeneration of endothelial cells. The long-term administration of EPCs substantially has limited effect in the progression of kidney damage in a mouse model of hyperlipidaemia.

Body Fluid-Independent Effects of Dietary Salt Consumption in Chronic Kidney Disease

The average dietary salt (i.e., sodium chloride) intake in Western society is about 10 g per day. This greatly exceeds the lifestyle recommendations by the WHO to limit dietary salt intake to 5 g. There is robust evidence that excess salt intake is associated with deleterious effects including hypertension, kidney damage and adverse cardiovascular health. In patients with chronic kidney disease, moderate reduction of dietary salt intake has important renoprotective effects and positively influences the efficacy of common pharmacological treatment regimens. During the past several years, it has become clear that besides influencing body fluid volume high salt also induces tissue remodelling and activates immune cell homeostasis. The exact pathophysiological pathway in which these salt-induced fluid-independent effects contribute to CKD is not fully elucidated, nonetheless it is clear that inflammation and the development of fibrosis play a major role in the pathogenic mechanisms of renal diseases. This review focuses on body fluid-independent effects of salt contributing to CKD pathogenesis and cardiovascular health. Additionally, the question whether better understanding of these pathophysiological pathways, related to high salt consumption, might identify new potential treatment options will be discussed.

The Association of Angiogenesis Markers With Acute Kidney Injury and Mortality After Cardiac Surgery

RATIONALE & OBJECTIVE

The process of angiogenesis after kidney injury may determine recovery and long-term outcomes. We evaluated the association of angiogenesis markers with acute kidney injury (AKI) and mortality after cardiac surgery.

STUDY DESIGN

Prospective cohort.

SETTING & PARTICIPANTS

1,444 adults undergoing cardiac surgery in the TRIBE-AKI (Translational Research Investigating Biomarker Endpoints for Acute Kidney Injury) cohort.

EXPOSURES

Plasma concentrations of 2 proangiogenic markers (vascular endothelial growth factor A [VEGF] and placental growth factor [PGF]) and 1 antiangiogenic marker (soluble VEGF receptor 1 [VEGFR1]), measured pre- and postoperatively within 6 hours after surgery.

OUTCOMES

AKI, long AKI duration (≥7 days), and 1-year all-cause mortality.

ANALYTICAL APPROACH

Multivariable logistic regression.

RESULTS

Following cardiac surgery, plasma VEGF concentrations decreased 2-fold, and PGF and VEGFR1 concentrations increased 1.5- and 8-fold, respectively. There were no meaningful associations of preoperative concentrations of angiogenic markers with outcomes of AKI and mortality. Higher postoperative VEGF and PGF concentrations were independently associated with lower odds of AKI (adjusted ORs of 0.89 [95% CI, 0.82-0.98] and 0.69 [95% CI, 0.55-0.87], respectively), long AKI duration (0.65 [95% CI, 0.49-0.87] and 0.48 [95% CI, 0.28-0.82], respectively), and mortality (0.74 [95% CI, 0.62-0.89] and 0.46 [95% CI, 0.31-0.68], respectively). In contrast, higher postoperative VEGFR1 concentrations were independently associated with higher odds of AKI (1.56; 95% CI, 1.31-1.87), long AKI duration (1.75; 95% CI, 1.09-2.82), and mortality (2.28; 95% CI, 1.61-3.22).

LIMITATIONS

Angiogenesis markers were not measured after hospital discharge, so we were unable to determine long-term trajectories of angiogenesis marker levels during recovery and follow-up.

CONCLUSIONS

Higher levels of postoperative proangiogenic markers, VEGF and PGF, were associated with lower AKI and mortality risk, whereas higher postoperative antiangiogenic VEGFR1 levels were associated with higher risk for AKI and mortality.

Astaxanthin ameliorates renal interstitial fibrosis and peritubular capillary rarefaction in unilateral ureteral obstruction

Loss of peritubular capillaries is a notable feature of progressive renal interstitial fibrosis. Astaxanthin (ASX) is a natural carotenoid with various biological activities. The present study aimed to evaluate the effect of ASX on unilateral ureteral obstruction (UUO)‑induced renal fibrosis in mice. For that purpose, mice were randomly divided into five treatment groups: Sham, ASX 100 mg/kg, UUO, UUO + ASX 50 mg/kg and UUO + ASX 100 mg/kg. ASX was administered to the mice for 7 or 14 days following UUO. The results demonstrated that UUO‑induced histopathological changes in the kidney tissue were prevented by ASX. Renal function was improved by ASX treatment, as evidenced by decreased blood urea nitrogen and serum creatinine levels. Furthermore, the extent of renal fibrosis and collagen deposition induced by UUO was suppressed by ASX. The levels of collagen I, fibronectin and α‑smooth muscle actin were increased by UUO in mice or by transforming growth factor (TGF)‑β1 treatment in NRK‑52E cells, and were reduced by ASX administration. In addition, ASX inhibited the UUO‑induced decrease in peritubular capillary density by upregulating vascular endothelial growth factor and downregulating thrombospondin 1 levels. Inactivation of the TGF‑β1/Smad signaling pathway was involved in the anti‑fibrotic mechanism of ASX in UUO mice and TGF‑β1‑treated NRK‑52E cells. In conclusion, ASX attenuated renal interstitial fibrosis and peritubular capillary rarefaction via inactivation of the TGF‑β1/Smad signaling pathway.

Hydrogen Sulfide Protects Hyperhomocysteinemia-Induced Renal Damage by Modulation of Caveolin and eNOS Interaction

The accumulation of homocysteine (Hcy) during chronic kidney failure (CKD) can exert toxic effects on the glomeruli and tubulo-interstitial region. Among the potential mechanisms, the formation of highly reactive metabolite, Hcy thiolactone, is known to modify proteins by N-homocysteinylation, leading to protein degradation, stress and impaired function. Previous studies documented impaired nitric oxide production and altered caveolin expression in hyperhomocysteinemia (HHcy), leading to endothelial dysfunction. The aim of this study was to determine whether Hhcy homocysteinylates endothelial nitric oxide synthase (eNOS) and alters caveolin-1 expression to decrease nitric oxide bioavailability, causing hypertension and renal dysfunction. We also examined whether hydrogen sulfide (H₂S) could dehomocysteinylate eNOS to protect the kidney. WT and Cystathionine β-Synthase deficient (CBS+/-) mice representing HHcy were treated without or with sodium hydrogen sulfide (NaHS), a H₂S donor (30 µM), in drinking water for 8 weeks. Hhcy mice (CBS+/-) showed low levels of plasma H₂S, elevated systolic blood pressure (SBP) and renal dysfunction. H₂S treatment reduced SBP and improved renal function. Hhcy was associated with homocysteinylation of eNOS, reduced enzyme activity and upregulation of caveolin-1 expression. Further, Hhcy increased extracellular matrix (ECM) protein deposition and disruption of gap junction proteins, connexins. H₂S treatment reversed the changes above and transfection of triple genes producing H₂S (CBS, CSE and 3MST) showed reduction of vascular smooth muscle cell proliferation. We conclude that during Hhcy, homocysteinylation of eNOS and disruption of caveolin-mediated regulation leads to ECM remodeling and hypertension, and H₂S treatment attenuates renovascular damage.

Association of different glucose traits with kidney function decline risk in a Chinese community-based population without chronic kidney disease

Background

Chronic kidney disease (CKD) has become a major issue worldwide and hyperglycemia is known as an important risk factor responsible for CKD progression. Few studies have investigated whether fasting plasma glucose (FPG) could predict kidney function decline (KFD) risk better than postprandial plasma glucose, and vice versa. In this study, we investigated the roles of FPG and 2-hour plasma glucose (2 h-PG) in predicting KFD risk in a Chinese community-based population without baseline deterioration of kidney functions.

Methods

Subjects with normal kidney function from an atherosclerosis cohort in Beijing, China were followed up for 2.3 years. The outcome was KFD (a drop in glomerular filtration rate category accompanied by 25% or greater decline of estimated glomerular filtration rate from the baseline or a sustained decline of more than 5 mL/min/1.73 m²/year rate).

Results

A total of 3,738 subjects were included of which, 7.7% of the subjects suffered from KFD. After covariates adjustments, both FPG (OR =1.23, P<0.001) and 2 h-PG (OR =1.07, P<0.001) were associated with KFD. Furthermore, FPG was independent of 2 h-PG to predict KFD (OR =1.26, P<0.001). Subgroup analyses and interaction tests including diabetes mellitus, after adjusting all covariates, revealed no significant heterogeneity among analyzed subgroups. We also found subjects with FPG level of 6.1–7.0 mmol/L and >7.0 mmol/L had 1.83 times and 2.51 times KFD risk respectively, compared to subjects with FPG level <5.6 mmol/L.

Conclusion

FPG was superior to 2 h-PG in predicting KFD in a Chinese community-based population without CKD. FPG screening may be an important measure for CKD primary prevention even in subjects with impaired fasting glucose.

Modified scanning electron microscopy reveals pathological crosstalk between endothelial cells and podocytes in a murine model of membranoproliferative glomerulonephritis

This study evaluated endothelial cells and podocytes, both being primary components of the glomerular filtration barrier, in the progression of membranoproliferative glomerulonephritis (MPGN) using modified scanning electron microscopy (mSEM) analysis. BXSB/MpJ-Yaa model mice exhibited autoimmune-mediated MPGN characterised by elevated serum autoantibody levels, albuminuria, renal dysfunctional parameters, and decreased glomerular endothelial fenestrations (EF) and podocyte foot process (PFP) effacement with immune cell infiltration. Similar to transmission electron microscopy, mSEM revealed a series of pathological changes in basement membrane and densities of EF and PFP in BXSB/MpJ-Yaa compared with control BXSB/MpJ at different stages. Further, immunopositive area of endothelial marker (CD34), podocyte functional molecules (Nephrin, Podocin, Synaptopodin, and Wilms’ tumour 1 (WT1)), and vascular endothelial growth factor A (VEGF A) significantly decreased in the glomerulus of BXSB/MpJ-Yaa compared with BXSB at final stage. The indices of glomerular endothelial injuries (EF density and immunopositive area of CD34 and VEGF A) and podocyte injuries (PEP density and immunopositive area of podocyte functional molecules) were also significantly correlated with each other and with indices of autoimmune disease and renal dysfunction. Thus, our results elucidated the pathological crosstalk between endothelial cells and podocytes in MPGN progression and the usefulness of mSEM for glomerular pathological analysis.

Effects of aristolochic acid I and/or hypokalemia on tubular damage in C57BL/6 rat with aristolochic acid nephropathy

BACKGROUND/AIMS

This study was designed to investigate the roles of aristolochic acid I (AA-I) and hypokalemia in acute aristolochic acid nephropathy (AAN).

METHODS

After an adaptation period (1 week), a total of 40 C57BL/6 mice (male, 8 weeks old) were divided into four groups: I (control group), II (low potassium [K] diet), III (normal K diet with administration of AA-I [10 mg/kg weight]), and IV (low K diet with AA-I). After collecting 24 hours of urine at 2 weeks, the mice were sacrificed, and their blood and kidneys were obtained to perform immunochemical staining and/or Western blot analysis.

RESULTS

Proteinuria, glycosuria, and increased fractional excretion of sodium and K were prominent in groups III and IV (p &lt; 0.05). Diffuse swelling and poor staining of collecting duct epithelial cells were evident in the medullas of group II. Typical lesions of toxic acute tubular injury were prominent in the cortices of groups III and IV. Α-Smooth muscle actin (α-SMA) was higher in the cortices of the mice in groups III and IV versus group II (p &lt; 0.05), and higher in the medullas of group IV than groups I and III (p &lt; 0.05). E-cadherin was higher in the cortices of groups III and IV compared to group I (p &lt; 0.05). The F4/80 value was higher in the cortices and medullas of groups II, III, and IV compared to group I (p &lt; 0.05), particularly in the case of group II.

CONCLUSIONS

AA-I can induce acquired Fanconi syndrome in the acute stage of AAN. Macrophages appear to play a key role in the pathogenesis of AAN and hypokalemic nephropathy. It remains uncertain whether hypokalemia plays any role in AAN and hypokalemia.

Cobalt treatment does not prevent glomerular morphological alterations in type 1 diabetic rats

Early renal morphological alterations including glomerular hypertrophy and mesangial expansion occur in diabetic kidney disease and correlate with various clinical manifestations of diabetes. The present study was designed to investigate the influence of pharmacological modulation of HIF-1α (hypoxia inducible factor-1 alpha) protein levels, on these glomerular changes in rodent model of type 1 diabetes. Male wistar rats were made diabetic (Streptozotocin 45 mg/kg; i.p.) and afterwards treated with HIF activator cobalt chloride for 4 weeks. Renal function was assessed by serum creatinine, albumin, proteinuria levels, oxidative stress: reduced glutathione levels and catalase activity, and renal tissue HIF-1α protein levels were determined by ELISA assay. Histological analysis of kidney sections was done by haematoxylin and eosin (glomeruli diameter), periodic acid Schiff (mesangial expansion and glomerulosclerosis) and sirius red (fibrosis, tubular dilation) staining. Diabetes rats displayed reduced serum albumin levels, marked proteinuria, lower kidney reduced glutathione content, glomerular hypertrophy, glomerulosclerosis, mesangial expansion, tubular dilation and renal fibrosis. Cobalt chloride treatment normalised renal HIF-1α protein levels, reduced development of proteinuria and tubulo-interstitial fibrosis, but the glomerular morphological alterations such as glomerulosclerosis, mesangial expansion, increased glomerular diameter and tubular vacoulations were not abrogated in diabetic kidneys. Glomerular morphological abnormalities might precede the development of proteinuria and renal fibrosis in experimental model of type 1 diabetes. Pharmacological modulation of renal HIF-1α protein levels does not influence glomerular and tubular dilatory changes in diabetic kidney disease.

Vitamin D Upregulates Endothelin-1, ETBR, eNOS mRNA Expression and Attenuates Vascular Remodelling and Ischemia in Kidney Fibrosis Model in Mice Vitamin D Upregulates Endothelin-1, ETBR, eNOS mRNA Expression and Attenuates Vascular Remodelling and Ischemia in Kidney Fibrosis Model in Mice

We examined the upregulation of ET-1/ETBR/eNOS signaling in renoprotective effect of vitamin D in kidney fibrosis model in mice using unilateral ureteral obstruction (UUO). One group was treated with intraperitoneal injection of 0.125 mg/kg of Calcitriol (UUO+VD). Vascular remodeling was quantified based on lumen area and lumen/wall area ratio (LWAR) of intrarenal arteries using Sirius Red staining. ET-1, ETBR, eNOS, CD31 and VEGF mRNA expressions were quantified using qRT-PCR. Focusing on endothelin-1 (ET-1) signaling in endothelial cells (EC), siRNA of ET-1 was performed in human umbilical vein endothelial cells (HUVEC) for reducing ET-1 expression. Then HUVECs were treated with and without 100 nM Calcitriol treatment in hypoxic and normoxic conditions to elucidate ET-1/eNOS signaling. Our in vivo study revealed vascular remodeling and renal ischemia attenuation after Calcitriol treatment. Vascular remodeling was attenuated in the UUO+VD group as shown by increasing lumen areas and LWAR in intrarenal arteries. These findings were associated with significant higher CD31 and VEGF mRNA expression compared to the UUO group. Vitamin D treatment also increased ET-1, ETBR and eNOS mRNA expressions. Our in vitro study demonstrated Calcitriol induced ET-1 and eNOS mRNA expressions upregulation in HUVEC under normoxic and hypoxic condition. Meanwhile, siRNA for ET-1 inhibited the upregulation of eNOS mRNA expression after Calcitriol treatment. Vitamin D ameliorates kidney fibrosis through attenuating vascular remodeling and ischemia with upregulating ET-1/ETBR and eNOS expression.

Vascular homeostasis in early (normo-albuminuric) type 2 diabetic nephropathy

Background: Renal microvascular disease and reduction in peritubular capillary flow are generally observed in type 2 diabetic nephropathy (DN). Earlier therapeutic strategy with vasodilators has improved renal function in normo-albuminuric type 2 DN. Objective: Study the mechanism of vascular homeostasis in twenty patients associated with normo-albuminuric type 2 DN. Results: Angiogenic factors were observed in normo-albuminuric type 2 DN, where vascular endothelial growth factor (VEGF), was 420 ± 341 vs. 428±291 pg/mL (normal), and vascular endothelial growth factor - receptor 1 (VEGF-R1) was 60±12 vs. 49±5 ng/mL (normal), which were not significantly different from the controls. Anti-angiogenic factors were observed in normo-albuminuric type 2 DN, where angiopoietin-2, was 2309+1125 vs. 1671±835 pg/mL (normal), and vascular endothelial growth factor - receptor 2 (VEGF-R2) was 5715±1400 vs.6126 ±1060 ng/mL (normal), which were not significantly different from the controls. Conclusion: The mechanism of vascular homeostasis was adequately functional in normo-albuminuric type 2 DN. This mechanism may explain the positive response to vasodilators and improved renal function in early stage of type 2 DN following the vasodilator treatment.