Renal Microvasculature Research Articles

Combining fractional flow reserve and the index of microcirculatory resistance for prognosis prediction in renal artery stenosis interventions: a feasibility sub-study of FAIR-pilot trial

Abstract Background Interventional therapies for renal artery stenosis (RAS) was debatable in previous randomized trials. Fractional flow reserve (FFR), while useful in coronary interventions, does not assess microcirculatory status, which may be critical in RAS. The index of microcirculatory resistance (IMR) provides additional microvascular information, which has not been used in RAS patients. Purpose To investigate the feasibility of IMR measurement in RAS patients and the association with the outcome. Methods FAIR-pilot study is a multicenter pilot randomized controlled trial exploring the application of FFR to guide the renal artery stenting in patients with renovascular hypertension (NCT05732077). A pressure-temperature sensor guidewire was used to measure the IMR. To derive mean transit time at rest, thermodilution curves were obtained by 3 injections of 4 mL of room temperature saline down the renal artery. Hyperemia was induced using dopamine 50μg/kg bolus to the renal artery. The IMR was calculated as distal arterial pressure (Pd) x mean transit time during hyperemia (TmnH) (Figure 1). Prognostic evaluation was based on improvements in postoperative blood pressure, which was assessed using both ambulatory blood pressure monitor (ABPM) and anti-hypertensive medication number, along with renal function, as determined by the estimated glomerular filtration rate (eGFR). Results The IMR was measured among five patients enrolled in FAIR-pilot study. As shown in Table 1 and 2, stent implantation was conducted on five lesions across patients 1 to 4 based on renal FFR < 0.8, with each experiencing varying degrees of improved blood pressure control subsequently. Patient 5 did not receive a stent and was lost to follow-up. At three-month, the recorded decrease in systolic blood pressure ranged from a maximum of 34 mmHg to a minimum decrease of -6 mmHg among the four patients. The antihypertensive medication number showed a maximum reduction of 2 and no change as the minimum. We observed a correlation between baseline IMR and baseline renal function. No significant change in IMR was noted after interventional procedures. Preliminary findings suggest that IMR measurement is feasible in patients with RAS, while the ∆T (temperature change time) was very small, which potentially increasing the measurement bias. Conclusion The study suggests measuring IMR in patients with RAS is feasible and can offer information into the renal microvasculature. However, the small ∆T encountered during measurement may introduce increased bias, which should be considered when interpreting results.

Nephropathy induced by cisplatin results from mitochondrial disruption, impaired energy metabolism, altered expression of renal transporters, and accumulation of urinary toxins

BackgroundThe administration of platinum-based drugs such as cisplatin and its derivatives, which are frequently used during clinical chemotherapy, is highly restricted due to the incidence of nephrotoxicity. The present study focused on investigating cisplatin-induced nephrotoxicity from the perspective of energy metabolism, renal transporter expression and urinary toxin accumulation. MethodsThis study investigated cisplatin's toxic effects, including nephrotoxicity, cardiotoxicity, hepatotoxicity, pulmonary toxicity, and splenotoxicity. We used transmission electron microscopy (TEM) and scanning electron microscopy (SEM) to characterize the accumulation of cisplatin in the kidney and the structure of renal mitochondria. The production of reactive oxygen species (ROS) induced by cisplatin in renal tubular epithelial cells was evaluated by in vitro experiments, and apoptosis of renal tubular epithelial cells and alterations to the renal microvasculature were assessed. Metabolites associated with the glycolytic and tricarboxylic acid pathways were measured, and renal transporters expression, autophagy, and urinary toxins (UTs) accumulation were also assessed. ResultsOur results reveal that cisplatin-induced varying degrees of damage to the heart, liver, spleen, lungs, and kidneys, including inflammatory and fibrotic damage. Accumulation of cisplatin in renal mitochondria disrupted mitochondrial structure and mitochondrial function, as evidenced by decreased levels of glucose 6-phosphate and ribose 5-phosphate and elevated levels of isocitric acid. Cisplatin-induced accumulation of ROS in renal tubular epithelial cells led to apoptosis and, ultimately, constriction or loss of renal microvasculature. Furthermore, dysregulation of renal transporter expression, activation of autophagy and increased accumulation of UTs was observed. ConclusionAccumulation of cisplatin in the kidney led to damage to mitochondrial structure and function, apoptosis of renal tubular epithelial cells, constriction or loss of renal microvasculature, dysfunction of renal transporters, activation of autophagy, and accumulation of UTs.

Sepsis induces heterogeneous transcription of coagulation- and inflammation-associated genes in renal microvasculature

BackgroundAcute kidney injury (AKI) in sepsis patients increases patient mortality. Endothelial cells are important players in the pathophysiology of sepsis-associated AKI (SA-AKI), yet knowledge regarding their spatiotemporal involvement in coagulation disbalance and leukocyte recruitment is lacking. This study investigated the identity and kinetics of responses of different microvascular compartments in kidney cortex in response to SA-AKI. MethodsLaser microdissected arterioles, glomeruli, peritubular capillaries, and postcapillary venules from kidneys of mice subjected to cecal ligation and puncture (CLP) were analyzed using RNA sequencing. Differential expression and pathway enrichment analyses identified genes involved in coagulation and inflammation. A selection of these genes was evaluated by RT-qPCR in microvascular compartments of renal biopsies from patients with SA-AKI. The role of two identified genes in lipopolysaccharide-induced endothelial coagulation and inflammatory activation were determined in vitro in HUVEC using siRNA-based gene silencing. ResultsCLP-sepsis in mice induced altered expression of approximately 400 genes in the renal microvasculature, with microvascular compartments exhibiting unique spatiotemporal responses. In mice, changes in gene expression related to coagulation and inflammation were most extensive in glomeruli at early and intermediate time points, with high induction of Plat, Serpine1, Thbd, Icam1, Stat3, and Ifitm3. In human SA-AKI, PROCR and STAT3 were induced in postcapillary venules, while SERPINE1 expression was diminished. IFITM3 was increased in arterioles and glomeruli. In vitro studies revealed that STAT3 and IFITM3 partly control endothelial coagulation and inflammatory activation. ConclusionRenal microvascular compartments in mice and humans exhibited heterogeneous changes in coagulation- and inflammation-related gene expression in response to SA-AKI. Additional research should aim at understanding the functional consequences of the here described heterogeneous microvascular responses to establish the usefulness of identified genes as therapeutic targets in SA-AKI.

Unveiling the pathogenesis and therapeutic approaches for diabetic nephropathy: insights from panvascular diseases.

Diabetic nephropathy (DN) represents a significant microvascular complication in diabetes, entailing intricate molecular pathways and mechanisms associated with cardiorenal vascular diseases. Prolonged hyperglycemia induces renal endothelial dysfunction and damage via metabolic abnormalities, inflammation, and oxidative stress, thereby compromising hemodynamics. Concurrently, fibrotic and sclerotic alterations exacerbate glomerular and tubular injuries. At a macro level, reciprocal communication between the renal microvasculature and systemic circulation establishes a pernicious cycle propelling disease progression. The current management approach emphasizes rigorous control of glycemic levels and blood pressure, with renin-angiotensin system blockade conferring renoprotection. Novel antidiabetic agents exhibit renoprotective effects, potentially mediated through endothelial modulation. Nonetheless, emerging therapies present novel avenues for enhancing patient outcomes and alleviating the disease burden. A precision-based approach, coupled with a comprehensive strategy addressing global vascular risk, will be pivotal in mitigating the cardiorenal burden associated with diabetes.

Reconfiguration and loss of peritubular capillaries in chronic kidney disease

Functional and structural alterations of peritubular capillaries (PTCs) are a major determinant of chronic kidney disease (CKD). Using a software-based algorithm for semiautomatic segmentation and morphometric quantification, this study analyzes alterations of PTC shape associated with chronic tubulointerstitial injury in three mouse models and in human biopsies. In normal kidney tissue PTC shape was predominantly elongated, whereas the majority of PTCs associated with chronic tubulointerstitial injury had a rounder shape. This was reflected by significantly reduced PTC luminal area, perimeter and diameters as well as by significantly increased circularity and roundness. These morphological alterations were consistent in all mouse models and human kidney biopsies. The mean circularity of PTCs correlated significantly with categorized glomerular filtration rates and the degree of interstitial fibrosis and tubular atrophy (IFTA) and classified the presence of CKD or IFTA. 3D reconstruction of renal capillaries revealed not only a significant reduction, but more importantly a substantial simplification and reconfiguration of the renal microvasculature in mice with chronic tubulointerstitial injury. Computational modelling predicted that round PTCs can deliver oxygen more homogeneously to the surrounding tissue. Our findings indicate that alterations of PTC shape represent a common and uniform reaction to chronic tubulointerstitial injury independent of the underlying kidney disease.

EFFECTS OF SMOKING ON CIRCADIAN ARTERIAL BLOOD PRESSURE PROFILE IN PATIENTS WITH NON-ST-SEGMENT ELEVATION ACUTE CORONARY SYNDROME AND CHRONIC KIDNEY DISEASE

The paper presents the results of a study of the effects of smoking on circadian arterial blood pressure (ABP) profile in patients with Non-ST-Segment Elevation Acute Coronary Syndrome (NSTE-ACS) and Chronic Kidney Disease (CKD).
 Aim. The research aims at studying the features of circadian blood pressure monitoring (CBPM) in patients with NSTE-ACS and CKD, smoking-dependent.
 Materials and Methods. The study includes 70 patients with NSTE-ACS and CKD aged 35 to 75 years. The patients were divided into 2 groups: Group I - 35 smokers (mean age - 60.09±1.66 years), Group II - 35 individuals who have never smoked (mean age - 62.31±1.04 years). The circadian blood pressure monitoring was carried out on the second day of hospital admission after stabilization of the patient's condition. The following indicators have been determined: systolic blood pressure (SBP) - daytime, nighttime, and average daily (24 hours) (SBPd, SBPn, and SBPav); diastolic blood pressure (DBPd, DBPn, and DBPav); pulse pressure (PBPd, PBPn, and PBPav); time index (TI) for SBPd and SBPn (SBPd TI and SBPn TI) and DBP (DBPd TI and DBPn TI); heart rate (HR). To study the renal functional status in the examined patients, the urine albumin-creatinine ratio (ACR) was determined using the semi-quantitative method. The glomerular filtration rate (GFR) was calculated using the CKD-EPI Creatinine Equation.
 Results. Mean SBP, DBP, and PBP levels were significantly higher in Group I patients compared to Group II patients: SBPd - by 5.10% (p<0.05), SBPn - by 6.60% (p<0.05); DBPd - by 9.60% (p=0.01), DBPn - by 14.10% (p<0.05); PBPd - by 7% (p=0.05), PBPn - by 8.50% (p<0.05). The mean TI value also turned out to be significantly higher in the group of smokers (I) versus non-smokers (II): SBPd TI - by 55.50% (p<0.01), SBPn TI - by 58.90% (p<0.01), DBPd TI - by 57.50% (p<0.01), DBPn TI - by 46.30% (p<0.01). The HR was higher by 10.80% in Group I patients compared to Group II patients (p<0.01). The mean GFR level in smokers is 13.00% lower than in non-smokers (p<0.05). A 57% significantly higher ACR level was found in the group of smokers (Group I) compared to non-smokers (Group II) (p<0.01).
 Conclusions. Mean SBP, DBP, PBP, TI, and HR levels were significantly higher in the group of smokers with NSTE-ACS and CKD. In the same Group, more distinct signs of kidney injury were found, namely, lower GFR values and higher ACR values, which indicates the probable adverse effect of smoking on ABP regulation and renal microvasculature.

Microvascular Dysfunction in Obesity-Hypertension.

This review aims to explore the role of microvascular dysfunction in obesity-hypertension, discuss the effects obesity has on renal microvasculature,reviewthe current methods for assessing microvascular dysfunction and availabletherapeutic options, and identify critical areas for further research. There is a strong association between obesity and hypertension. However, the pathophysiology of obesity-hypertension is not clear. Microvascular dysfunction has been linked to hypertension and obesity and could be an important mediator of obesity-related hypertension. Newer therapies for hypertension and obesity could have ameliorating effects on microvascular dysfunction, including GLP-1 agonists and SGLT-2 inhibitors. There is still much progress to be made in our understanding of the complex interplay between obesity, hypertension, and microvascular dysfunction. Continued efforts to understand microvascular dysfunction and its role in obesity-hypertension are crucial to develop precision therapy to target obesity-hypertension.

#6465 MIR-451B AND CHRONIC KIDNEY DISEASE: A NOVEL TARGET TO MODULATE RENAL VEGF SIGNALING

Abstract Background and Aims Chronic kidney disease (CKD) is a progressive disorder that affects over 15% of adults worldwide. A major component of CKD pathophysiology is renal microvascular rarefaction and loss that pairs the progression of the disease and complications. We developed a translational swine model of CKD and showed that loss of renal function associates with a significant decrease in renal vascular endothelial growth factor (VEGF) signaling and progressive microvascular (MV) rarefaction. VEGF is a key endogenous cytokine for MV proliferation and repair, but underlying mechanisms of renal VEGF downregulation in CKD are unknown. We hypothesized that micro-RNA (miRNA)-mediated processes contribute to the downregulation of renal VEGF signaling in CKD. Method Unbiased renal micro-RNA (miRNA)-seq was performed in a swine model of CKD stage 3 (14 weeks of bilateral renal artery stenosis + atherogenic diet) and normal controls (n = 5/group). Micro-RNAs up- (>1.4 FC, p<0.05) and down-regulated (<0.7 FC, p<0.05) were identified, followed by target prediction analysis (miRwalk 3.0, Target Scan 7.2). Renal gene and protein expression of VEGF was measured by qPCR and western blot, respectively, and renal MV architecture was studied by 3D micro-CT. Results Unbiased miRNA-seq and target prediction analysis identified four miRs upregulated in the kidney of CKD pigs vs. controls, of which miR-451b (validated by qPCR), broadly conserved among species, was capable of targeting VEGFA (FC = 4.46, p = 0.04). Renal gene and protein expression of VEGF was downregulated in CKD vs. controls, associated with significant cortical and medullary microvascular rarefaction (Figure 1). Conclusion Our data suggest that post-transcriptional modulation of renal VEGF signaling may serve as a prominent mechanism of VEGF downregulation, which leads to MV rarefaction and disease progression in CKD. Furthermore, this work in progress identified a novel candidate (miR-451b) and may set the stage for its targeted modulation to preserve VEGF signaling as a potential strategy to protect the renal microvasculature in CKD.

Yue-bi-tang attenuates adriamycin-induced nephropathy edema through decreasing renal microvascular permeability via inhibition of the Cav-1/ eNOS pathway.

Edema is one of the most typical symptoms of nephrotic syndrome. Increased vascular permeability makes a significant contribution to the progression of edema. Yue-bi-tang (YBT) is a traditional formula with excellent clinical efficacy in the treatment of edema. This study investigated the effect of YBT on renal microvascular hyperpermeability-induced edema in nephrotic syndrome and its mechanism. In our study, the content of target chemical components of YBT was identified using UHPLC-Q-Orbitrap HRMS analysis. A nephrotic syndrome model was replicated based on male Sprague-Dawley rats with Adriamycin (6.5mg/kg) by tail vein injection. The rats were randomly divided into control, model, prednisone, and YBT (22.2g/kg, 11.1g/kg, and 6.6g/kg) groups. After 14d of treatment, the severity of renal microvascular permeability, edema, the degree of renal injury, and changes in the Cav-1/eNOS pathway were assessed. We found that YBT could regulate renal microvascular permeability, alleviate edema, and reduce renal function impairment. In the model group, the protein expression of Cav-1 was upregulated, whereas VE-cadherin was downregulated, accompanied by the suppression of p-eNOS expression and activation of the PI3K pathway. Meanwhile, an increased NO level in both serum and kidney tissues was observed, and the above situations were improved with YBT intervention. It thus indicates YBT exerts therapeutic effects on the edema of nephrotic syndrome, as it improves the hyperpermeability of renal microvasculature, and that YBT is engaged in the regulation of Cav-1/eNOS pathway-mediated endothelial function.

Elastin haploinsufficiency accelerates age-related structural and functional changes in the renal microvasculature and impairment of renal hemodynamics in female mice.

Age-related decline in functional elastin is associated with increased arterial stiffness, a known risk factor for developing cardiovascular disease. While the contribution of elastin insufficiency to the stiffening of conduit arteries is well described, little is known about the impact on the structure and function of the resistance vasculature, which contributes to total peripheral resistance and the regulation of organ perfusion. In this study, we determined how elastin insufficiency impinges on age-related changes in the structure and biomechanical properties of the renal microvasculature, altering renal hemodynamics and the response of the renal vascular bed to changes in renal perfusion pressure (RPP) in female mice. Using Doppler ultrasonography, we found that resistive index and pulsatility index were elevated in young Eln +/- and aged mice. Histological examination showed thinner internal and external elastic laminae, accompanied by increased elastin fragmentation in the medial layer without any calcium deposits in the small intrarenal arteries of kidneys from young Eln +/- and aged mice. Pressure myography of interlobar arteries showed that vessels from young Eln +/- and aged mice had a slight decrease in distensibility during pressure loading but a substantial decline in vascular recoil efficiency upon pressure unloading. To examine whether structural changes in the renal microvasculature influenced renal hemodynamics, we clamped neurohumoral input and increased renal perfusion pressure by simultaneously occluding the superior mesenteric and celiac arteries. Increased renal perfusion pressure caused robust changes in blood pressure in all groups; however, changes in renal vascular resistance and renal blood flow (RBF) were blunted in young Eln +/- and aged mice, accompanied by decreased autoregulatory index, indicating greater impairment of renal autoregulation. Finally, increased pulse pressure in aged Eln +/- mice positively correlated with high renal blood flow. Together, our data show that the loss of elastin negatively affects the structural and functional integrity of the renal microvasculature, ultimately worsening age-related decline in kidney function.

P204 Biomechanical Phenotype of Circulating Neutrophils Is Altered in ANCA Associated Vasculitis

Abstract Background/Aims Real Time-Deformability Cytometry (RT-DC) is a novel technique able to identify morpho-rheological characteristics of individual cells such as size, deformability, and elasticity using only 50µl of whole blood. Cells in suspension flow through a microfluidic channel while hydrodynamic force is applied, leading to reversible deformation of individual cells from shear stress and pressure gradients. Cell brightness and area can be used to identify individual cell types. The morpho-rheological characteristics of immune cells in ANCA associated vasculitis (AAV) are unknown. Methods Whole blood from healthy controls (HC), patients with active AAV, or patients with AAV in remission was analysed using RT-DC. The diagnosis of AAV was based upon positive ANCA testing, with either (i) pauci-immune glomerulonephritis, or (ii) typical clinical features of extra-renal AAV. Patients with active disease may have received steroids prior to sampling but those who received other immunosuppression or cytotoxics were excluded. Remission was defined as BVAS of 0 with prednisolone dose ≤7.5mg/day. Blood was collected into K2 EDTA and diluted 1:20 in 1xPBS/0.6% methylcellulose. Cell suspensions were flowed across a Flic20 polydimethylsiloxane microfluidic chip, containing reservoirs connected by a measurement channel with a 20x20 μm2 cross-section. RT-DC measurements were collected at a flow rate of 0.12μL/s using a high-speed CMOS camera to capture images at a rate of 2000 frames/second. ShapeOut software was used to calculate cell size, deformation, and elasticity. Results There was no difference in neutrophil size between patients with active AAV (n = 15), patients with AAV in remission (n = 31), and HC (n = 15). Neutrophils from patients with active AAV were significantly stiffer than patients in remission or HC, displaying decreased deformation (median 0.084, 0.085, and 0.078 au respectively, p = 0.0068) and increased elasticity (median 0.973, 0.968 and 1.006 au respectively, p = 0.0196). In patients with active AAV, there was strong inverse correlation between neutrophil deformation and disease activity measured by BVAS score (r=-0.573, p = 0.032). Neutrophils isolated from healthy donors exhibited a trend towards decreased deformability when primed with TNF and stimulated with MPO-ANCA IgG compared to unstimulated or cells treated with healthy donor IgG (median 0.086, 0.085, and 0.083 for unstimulated, control IgG, and MPO-ANCA IgG respectively, ns). Conclusion Neutrophils from patients display distinct physical properties in active AAV which correlate with disease activity. Similar results are seen when neutrophils are stimulated in vitro with MPO-ANCA IgG. This phenotype of increased cell stiffness may lead to increased neutrophil retention in pulmonary and renal microvasculature, thus increasing the potential for neutrophil-endothelial cell interactions and microvascular damage. Morphorheological parameters can be rapidly measured using a small volume of whole blood; thus, RT-DC may be a useful technique to aid identification of disease activity in AAV and to guide treatment. Disclosure N. Pisacano: None. S.P. McAdoo: None. J. Guck: None. C.D. Pusey: None. E.R. Chilvers: None. A.C. Cowburn: None. K.M. Lodge: None. M.F. Prendecki: None.

Targeted VEGFA therapy in regulating early acute kidney injury and late fibrosis.

Damage to peritubular capillaries is a key process that contributes to acute kidney injury (AKI) progression. Vascular endothelial growth factor A (VEGFA) plays a critical role in maintaining the renal microvasculature. However, the physiological role of VEGFA in various AKI durations remains unclear. A severe unilateral ischemia‒reperfusion injury model was established to provide an overview of VEGFA expression and the peritubular microvascular density from acute to chronic injury in mouse kidneys. Therapeutic strategies involving early VEGFA supplementation protecting against acute injury and late anti-VEGFA treatment for fibrosis alleviation were analyzed. A proteomic analysis was conducted to determine the potential mechanism of renal fibrosis alleviation by anti-VEGFA. The results showed that two peaks of extraglomerular VEGFA expression were observed during AKI progression: one occurred at the early phase of AKI, and the other occurred during the transition to chronic kidney disease (CKD). Capillary rarefaction progressed despite the high expression of VEGFA at the CKD stage, and VEGFA was associated with interstitial fibrosis. Early VEGFA supplementation protected against renal injury by preserving microvessel structures and counteracting secondary tubular hypoxic insults, whereas late anti-VEGFA treatment attenuated renal fibrosis progression. The proteomic analysis highlighted an array of biological processes related to fibrosis alleviation by anti-VEGFA, which included regulation of supramolecular fiber organization, cell-matrix adhesion, fibroblast migration, and vasculogenesis. These findings establish the landscape of VEGFA expression and its dual roles during AKI progression, which provides the possibility for the orderly regulation of VEGFA to alleviate early acute injury and late fibrosis.

Paricalcitol Improves the Angiopoietin/Tie-2 and VEGF/VEGFR2 Signaling Pathways in Adriamycin-Induced Nephropathy.

Renal endothelial cell (EC) injury and microvascular dysfunction contribute to chronic kidney disease (CKD). In recent years, increasing evidence has suggested that EC undergoes an endothelial-to-mesenchymal transition (EndoMT), which might promote fibrosis. Adriamycin (ADR) induces glomerular endothelial dysfunction, which leads to progressive proteinuria in rodents. The activation of the vitamin D receptor (VDR) plays a crucial role in endothelial function modulation, cell differentiation, and suppression of the expression of fibrotic markers by regulating the production of nitric oxide (NO) by activating the endothelial NO synthase (eNOS) in the kidneys. This study aimed to evaluate the effect of paricalcitol treatment on renal endothelial toxicity in a model of CKD induced by ADR in rats and explore mechanisms involved in EC maintenance by eNOS/NO, angiopoietins (Angs)/endothelium cell-specific receptor tyrosine kinase (Tie-2, also known as TEK) and vascular endothelial growth factor (VEGF)-VEGF receptor 2 (VEGFR2) axis. The results show that paricalcitol attenuated the renal damage ADR-induced with antiproteinuric effects, glomerular and tubular structure, and function protection. Furthermore, activation of the VDR promoted the maintenance of the function and structure of glomerular, cortical, and external medullary endothelial cells by regulating NO production. In addition, it suppressed the expression of the mesenchymal markers in renal tissue through attenuation of (transforming growth factor-beta) TGF-β1/Smad2/3-dependent and downregulated of Ang-2/Tie-2 axis. It regulated the VEGF/VEGFR2 pathway, which was ADR-deregulated. These effects were associated with lower AT1 expression and VDR recovery to renal tissue after paricalcitol treatment. Our results showed a protective role of paricalcitol in the renal microvasculature that could be used as a target for treating the beginning of CKD.

Maladaptation of renal hemodynamics contributes to kidney dysfunction resulting from thoracic spinal cord injury in mice.

Renal dysfunction is a hallmark of spinal cord injury (SCI). Several SCI sequalae are implicated; however, the exact pathogenic mechanism of renal dysfunction is unclear. Herein, we found that T3 (T3Tx) or T10 (T10Tx) complete thoracic spinal cord transection induced hypotension, bradycardia, and hypothermia immediately after injury. T3Tx-induced hypotension but not bradycardia or hypothermia slowly recovered to levels in T10Tx SCI and uninjured mice ∼16 h after injury as determined by continuous radiotelemetry monitoring. Both types of thoracic SCI led to a marked decrease in albuminuria and proteinuria in all phases of SCI, whereas the kidney injury marker neutrophil gelatinase-associated lipocalin rapidly increased in the acute phase, remaining elevated in the chronic phase of T3Tx SCI. Renal interstitial and vascular elastin fragmentation after SCI were worsened during chronic T3Tx SCI. In the chronic phase, renal vascular resistance response to a step increase in renal perfusion pressure or a bolus injection of angiotensin II or norepinephrine was almost completely abolished after T3Tx SCI. Bulk RNA-sequencing analysis showed enrichment of genes involved in extracellular matrix remodeling and chemokine signaling in the kidney from T3Tx SCI mice. The serum level of interleukin-6 was elevated in the acute but not chronic phase of T3Tx and T10Tx SCI, whereas the serum amyloid A1 level was elevated in both acute and chronic phases. We conclude that tissue fibrosis and hemodynamic impairment are involved in renal dysfunction resulting from thoracic SCI; these pathological alterations, exacerbated by high thoracic-level injury, is mediated at least partly by renal microvascular extracellular matrix remodeling.NEW & NOTEWORTHY Urinary complications resulting from thoracic spinal cord injury (SCI) greatly affects quality of life and contributes to morbidity and mortality in patients with SCI. Herein, we showed that thoracic SCI initiates changes in the structure and function of the renal microvasculature that leads to autoregulation failure in the chronic phase of high thoracic-level injury. Our study identified extracellular matrix regulators and cytokine/chemokine signaling as potential targets for developing novel therapeutics for restoring renal function following SCI.

Liraglutide treatment attenuates inflammation markers in the cardiac, cerebral and renal microvasculature in streptozotocin-induced diabetic rats.

BackgroundDiabetes mellitus (DM) induces cardiac and cerebral microvascular dysfunction via increased glycation, oxidative stress and endothelial activation. Liraglutide, a glucagon‐like peptide‐1 analogue, inhibited NOX2 and adhesion molecules in isolated endothelial cells. Here, we have studied how Liraglutide affects advanced glycation, NOX expression and inflammation of the cardiac, cerebral and renal microvasculature in diabetic rats.MethodsDM was induced in Sprague–Dawley rats (n = 15) via intraperitoneal streptozotocin (STZ) injection (60 mg/kg bodyweight). Ten control rats remained nondiabetic. From day 9 post‐STZ injection, Liraglutide (200 μg/kg bodyweight; n = 7) or vehicle (n = 8) was injected subcutaneously daily until termination on day 29. The advanced glycation endproduct N‐ε‐(carboxymethyl)lysine (CML), NOX2, NOX4, ICAM‐1 and VCAM‐1 were subsequently immunohistochemically analysed and quantified to compare Liraglutide treatment with placebo.ResultsIn the heart, Liraglutide treatment significantly reduced the DM‐increased scores/cm2 for CML in both ventricles (from 253 ± 53 to 72 ± 12; p = .003) and atria (343 ± 29 to 122 ± 8; p = .0001) and for NOX2, ICAM‐1 and VCAM‐1, but not for NOX4. Also in the cerebrum and cerebellum of the brain, Liraglutide significantly reduced the scores/cm2 for CML (to 60 ± 7 (p = .0005) and 47 ± 13 (p = .02), respectively), and for NOX2 and NOX4. In the kidney, the DM‐induced expression of ICAM‐1 and VCAM‐1 was decreased in the blood vessels and glomeruli by Liraglutide treatment. Liraglutide did not affect blood glucose levels or bodyweight.ConclusionsOur study implies that Liraglutide protects the cardiac, cerebral and renal microvasculature against diabetes‐induced dysfunction, independent of lowering blood glucose in a type 1 diabetes rat model.

Elastin Insufficiency Accelerates Age‐Related Impairment of Renal Hemodynamics

Gradual loss of functional elastin fibers during aging leads to increased arterial stiffening and decreased compliance. Elastin insufficiency in mice and humans has been shown to be associated with arteriopathy and the development of hypertension. However, it is unclear whether elastin insufficiency in the resistance vasculature, as occurs in the renal vascular bed, contributes to age‐related decline in renal function. We hypothesized that elastin insufficiency exacerbates age‐related impairment of renal hemodynamics by accelerating functional and structural changes of the renal microvasculature. We assessed renal hemodynamics in anesthetized young (4‐6‐month‐old) and old (14–16‐month‐old) female wild‐type (WT) and elastin heterozygous (Eln+/‐) mice. Renal autoregulation was assessed by a stepwise increase in renal perfusion pressure (RPP) by simultaneously occluding the superior mesenteric and celiac arteries. Autonomic activity was clamped by continuous infusion of a cocktail containing vasoactive hormones. Baseline systolic blood pressure (SBP; 91.1±4.2 vs 90.1±3.1mmHg) and renal vascular resistance (RVR; 13.1±2.4 vs 10.0±1.5 mmHg/μL/min/g left kidney weight) were elevated in old versus young WT mice. Renal blood flow (RBF; 7.3±1.7 vs 9.8±1.4 μL/min/g left kidney weight), renal plasma flow (RPF; 5±1.2 vs 6±1mL/min/g left kidney weight) and glomerular filtration rate (GFR), all trended lower in old WT mice compared to young WT mice. However, in Eln+/‐mice, SBP was lower in old mice (78.2±9.4 vs 104.6±4.9mmHg), while RVR (13.5± 2.6 vs 14.4±1.1), RBF (6.7±1.2 vs 7.5±0.6), RPF (4.2±0.7 vs 4.5±0.3) and GFR were all similar between young and old mice. Increasing RPP caused a robust RVR and RPF response in young vs old WT mice. In contrast, the maximal changes in RBF (5.8±0.6 vs 5.5±1 μL/min/g left kidney weight), RVR (23.8±2.5 vs 21.8±7.0 mmHg/μL/min/g left kidney weight) were less robust and similar between young and old Eln+/‐mice. Autoregulatory index average values were closer to 0 in young and old Eln+/‐and old WT miceindicating greater impairment of renal autoregulation compared to young WT mice. Correlation analysis between pulse pressure and RBF showed that a high pulse pressure was more positively correlated to high RBF in young and old Eln+/‐mice as well as old WT mice. Together, our data demonstrate that elastin insufficiency accelerates age‐related impairment of renal hemodynamics and autoregulation likely mediated by functional and structural remodeling of the renal microvasculature.

Using 2-Photon Microscopy to Quantify the Effects of Chronic Unilateral Ureteral Obstruction on Glomerular Processes.

Applying novel microscopy methods to suitable animal disease models to explore the dynamic physiology of the kidney remains a challenge. Rats with surface glomeruli provide a unique opportunity to investigate physiological and pathophysiological processes using intravital 2-photon microscopy. Quantification of glomerular capillary blood flow and vasoconstriction and dilatation in response to drugs, permeability, and inflammation are just some of the processes that can be studied. In addition, transgenic rats, i.e., podocytes labeled with fluorescent dyes and other molecular biomarker approaches, provide increased resolution to directly monitor and quantify protein-protein interactions and the effects of specific molecular alterations. In mice, which lack surface glomeruli after four weeks of age, unilateral ureteral obstruction (UUO) for several weeks has been used to induce surface glomeruli. As this induction model does not allow for baseline studies, we quantified the effects of UUO on glomerular processes in the UUO model in Munich Wistar Frömter (MWF) rats, which have surface glomeruli under physiologic conditions. The UUO model for five weeks or more induced significant alterations to gross renal morphology, the peritubular and glomerular microvasculature, as well as the structure and function of tubular epithelia. Glomerular and peritubular red blood cell (RBC) flow decreased significantly (p < 0.01), probably due to the significant increase in the adherence of white blood cells (WBCs) within glomerular and peritubular capillaries. The glomerular sieving coefficient of albumin increased from 0.015 ± 0.002 in untreated MWFs to 0.045 ± 0.05 in 5-week-old UUO MWF rats. Twelve weeks of UUO resulted in further increases in surface glomerular density and glomerular sieving coefficient (GSC) for albumin. Fluorescent albumin filtered across the glomeruli was not reabsorbed by the proximal tubules. These data suggest that using UUO to induce surface glomeruli limits the ability to study and interpret normal glomerular processes and disease alterations.

Using 2-Photon Microscopy to Quantify the Effects of Chronic Unilateral Ureteral Obstruction on Glomerular Processes

Applying novel microscopy methods to suitable animal disease models to explore the dynamic physiology of the kidney remains a challenge. Rats with surface glomeruli provide a unique opportunity to investigate physiological and pathophysiological processes using intravital 2-photon microscopy. Quantification of glomerular capillary blood flow and vasoconstriction and dilatation in response to drugs, permeability, and inflammation are just some of the processes that can be studied. In addition, transgenic rats, i.e., podocytes labeled with fluorescent dyes and other molecular biomarker approaches, provide increased resolution to directly monitor and quantify protein-protein interactions and the effects of specific molecular alterations. In mice, which lack surface glomeruli after four weeks of age, unilateral ureteral obstruction (UUO) for several weeks has been used to induce surface glomeruli. As this induction model does not allow for baseline studies, we quantified the effects of UUO on glomerular processes in the UUO model in Munich Wistar Frömter (MWF) rats, which have surface glomeruli under physiologic conditions. The UUO model for five weeks or more induced significant alterations to gross renal morphology, the peritubular and glomerular microvasculature, as well as the structure and function of tubular epithelia. Glomerular and peritubular red blood cell (RBC) flow decreased significantly (p < 0.01), probably due to the significant increase in the adherence of white blood cells (WBCs) within glomerular and peritubular capillaries. The glomerular sieving coefficient of albumin increased from 0.015 ± 0.002 in untreated MWFs to 0.045 ± 0.05 in 5-week-old UUO MWF rats. Twelve weeks of UUO resulted in further increases in surface glomerular density and glomerular sieving coefficient (GSC) for albumin. Fluorescent albumin filtered across the glomeruli was not reabsorbed by the proximal tubules. These data suggest that using UUO to induce surface glomeruli limits the ability to study and interpret normal glomerular processes and disease alterations.

POS-059 INTRAVITAL IMAGING TO QUANTIFY ROULEAUX FORMATION WITHIN THE PERITUBULAR VASCULATURE

Rouleaux formation is marked by the aggregation of red blood cells within the renal microvasculature and acts as a hallmark of ischemia. The use of intravital two-photon microscopy has previously shown the ability to identify such injury in the kidney. Thus, we wanted to extend this approach to quantify rouleaux development in real-time during ischemia-reperfusion injury (IRI).

Dementia associated with chronic kidney disease is accompanied by increase in plasma amyloid beta and cardiovascular dysfunction.

In end-stage chronic kidney disease (CKD) the prevalence of cognitive impairment (CI) has been estimated at 30-60%. Cardiovascular diseases (CVD) including increased central arterial stiffness (CAS) accompany CKD development. CAS drives pulse pressure (PP) and pulsatile component index (PCI) increases and cerebral microvascular damage resulting in a reduction of blood supply to the brain hereby contributing to CI. Elevated PP and PCI are associated with higher mortality in CVD and CKD independently of BP. The aim of the study was to determine whether CKD potentiates CI development due to CAS and the resultant increase in the PCI, a major contributor to brain and renal microvasculature damage. Measurements of systolic and diastolic blood pressure (SBP, DBP), echocardiography (ECHO), plasma amyloid beta-40 (Aβ-40), BUN, creatinine, aspartate aminotransferase (AST), brain natriuretic peptide (BNP), and mini-mental status examination (MMSE) were performed in 25 patients with stage IV CKD and in 22 age- and sex-matched healthy controls (Table 1). PCI was calculated as a function of SBP and DBP. The data were analyzed by unpaired two-tailed t-test, Pearson correlation with P values adjusted for false discovery rate, and are presented as mean±SEM. CKD patients had higher SBP, PP, PCI, LV systolic and diastolic volume, lower LV ejection fraction, higher plasma BNP and AST (CVD markers), plasma Aβ-40 (Alzheimer's disease marker), BUN and creatinine (CKD markers) and lower score in MMSE vs. healthy control (Table 1). Cognitive test results positively correlated with LV stroke volume, negatively correlated with PCI, a measurement of pulsatility of BP, and negatively correlated with plasma ASP, a marker of CVD (Table 2). SBP and DBP did not correlate with cognitive parameters. Further investigation of the possible metabolic role of Aβ-40 in the development of CI in CKD patients, and whether plasma AST can be a marker of CI in CKD, will be assessed in the future studies. Higher PP, PCI and lower score in MMSE in CKD patients supports our hypothesis that cardiovascular remodeling in CKD is a key component of CI progression. Supported by the NIH Grant 1R15HL150721 (K.S.), and in part by NIH/NIA Intramural Research Program.