Lerman, Lilach O.

The significance of peristenotic collateral circulation (PCC) development around a stenotic renal artery is unknown. We tested the hypothesis that PCC is linked to loss of kidney function and recovery potential in patients with atherosclerotic renovascular disease (ARVD). Thirty-four patients with ARVD were assigned to medical-therapy with or without revascularization based on clinical indications. The PCC was visualized using multidetector computed tomography and defined relative to segmental arteries in patients with essential hypertension. PCC number before and 3 months after treatment was correlated with various renal parameters. Thirty-four stenotic kidneys from 30 patients were analyzed. PCC number correlated inversely with kidney volume. ARVD–stenotic kidneys with baseline PCC (collateral ARVD [C-ARVD], n=13) associated with elevated 24-hour urine protein and stenotic kidney vein level of tumor necrosis factor-α, lower single-kidney volume and blood flow, and greater hypoxia than in stenotic kidneys with no PCC (no collateral ARVD [NC-ARVD], n=17). Revascularization (but not medical-therapy alone) improved stenotic kidney function and reduced inflammation in both NC-ARVD and C-ARVD. In C-ARVD, revascularization also increased stenotic kidney volume, blood flow, and oxygenation to levels comparable to NC-ARVD, and induced PCC regression. However, revascularization improved systolic blood pressure, plasma renin activity, and filtration fraction only in NC-ARVD. Therefore, patients with C-ARVD have greater kidney dysfunction, atrophy, hypoxia, and inflammation compared with patients with NC-ARVD, suggesting that PCC does not effectively protect the stenotic kidney in ARVD. Renal artery revascularization improved in C-ARVD stenotic kidney function, but not hypertension or renin-angiotensin system activation. These observations may help direct management of patients with ARVD.

Abstract Background and Aims Novel therapies are needed to address the increasing prevalence of chronic kidney disease. Mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (EVs) augment tissue repair. EVs have practical benefits, but their efficacy relative to MSCs is incompletely understood. We tested the hypothesis that EVs are as effective as MSCs in protecting the stenotic kidney but target different injury pathways. Method Pigs were studied after 16 weeks of renal injury achieved by diet-induced metabolic syndrome (Mets) and renal artery stenosis (RAS). Pigs were untreated or treated four weeks earlier with a single intrarenal delivery of autologous adipose tissue-derived MSCs (1 × 107) or EVs (1 × 1010). Lean pigs and sham RAS served as controls (n=6 each). Stenotic kidney function was studied in-vivo using CT. Histopathology and expression of necroptosis markers (RIPK-1 and RIPK-3), inflammatory and growth factors (angiopoeitin-1 and VEGF) was studied ex-vivo. Results Stenotic-kidney glomerular filtration rate and blood flow in Mets+RAS were both lower than Mets, increased in Mets+RAS+MSCs, and further improved in Mets+RAS+EV. Both MSCs and EVs improved renal function, hypoxia, and decreased renal fibrosis and apoptosis. MSC were slightly more effective in preserving microvascular density (0.02-0.2mm in diameter), and prominently attenuated renal inflammation. However, EVs more significantly upregulated growth-factor expression and decreased necropotosis. Conclusion: Adipose tissue-derived MSCs and their EVs both improve stenotic kidney function and decrease tissue injury in Mets+RAS. MSCs more effectively preserve the microcirculation, while EVs bestow better preservation of renal cellular integrity. These findings encourage further exploration of this novel approach to attenuate renal injury.

Abstract Background and Aims Endothelial progenitor cells (EPCs) patrol the circulation and contribute to endothelial cell regeneration and tissue revascularization. Atherosclerotic renal artery stenosis (ARAS) induces microvascular loss in the stenotic kidney. A regimen of low–energy shockwave therapy (SW) induces angiogenesis and reduces chronic ischemia, but the mechanism remains unclear. This study tested the hypothesis that SW increases EPCs homing to the stenotic kidney and increases renal capillary regeneration in a unilateral ARAS swine model. Method Domestic pigs were randomized to normal control or unilateral ARAS (induced by a local irritant coil in the renal artery and a high-fat diet). ARAS pigs were treated with low-energy SW (0.1 mJ/mm2) or sham (n=6 each group), bi-weekly for 3 consecutive weeks, starting after 3 weeks of ARAS. Blood samples for EPCs (CD34+ and KDR+ by flow cytometry) and the homing factor SDF-1 were collected 4 weeks after completion of SW treatment from the inferior vena cava (IVC) and the stenotic kidney (STK) vein and artery. Urine was collected from the urinary bladder. Kidneys were studied ex vivo for morphology and expression of an endothelial cell marker (CD31) and the pro- angiogenic growth factor angiopoietin (Ang)-1. Results In ARAS, tubulointerstitial fibrosis, tubular score, urinary protein, serum creatinine and mean arterial pressure were significantly increased and capillary count (Fig. 1A) decreased (P<0.05 vs. control), but all markedly improved in ARAS+SW (P<0.05 vs. ARAS). EPC number was decreased in the IVC and renal artery of ARAS pigs (Fig. 1B), but improved in ARAS+SW. SDF-1 levels in the IVC, STK vein and artery, and Ang-1 expression in the kidney of ARAS+SW, were all increased (P<0.05 vs. ARAS). Conclusion Low-energy shockwave improves ischemic kidney capillary density, which is associated with and may be at least in part mediated by promoting EPC mobilization and homing to the stenotic kidney.

Abstract Background and Aims Tumor necrosis factor-α-induced gene/protein (TSG)-6 is a key factor influencing mesenchymal stem cells (MSCs) immunomodulatory properties, but its renoprotective efficacy is unknown. Using a novel swine model of renal artery stenosis (RAS) complicated by metabolic syndrome (Mets), we assessed the therapeutic effects of adipose tissue-derived MSCs-produced TSG-6 and mechanisms underlying the immunomodulatory properties of MSCs. Method Five groups of pigs (n=6 each) were studied after 16 weeks of diet-induced Mets and unilateral RAS (Mets+RAS), either untreated or treated 4 weeks earlier with a single intra-renal delivery of autologous posrcine adipose tissue-derived MSCs (pMSC). Lean, Mets, and RAS shams served as controls. We studied renal function in vivo (using CT imaging) and kidney histopathology and macrophage phenotype ex vivo. In vitro, TSG-6 levels were measured in conditioned media of human MSCs (hMSCs) incubated with or without TNF-α. Additionally, levels of the tubular injury marker LDH were measured in conditioned media after co-culturing macrophages with injured HK-2 cells (achieved by TNF-α and antimycin-A, AMA) with or without addition of TSG-6. The effects of TSG-6 on macrophage phenotype (M1/M2), adhesion, and migration capability were determined. Results Mets+RAS pigs showed increased renal M1 macrophages and renal vein TNF-α levels. After p-MSCs delivery, renal vein TSG-6 increased and TNF-α decreased, M1 macrophage switched to M2 (Fig. A),, renal function improved, and fibrosis alleviated. In vitro, TNF-α increased TSG-6 secretion by h-MSCs. TSG-6 decreased LDH release from injured HK-2, induced a macrophage phenotypic switch from M1 to M2 (Fig. B), and reduced M1 macrophage adhesion and migration (Fig. C). Conclusion TNF-α-induced TSG-6 release from MSCs in vivo and in vitro may decrease renal tubular cells injury, which is associated with and may be at least in part mediated by regulating macrophage function and phenotype.

Scattered tubular-like cells (STCs) are dedifferentiated surviving tubular epithelial cells that repair neighboring injured cells. Experimental renal artery stenosis (RAS) impairs STC reparative potency by inducing mitochondrial injury, but the exact mechanisms of mitochondrial damage remain unknown. We hypothesized that RAS alters expression of mitochondria-related genes, contributing to mitochondrial structural damage and dysfunction in swine STCs. CD24+/CD133+STCs were isolated from pig kidneys after 10 wk of RAS or sham ( n = 3 each). mRNA sequencing was performed, and nuclear DNA (nDNA)-encoded mitochondrial genes and mitochondrial DNA (mtDNA)-encoded genes were identified. Mitochondrial structure, ATP generation, biogenesis, and expression of mitochondria-associated microRNAs were also assessed. There were 96 nDNA-encoded mitochondrial genes upregulated and 12 mtDNA-encoded genes downregulated in RAS-STCs versus normal STCs. Functional analysis revealed that nDNA-encoded and mtDNA-encoded differentially expressed genes were primarily implicated in mitochondrial respiration and ATP synthesis. Mitochondria from RAS STCs were swollen and showed cristae remodeling and loss and decreased ATP production. Immunoreactivity of the mitochondrial biogenesis marker peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α and expression of the mitochondria-associated microRNAs miR-15a, miR-181a, miR-196a, and miR-296-3p, which target several mtDNA genes, were higher in RAS-STCs compared with normal STCs, suggesting a potential modulation of mitochondria-related gene expression. These results demonstrate that RAS induces an imbalance in mtDNA- and nDNA-mitochondrial gene expression, impairing mitochondrial structure and function in swine STCs. These observations support development of gene gain- and loss-of-function strategies to ameliorate mitochondrial damage and preserve the reparative potency of STCs in patients with renal ischemia.

AbstractEffective therapeutic strategies are needed to preserve renal function in patients with atherosclerotic renal artery stenosis (ARAS). Low‐energy shockwave therapy (SW) and adipose tissue‐derived mesenchymal stem/stromal cells (MSCs) both stimulate angiogenesis repair of stenotic kidney injury. This study tested the hypothesis that intrarenal delivery of adipose tissue‐derived MSCs would enhance the capability of SW to preserve stenotic kidney function and structure. Twenty‐two pigs were studied after 16 weeks of ARAS, ARAS treated with a SW regimen (bi‐weekly for 3 weeks) with or without subsequent intrarenal delivery of adipose tissue‐derived MSCs and controls. Four weeks after treatment, single‐kidney renal blood flow (RBF) before and after infusion of acetylcholine, glomerular filtration rate (GFR), and oxygenation were assessed in vivo and the renal microcirculation, fibrosis, and oxidative stress ex vivo. Mean arterial pressure remained higher in ARAS, ARAS + SW, and ARAS + SW + MSC compared with normal. Both SW and SW + MSC similarly elevated the decreased stenotic kidney GFR and RBF observed in ARAS to normal levels. Yet, SW + MSC significantly improved RBF response to acetylcholine in ARAS, and attenuated capillary loss and oxidative stress more than SW alone. Density of larger microvessels was similarly increased by both interventions. Therefore, although significant changes in functional outcomes were not observed in a short period of time, adjunct MSCs enhanced pro‐angiogenic effect of SW to improve renal microvascular outcomes, suggesting this as an effective stratege for long‐term management of renovascular disease.

Cell-derived extracellular vesicles (EVs) can be isolated from various body fluids, including urine. Urinary EVs have gained important recognition as potential diagnostic biomarkers in renal disease since their cargo includes nucleic acids, proteins, and other cellular components, which likely mirror the physiological and possibly pathophysiological state of cells along the nephron. Accumulating evidence highlights the feasibility of using EVs as biomarkers for diagnostic, prognostic, and therapeutic purposes in several forms of renal disease, such as acute kidney injury, glomerulonephritis, and renal transplantation. Additionally, exogenous delivery of EVs released in vitro by cells in culture may have salutary benefits for renal diseases. In this review, we introduce recent studies that attempt to identify urinary EVs as candidate biomarkers for human kidney diseases and consider their potential implication as a therapeutic option in key kidney diseases.

Background Peripheral microvascular endothelial dysfunction (PMED) has been linked to an increased risk of cardiovascular events, but there is a lack of information characterizing the predictive value of PMED for future risk of ischemic stroke (IS). Methods and Results This retrospective observational cohort study enrolled 637 patients who underwent non‐invasive microvascular endothelial function assessment using reactive hyperemia peripheral arterial tonometry. Reactive hyperemia peripheral arterial tonometry index ≤2 was defined as PMED. Of 280 patients with PMED, 12 (4.3%) patients developed IS, compared with only 4 (1.1%) of 357 patients without PMED during a median follow‐up of 5.3 years. Patients with PMED had lower IS‐free survival compared with patients without PMED (log‐rank P =0.03). Cox proportional hazard ratio (HR) analyses showed that PMED predicted the incidence of IS, with a HR of 3.43, 95% CI, 1.10–10.63 ( P =0.03); adjusted HR of 3.70, 95% CI, 1.18–11.59 ( P =0.02) after adjusting for sex, smoking history, and atrial fibrillation; adjusted HR of 3.45, 95% CI, 1.11–10.72 ( P =0.03) after adjusting for CHA 2 DS 2 ‐VASc score; adjusted HR of 5.70, 95% CI, 1.40–23.29 ( P =0.02) after adjusting for revised Framingham Stroke Risk Score. Reactive hyperemia peripheral arterial tonometry index improved discrimination of risk for IS after adding reactive hyperemia peripheral arterial tonometry index to CHA 2 DS 2 ‐VASc score and revised Framingham Stroke Risk Score. Conclusions PMED was associated with a >3‐fold increased risk of IS. These findings underscore the concept of the systemic nature of endothelial dysfunction, which could act as a potential marker to predict future risk of IS.

Background Coronary artery disease risk factors are associated with atrial fibrillation ( AF ) and coronary endothelial dysfunction ( CED ). We hypothesized that CED is associated with increased risk of incident AF among patients with chest pain and nonobstructive coronary artery disease. Methods and Results Three hundred patients with chest pain, nonobstructive coronary artery disease, and no history of AF underwent intracoronary acetylcholine infusion for evaluation of baseline epicardial (decrease in mid–left anterior descending coronary artery diameter in response to acetylcholine) and microvascular (<50% increase in coronary blood flow in response to acetylcholine) CED . Primary outcome was incident AF over a mean follow‐up period of 10.5±5.5 years. Mean age was 53.3±10.8 years, and 70% were women. Baseline clinical and echocardiographic characteristics were similar between patients with CED (n=256) and those with normal endothelial function (n=44). Overall, 35 of 300 (12%) patients developed AF , among whom 34 of 35 (97%) had CED at baseline. Compared with normal endothelial function, the presence of CED was associated with 11% increased absolute risk and 5.8‐fold increased relative risk of incident AF . Moreover, CED ( odds ratio , 3.87; 95% CI , 1.27–47.0) and increased (>34 mL/m 2 ) left atrial volume index (odds ratio, 3.87; 95% CI , 1.60–9.11) were independent predictors of incident AF . Conclusions Patients with normal coronary endothelial function, as compared with those with CED and similar AF risk factors, have significantly lower incidence of AF on long‐term follow‐up. The potential mechanistic link between vascular dysfunction and AF development warrants further investigation.