Lerman, Lilach O.

The single-cell platform mass cytometry (CyTOF) enables detection of significant changes in one million of renal cells, especially in subsets of immune cells in ischemic human kidneys distal to renal artery stenosis (RAS). We found that pro-repair cell types such as scattered tubular-progenitor-like cells, aged neutrophils, and regulatory B cells show a compensatory increase in RAS. Immune cell phenotype changes may reflect ongoing inflammation and impaired immune defense capability in the kidneys.

Monoamine Oxidase (MAO), an outer mitochondrial enzyme, catalyzes the oxidative deamination of neurotransmitters and biological amines, and in the process, produces a reactive aldehyde and H2O2. Our lab has recently shown that MAO activity (i.e., H2O2 production) in human right atrial myocardium is associated with postoperative atrial fibrillation. Furthermore, our lab has shown that diabetic patients have higher MAO‐A and ‐B content and rates of activity in this tissue, compared to nondiabetics. While recent studies have explored the connection between MAO and cardiac dysfunction, the chamber‐specific content and activity of MAO within the heart is still unknown. Therefore, we characterized the regional enzymatic activity of MAO‐A and ‐B based upon the hypothesis that the atria would have the highest MAO activity due to the greater density of local sympathetic nerve innervation in this region. For this study, porcine hearts were isolated from domestic pigs, as this model closely recapitulates the physiology of the human heart. One group of pigs were fed a high fat, high sucrose diet for 16 weeks to induce obesity/metabolic syndrome (n=4). Three MAO substrates (dopamine, norepinephrine, serotonin) and two isoform‐selective inhibitors (clorgyline=MAO‐A, deprenyl=MAO‐B) were used to characterize MAO activities. Enzyme content was measured using ELISA and confirmed with immunoblots. Kinetic analysis showed that, across all substrates, when normalized to tissue protein, the left atrium has the highest maximal MAO‐A and –B activity while the other three chambers are similar. Furthermore, maximal MAO activity in the left ventricle of pigs with metabolic syndrome is significantly greater (P<0.05) than left ventricle of control group. Our findings suggest that MAO activity differs by location in the heart (i.e., chamber heterogeneity). This information will be useful to inform future experimental and clinical pharmacology applications where MAO inhibitors might be used. Moreover, increased MAO in left ventricle of pigs with obesity/metabolic syndrome is important as it provides a rationale for exploring MAO inhibitors as therapeutic strategy to mitigate cardiac complications of diabetes. Support or Funding Information R01HL122863

Background Superimposition of the metabolic syndrome (MetS) on renovascular disease (RVD) amplifies intrarenal microvascular loss. Extracellular vesicles (EVs) released from adipose tissue‐derived mesenchymal stem/stromal cells (MSCs) may mediate their paracrine effect, but their efficacy to protect the renal microcirculation in RVD complicated by MetS remains unclear. Using a novel swine model, we tested the hypothesis that EVs would attenuate microvascular loss in MetS+RVD. Methods Four groups of pigs (n=7 each) were studied after 16 weeks of diet‐induced MetS and unilateral RVD (MetS+RVD), MetS+RVD treated 4 weeks earlier with a single intra‐renal delivery of pre‐labeled EVs harvested from autologous MSCs, and Lean and MetS Sham controls. Stenotic‐kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were measured in‐vivo (fast CT), whereas EV characteristics, renal microvascular architecture (micro‐CT), and injury pathways ex‐vivo. Results mRNA sequencing of EVs and their parent MSCs revealed that EVs were enriched with pro‐angiogenic genes, including vascular endothelial growth factor (VEGF)‐A, VEGF–C, and Von Willebrand Factor (vWF)‐A Domain Containing‐1 (VWA)‐1 (). In addition, protein expression of VEGF and vWF was higher in EVs compared to MSCs (). EVs were detected in the stenotic‐kidney ex‐vivo internalized by tubular and endothelial cells. EVs restored renal expression of the pro‐angiogenic factors VEGF, Notch‐1, and Notch ligand delta‐like‐4 (DLL4) and improved cortical microvascular density (). Tubulointerstitial fibrosis increased and RBF and GFR decreased in MetS+RVD vs. MetS, but were restored in MetS+RVD+EV (). Conclusions Intra‐renal delivery of MSC‐derived EVs bearing pro‐angiogenic properties in swine MetS+RVD restored stenotic‐kidney microcirculation, and in turn its hemodynamics and function. Our study suggests a novel therapeutic potential for MSC‐derived EVs in restoring renal function in chronic experimental MetS+RVD. Support or Funding Information This study was partly supported by NIH grant numbers DK73608, DK104273, HL123160, and DK102325, DK106427, the Mayo Clinic Center for Regenerative Medicine, and the Mayo Clinic Mary Kathryn and Michael B. Panitch Career Development Award.

Diffusion measurements in the kidney are affected not only by renal microstructure but also by physiological processes (i.e., glomerular filtration, water reabsorption, and urine formation). Because of the superposition of passive tissue diffusion, blood perfusion, and tubular pre‐urine flow, the limitations of the monoexponential apparent diffusion coefficient (ADC) model in assessing pathophysiological changes in renal tissue are becoming apparent and motivate the development of more advanced diffusion‐weighted imaging (DWI) variants. These approaches take advantage of the fact that the length scale probed in DWI measurements can be adjusted by experimental parameters, including diffusion‐weighting, diffusion gradient directions and diffusion time. This forms the basis by which advanced DWI models can be used to capture not only passive diffusion effects, but also microcirculation, compartmentalization, tissue anisotropy. In this review, we provide a comprehensive overview of the recent advancements in the field of renal DWI. Following a short introduction on renal structure and physiology, we present the key methodological approaches for the acquisition and analysis of renal DWI data, including intravoxel incoherent motion (IVIM), diffusion tensor imaging (DTI), non‐Gaussian diffusion, and hybrid IVIM‐DTI. We then briefly summarize the applications of these methods in chronic kidney disease and renal allograft dysfunction. Finally, we discuss the challenges and potential avenues for further development of renal DWI.Level of Evidence5Technical EfficacyStage 2

Introduction: The carotid artery rim sign on CTA is characterized by soft-plaque components surrounded by a rind of thin, adventitial calcification and its role in plaque instability is not established yet. Intraplaque hemorrhage (IPH) and the inflammatory microenvironment in carotid atheroma are considered features of atherosclerotic plaque vulnerability leading to cerebrovascular events. Hypothesis: The association between rim sign on CTA and carotid IPH and inflammation remains scantly investigated. In this study, we aimed to determine whether rim sign is associated with IPH on MRA and with the extent of IPH and inflammation on histology. We hypothesized that rim sign may be a radiological predictor of carotid IPH and inflammation. Methods: We retrospectively enrolled 100 consecutive patients who underwent carotid endarterectomy (CEA) and neck CTA before CEA. On CTA, the ipsilateral rim sign was defined as the presence of adventitial calcifications with internal soft-tissue plaque of ≥2 mm in maximum thickness. Of the included patients, 25 had MRA with 3D magnetization-prepared rapid acquisition with gradient echo (MPRAGE) sequence. Carotid plaque specimens were collected and stained with H&E to quantify IPH (%). Histologically, we defined IPH as an area of carotid plaque with blood elements, and inflammatory microenvironment as the presence of lymphocytes and plasma cells (chronic inflammation) and foam cells. Results: The rim sign on CTA was present in 56 (56%) of patients. IPH on MRA was present in 11 (44%) patients. The rim sign was significantly associated with the presence of IPH on MRA [9 (81.8%) vs 2 (14.3%); p=0.003]. On histology, the rim sign was associated with a higher extent of IPH [5.0 % (IQR 2.0-25.0) vs 5.0% (IQR 0.0-10.0); p=0.017], with chronic inflammation [44 (78.6%) vs 12 (21.4%); p=0.003], and foam cells [51 (91.1%) vs 5 (8.9%); p<0.001]. Conclusions: These findings suggest that rim sign on CTA may be proposed as a potential imaging marker of IPH as well as a histologic predictor of IPH extent and carotid plaque inflammatory microenvironment.

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

Cardiovascular disease is often a disease of aging. Considerable advances in our understanding of the biological mechanisms of aging have been made; yet, cardiovascular disease remains the leading cause of death in the United States urging a continued search for novel risk factors to target for preventing and treating disease. Mental stress (MS) is emerging as an important risk factor, and while progress has been made in understanding the link between MS and cardiovascular disease, the precise mechanisms of a putative causal relationship require greater clarification. In the current review, we (1) summarize our current understanding of the pathological effects of MS on vascular health; (2) describe important aspects of the pathobiology of vascular aging including inflammation, oxidative stress, mitochondrial dysfunction as well as novel processes such as genomic instability, epigenetic alterations, and nutrient signal pathways; (3) highlight similarities in the downstream biologic effects of aging and MS on vascular health with an emphasis on cellular and molecular processes that could be used to develop novel prognostic markers and treatment strategies for cardiovascular disease; (4) discuss lifestyle and pharmacological methods that target indicators of aging whose role could be translated into approaches managing the effects of MS; and (5) outline important future steps that should be considered in this area of research including the need for prospective clinical trials and for creating greater collaboration between preclinical aging researchers and clinical investigators managing MS.