Zhu, Xiangyang

Renovascular disease (RVD) and hypertension (HT) are cardiovascular risk factors, but if recovery of renal function can reverse cardiac dysfunction remained unclear. We hypothesized that improved stenotic kidney function would rescue myocardial microvascular (MMV) function in renovascular HT by reducing oxidative stress and inflammation. Single‐kidney hemodynamics and function and MMV permeability were assessed in pigs in vivo using CT after 6 weeks of RVD. Autologous endothelial progenitor cells (EPC) were then infused intra‐renally, and studies repeated 4 weeks later (RVD+EPC, n=7). Normal and untreated RVD (n=7 each) served as controls. Blood pressure was similarly increased in RVD and RVD+EPC pigs. Compared to normal, RVD showed elevated systemic TNF‐alpha (142.3± 3.7 vs 43.3 ± 3.5 pg/ml, p<0.001) and oxidized‐LDL, blunted glomerular filtration rate (47.9±10.1 vs 70.8 ± 4.3 ml/min, p<0.05), decreased MMV volume fraction, increased MMV permeability, and myocardial fibrosis. EPC were rarely observed in myocardium. However, RVD+EPC showed a decrease in TNF‐alpha (90.5± 2.9, p<0.01 vs RVD) and oxidized‐LDL, implying decreased inflammation and oxidative stress. Furthermore, not only renal, but also MMV function were significantly improved in RVD+EPC. In conclusion, selective improvement in renal function reduces oxidative stress and inflammation and preserves remote MMV function, underscoring functionally important cardiorenal crosstalk.

Significance Statement Renal artery stenosis (RAS) engenders stenotic-kidney ischemia, dysfunction, and injury, but whether these are mediated by cellular senescence has not been elucidated. INK-ATTAC transgenic mice, high-resolution imaging, and unbiased single-cell RNA sequencing of murine kidneys demonstrated cellular senescence as an important mechanism of progressive injury to epithelial/stromal cells within poststenotic kidneys. Both p16-specific and broad quercetin/dasatinib interventions to blunt senescence improved renal function and structure, underscoring the central role of senescence in the pathogenesis. Furthermore, this mechanism was conserved in human subjects with RAS. These observations reveal new mechanisms that contribute to the pathogenesis of chronic ischemic renal injury, and support the development of senolytic therapy to reduce senescent cell burden and delay renal injury. Background Peripheral vascular diseases may induce chronic ischemia and cellular injury distal to the arterial obstruction. Cellular senescence involves proliferation arrest in response to stress, which can damage neighboring cells. Renal artery stenosis (RAS) induces stenotic-kidney dysfunction and injury, but whether these arise from cellular senescenceand their temporal pattern remain unknown. Methods Chronic renal ischemia was induced in transgenic INK-ATTAC and wild type C57BL/6 mice by unilateral RAS, and kidney function ( in vivo micro-MRI) and tissue damage were assessed. Mouse healthy and stenotic kidneys were analyzed using unbiased single-cell RNA-sequencing. To demonstrate translational relevance, cellular senescence was studied in human stenotic kidneys. Results Using intraperitoneal AP20187 injections starting 1, 2, or 4 weeks after RAS, selective clearance of cells highly expressing p16 Ink4a attenuated cellular senescence and improved stenotic-kidney function; however, starting treatment immediately after RAS induction was unsuccessful. Broader clearance of senescent cells, using the oral senolytic combination dasatinib and quercetin, in C57BL/6 RAS mice was more effective in clearing cells positive for p21 ( Cdkn1a ) and alleviating renal dysfunction and damage. Unbiased, single-cell RNA sequencing in freshly dissociated cells from healthy and stenotic mouse kidneys identified stenotic-kidney epithelial cells undergoing both mesenchymal transition and senescence. As in mice, injured human stenotic kidneys exhibited cellular senescence, suggesting this process is conserved. Conclusions Maladaptive tubular cell senescence, involving upregulated p16 ( Cdkn2a ), p19 ( Cdkn2d ), and p21 ( Cdkn1a ) expression, is associated with renal dysfunction and injury in chronic ischemia. These findings support development of senolytic strategies to delay chronic ischemic renal injury.

Introduction: Subjects with renovascular hypertension (RVH) often manifest with metabolic syndrome (MetS), increasing risk for heart failure, yet the mechanisms underlying cardiac injury remain unknown. Reduced mitophagy and accumulation of impaired mitochondria have been linked to progression of heart failure. Hypothesis: We hypothesized that superimposition of MetS on RVH in swine inhibits myocardial mitophagy, aggravating mitochondrial damage, cardiac injury and dysfunction. Methods: Pigs were studied after 16 weeks of RVH (renal artery stenosis) with or without diet-induced MetS, and Lean controls (n=6 each). Cardiac function was assessed in vivo (multidetector-CT), and cardiac mitochondrial structure, function, mitophagy, and myocardial fibrosis ex vivo. Results: MetS groups developed obesity, whereas RVH groups developed hypertension (Table). Mitochondrial matrix density and ATP production were lower and H2O2 production higher in both RVH groups vs. Lean and MetS (Fig. AB). However, MetS+RVH failed to activate mitophagy and downregulate myocardial expression of mitophagy-related microRNAs achieved by Lean+RVH (Fig. CD). Myocardial expression of the mitophagy marker PTEN-induced kinase (PINK)-1 inversely correlated with myocardial fibrosis (R 2 =0.195, p=0.031). Cardiac fibrosis, hypertrophy, and diastolic dysfunction (decreased E/A ratio) were greater in MetS+RVH vs. Lean+RVH (Table, Fig. E). Conclusions: MetS aggravates myocardial mitochondrial damage and dysfunction in swine RVH. MetS+RVH failed to activate mitophagy, resulting in greater cardiac remodeling, fibrosis, and diastolic dysfunction. Mitochondrial injury and impaired mitophagy may constitute important mechanisms and potential therapeutic targets to ameliorate cardiac structural damage and dysfunction in patients with coexisting MetS and RVH.

Mesenchymal stem/stromal cells (MSCs) facilitate repair in experimental diabetic kidney disease (DKD). However, the hyperglycemic and uremic milieu may diminish regenerative capacity of patient-derived therapy. We hypothesized that DKD reduces human MSC paracrine function. Adipose-derived MSC from 38 participants with DKD and 16 control subjects were assessed for cell surface markers, trilineage differentiation, RNA sequencing (RNA-seq), in vitro function (coculture or conditioned medium experiments with T cells and human kidney cells [HK-2]), secretome profile, and cellular senescence abundance. The direction of association between MSC function and patient characteristics were also tested. RNA-seq analysis identified 353 differentially expressed genes and downregulation of several immunomodulatory genes/pathways in DKD-MSC versus Control-MSC. DKD-MSC phenotype, differentiation, and tube formation capacity were preserved, but migration was reduced. DKD-MSC with and without interferon-γ priming inhibited T-cell proliferation greater than Control-MSC. DKD-MSC medium contained higher levels of anti-inflammatory cytokines (indoleamine 2,3-deoxygenase 1 and prostaglandin-E2) and prorepair factors (hepatocyte growth factor and stromal cell–derived factor 1) but lower IL-6 versus control-MSC medium. DKD-MSC medium protected high glucose plus transforming growth factor-β–exposed HK-2 cells by reducing apoptotic, fibrotic, and inflammatory marker expression. Few DKD-MSC functions were affected by patient characteristics, including age, sex, BMI, hemoglobin A1c, kidney function, and urine albumin excretion. However, senescence-associated β-galactosidase activity was lower in DKD-MSC from participants on metformin therapy. Therefore, while DKD altered the transcriptome and migratory function of culture-expanded MSCs, DKD-MSC functionality, trophic factor secretion, and immunomodulatory activities contributing to repair remained intact. These observations support testing of patient-derived MSC therapy and may inform preconditioning regimens in DKD clinical trials.

AbstractPercutaneous transluminal renal angioplasty (PTRA) has been used to treat renovascular disease (RVD), a chronic condition characterized by renal ischemia and metabolic abnormalities. Mitochondrial injury has been implicated as a central pathogenic mechanism in RVD, but whether it can be reversed by PTRA remains uncertain. We hypothesized that PTRA attenuates mitochondrial damage, renal injury, and dysfunction in pigs with coexisting renal artery stenosis (RAS) and metabolic syndrome (MetS). Four groups of pigs (n = 6 each) were studied after 16 weeks of diet‐induced MetS and RAS (MetS + RAS), MetS + RAS treated 4 weeks earlier with PTRA, and Lean and MetS Sham controls. Single‐kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were assessed in vivo with multidetector computed tomography, and renal tubular mitochondrial structure and function and renal injury ex vivo. PTRA successfully restored renal artery patency, but mean arterial pressure remained unchanged. Stenotic kidney RBF and GFR, which fell in MetS + RAS compared to MetS, rose after PTRA. PTRA attenuated MetS + RAS‐induced mitochondrial structural abnormalities in tubular cells and peritubular capillary endothelial cells, decreased mitochondrial H202 production, and increased renal cytochrome‐c oxidase‐IV activity and ATP production. PTRA also improved cortical microvascular and peritubular capillary density and ameliorated tubular injury and tubulointerstitial fibrosis in the poststenotic kidney. Importantly, renal mitochondrial damage correlated with poststenotic injury and dysfunction. Renal revascularization attenuated mitochondrial injury and improved renal hemodynamics and function in swine poststenotic kidneys. This study suggests a novel mechanism by which PTRA might be relatively effective in ameliorating mitochondrial damage and improving renal function in coexisting MetS and RAS.

AbstractCell stress may give rise to insuperable growth arrest, which is defined as cellular senescence. Stenotic kidney (STK) ischemia and injury induced by renal artery stenosis (RAS) may be associated with cellular senescence. Mesenchymal stem cells (MSCs) decrease some forms of STK injury, but their ability to reverse senescence in RAS remains unknown. We hypothesized that RAS evokes STK senescence, which would be ameliorated by MSCs. Mice were studied after 4 weeks of RAS, RAS treated with adipose tissue‐derived MSCs 2 weeks earlier, or sham. STK senescence‐associated β‐galactosidase (SA‐β‐Gal) activity was measured. Protein and gene expression was used to assess senescence and the senescence‐associated secretory phenotype (SASP), and staining for renal fibrosis, inflammation, and capillary density. In addition, senescence was assessed as p16+ and p21+ urinary exosomes in patients with renovascular hypertension (RVH) without or 3 months after autologous adipose tissue‐derived MSC delivery, and in healthy volunteers (HV). In RAS mice, STK SA‐β‐Gal activity increased, and senescence and SASP marker expression was markedly elevated. MSCs improved renal function, fibrosis, inflammation, and capillary density, and attenuated SA‐β‐Gal activity, but most senescence and SASP levels remained unchanged. Congruently, in human RVH, p21+ urinary exosomes were elevated compared to HV, and only slightly improved by MSC, whereas p16+ exosomes remained unchanged. Therefore, RAS triggers renal senescence in both mice and human subjects. MSCs decrease renal injury, but only partly mitigate renal senescence. These observations support exploration of targeted senolytic therapy in RAS.

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.

Metabolic syndrome (MetS) profoundly changes the contents of mesenchymal stem cells and mesenchymal stem cells–derived extracellular vesicles (EVs). The anti-inflammatory TGF-β (transforming growth factor-β) is selectively enriched in EVs from Lean but not from MetS pigs, but the functional impact of this endowment remains unknown. We hypothesized that Lean-EVs more effectively induce regulatory T cells in injured kidneys. Five groups of pigs (n=7 each) were studied after 16 weeks of diet-induced MetS and unilateral renal artery stenosis (RAS; MetS+RAS). Two groups of MetS+RAS were treated 4 weeks earlier with an intrarenal injection of either Lean-EVs or MetS-EVs. MetS+RAS had lower renal volume, renal blood flow, and glomerular filtration rate than MetS pigs. Compared with Lean-EVs, MetS-EVs were less effective in improving renal function and decreasing tubular injury and fibrosis in MetS+RAS. Lean-EVs upregulated TGF-β expression in stenotic kidney and increased regulatory T cells numbers more prominently. Furthermore, markedly upregulated anti-inflammatory M2 macrophages reduced proinflammatory M1 macrophages, and CD8 + T cells were detected in stenotic kidneys treated with Lean-EVs compared with MetS-EVs, and renal vein levels of interleukin-1β were reduced. In vitro, coculture of Lean-EVs with activated T cells led to greater TGF-β-dependent regulatory T cells induction than did MetS-EVs. Therefore, the beneficial effects of mesenchymal stem cells–derived EVs on injured kidneys might be partly mediated by their content of TGF-β signaling components, which permitting increased Treg preponderance. Modulating EV cargo and transforming their functionality might be useful for renal repair.

Objective Activin A, an inflammatory mediator implicated in cellular senescence-induced adipose tissue dysfunction and profibrotic kidney injury, may become a new target for the treatment of diabetic kidney disease (DKD) and chronic kidney diseases. We tested the hypothesis that human DKD-related injury leads to upregulation of activin A in blood and urine and in a human kidney cell model. We further hypothesized that circulating activin A parallels kidney injury markers in DKD. Research design and methods In two adult diabetes cohorts and controls (Minnesota, USA; Galway, Ireland), the relationships between plasma (or urine) activin A, estimated glomerular filtration rate (eGFR) and DKD injury biomarkers were tested with logistic regression and correlation coefficients. Activin A, inflammatory, epithelial-mesenchymal-transition (EMT) and senescence markers were assayed in human kidney (HK-2) cells incubated in high glucose plus transforming growth factor-β1 or albumin. Results Plasma activin A levels were elevated in diabetes (n=206) compared with controls (n=76; 418.1 vs 259.3 pg/mL; p<0.001) and correlated inversely with eGFR (r s =−0.61; p<0.001; diabetes). After eGFR adjustment, only albuminuria (OR 1.56, 95% CI 1.16 to 2.09) and tumor necrosis factor receptor-1 (OR 6.40, 95% CI 1.08 to 38.00) associated with the highest activin tertile. Albuminuria also related to urinary activin (r s =0.65; p<0.001). Following in vitro HK-2 injury, activin, inflammatory, EMT genes and supernatant activin levels were increased. Conclusions Circulating activin A is increased in human DKD and correlates with reduced kidney function and kidney injury markers. DKD-injured human renal tubule cells develop a profibrotic and inflammatory phenotype with activin A upregulation. These findings underscore the role of inflammation and provide a basis for further exploration of activin A as a diagnostic marker and therapeutic target in DKD.