Citations

Our study demonstrates a novel pericyte-based therapy for the injured kidney. The beneficial effect of pericyte delivery appears to be mediated by ameliorating oxidative stress, inflammation, cellular apoptosis, and senescence in the stenotic kidney and improved tissue hypoxia, vascular loss, fibrosis, and tubular atrophy. Our data may form the basis for pericyte-based therapy, and additional research studies are needed to gain further insight into their role in improving renal function.

Background: Scattered tubular-like cells (STCs) are dedifferentiated renal tubular cells endowed with progenitor-like characteristics to repair injured parenchymal cells. STCs may be damaged and rendered ineffective by renal artery stenosis (RAS), but the underlying processes remain unclear. We hypothesized that RAS alters the epigenetic landscape on DNA and the ensuing gene transcriptional profile of swine STCs. Methods: CD24+/CD133+ STCs were isolated from pig kidneys after 10 weeks of RAS or sham (n = 3 each) and their whole 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) profiles were examined by 5mC and 5hmC immunoprecipitation sequencing (MeDIP-/hMeDIP-seq, respectively). A subsequent integrated (MeDIP/hMeDIP-seq/mRNA-seq) analysis was performed by comparing all online available gene sets using Gene Set Enrichment Analysis. Apoptosis, proteolysis, and mitochondrial structure and function were subsequently evaluated in vitro. Results: Differential expression (DE) analysis revealed 239 genes with higher and 236 with lower 5mC levels and 275 genes with higher and 315 with lower 5hmC levels in RAS-STCs compared to Normal-STCs (fold change ≥1.4 or ≤0.7, p ≤ 0.05). Integrated MeDIP-/hMeDIP-seq/mRNA-seq analysis identified several overlapping (DE-5mC/mRNA and DE-5hmC/mRNA levels) genes primarily implicated in apoptosis, proteolysis, and mitochondrial functions. Furthermore, RAS-STCs exhibited decreased apoptosis, mitochondrial matrix density, and ATP production, and increased intracellular amino acid concentration and ubiquitin expression. Conclusions: Renal ischemia induces epigenetic changes in apoptosis-, proteolysis-, and mitochondria-related genes, which correlate with alterations in the transcriptomic profile and corresponding function of swine STCs. These observations may contribute to developing novel targeted interventions to preserve the reparative potency of STCs in renal disease.

ABSTRACT Background Renal artery stenosis (RAS) is an important cause of chronic kidney disease and secondary hypertension. In animal models, renal ischemia leads to downregulation of growth factor expression and loss of intrarenal microcirculation. However, little is known about the sequelae of large-vessel occlusive disease on the microcirculation within human kidneys. Method This study included five patients who underwent nephrectomy due to renovascular occlusion and seven nonstenotic discarded donor kidneys (four deceased donors). Micro-computed tomography was performed to assess microvascular spatial densities and tortuosity, an index of microvascular immaturity. Renal protein expression, gene expression and histology were studied in vitro using immunoblotting, polymerase chain reaction and staining. Results RAS demonstrated a loss of medium-sized vessels (0.2–0.3 mm) compared with donor kidneys (P = 0.037) and increased microvascular tortuosity. RAS kidneys had greater protein expression of angiopoietin-1, hypoxia-inducible factor-1α and thrombospondin-1 but lower protein expression of vascular endothelial growth factor (VEGF) than donor kidneys. Renal fibrosis, loss of peritubular capillaries (PTCs) and pericyte detachment were greater in RAS, yet they had more newly formed PTCs than donor kidneys. Therefore, our study quantified significant microvascular remodeling in the poststenotic human kidney. RAS induced renal microvascular loss, vascular remodeling and fibrosis. Despite downregulated VEGF, stenotic kidneys upregulated compensatory angiogenic pathways related to angiopoietin-1. Conclusions These observations underscore the nature of human RAS as a microvascular disease distal to main vessel stenosis and support therapeutic strategies directly targeting the poststenotic kidney microcirculation in patients with RAS.

Background: The expansion of adipose mass requires adipocyte precursor cells that originate from multipotent mesenchymal stem cells (MSC). The inflammatory milieu in obesity often involves high levels of tumor necrosis factor (TNF)-α in adipose tissue, but whether this affects MSC function remains unknown. We tested the hypothesis that microenvironmental changes during the evolution of obesity affect MSC function, which may in turn promote obesity. Methods: Domestic pigs were fed with an adipogenic (n=7) or normal (n=7) diet for 16 weeks. Abdominal adipose tissue biopsies were collected at 8, 12, and 16 weeks for histology and MSC culture. Adipose tissue inflammation and MSC levels were evaluated in situ using immunohistochemistry staining for TNF-α, CD34, and Von Willebrand factor (vWF). The adipogenic propensity of MSC was tested in vitro using appropriate differentiation media, with or without supplementation of TNF-α or anti-TNF-α antibody for 3 weeks. Results: Obese pigs had increased body weight and abdominal fat mass (by CT) compared with lean pigs. TNF-α expression in adipose tissue (Figure 1A) was upregulated in obese pigs at 12 and 16 weeks, accompanied by increased numbers of MSC (CD34 + /vWF - ) at 16 weeks. In vitro, MSC derived from obese adipose tissue at 16weeks showed enhanced adipogenesis, which was abolished by anti-TNF-α treatment. Similarly, in lean MSC TNF-α treatment enhanced adipogenesis (Figure 1B). Conclusion: Obesity-induced adipose tissue inflammation may stimulate MSC differentiation into adipocytes, which further increase the adipose tissue mass. Our results support development of anti-inflammatory strategies for obesity management.

Objectives Quantitative magnetization transfer (qMT) is useful for measurement of murine renal fibrosis at high and ultrahigh field strengths. However, its utility at clinical field strengths and in human-like kidneys remains unknown. We tested the hypothesis that qMT would successfully detect fibrosis in swine kidneys with unilateral renal artery stenosis (RAS) at 3.0 T. Methods The qMT protocol is composed of MT scans with variable flip angles and offset frequencies, and of B0 , B1 , and T1 mapping. Pigs were scanned 10 weeks after RAS or control. A 2-pool model was used to fit the bound pool fraction f of the renal cortex (CO) and outer medulla (OM). Then qMT-derived f in 5 normal and 10 RAS pigs was compared with histological fibrosis determined using Masson's trichrome staining and to renal perfusion assessed with computed tomography. Results The qMT 2-pool model provided accurate fittings of data collected on swine kidneys. Stenotic kidneys showed significantly elevated f in both the CO (9.8% ± 2.7% vs 6.4% ± 0.9%, P = 0.002) and OM (7.6% ± 2.2% vs 4.7% ± 1.1%, P = 0.002), as compared with normal kidneys. Histology-measured renal fibrosis and qMT-derived f correlated directly in both the cortex (Pearson correlation coefficient r = 0.93, P < 0.001) and OM (r = 0.84, P = 0.002), and inversely with stenotic kidney perfusion (r = 0.85, P = 0.002). Conclusions This study demonstrates the feasibility of qMT for measuring fibrosis in human-like swine kidneys, and the association between tissue macromolecule content and renal perfusion. Therefore, qMT may be useful as a tool for noninvasive assessment of renal fibrosis in subjects with RAS at clinical field strengths.

AbstractImmune‐modulatory properties of adipose tissue‐derived mesenchymal stem/stromal cells (MSCs) might be susceptible to metabolic disturbances. We hypothesized that the immune‐modulatory function of MSCs might be blunted in obese human subjects. MSCs were collected from abdominal subcutaneous fat of obese and lean subjects during bariatric or kidney donation surgeries, respectively. MSCs were co‐cultured in vitro for 24 h with M1 macrophages, which were determined as M1or M2 phenotypes by flow cytometry, and cytokines measured in conditioned media. In vivo, lean or obese MSCs (5 × 105), or PBS, were injected into mice two weeks after unilateral renal artery stenosis (RAS) or sham surgeries (n = 6 each). Fourteen days later, kidneys were harvested and stained with M1 or M2 markers. Lean MSCs decreased macrophages M1 marker intensity, which remained elevated in macrophages co‐cultured with obese MSCs. TNF‐α levels were four‐fold higher in conditioned media collected from obese than from lean MSCs. RAS mouse kidneys were shrunk and showed increased M1 macrophage numbers and inflammatory cytokine expression compared with normal kidneys. Lean MSCs decreased M1 macrophages, M1/M2 ratio and inflammation in RAS kidneys, whereas obese MSCs did not. MSCs isolated from lean human subjects decrease inflammatory M1 macrophages both in vivo and in vitro, an immune‐modulatory function which is blunted in MSCs isolated from obese subjects.

Introduction: Morbidity and mortality attributable to hypertension are higher in African American (AAEH) compared to Caucasian essential hypertensive (EH) patients, possibly related to a differential effect on vascular injury and repair. While circulating endothelial progenitor cells (EPC) preserve endothelial integrity IEC detach from sites of injury and represent markers of vascular damage. We hypothesized that plasma levels of IEC and inflammatory markers would be higher in AAEH compared to EH patients. METHODS: Inferior vena cava levels of CD34+/KDR+ (EPC) and VAP-1+ (IEC) cells were measured by FACS in EH and AAEH under fixed sodium intake (150 mEq/d) and blockade of the renin-angiotensin-system, and compared to systemic levels in normotensive control subjects (n=19 each). Systemic levels of inflammatory cytokines and EPC homing factors were measured by Luminex. Results: Blood pressure, serum creatinine, lipids, antihypertensive medications, and EPC levels did not differ between EH and AAEH patients. Circulating IEC were higher in AAEH, and inversely correlated with EPC levels (Figure). Systemic levels of inflammatory cytokines and EPC homing factors were higher in AAEH compared to EH patients (Table), and correlated directly with IEC. Conclusion: Despite preserved kidney function and controlled BP, circulating inflammatory markers were elevated in AAEH and correlated with increased IEC and decreased EPC levels. Increased release of cytokines and IEC in AAEH may impair EPC reparative capacity and predispose to hypertensive vascular injury. This process may aggravate vascular damage and accelerate hypertension-related morbidity/mortality rates in AAEH.

Background : Renovascular disease (RVD) and impaired renal function are important risk factors for cardiac disease, but it remained unclear whether selective recovery of renal function can reverse cardiac dysfunction. Aims: This study tested the hypothesis that improvement in renal function using selective intra-renal administration of endothelial progenitor cells (EPC) in swine renovascular hypertension would improve myocardial microvascular (MV) integrity. Methods: The functions of the myocardial MV (response to IV adenosine) and the stenotic kidney of 7 pigs were assessed in-vivo using multi-detector CT after 6 weeks of RVD and hypertension. Autologous EPC expanded in culture were then infused (10x10 6 cells) intra-renally, and in vivo studies repeated 4 wks later. Six normal pigs served as controls. Results : Glomerular filtration rate was lower in RVD compared to normal (47.9±10.1 vs. 70.8±4.3 mL/min, p<0.05) and improved after EPC (to 62.7±1.5 mL/min, p=NS vs. normal), as did renal blood flow. Mean arterial pressure remained elevated after EPC (120.7±11 and 129.4±6 vs. 99.9±4.7 mmHg in normal, p<0.05), and plasma renin activity was unchanged. Myocardial MV permeability-surface area increased in RVD in response to adenosine (0.009±0.001 to 0.011±0.002 AU, p=0.01), while MV volume fraction decreased (4.3±0.8 to 2.7±0.6%, p=0.01), indicating impaired MV barrier function and integrity. Contrarily, both remained unchanged in response to adenosine 4 wks after EPC (0.01±0.002 to 0.01±0.002 AU, p=0.24, and 3.5±0.8 to 3.4±0.5%, p=0.46, respectively), as did normal MV. Conclusion : A single intra-renal infusion of EPC that improved renal function in experimental RVD also preserved remote myocardial MV function, despite sustained systemic hypertension. These findings underscore the cross talk between renal and cardiac function, and the potential of selective renal EPC intervention to preserve both the kidney and heart in RVD. Renal and myocardial microvascular function change in normal and RVD before and after EPC treatment

Background Mesenchymal stem/stromal cells (MSCs) release extracellular vesicles (EVs), which shuttle proteins to recipient cells, promoting cellular repair. We hypothesized that cardiovascular risk factors may alter the pattern of proteins packed within MSC‐derived EVs, blunting their capacity to preserve the post‐stenotic kidney in pigs with metabolic syndrome (MetS) and renal artery stenosis (RAS). Methods We compared the protein cargo of EVs to their parent MSCs obtained from pigs with MetS and Lean controls. Porcine MSCs were harvested from abdominal fat after 16 weeks of Lean‐ or MetS‐diet (n=5 each), and their EVs isolated. Following LC‐MS/MS proteomics, clustering analysis was performed to identify primary functional categories of proteins enriched in Lean‐ and MetS‐EVs. In addition, MetS pigs were studied after 16 weeks of RAS untreated or treated 4 weeks earlier with a single intrarenal delivery of allogeneic labeled Lean‐ or MetS‐EVs (2.5x10^5/Kg). Lean and MetS Sham served as controls (n=6 each). Single‐kidney volume, renal blood flow (RBF), and glomerular filtration rate (GFR) were studied in‐vivo (multi‐detector CT), and tubular injury (Periodic Acid Schiff) and fibrosis (Trichrome) ex‐vivo. Results Proteomics analysis identified 6,690 and 6,790 distinct proteins in Lean‐ and MetS‐EVs, respectively. Differential expression analysis revealed that 91 proteins were upregulated in Lean‐EVs and 130 proteins in MetS‐EVs compared to their parent MSCs (FDR<0.05 and log2 fold‐change EVs/MSCs>2). Proteins enriched exclusively in Lean‐EVs modulate pathways related to the MSC reparative capacity, including cell proliferation, differentiation, and activation, as well as transforming growth factor‐β signaling (Figure 1A). Contrarily, proteins enriched only in MetS‐EVs are linked to pro‐inflammatory pathways, including acute inflammatory response, leukocyte transendothelial migration, and cytokine production (Figure 1B). Blood pressure was elevated in all MetS groups and all RAS groups develop moderate, but significant stenosis of a similar degree (Table). EVs were detected in the stenotic‐kidney 4 weeks after injection (Figure 2A). Renal volume, RBF, and GFR, which increased in MetS compared to Lean (consistent with hyperfiltration), fell in MetS+RAS, but restored in pigs treated with Lean‐EVs. Lean‐EVs also attenuated tubular injury and renal fibrosis (Figure 2B). Yet, these renoprotective effects were blunted in pigs treated with MetS‐EVs. Conclusion MetS alters the protein cargo of porcine MSC‐derived EVs, selectively packaging specific pro‐inflammatory signatures. Intrarenal delivery of Lean‐EVs attenuated renal injury and fibrosis and improved function in pigs with MetS+RAS, whereas these beneficial effects were blunted in pigs treated with MetS‐EVs. Therefore, our observations suggest that approaches to improve the therapeutic efficacy of autologous MSC‐derived EVs might be useful for patients with MetS+RAS. Support or Funding Information This study was partly supported by the National Institutes of Health grant numbers: DK104273, HL123160, DK102325, and DK106427. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .