Citations

Scattered tubular-like cells (STCs) are dedifferentiated renal tubular cells that repair other damaged kidney cells. This study shows that renovascular disease (RVD) induces site-specific 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) modifications in DNA associated with transcriptional changes and impaired proliferative capacity of swine STCs, which could be mitigated in RVD-STCs treated with an epigenetic modulator. Therefore, our observations may contribute to the development of novel approaches to preserve the reparative capacity of STCs in individuals with RVD.

Objective: This study aims to develop a contrast-free, high-sensitivity ultrasound method, denoted as Radon transform-based flow measurement (R-Flow), for in vivo mapping of microvascular flow vectors and for establishing R-Flow-derived vector-field metrics to noninvasively quantify microcirculatory patterns in liver cirrhosis. Impact Statement: R-Flow enables robust, contrast-free imaging of microvascular dynamics and demonstrates translational feasibility in the human liver. Its direction-aware indices offer pilot in vivo quantification of flow redistribution and remodeling, providing unique insights into hepatic flow dynamics. Introduction: Microvascular dysfunction is a hallmark of many diseases, yet noninvasive visualization and quantitative assessment of abnormal microcirculation remain limited. Methods: R-Flow leverages Radon transform to decode red blood cell dynamics from the spatiotemporal domain of ultrasound flow signals, reconstructing velocity vectors at microvascular scale. From these vector maps, unique direction-aware indices are further derived to characterize flow distribution and heterogeneity. Results: Validated across simulations, phantoms, and in vivo studies, R-Flow provides robust velocity estimation across a wide range (1 to 60 mm/s). Notably, it enables high-sensitivity microvascular flow vector mapping of human liver, showing strong agreement with references ( r > 0.9). In a rat model, these direction-aware indices revealed a shift from healthy multipath perfusion in control livers to directionally biased vascular pattern in cirrhotic livers, demonstrating significant correlation with pathological indicators. Conclusion: R-Flow enables noninvasive, contrast-free mapping of microvascular blood flow velocity and offers a promising approach for high-resolution assessment of microvascular flow characteristics.

Abstract Kidney injury is a major medical burden and one of the most common reasons for hospitalization and poor life quality. Kidney injury can include acute kidney injury, chronic kidney disease, and immune-mediated kidney diseases most of which have no definitive therapy. The spleen is a secondary lymphoid organ in the reticuloendothelial system that plays an important role in protecting the body from various diseases. Notably, spleen tyrosine kinase, a non-receptor tyrosine kinase, is a crucial player that aids in immunity and protection and is highly expressed in the kidney and hematopoietic cells. It has been shown that alterations in spleen tyrosine kinase function or expression could lead to a wide range of diseases and abnormalities. Over the past decade, the role of spleen and spleen tyrosine kinase in multiple kidney diseases has emerged. Evidence suggests that modulating the spleno-renal connection through activation of the cholinergic anti-inflammatory pathway can be a promising strategy for protecting against kidney injury. Imitating the protective function of the spleen through interleukin-10-extracellular vesicles can also be of therapeutic value. In addition, evidence showed that inhibition of the spleen tyrosine kinase leads to amelioration of the kidney injury. However, further exploration and long-term studies are needed to unravel the spleno-renal connection, as well as the efficacy of spleen tyrosine kinase inhibitors, before they can be used as means for treatment of kidney injury. Graphical Abstract

Key Points Renovascular disease impairs the capacity of human adipose tissue–derived mesenchymal stem/stromal cells to repair ischemic murine kidneys. miR-378h modulated the capacity of renovascular disease adipose tissue–derived mesenchymal stem/stromal cells to repair ischemic kidneys in vivo . Background Renovascular disease leads to renal ischemia, hypertension, and eventual kidney failure. Autologous transplantation of adipose tissue–derived mesenchymal stem/stromal cells (MSCs) improves perfusion and oxygenation in stenotic human kidneys, but associated atherosclerosis and hypertension might blunt their effectiveness. We hypothesized that renovascular disease alters the human MSC transcriptome and impairs their reparative potency. Methods MSCs were harvested from subcutaneous abdominal fat of patients with renovascular disease and healthy volunteers ( n =3 each), characterized and subsequently injected (5×10 5 /200 μ l) into mice 2 weeks after renal artery stenosis or sham surgery ( n =6/group). Two weeks later, mice underwent imaging and tissue studies. MSCs from healthy volunteers and in those with renovascular disease were also characterized by mRNA/microRNA (miRNA) sequencing. Based on these, MSC proliferation and mitochondrial damage were assessed in vitro before and after miRNA modulation and in vivo in additional renal artery stenosis mice administered with MSCs from renovascular disease pretreated with miR-378h mimic ( n =5) or inhibitor ( n =4). Results MSCs engrafted in stenotic mouse kidneys. Healthy volunteer MSCs (but not renovascular disease MSCs) decreased BP, improved serum creatinine levels and stenotic-kidney cortical perfusion and oxygenation, and attenuated peritubular capillary loss, tubular injury, and fibrosis. Genes upregulated in renovascular disease MSCs versus healthy volunteer MSCs were mostly implicated in transcription and cell proliferation, whereas those downregulated encoded mainly mitochondrial proteins. Upregulated miRNAs, including miR-378h, primarily target nuclear-encoded mitochondrial genes, whereas downregulated miRNAs mainly target genes implicated in transcription and cell proliferation. MSC proliferation was similar, but their mitochondrial structure and reparative function both in vivo and in vitro improved after miR-378h inhibition. Conclusions Renovascular disease impaired the reparative capacity of human MSCs, possibly by dysregulating miR-378h that targets mitochondrial genes. Podcast This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/JASN/2024_08_21_ASN0000000000000440.mp3

Extracellular vesicles are important vectors for cell-cell communication and show potential value for diagnosis and treatment of kidney diseases. The pathologic diagnosis of kidney diseases relies on kidney biopsy, whereas collection of extracellular vesicles from urine or circulating blood may constitute a less invasive diagnostic tool. In particular, urinary extracellular vesicles released mainly from resident kidney cells might provide an alternative tool for detection of kidney injury. Because extracellular vesicles mirror many features of their parent cells, cargoes of several populations of urinary extracellular vesicles are promising biomarkers for disease processes, like diabetic kidney disease, kidney transplant, and lupus nephritis. Contrarily, extracellular vesicles derived from reparative cells, such as mesenchymal stem cells, tubular epithelial progenitor cells, and human umbilical cord blood represent promising regenerative tools for treatment of kidney diseases. Furthermore, induced pluripotent stem cells–derived and engineered extracellular vesicles are being developed for specific applications for the kidney. Nevertheless, some assumptions regarding the specificity and immunogenicity of extracellular vesicles remain to be established. This review focuses on the utility of extracellular vesicles as therapeutic and diagnostic (theranostic) tools in kidney diseases and future directions for studies.

Background: Percutaneous transluminal renal angioplasty (PTRA) confers clinical and mortality benefits in select ‘high-risk’ patients with renovascular disease (RVD). Intra-renal-delivered extracellular vesicles (EVs) released from mesenchymal stem/stromal cells (MSCs) protect the kidney in experimental RVD, but have not been compared side-by-side to clinically applied interventions, such as PTRA. We hypothesized that MSC-derived EVs can comparably protect the post-stenotic kidney via direct tissue effects. Methods: Five groups of pigs (n = 6 each) were studied after 16 weeks of RVD, RVD treated 4 weeks earlier with either PTRA or MSC-derived EVs, and normal controls. Single-kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were assessed in vivo with multi-detector CT, and renal microvascular architecture (3D micro CT) and injury pathways ex vivo. Results: Despite sustained hypertension, EVs conferred greater improvement of intra-renal microvascular and peritubular capillary density compared to PTRA, associated with attenuation of renal inflammation, oxidative stress, and tubulo-interstitial fibrosis. Nevertheless, stenotic kidney RBF and GFR similarly rose in both PTRA- and EV-treated pigs compared RVD + Sham. mRNA sequencing reveled that EVs were enriched with pro-angiogenic, anti-inflammatory, and antioxidants genes. Conclusion: MSC-derived EVs elicit a better preservation of the stenotic kidney microvasculature and greater attenuation of renal injury and fibrosis compared to PTRA, possibly partly attributed to their cargo of vasculo-protective genes. Yet, both strategies similarly improve renal hemodynamics and function. These observations shed light on diverse mechanisms implicated in improvement of post-stenotic kidney function and position EVs as a promising therapeutic intervention in RVD.

Tumor necrosis factor-α-induced gene/protein (TSG)-6 regulates the immunomodulatory properties of MSCs, but its ability to protect the ischemic kidney is unknown. In pigs with renal artery stenosis, we show that MSC delivery increased renal vein TSG-6, decreased kidney inflammatory macrophages, and improved renal function. In vitro, TSG-6 decreased inflammatory macrophages and tubular cell injury. Therefore, TSG-6 released from MSCs may decrease renal tubular cell injury, which is associated with regulating macrophage function and phenotype.

Scattered tubular-like cells (STCs), dedifferentiated renal tubular epithelial cells, contribute to renal self-healing, but severe injury might blunt their effectiveness. We hypothesized that ischemic renovascular disease (RVD) induces senescence in STC and impairs their reparative potency. CD24+/CD133+ STCs were isolated from swine kidneys after 16 weeks of RVD or healthy controls. To test their reparative capabilities in injured kidneys, control or RVD-STC (5×10 5 ) were prelabeled and injected into the aorta of 2 kidneys, 1-clip (2k,1c) mice 2 weeks after surgery. Murine renal function and oxygenation were studied in vivo 2 weeks after injection using micro-magnetic resonance imaging, and fibrosis, tubulointerstitial injury, capillary density, and expression of profibrotic and inflammatory genes ex vivo. STC isolated from swine RVD kidneys showed increased gene expression of senescence and senescence-associated secretory phenotype markers and positive SA-β-gal staining. Delivery of normal pig STCs in 2k,1c mice improved murine renal perfusion, blood flow, and glomerular filtration rate, and downregulated profibrotic and inflammatory gene expression. These renoprotective effects were blunted using STC harvested from RVD kidneys, which also failed to attenuate hypoxia, fibrosis, tubular injury, and capillary loss in injured mouse 2k,1c kidneys. Hence, RVD may induce senescence in endogenous STC and impair their reparative capacity. These observations implicate cellular senescence in the pathophysiology of ischemic kidney disease and support senolytic therapy to permit self-healing of senescent kidneys.

Abstract BACKGROUND Renovascular hypertension (RVH) often manifest with metabolic syndrome (MetS) as well. Coexisting MetS and hypertension increases cardiovascular morbidity and mortality, but the mechanisms underlying cardiac injury remain unknown. We hypothesized that superimposition of MetS induces myocardial mitochondrial damage, leading to cardiac injury and dysfunction in swine RVH. METHODS Pigs were studied after 16 weeks of diet-induced MetS with or without RVH (unilateral renal artery stenosis), and Lean controls (n = 6 each). Systolic and diastolic cardiac function were assessed by multidetector CT, and cardiac mitochondrial morphology (electron microscopy) and myocardial function in tissue and isolated mitochondria. RESULTS Body weight was similarly higher in MetS groups vs. Lean. RVH groups achieved significant stenosis and developed hypertension. Mitochondrial matrix density and adenosine triphosphate production were lower and H2O2 production higher in RVH groups vs. Lean and MetS. Lean + RVH (but not MetS + RVH) activated mitophagy, which was associated with decreased myocardial expression of mitophagy-related microRNAs. MetS groups exhibited higher numbers of intermitochondrial junctions, which could have prevented membrane depolarization/activation of mitophagy in MetS + RVH. Cardiac fibrosis, hypertrophy (increased left ventricular muscle mass), and diastolic function (decreased E/A ratio) were greater in MetS + RVH vs. Lean + RVH. CONCLUSIONS MetS+RVH induces myocardial mitochondrial damage and dysfunction. 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 therapeutic targets to ameliorate cardiac damage and dysfunction in patients with coexisting MetS and RVH.

Background. Coexisting metabolic syndrome (MetS) and renal artery stenosis (RAS) are linked to poor renal outcomes. Mesenchymal stem/stromal cell- (MSC-) derived extracellular vesicles (EVs) from lean animals show superior ability to repair the experimental MetS+RAS kidney compared to EVs from MetS pig MSCs. We hypothesized that MetS leads to selective packaging in porcine EVs of microRNAs capable of targeting mitochondrial genes, interfering with their capacity to repair the MetS+RAS kidney. Methods. Five groups of pigs ( n = 7 each) were studied after 16 weeks of diet-induced MetS and RAS (MetS+RAS) and MetS+RAS 4 weeks after a single intrarenal delivery of EVs harvested from allogeneic adipose tissue-derived MSCs isolated from Lean or MetS pigs, and Lean or MetS sham controls. Single-kidney blood flow (RBF) and glomerular filtration rate (GFR) were assessed in vivo with multidetector CT, whereas EV microRNA cargo, renal tubular mitochondrial structure and bioenergetics, and renal injury pathways were assessed ex vivo. Results. microRNA sequencing revealed 19 dysregulated microRNAs capable of targeting several mitochondrial genes in MetS-EVs versus Lean-EVs. Lean- and MetS-EVs were detected in the stenotic kidney 4 weeks after administration. However, only MetS-EVs failed to improve renal mitochondrial density, structure, and function or attenuate oxidative stress, tubular injury, and fibrosis. Furthermore, Lean-EVs but not MetS-EVs restored RBF and GFR in MetS+RAS. Conclusion. MetS alters the cargo of mitochondria-related microRNAs in swine MSC-derived EVs, which might impair their capacity to repair the poststenotic kidney in MetS+RAS. These observations may contribute to develop approaches to improve the efficacy of MSC-EVs for patients with MetS.