Krier, James D.

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.

Injection of A-MSC-derived EVs harvested from patients who are lean can resolve myocardial injury in mice with experimental renovascular hypertension more effectively than A-MSC-derived EVs from patients with obesity. These observations underscore and might have important ramifications for the self-healing capacity of patients with obesity and for the use of autologous EVs as a regenerative tool.

Renal fibrosis is an important marker in the progression of chronic kidney disease, and renal biopsy is the current reference standard for detecting its presence. Currently, non-invasive methods have only been partially successful in detecting renal fibrosis. Magnetization transfer imaging (MTI) allows estimates of renal fibrosis but may vary with scanning conditions. We hypothesized that MTI-derived renal fibrosis would be reproducible at 1.5T and 3T MRI and over time in fibrotic kidneys. Fifteen pigs with unilateral renal artery stenosis (RAS, n = 9) or age-matched sham controls (n = 6) underwent MTI-MRI at both 1.5T and 3T 6 weeks post-surgery and again 4 weeks later. Magnetization transfer ratio (MTR) measurements of fibrosis in both kidneys were compared between 1.5T and 3T, and the reproducibility of MTI at the two timepoints was evaluated at 1.5T and 3T. MTR at 3T with 600 Hz offset frequency successfully distinguished between normal, stenotic, and contralateral kidneys. There was excellent reproducibility of MTI at 1.5T and 3T over the two timepoints and no significant differences between MTR measurements at 1.5T and 3T. Therefore, MTI is a highly reproducible technique which is sensitive to detect changes in fibrotic compared to normal kidneys in the RAS porcine model at 3T.

Abstract Atherosclerotic renal artery stenosis (ARAS) is associated with irreversible parenchymal renal disease and regenerative stem cell therapies may improve renal outcomes. Hypoxia preconditioning (HPC) may improve the regenerative functions of adipose tissue-derived mesenchymal stem cells (AMSC) by affecting DNA 5-hydroxymethylcytosine (5hmC) marks in angiogenic genes. Here, we investigated using a porcine ARAS model, whether growth of ARAS AMSCs in hypoxia (Hx) versus normoxia (Nx) would enhance renal tissue repair, and comprehensively analyze how HPC modifies DNA hydroxymethylation compared to untreated ARAS and healthy/normal pigs (n=5 each). ARAS pigs exhibited elevated serum cholesterol, serum creatinine and renal artery stenosis, with a concomitant decrease in renal blood flow (RBF) and increased blood pressure (BP) compared to healthy pigs. Renal artery injection of either autologous Nx or Hx AMSCs improved diastolic BP, reduced kidney tissue fibrosis, and inflammation (CD3+ T-cells) in ARAS pigs. In addition, renal medullary hypoxia significantly lowered with Nx but not Hx AMSC treatment. Mechanistically, levels of epigenetic 5hmC marks (which reflect gene activation) estimated using DNA immunoprecipitation technique were elevated in profibrotic and inflammatory genes in ARAS compared with normal AMSCs. HPC significantly reduced 5hmC levels in cholesterol biosynthesis and oxidative stress response pathways in ARAS AMSCs. Thus, autologous AMSCs improve key renovascular parameters and inflammation in ARAS pigs, with HPC mitigating pathological molecular effects on inflammatory and profibrotic genes which may play a role in augmenting regenerative capacity of AMSCs.

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 : 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

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.