Alpha-1-Antitrypsin Protects Vascular Grafts of Brain-Dead Rats Against Ischemia/Reperfusion Injury.

INTRODUCTION: Endothelial dysfunction is a potential side effect of brain death (BD). Ischemia/reperfusion (IR) injury during heart transplantation may lead to further endothelial damage. Protective effects of alpha-1-antitrypsin (AAT), a human neutrophil serine protease inhibitor, have been demonstrated against IR injury. We hypothesized that AAT protects brain-dead rats' vascular grafts from IR injury. METHODS: Donor rats were subjected to BD by inflation of a subdural balloon. After 5.5 h, aortic rings were immediately mounted in organ baths (BD, n = 6 rats) or preserved in saline, supplemented either with vehicle (BD-IR, n = 8 rats) or AAT (BD-IR + AAT, n = 14 rats) for 24 h. During organ bath experiment, rings from both IR groups were exposed to hypochlorite to simulate warm reperfusion-associated endothelial injury. Endothelial function was measured ex vivo. Immunohistochemical staining for caspases was carried out and DNA-strand breaks were evaluated using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling. Data are presented as median (interquartile range). RESULTS: AAT improved IR-induced decreased maximum endothelium-dependent vasorelaxation to acetylcholine in the BD-IR + AAT aortas compared to the BD-IR group (BD: 83 (9-28) % versus BD-IR: 49 (39-60) % versus BD-IR + AAT: 64 (24-42) %, P < 0.05). Additionally, an increase in the rings' sensitivity to acetylcholine was noted after AAT (pD2-value: BD-IR + AAT: 7.35 (7.06-7.89) versus BD-IR: 6.96 (6.65-7.21), P < 0.05). Caspase-3, -8, -9, and -12 immunoreactivity and the number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells were significantly decreased by AAT. CONCLUSIONS: AAT alleviates endothelial dysfunction, prevents increased caspase-3, -8, -9, and -12 levels, and decreases apoptotic DNA breakage due to BD and IR injury. This suggests that AAT treatment may be therapeutically beneficial to reduce IR-induced vascular damage.

Netrin-1 Monoclonal Antibody-Functionalized Nanoparticle Loaded with Metformin Prevents the Progression of Abdominal Aortic Aneurysms.

Background: Abdominal aortic aneurysms (AAAs) are a global health and economic burden. Therapeutic strategies to inhibit the progression of AAAs are currently lacking. Recently, the therapeutic effect of metformin on aneurysms has attracted considerable interest. However, the unfavorable pharmacokinetic properties of metformin limit its feasibility for AAA treatment. Methods and Results: We constructed a metformin-loaded netrin-1-responsive AAA-targeted nanoparticle (Tgt-NP-Met) for AAA management. Evaluation of the therapeutic effect of Tgt-NP-Met was performed by in vitro and in vivo experiments. Our results showed that the binding of netrin-1 monoclonal antibodies enhanced the AAA-targeting capability of nanoparticles (NPs). Moreover, Tgt-NP-Met administration prevented AAA development and reduced the aneurysm diameter in apolipoprotein E (ApoE)-deficient (ApoE-/-) mice that received continuous infusion of angiotensin II. Furthermore, metformin prevented AAA progression by inhibiting the transformation of vascular smooth muscle cells (VSMCs) from a contractile phenotype to a synthetic phenotype, which is mediated by macrophage infiltration and activation. Conclusion: Our findings identify metformin as a functional suppressor for macrophage-mediated phenotypic transformation of VSMCs and Tgt-NP-Met as an efficient therapeutic strategy for AAA management.

ADGRG1 enriches for functional human hematopoietic stem cells following ex vivo expansion-induced mitochondrial oxidative stress.

The heterogeneity of human hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) under stress conditions such as ex vivo expansion is poorly understood. Here, we report that the frequencies of SCID-repopulating cells were greatly decreased in cord blood (CB) CD34+ HSCs and HPCs upon ex vivo culturing. Transcriptomic analysis and metabolic profiling demonstrated that mitochondrial oxidative stress of human CB HSCs and HPCs notably increased, along with loss of stemness. Limiting dilution analysis revealed that functional human HSCs were enriched in cell populations with low levels of mitochondrial ROS (mitoROS) during ex vivo culturing. Using single-cell RNA-Seq analysis of the mitoROS low cell population, we demonstrated that functional HSCs were substantially enriched in the adhesion GPCR G1-positive (ADGRG1+) population of CD34+CD133+ CB cells upon ex vivo expansion stress. Gene set enrichment analysis revealed that HSC signature genes including MSI2 and MLLT3 were enriched in CD34+CD133+ADGRG1+ CB HSCs. Our study reveals that ADGRG1 enriches for functional human HSCs under oxidative stress during ex vivo culturing, which can be a reliable target for drug screening of agonists of HSC expansion.

Monitoring of perfusion quality and prediction of donor heart function during ex-vivo machine perfusion by myocardial microcirculation versus surrogate parameters.

Currently, lactate (Lac) is used to evaluate machine perfusion (MP) of hearts, donated after circulatory death (DCD). We hypothesize that monitoring of myocardial microcirculation (mLDP) by Laser-Doppler-Perfusion is superior to Lac to evaluate perfusion and predict contractility. In a pig model, DCD-hearts were perfused 4 hours followed by reperfusion and left ventricular contractility measurement. Lac and mLDP were measured every 30 min in successfully (N = 9) and unsuccessfully (N = 7) maintained hearts. Successfully maintained hearts showed decreasing Lac (5.6 to 2.8 mmol/L) and slightly downregulated (92%) mLDP. In unsuccessfully maintained hearts Lac first decreased (5.1 to 3.8 mmol/L) followed by increase and mLDP dropped to 39%. In a single-variable regression only mLDP showed a significant r² for systolic (0.514, p = 0.045) and diastolic (0.501, p = 0.049) parameters. The combination of mLDP and Lac (r2 = 0.876, p = 0.005) showed best results. mLDP seems to be superior to Lac to show perfusion disorders and predict DCD-heart contractility.

Machine perfusion of circulatory determined death hearts: A scoping review.

BACKGROUND: Ex vivo machine perfusion (EVMP) is reported to can successfully be applied for donor heart preservation. To respond to the organ shortage, some centres also accept hearts from marginal donors such as non-heart beating donors (NHBD) or hearts donated after cardiac death (DCD) for heart transplantation (HTx). Clinical as well as preclinical science on EVMP of DCD hearts seems to be promising but the ideal perfusion practice itself appears unclear. OBJECTIVES: In accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA), this systematic review scopes all EVMP techniques for human and animal DCD heart preservation and addresses three specific questions, which refer to (a) the perfusion solutions, (b) the perfusion parameters and respective target values and (c) if possible, a direct comparison between cold static storage (CSS) and EVMP. RESULTS: Search results predominantly consisted of animal studies. Either perfusion with a crystalloid or blood-based solution, each with cardioplegic or non-cardioplegic properties was used. Some perfusates were supplemented with specific pharmacological medication to block pathophysiological pathways, which are involved in ischemia/reperfusion injury or edema formation. Besides normothermic EVMP with oxygenated blood, a wide range of temperature was applied in all approaches, with the lowest temperature at 4 °C. Pressure controlled anterograde Langendorff perfusion was applied mostly. If investigated, crystalloid machine perfusion was presented superior to CSS. CONCLUSIONS: Only blood based EVMP was introduced into clinical practice. More research, clinical as well as preclinical, is needed to develop the ideal EVMP technique, in terms of blood or crystalloid perfusion.

Immobilization of perrhenate using synthetic pyrite particles: Effectiveness and remobilization potential.

Radioactive pertechnetate (TcO4-) has been detected in nuclear waste affected soil and groundwater, posing significant effect on human health and the environment. Yet, cost-effective remediation of Tc-contaminated soil and groundwater remains challenging. To address this critical technology need, we prepared a class of pyrite (FeS2) particles for effective immobilization of pertechnetate. Using perrhenate (ReO4-) as a non-radioactive surrogate of TcO4-, we tested the immobilization effectiveness of the material through batch kinetic experiments, and evaluated the remobilization potential of immobilized Re under anoxic (sealed from air) and oxic (exposed to air) conditions and in the presence of humic acid (HA), EDTA, nitrate, and a Chinese loess soil. The results showed that more acidic pH gave faster Re(VII) removal due to more abundant electron sources (Fe2+ and S22-). X-ray diffraction (XRD) and/or X-ray photoelectron spectroscopy (XPS) analyses confirmed formation of ReO2/ReS2 as the major reduction products. The immobilized Re remained highly stable when aged for 360 days under anoxic conditions at different influence factors. Yet, the immobilized Re was vulnerable to oxygen oxidation, and about 78% of Re was remobilized after 40 days of exposure to air regardless of the initial pH (3.5-9.0) due to excessive pyrite oxidation and the associated pH drop (~2). HA at 120 mg/L inhibited Re remobilization under oxic conditions, which lowered the Re remobilization by ~21% after 40 days of oxic aging. The presence of EDTA facilitated dissolution of Fe but inhibited the dissolution of Re under oxic conditions. Nitrate showed negligible effect on Re remobilization. The presence of a Chinese loess soil effectively inhibited Re remobilization under both oxic and anoxic conditions, lowering the leachable Re by ~32% under oxic conditions. The findings may guide engineered application of pyrite particles as a long-lasting reducing material for immobilization pertechnetate or similar redox-active contaminants in soil and water.

Brain-dead donor heart conservation with a preservation solution supplemented by a conditioned medium from mesenchymal stem cells improves graft contractility after transplantation.

Hearts are usually procured from brain-dead (BD) donors. However, brain death may induce hemodynamic instability, which may contribute to posttransplant graft dysfunction. We hypothesized that BD-donor heart preservation with a conditioned medium (CM) from mesenchymal stem cells (MSCs) would improve graft function after transplantation. Additionally, we explored the PI3K pathway's potential role. Rat MSCs-derived CM was used for conservation purposes. Donor rats were either exposed to sham operation or brain death by inflation of a subdural balloon-catheter for 5.5 hours. Then, the hearts were explanted, stored in cardioplegic solution-supplemented with either a medium vehicle (BD and sham), CM (BD + CM), or LY294002, an inhibitor of PI3K (BD + CM + LY), and finally transplanted. Systolic performance and relaxation parameters were significantly reduced in BD-donors compared to sham. After transplantation, systolic and diastolic functions were significantly decreased, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells and endonuclease G positive cells were increased in the BD-group compared to sham. Preservation of BD-donor hearts with CM resulted in a recovery of systolic graft function (dP/dtmax : BD + CM: 3148 ± 178 vs BD: 2192 ± 94 mm Hg/s at 110 µL, P < .05) and reduced apoptosis. LY294002 partially lowered graft protection afforded by CM in the BD group. Our data suggest that PI3K/Akt pathway is not the primary mechanism of action of CM in improving posttransplant cardiac contractility and preventing caspase-independent apoptosis.

Two-dimensional numerical modeling of 90Sr transport in an unsaturated Chinese loess under artificial sprinkling.

(90)Sr is a fission byproduct of uranium and plutonium, and it presents a major health problem in the environment. A field test on the transport of various radionuclides including (90)Sr in an unsaturated Chinese loess was conducted under artificial rain conditions from July 1997 to August 2000. The vertical concentration distribution of (90)Sr displayed an unusual profile of double concentration peaks, which were separated by a thin (0.7 cm) source layer. In order to interpret the double-peak concentration profile, the transport of (3)H and (90)Sr in the unsaturated Chinese loess under artificial sprinkling conditions was simulated using WATERM, a numerical code for simulating flow field, and NESOR, also a numerical code but for simulating nuclide migration. The models were able to adequately simulate the double-peak concentration profile. The observation suggested that the fine arenaceous quartz layer, though 0.7 cm thick, formed a capillary barrier together with the local loess, which prevented water from penetrating. A significant discrepancy was observed between the model-fitted distribution coefficient (K(d)) of (90)Sr and that determined from independent laboratory experiments, which can be attributed to a number of factors such as the capillary barrier effect, solution-to-solid ratio and soil water content. Therefore, when the model is used for predictive purposes where K(d) is used as an input parameter, K(d) must be determined under well controlled conditions by taking into account these factors as well as the heterogeneity in the field.