Model Of Acute Ischemia Research Articles

Effects of a novel hydrogen sulfide prodrug in a porcine model of acute limb ischemia

ObjectivePrevious studies have shown that hydrogen sulfide (H2S) exerts potent proangiogenic properties under in vitro conditions and in rodent models. We sought to determine whether a novel H2S prodrug promotes peripheral revascularization in a swine model of acute limb ischemia (ALI). MethodsALI was induced in 17 female miniswine via intravascular occlusion of the external iliac. At day 7 after ALI induction, miniswine (n = 17) were randomized to received placebo or the H2S prodrug, SG-1002 (800 mg per os twice a day), for 35 days. At day 35 SG-1002 increased circulating levels of H2S (5.0 ± 1.2 μmol/L vs 1.8 ± 0.50 μmol/L; P < .05), sulfane sulfur (10.6 ± 2.3 μmol/L vs 2.6 ± 0.8 μmol/L; P < .05), and nitrite (0.5 ± 0.05 μmol/L vs 0.3 ± 0.03 μmol/L; P < .005) compared with placebo. SG-1002 therapy increased angiographic scoring in ischemic limb vessel number (27.6 ± 1.6 vs 22.2 ± 1.8; P < .05) compared with placebo. Treatment with SG-1002 preserved existing capillaries in ischemic limbs (128.3 ± 18.7 capillaries/mm2 vs 79.0 ± 9.8 capillaries/mm2; P < .05) compared with placebo. Interestingly, treatment with SG-1002 also improved coronary vasorelaxation responses to bradykinin and substance P in miniswine with ALI. ConclusionsOur results suggest that daily administration of the H2S prodrug, SG-1002, leads to an increase in circulating H2S and nitric oxide signaling and preserves vessel number and density in ischemic limbs. Furthermore, SG-1002 therapy improved endothelial-dependent coronary artery vasorelaxation in the setting of ALI. Our data demonstrate that SG-1002 preserves the vascular architecture in ischemic limbs and exerts vascular protective effects in the coronary vasculature in a model of peripheral vascular disease.

Кишечная стенка при острой ишемии: данные прижизненной оптической когерентной томографии и гистологического анализа

The objective is to study the morphometric signs of small bowel ischemic damage basing on intravital optical coherence tomography data and further histological analysis Materials and methods. The study was carried out on male Wistar rats with the use of two models of acute intestinal ischemia: acute occlusive mesenteric ischemia by а. jejunales ligation (group “I”) and acute arteriovenous ischemia by a small bowel loop and frill strangulation together with а. et v. jejunales (group “II”). The state of intramural vessels in vivo was evaluated with the use of optical coherence angiography (OCA). After the macroscopic signs of non-viability appeared the bowel was resected and its stepwise histological analysis was carried out. Results. Ischemic damage development in group “I” was accompanied by decrease of bowel wall thickness by 34,8-42,4% (p=0,032) due to submucous layer destruction - based on histological analysis data and also by decrease of total length of functioning intramural vessels by 4,6% (p=0,004) - based on OCA data. According to the OCA data in group “II” the length of functioning vessels decreased by 89,6%in the strangulated bowel loop and by 6,1% in adducent and abducent sections (p=0,001). In the strangulated loop histological specimens sharply dilated thrombosed veins were seen in all layers of bowel wall, seromuscular layer oedema and diapedesis hemorrhages of mucous coat also took place as well as bowel wall thickening by 25,2% in comparison with the intact one. Conclusions. Сomplex analysis of in vivo optical coherence tomography results and further histological analysis of ischemic small bowel wall made it possible to determine the morphological manifestations which are specific for arterial and arteriovenous mesenteric blood flow disorder. In cases of mesenteric artery occlusion hypoperfusion and mucous coat ischemia are predominant among pathogenetic mechanisms of bowel wall alteration. In the strangulated bowel the main factor of destruction and necrosis is acute insufficiency of venous outflow.

Influence of dibornol-HES on electrophysiological parameters in the period of restoration of blood flow in rabbit myocardium

Objective. Dibornol-HES, a water-soluble drug based on the derivative of 2,6-diisobornyl-4-methylphenol Dibornol conjugated with hydroxyethyl starch, can reduce the occurrence and severity of arrhythmias by preventive intravenous administration, but it is unknown whether the drug could reduce the myocardial arrhythmogenicity once ischemia has developed at the developed ischemia.Materials and methods. In the model of acute ischemia / reperfusion of the rabbit heart, the effect of Dibornol-HEC (80 mg/kg body weight of the animal) on the electrophysiological indices characterizing myocardial arrhythmogenicity (global and border dispersion of repolarization) was studied during the restoration of blood flow. In the model of acute ischemia / reperfusion with 64 unipolar epicardial leads, the activation-recovery intervals were measured and global and border dispersion of repolarization in the native rabbits (control group, n = 9) and in the rabbits treated by Dibornol-HES (on the 25th minute of occlusion, the experimental group, n = 6).Results. The introduction of Dibornol-HES did not lead to a change in the electrocardiographic parameters of rabbits. By the 30th minute of the coronary occlusion on the ECG in the animals of the control and the experimental groups, the intervals RR, QT, QTc were shortened (p &lt; 0.05). In the animals of both groups by the 30th minute of coronary occlusion, the global dispersion of repolarization increased (p &lt; 0.05), the boundary dispersion of repolarization also increased (p &lt; 0.05), due to the decrease in the duration of the activation-recovery intervals in the ischemic zone (p &lt; 0.05). During the 30-minute reperfusion the magnitude of the global dispersion of repolarization did not change in animals of the both groups, and the magnitude of the border dispersion of repolarization in the control rabbits decreased (p &lt; 0.05), while in the rabbits treated by Dibornol-HES the border dispersion of repolarization did not changed.Conclusion. In rabbits of the experimental group, the values of the global and border dispersions of repolarization did not differ from those of the animals in the control group. Therefore, the administration to Dibornol-HES just prior to reperfusion does not lead to the decrease in the dispersion of repolarization increased as a result of acute ischemic myocardial damage.

A rat model of acute kidney injury through systemic hypoperfusion evaluated by micro-US, color and PW-Doppler.

To create an animal model of acute renal ischemia induced by systemic hypoperfusion, controllable and reproducible to study, in real time, hemorrhagic shock changes with micro-imaging. Hemorrhagic shock was induced in rats activating a syringe pump setup to remove 1mL/min of blood, through the femoral artery catheter. The withdrawal was continued until the mean arterial pressure (MAP) dropped to 25-30mmHg. For the next 60min, the MAP was maintained at a constant pressure value, by automatic pump infusion and withdrawal. Micro-ultrasound imaging was performed using the Vevo 2100 system with the MS250 transducer (13-24MHz). Renal size, morphology and echogenicity were evaluated in B-mode. Renal blood flow was evaluated using color and PW-Doppler. After 1h of ischemia, B-mode images documented slight changes in kidney echogenicity. Color and PW-Doppler analysis showed a reduction in renal blood flow in kidneys during the hypoperfusion with a progressive and significant change from baseline values of resistive index (RI). At the histological evaluation, 60min of hypoperfusion resulted in ischemic changes in the kidneys. The results of this experimental study encourage the use of the described model to study acute renal ischemia trough severe hypoperfusion. The histological data confirmed that the model was able to produce injury in renal parenchyma. It can be used to assess acute ischemic damage not only in the kidney but also in other organs by using all available dedicated small animals imaging techniques.

PDGF enhances the protective effect of adipose stem cell-derived extracellular vesicles in a model of acute hindlimb ischemia

We previously have shown that platelet-derived growth factor (PDGF) modulates the biological activity of extracellular vesicles released by adipose-derived mesenchymal stem cells (ASC-EVs). ASC-EVs may interact with blood and vessel cells by transferring proteins and nucleic acids and regulate their functions. In this study, we investigated immunomodulatory activity and protection from acute hindlimb ischemia of EVs released by PDGF-stimulated ASC (PDGF-EVs). PDGF treatment of ASC changed protein and RNA composition of released EVs by enhancing the expression of anti-inflammatory and immunomodulatory factors. In vitro, control EVs (cEVs) derived from non-stimulated ASC increased the secretion of both the IL-1b, IL-17, IFNγ, TNFα pro-inflammatory factors and the IL-10 anti-inflammatory factor, and enhanced the in vitro peripheral blood mononuclear cell (PBMC) adhesion on endothelium. In contrast, PDGF-EVs enhanced IL-10 secretion and induced TGF-β1 secretion by PBMC. Moreover, PDGF-EVs stimulated the formation of T regulatory cells. In vivo, PDGF-EVs protected muscle tissue from acute ischemia, reduced infiltration of inflammatory cells and increased T regulatory cell infiltration in respect to cEVs. Our results suggest that PDGF-EVs are enriched in anti-inflammatory and immunomodulatory factors and induced in PBMC an enhanced production of IL-10 and TGF-β1 resulting in protection of muscle from acute ischemia in vivo.

Targeting ability of self-assembled nanomedicines in rat acute limb ischemia model is affected by size

Peripheral artery disease (PAD) is one of the most spreading diseases all over the world. The treatment strategies are limited to surgical or endovascular procedures for final stage chronic PAD or acute limb ischemia, and no pharmacological approaches have been achieved to prevent the worsening of chronic PAD or to regenerate the tissues of acute limb ischemia. Therefore, the improvement of therapeutic strategy is strongly demanded in clinics. Here, we adopted an acute hindlimb ischemia model in rats, which provides concomitant inflammatory response, to evaluate the application of drug delivery system against PAD. Through comparative experiments by using different-sized nanomedicine analogues, polyion complex (PIC) micelles with 30 nm diameter and PIC vesicles with 100- and 200-nm diameter (PICs-30, −100, −200 respectively), we found the size-dependent accumulation and retention in the collateral arteries. In contrast to PICs-30 and -200, histological analysis showed that PICs-100 were around the arterioles and co-localized with macrophages, which indicates that the PICs-100 can achieve moderate interaction with phagocytes. Our data suggests that controlling the size of nanomedicines has promise for developing novel angiogenic treatments toward the effective management of collateral arteries.

In the Experimental Model of Acute Mesenteric Ischemia, The Correlation of Blood Diagnostic Parameters with the Duration of Ischemia and their Effects on Choice of Treatment

ABSTRACTPurpose/Aim: Acute mesenteric ischemia is a syndrome characterized by sudden onset abdominal pain followed by intestinal necrosis. Morbidity and mortality increase with delayed diagnosis. Even with the latest radiological diagnostic methods, early diagnosis and initiation of treatment can be delayed. Using an experimental model, here we aim to determine the relationship between the laboratory parameters used to detect acute mesenteric ischemia and the duration of irreversible ischemia. Materials and Methods: A total of 30 male Wistar albino rats were divided into five groups, all of which underwent general anesthesia: (i) Superior mesenteric artery (SMA) dissection with laparotomy was performed, and blood samples and intestinal segment samples were taken after 2 hr (Sham group); (ii) volvulus of one-third of the small intestines was performed manually by laparotomy, and blood samples and intestinal segment samples were taken after 2 hr (Volvulus group); (iii) SMA was ligated with laparotomy, and blood samples and intestinal segment samples were taken after 2 hr (SMA+ligated 2-hr group); (iv) SMA was ligated with laparotomy, and blood samples and intestinal segment samples were taken after 4 hr (SMA+ligated 4-hr group); and (v) SMA was ligated with laparotomy, and blood samples and intestinal segment samples were taken after 6 hr (SMA+ligated 6-hr group). Results: The mean lactate dehydrogenase (LDH) activities of the SMA+ligated 2-hr and SMA+ligated 6-hr groups were statistically higher than the control group (p = .004). Compared to the Sham and Volvulus groups, the mean lactate level of the SMA+ligated 6-hr group was significantly higher (p = .004). Compared to the Sham and Volvulus groups, the mean D-dimer levels of the SMA+ligated 4-hr and SMA+ligated 6-hr groups were significantly higher (p = .004 and .003, respectively). By histopathological evaluation, we found that pathological damage increased as the ischemia lengthened. Conclusions: Mesenteric ischemia leads to an irreversible loss of intestinal perfusion and an increase in parameters of ischemia. Irreversible tissue damage occurs after 4 hr of ischemia and peaks after 6 hr, whereas parameters of ischemia (D-dimer, LDH, and L-Lactate levels) are highest at 2 hr after the onset of ischemia.

Abstract TP72: Transcranial Direct Current Stimulation (tDCS) for Neuroprotection in Acute Cerebral Ischemia: Meta-analysis of Preclinical Studies and Implications for Human Clinical Trials

Introduction: Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation technique safe and promising in early human studies of nonacute disorders (depression, OCD, stroke recovery), and also reported to confer direct neuroprotection and vasodilation in animal models of acute cerebral ischemia. Systematic review of preclinical acute cerebral ischemia studies would aid planning for potential initial human clinical trials. Method: A systematic Medline search identified controlled, preclinical studies of tDCS in acute ischemic stroke. Studies were categorized according to stimulation type (hemispheric cathodal; hemispheric anodal; targeted cerebellar fastigial nucleus). Stratified meta-analysis assessed effect of tDCS on final infarct volume. Results: The systematic search identified 17 controlled comparisons of tDCS in preclinical acute cerebral ischemia models, including a total of 256 animals, all with middle cerebral artery occlusion. Hemispheric cathodal stimulation was used in 3 experiments (32 animals), hemispheric anodal stimulation in 1 experiment (8 animals) and fastigial nucleus stimulation in 13 experiments (91 animals). Overall, tDCS reduced final infarct volume by 27.5 cc (95% CI 25.33-29.74, P&lt;0.00001). Heterogeneity of effect by stimulation type was noted (I 2 =90.5%), with the greatest infarct reduction with cathodal - 34.9 cc (95% CI 30.60-39.18, P&lt; 0.00001), followed by targeted fastigial nucleus - 26.8 cc (95% CI 25.33-29.53, P&lt; 0.00001), and anodal - 17.8 cc (95% CI 11.42-24.18, P&lt; 0.00001). In the cathodal studies, stimulation was started 30-45 minutes after ischemia onset. Conclusions: Transcranial direct current stimulation reduces final infarct volume across animal preclinical studies. The greatest neuroprotective effect is observed with hemispheric cathodal stimulation, with treatment initiation in a time frame achievable in human prehospital clinical trials. Human clinical trials of hemispheric cathodal tDCS are warranted.

EphrinA1-Fc attenuates myocardial ischemia/reperfusion injury in mice

EphrinA1, a membrane-bound receptor tyrosine kinase ligand expressed in healthy cardiomyocytes, is lost in injured cells following myocardial infarction. Previously, we have reported that a single intramyocardial injection of chimeric ephrinA1-Fc at the time of ischemia reduced injury in the nonreperfused myocardium by 50% at 4 days post-MI by reducing apoptosis and inflammatory cell infiltration. In a clinically relevant model of acute ischemia (30min)/reperfusion (24hr or 4 days) injury, we now demonstrate that ephrinA1-Fc reduces infarct size by 46% and completely preserves cardiac function (ejection fraction, fractional shortening, and chamber dimensions) in the short-term (24hrs post-MI) as well as long-term (4 days). At 24 hours post-MI, diminished serum inflammatory cell chemoattractants in ephrinA1-Fc-treated mice reduces recruitment of neutrophils and leukocytes into the myocardium. Differences in relative expression levels of EphA-Rs are described in the context of their putative role in mediating cardioprotection. Validation by Western blotting of selected targets from mass spectrometry analyses of pooled samples of left ventricular tissue homogenates from mice that underwent 30min ischemia and 24hr of reperfusion (I/R) indicates that ephrinA1-Fc administration alters several regulators of signaling pathways that attenuate apoptosis, promote autophagy, and shift from FA metabolism in favor of increased glycolysis to optimize anaerobic ATP production. Taken together, reduced injury is due a combination of adaptive metabolic reprogramming, improved cell survival, and decreased inflammatory cell recruitment, suggesting that ephrinA1-Fc enhances the capacity of the heart to withstand an ischemic insult.

An Elastomeric Polymer Matrix, PEUU-Tac, Delivers Bioactive Tacrolimus Transdurally to the CNS in Rat

Central nervous system (CNS) neurons fail to regrow injured axons, often resulting in permanently lost neurologic function. Tacrolimus is an FDA-approved immunosuppressive drug with known neuroprotective and neuroregenerative properties in the CNS. However, tacrolimus is typically administered systemically and blood levels required to effectively treat CNS injuries can lead to lethal, off-target organ toxicity. Thus, delivering tacrolimus locally to CNS tissues may provide therapeutic control over tacrolimus levels in CNS tissues while minimizing off-target toxicity. Herein we show an electrospun poly(ester urethane) urea and tacrolimus elastomeric matrix (PEUU-Tac) can deliver tacrolimus trans-durally to CNS tissues. In an acute CNS ischemia model in rat, the optic nerve (ON) was clamped for 10s and then PEUU-Tac was used as an ON wrap and sutured around the injury site. Tacrolimus was detected in PEUU-Tac wrapped ONs at 24h and 14days, without significant increases in tacrolimus blood levels. Similar to systemically administered tacrolimus, PEUU-Tac locally decreased glial fibrillary acidic protein (GFAP) at the injury site and increased growth associated protein-43 (GAP-43) expression in ischemic ONs from the globe to the chiasm, consistent with decreased astrogliosis and increased retinal ganglion cell (RGC) axon growth signaling pathways. These initial results suggest PEUU-Tac is a biocompatible elastic matrix that delivers bioactive tacrolimus trans-durally to CNS tissues without significantly increasing tacrolimus blood levels and off-target toxicity.

Migration of normal stem CD34 + cells to the brain in experimental models of ischemic stroke and glioblastoma

Background: Glyoblastoma is one of the most common brain tumors, which is characterized by high aggressiveness and unfavorable prognosis. One of the leading causes of the therapeutic resistance of glioblastoma is associated with tumor stem cells (TSC). One of the promising ways to solve this problem is the creation of biomedical products based on stem and progenitor cells of the human bone marrow. We have established, in vitro, that the stem CD34 + cells of the bone marrow are able to migrate toward the cells of different types. In vivo, stem cells of bone marrow CD 34+ actively migrate to the tumor tissue, where they accumulate in the area of invasion and penetrate into the hypoxic zones of the tumor. We suggested that the appearance of CD34 + cells in the neoplastic tissue is associated with the processes of neoplastic angiogenesis, and the role of hypoxia in this case is secondary. The study of migration processes and the homing of stem cells in the pathological focus in the brain on experimental models of acute ischemia and glioblastoma. Methods: The work was performed on 60 mature Wistar female rats divided into 2 groups (N = 30). The animals of the first group underwent stereotactic implantation of C6 glioma cells in the brain, tumor development was confirmed by magnetic resonance imaging (MRI) data; the second group - the ligation of the common and internal carotid artery on the left was performed surgically. The development of the stroke was confirmed by MRI data. The haploidentical CD34 + stem cells stained with the fluorescent vital dye Vybrant® CFDA SE (V12883, Molecular Probes, USA) were injected into the tail vein. The animals were removed from the experiment on days 4 and 8, the material was subjected to morphological and immunohistochemical analysis. Results: Four days after the infusion of cells on the glioblastoma model, the fluorescent label was detected at the periphery of the tumor site, which was associated with localized blood vessels in this region. On day 8, the area of fluorescing objects was 12.7 ± 9.2% at the tumor boundary, 47.6 ± 9.3% in the parenchyma of the tumor tissue. In the experimental model of ischemia, fluorescent substances in the spectrum of characteristic CFDA on days 4 and 8 were not detected. Conclusions: Hypoxic brain damage is not enough to ensure the effective homing of cells in the tumor. With a glioblastome formed a specific type of microglia, this circumstance allows one to assume the possibility of increasing the life expectancy of patients with glioblastoma. Legal entity responsible for the study: School of Biomedicine, Far Eastern Federal University, Russian Federation Funding: Russian Scientific Fund (14-15-00084) Disclosure: All authors have declared no conflicts of interest.

Serum-derived extracellular vesicles (EVs) impact on vascular remodeling and prevent muscle damage in acute hind limb ischemia

Serum is an abundant and accessible source of circulating extracellular vesicles (EVs). Serum-EV (sEV) pro-angiogenic capability and mechanisms are herein analyzed using an in vitro assay which predicts sEV angiogenic potential in vivo. Effective sEVs (e-sEVs) also improved vascular remodeling and prevented muscle damage in a mouse model of acute hind limb ischemia. e-sEV angiogenic proteomic and transcriptomic analyses show a positive correlation with matrix-metalloproteinase activation and extracellular matrix organization, cytokine and chemokine signaling pathways, Insulin-like Growth Factor and platelet pathways, and Vascular Endothelial Growth Factor signaling. A discrete gene signature, which highlights differences in e-sEV and ineffective-EV biological activity, was identified using gene ontology (GO) functional analysis. An enrichment of genes associated with the Transforming Growth Factor beta 1 (TGFβ1) signaling cascade is associated with e-sEV administration but not with ineffective-EVs. Chromatin immunoprecipitation analysis on the inhibitor of DNA binding I (ID1) promoter region, and the knock-down of small mother against decapentaplegic (SMAD)1–5 proteins confirmed GO functional analyses. This study demonstrates sEV pro-angiogenic activity, validates a simple, sEV pro-angiogenic assay which predicts their biological activity in vivo, and identifies the TGFβ1 cascade as a relevant mediator. We propose serum as a readily available source of EVs for therapeutic purposes.

Effect of Alloxan-induced diabetes mellitus on the functions of bone marrow-derived and circulating endothelial progenitor cells

Objective: To explore whether diabetes mellitus (DM) impairs functions of bone marrow-derived endothelial progenitor cells (BM-EPC) and circulating EPC. Methods: Diabetic model of rabbit was induced by Alloxan injection and the rabbits were then randomly divided into three groups: BM-EPC group, circulating EPC group, and DM group, with six rabbits in each group. Another 6 normal rabbits were enrolled as normal control group as well. 8 weeks later, BM-EPC and circulating EPC from diabetic and healthy rabbits were isolated and cultured. Colony number, proliferation, adhesion and tube formation function were detected. Exogenous diabetic BM-EPC and circulating EPC were analyzed for therapeutic efficacy in acute ischemia model of diabetic rabbits. Left ventricular (LV) function was assessed using Echocardiography. Capillary density and fibrosis area were evaluated by confocal laser scanning microscope (CLSM) and Masson-trichrome staining. The mRNA expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) was analyzed using real-time quantitive PCR. Results: Colony number, proliferation, adhesion and tube formation function of diabetic circulating EPC were significantly reduced compared with healthy rabbits. DM impaired tube-forming ability of BM-EPC, but did not influence colony number, proliferation and adhesion function. Compared with circulating EPC and control group, BM-EPC group had fewer fibrosis area (6.98%±0.94% vs 13.03%±2.97% and 15.84%±4.74%, both P=0.001), higher capillary density [(792±87) vs (528±71) and (372±77) vessels/mm(2,) both P<0.001], higher mRNA expression of VEGF (6.25±2.33 vs 2.19±1.01 and 1.55±0.52, both P<0.001) and bFGF (6.38±2.65 vs 1.24±0.76 and 1.18±0.82, both P<0.001), higher left ventricular ejection fraction (LVEF) (61%±4% vs 47%±5% and 50%±10%, both P<0.05). Conclusions: DM not only impaired functions of circulating EPC, but also influenced tube formation function of BM-EPC. Auto transplantation of BM-EPC may rescue the ischemic myocardium by neovascularization and paracrine effect in diabetic rabbits.

Spinal cord stimulation reduces ventricular arrhythmias during acute ischemia by attenuation of regional myocardial excitability.

Myocardial ischemia creates autonomic nervous system imbalance and can trigger cardiac arrhythmias. We hypothesized that neuromodulation by spinal cord stimulation (SCS) will attenuate local cardiac sympathoexcitation from ischemia-induced increases in afferent signaling, reduce ventricular arrhythmias, and improve myocardial function during acute ischemia. Yorkshire pigs (n = 20) were randomized to SCS (50 Hz at 200-μs duration, current 90% motor threshold) or sham operation (sham) for 30 min before ischemia. A four-pole SCS lead was placed percutaneously in the epidural space (T1-T4), and a 56-electrode mesh was placed over the heart for high-resolution electrophysiological recordings, including activation recovery intervals (ARIs), activation time, repolarization time, and dispersion of repolarization. Electrophysiological and hemodynamic measures were recorded at baseline, after SCS/sham, during acute ischemia (300-s coronary artery ligation), and throughout reperfusion. SCS 1) reduced sympathoexcitation-induced ARI and repolarization time shortening in the ischemic myocardium; 2) attenuated increases in the dispersion of repolarization; 3) reduced ventricular tachyarrythmias [nonsustained ventricular tachycardias: 24 events (3 sham animals) vs. 1 event (1 SCS animal), P < 0.001]; and 4) improved myocardial function (dP/dt from baseline to ischemia: 1,814 ± 213 to 1,596 ± 282 mmHg/s in sham vs. 1,422 ± 299 to 1,380 ± 299 mmHg/s in SCS, P < 0.01). There was no change in ventricular electrophysiology during baseline conditions without myocardial stress or in the nonischemic myocardium. In conclusion, in a porcine model of acute ventricular ischemia, SCS reduced regional myocardial sympathoexcitation, decreased ventricular arrhythmias, and improved myocardial function. SCS decreased sympathetic nerve activation locally in the ischemic myocardium with no effect observed in the normal myocardium, thus providing mechanistic insights into the antiarrhythmic and myocardial protective effects of SCS.NEW & NOTEWORTHY In a porcine model of ventricular ischemia, spinal cord stimulation decreased sympathetic nerve activation regionally in ischemic myocardium with no effect on normal myocardium, demonstrating that the antiarrhythmic effects of spinal cord stimulation are likely due to attenuation of local sympathoexcitation in the ischemic myocardium and not changes in global myocardial electrophysiology.

Selective Localization of a Novel Dendrimer Nanoparticle in Myocardial Ischemia-Reperfusion Injury

Dendrimer nanoparticle therapies representpromising new approaches to drug delivery, particularly in diseases associated with inflammatory injury. However, their application has not been fully explored in models of acute myocardial ischemia (MI) and reperfusion injury. White male New Zealand rabbits underwent left thoracotomy with 30-minute temporary left anterior descending artery occlusion and MI confirmed by electrocardiography and histology (MI rabbits, n= 9), or left thoracotomy and pericardial opening for 30 minutes but no left anterior descending artery occlusion (control [C] rabbits, n= 9) rabbits. Following the 30-minute period, a dendrimer (generation 6 dendrimer conjugated to cyanine-5 fluorescent dye [G6-Cy5], 6.7 nm diameter) was administered intravenously and the chest closed in layers. Animals were sacrificed at 3 hours (3 MI, 3 C), 24 hours (3 MI, 3 C), or 48 hours (3 MI, 3 C) postsurgery. As compared to controls, MI rabbits had twofold G6-Cy5 uptake in the myocardial anterior wall as compared to the same region in nonischemic control rabbits at 24 hours postsurgery (6.01 ± 0.57 μg/g versus 2.85 ± 0.85 μg/g; p= 0.04). This trend was also present at48 hours (6.38 ± 1.53 μg/g versus 3.95 ± 0.60 μg/g, p=0.21) and was qualitatively evident on confocal microscopy. G6-Cy5 half-life in serum was approximately 12 hours, with 22% of the injected G6-Cy5 dose remaining at 48 hours. This study demonstrates for the first time that dendrimer nanodevices selectively localize in ischemic as compared to healthy myocardium. This indicates that dendrimer nanodevices are promising agents to deliver drugs specifically to the ischemic myocardium to attenuate the injury. Subsequent studies will assess the efficacy of a dendrimer-drug conjugate in ameliorating reperfusion injury following MI.

Sensitivity of diffusion MRI to perilesional reactive astrogliosis in focal ischemia.

Reactive astrogliosis is a response to injury in the central nervous system that plays an essential role in inflammation and tissue repair. It is characterized by hypertrophy of astrocytes, alterations in astrocyte gene expression and astrocyte proliferation. Reactive astrogliosis occurs in multiple neuropathologies, including stroke, traumatic brain injury and Alzheimer's disease, and it has been proposed as a possible source of the changes in diffusion magnetic resonance imaging (dMRI) metrics observed with these diseases. In this study, the sensitivity of dMRI to reactive astrogliosis was tested in an animal model of focal acute and subacute ischemia induced by the vasoconstricting peptide, endothelin-1. Reactive astrogliosis in perilesional cortex was quantified by calculating the astrocyte surface density as determined with a glial fibrillary acidic protein (GFAP) antibody, whereas perilesional diffusion changes were measured in vivo with diffusional kurtosis imaging. We found substantial changes in the surface density of GFAP-positive astrocyte processes and modest changes in dMRI metrics in the perilesional motor cortex following stroke. Although there are time point-specific correlations between dMRI and histological measures, there is no definitive evidence for a causal relationship.

Human adipose-derived mesenchymal stem cell could participate in angiogenesis in a mouse model of acute hindlimb ischemia

Mesenchymal stem cells (MSCs) transplantation for the treatment of acute hindlimb ischemia is recently attracting the attention of many scientists. Identifying the role of donor cells in the host is a crucial factor for improving the efficiency of treatment. This study evaluated the injury repair role of xenogeneic adipose-derived stem cell (ADSC) transplantation in acute hindlimb ischemia mouse model. Human ADSCs were transplanted into the limb of ischemic mouse. The survival rate of grafted cells and expression of human VEGF-R2 and CD31 positive cells were assessed in the mouse. In addition, the morphological and functional recovery of ischemic hindlimb was also assessed. The results showed that one-day post cell transplantation, the survival percentage of grafted cells was 3.62% ± 2.06% at the injection site and 15.71% ± 12.29% around the injection site. The rate of VEGFR2-positive cells had highest expression at 4 days post transplantation, 5.46% ± 2.13% at the injection site; 9.12% ± 7.17% at the opposite of injection site, and 7.22% ± 4.59% at the lateral gastrocnemius. The percentage of CD31 positive cells increased on day 4 at the injection site to 0.8% ± 1.60%, and further increased on day 8 at the lateral gastrocnemius site and the opposite injection site to 1.56% ± 0.44% and 1.17% ± 1.69%, respectively. After 14 days, the cell presentation and the angiogenesis marker expression were decreased to zero, except for CD31 expression at the opposite of injection site (0.72% ± 1.03%). Histological structure of the cell-injected muscle tissue remained stable as that of the normal muscle. New small blood vessels were found growing in hindlimb. On the other hand, approximately 66.67% of mice were fully recovered from ischemic hindlimb at grade 0 and I after cell injection. Thus, xenotransplantation of human ADSCs might play a significant role in the formation of new blood vessel and can assist in the treatment of mouse with acute hindlimb ischemia.

Protective effect of active perfusion in porcine models of acute myocardial ischemia.

Mortality rates associated with off-pump coronary artery bypass (CAB) are relatively high, as the majority of patients requiring CAB are at a high risk for cardiac events. The present study aimed to establish porcine models of acute myocardial ischemia, and evaluate the protective role of shunt and active perfusion. A total of 30 pigs were randomly assigned to five groups, as follows: i) Sham (control); ii) A1 (shunt; stenosis rate, 55%); iii) A2 (shunt; stenosis rate, 75%); iv) B1 (active perfusion; stenosis rate, 55%); and v) B2 (active perfusion; stenosis rate, 75%) groups. Aortic pressure (P0), left anterior descending coronary pressure (P1), and coronary effective perfusion pressure (P1/P0) were measured. The expression levels of tumor necrosis factor-α (TNF-α), cardiac troponin (cTnI), creatine kinase-myocardial band (CK-MB), interleukin (IL)-6, IL-10, B-cell lymphoma 2 (Bcl-2), and caspase-3 were detected using enzyme-linked immunosorbent assay or western blotting. The myocardial apoptosis rate was determined using the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Ischemia models with stenosis rates of 55 and 75% were successfully constructed following suturing of the descending artery. Compared with the control, the 55 and 75% stenosis groups demonstrated significantly decreased P1/P0, increased expression levels of TNF-α, cTnI, CK-MB, IL-6, IL-10 and caspase-3, an increased rate of myocardial apoptosis, and a decreased expression level of anti-apoptotic protein, Bcl-2. At 30 min following successful establishment of the model (ST segment elevation to 1 mm), group B demonstrated significantly increased P1/P0, decreased expression levels of TNF-α, cTnI, CK-MB, IL-6, IL-10 and caspase-3, a decreased rate of myocardial apoptosis, and an increased expression level of anti-apoptotic protein, Bcl-2. Furthermore, the current study indicated that active perfusion was more efficacious in maintaining myocardial perfusion and alleviating ischemic injury when compared with traditional shunt perfusion.

Angiogenic Synergistic Effect of Adipose-Derived Stromal Cell Spheroids with Low-Level Light Therapy in a Model of Acute Skin Flap Ischemia

Human adipose-derived mesenchymal stem cells (hASCs) are an attractive cell source for tissue engineering. However, one obstacle to this approach is that the transplanted hASC population can decline rapidly in the recipient tissue. The aim of this study was to investigate the effects of low-level light therapy (LLLT) on transplanted spheroid hASCs in skin flaps of mice. hASCs were cultured in monolayers or spheroids. LLLT, hASCs, spheroids and spheroids transplanted with LLLT were applied to the skin flaps. Healing of the skin flaps was assessed by gross evaluation and by hematoxylin and eosin staining and elastin van Gieson staining. Compared with the spheroid group, skin flap healing was enhanced in the spheroid + LLLT group, including the neovascularization and regeneration of skin appendages. The survival of hASCs was enhanced by decreased apoptosis of hASCs in the skin flaps of the spheroid + LLLT group. The secretion of growth factors was stimulated in the spheroid + LLLT group compared with the ASC and spheroid groups. These data suggest that LLLT was an effective biostimulator of spheroid hASCs in the skin flaps, enhancing the survival of hASCs and stimulating the secretion of growth factors.

The value of combined elevation of D-dimer and neopterin as a predictive parameter for early stage acute mesenteric ischemia: An experimental study.

Background The diagnosis of acute mesenteric ischemia is variable. Early diagnosis is important for reducing the mortality and morbidity rates. Aim This experimental study aims to investigate the diagnostic utility of D-dimer and neopterin as a marker for the early stage of acute mesenteric ischemia caused by occlusion of superior mesenteric artery. Methods The levels of D-dimer and neopterin were measured using an animal acute mesenteric ischemia model in 21 male rabbits. Superior mesenteric artery occlusion (Group 1, n = 14) and control (Group 2, n = 7) groups were identified. Blood samples at different times are collected from each rabbits. Blood samples from superior mesenteric artery occlusion group were taken 30 min after anesthesia but before laparotomy, 1, 2, and 3 h after superior mesenteric artery ligation. Blood samples from control group were taken 1 h before, 1 and 3 h after anesthesia and laparotomy. The D-dimer and neopterin levels of each blood sample were measured. Results The probability of acute mesenteric ischemia was found to be 36 times higher when the D-dimer level was over 0.125 ng/L, whereas the probability was 19.2 times higher when the neopterin level was over 1.25 nmol/L. Conclusions In this experimental study, the combined elevation of two significant markers, D-dimer and neopterin, may be helpful for the early diagnosis of acute mesenteric ischemia.