Delayed inhaled carbon monoxide mediates the regression of established neointimal lesions.

OBJECTIVE: Intimal hyperplasia (IH) contributes to the failure of vascular interventions. While many investigational therapies inhibit the development of IH in animal models, few of these potential therapies can reverse established lesions. Inhaled carbon monoxide (CO) dramatically inhibits IH in both rats and pigs when given perioperatively. It also prevented the development of pulmonary arterial hypertension in rodents. Interestingly, CO could reverse pulmonary artery structural changes and right heart hemodynamic changes when administered after the establishment of pulmonary hypertension. Thus, we hypothesize that inhaled CO may mediate the regression of established neointimal lesions. METHODS: Rats underwent carotid artery balloon angioplasty injury. Carotid arteries were collected at 2 and 4 weeks after injury for morphometric analysis of the neointima. Another group was treated with inhaled CO (250 parts per million) for 1 hour daily from week 2 until week 4. Additional rats were sacrificed 3 days after initiating CO treatment, and the carotid arteries were examined for apoptosis by terminal deoxynucleotidyl transferase dUTP nick end-labeling, proliferation by Ki67 staining, and autophagy by microtubule-associated protein light chain 3 I/II staining. RESULTS: At 2 weeks following injury, sizable neointimal lesions had developed (intimal/media = 0.92 ± 0.22). By 4 weeks, lesion size remained stable (0.80 ± 0.09). Delayed inhaled CO treatment greatly reduced neointimal lesion size vs the 2- and 4-week control mice (0.38 ± 0.05; P < .05). Arteries from the CO-treated rats exhibited significantly reduced apoptosis compared with control vessels (3.18% ± 1.94% vs 16.26% ± 5.91%; P = .036). Proliferation was also dramatically reduced in the CO-treated animals (2.98 ± 1.55 vs 10.37 ± 2.80; P = .036). No difference in autophagy between control and CO-treated rats was detected. CONCLUSIONS: Delayed administration of inhaled CO reduced established neointimal lesion size. This effect was mediated by the antiproliferative effect of CO on medial and intimal smooth muscle cells without increases in arterial wall apoptosis or autophagy. Future studies will examine additional time points to determine if there is temporal variation in the rates of apoptosis and autophagy.

Ventral hernias in morbidly obese patients: a suggested algorithm for operative repair.

With the rise in prevalence of obesity, most general surgeons will have to face the problem of the obese patient with an abdominal wall defect. Treatment of these bariatric patients raises unique challenges, and at this time there is still no consensus on the best treatment option. This study was performed in a high-volume bariatric and minimally invasive surgery center at a tertiary care facility in the USA. Twenty-eight morbidly obese patients treated at our facility between 2003 and 2008 were separated into four groups according to anatomic features and symptoms. Patients with the following characteristics were classified as having a favorable anatomy: body mass index not exceeding 50 kg/m(2), gynecoid body habitus, reducible hernias found in a central location, abdominal wall thickness less than 4 cm, and the defect's largest diameter not exceeding 8 cm. All other patients were classified as having an unfavorable anatomy. In this study, we report a systematic treatment approach for the morbidly obese patient presenting with a ventral hernia based on whether the hernia is symptomatic or asymptomatic, as well as the distinct characteristics of the hernia and body habitus features. We followed up on these patients postoperatively for at least 2 years, with a mean follow-up period of 30 months. Only a total of three hernia recurrences were observed. Successful treatment of ventral hernias in morbidly obese patients should be individualized based on the patient's symptoms and defined hernia characteristics.

Liver-assist device with a microfluidics-based vascular bed in an animal model.

OBJECTIVE: This study evaluates a novel liver-assist device platform with a microfluidics-modeled vascular network in a femoral arteriovenous shunt in rats. SUMMARY OF BACKGROUND DATA: Liver-assist devices in clinical trials that use pumps to force separated plasma through packed beds of parenchymal cells exhibited significant necrosis with a negative impact on function. METHODS: Microelectromechanical systems technology was used to design and fabricate a liver-assist device with a vascular network that supports a hepatic parenchymal compartment through a nanoporous membrane. Sixteen devices with rat primary hepatocytes and 12 with human HepG2/C3A cells were tested in athymic rats in a femoral arteriovenous shunt model. Several parenchymal tube configurations were evaluated for pressure profile and cell survival. The blood flow pattern and perfusion status of the devices was examined by laser Doppler scanning. Cell viability and serum protein secretion functions were assessed. RESULTS: Femoral arteriovenous shunt was successfully established in all animals. Blood flow was homogeneous through the vascular bed and replicated native flow patterns. Survival of seeded liver cells was highly dependent on parenchymal chamber pressures. The tube configuration that generated the lowest pressure supported excellent cell survival and function. CONCLUSIONS: This device is the first to incorporate a microfluidics network in the systemic circulatory system. The microvascular network supported viability and function of liver cells in a short-term ex vivo model. Parenchymal chamber pressure generated in an arteriovenous shunt model is a critical parameter that affects viability and must be considered in future designs. The microfluidics-based vascular network is a promising platform for generating a large-scale medical device capable of augmenting liver function in a clinical setting.

Effect of PJ34 on spinal cord tissue viability and gene expression in a murine model of thoracic aortic reperfusion injury.

INTRODUCTION: These studies were designed to determine whether PJ34, a novel Poly-ADP Ribose Polymerase Inhibitor, modulates expression of markers of stress and inflammation in the spinal cord following ischemia/ reperfusion(TAR). METHODS: 129S1/SvImj mice were subjected to thoracic aortic occlusion and 48 hours of reperfusion (n = 38). EXPERIMENTAL GROUPS INCLUDED: Untreated Control (UC, n = 21); PJ34 (PJ34, n = 11) and sham (S, n = 6). At 48 hours, mice were euthanized for mRNA analysis and assessment of spinal cord viability. RESULTS: PJ34 improved spinal cord tissue viability following TAR (UC:53.1 +/- 6.3, PJ34:73.5 +/- 4.1% sham, p < 0.01). mRNA analysis revealed significant expression of stress response genes in UC and PJ34 treated mice. CONCLUSIONS: PJ34 enhanced mitochondrial activity and preserved neurologic function following TAR despite the expression of stress and pro-inflammatory markers within the spinal cord. The ongoing cord stress response in neurologically intact PJ34 treated mice may indicate the potential to develop delayed neurologic dysfunction.

PJ34, a poly-ADP-ribose polymerase inhibitor, modulates visceral mitochondrial activity and CD14 expression following thoracic aortic ischemia-reperfusion.

BACKGROUND: Visceral ischemia-reperfusion injury (VI) contributes to adverse outcomes following the repair of thoracoabdominal aneurysms. Experiments were designed to determine whether a poly-adenosine diphosphate-ribose polymerase (PARP) inhibitor modulates indexes of metabolic function (mitochondrial activity), inflammatory cell activation, and tissue inflammation (lipopolysaccharide receptor CD14 messenger ribonucleic acid) following VI. METHODS: 129S1/SvImj mice were subjected to thoracic aortic occlusion followed by 48 hours of reperfusion. Normal saline was administered to 25 untreated control mice and PJ34 to 21 mice before and immediately after thoracic aortic ischemia-reperfusion. Sham mice (n = 13) underwent median sternotomy alone. At 48 hours, all animals were euthanized and tissues harvested for quantitative analysis. RESULTS: PJ34 improved intestinal (P < .05) but not hepatic mitochondrial activity following reperfusion. CD14 messenger ribonucleic acid levels in liver (P < .004), kidney (P < .003), and spinal cord (P < .03) tissue were less in PJ34-treated mice. CONCLUSIONS: PJ34 preserved the metabolic function of intestinal but not hepatic tissue during reperfusion. PJ34 uniformly decreased the expression of an important marker of inflammatory cell activation and tissue inflammation in visceral tissue following VI. PARP inhibitors may serve as a therapeutic modality to abrogate the stress response to VI.

Effects of acute global venous obstruction and unfractionated heparin on muscle cytokine synthesis.

Phlegmasia cerulea dolens is a devastating complication of massive deep venous thrombosis, which is clinically characterized by massive lower extremity tissue edema and subsequent arterial insufficiency. These experiments evaluated the local tissue effects of acute global venous obstruction combined with partial arterial ischemia. Experiments were performed to assess the effects of heparin on the cytokine response to simultaneous venous and partial arterial obstruction. Murine hind limbs were subjected to conditions of unilateral venous occlusion and partial tourniquet limb ischemia, which was confirmed by laser Doppler imaging (LDI). Mice underwent either hind limb venous obstruction with intravenous unfractionated heparin (200IU/kg) or intravenous saline 5min before venous occlusion. Sham-treated mice were subjected to anesthesia alone without venous occlusion. After 3hr, the mice were killed and tissue was harvested for measurement of edema (wet to dry weight ratio, W/D), muscle viability, indices of local thrombosis (thrombin-antithrombin complex [TAT]), and cytokine analysis for growth-related oncogene-1 (GRO-1) and interleukin-6 (IL-6, protein via enzyme-linked immunoassay and mRNA via reverse transcriptase polymerase chain reaction). Bleeding time and volume were documented in saline- and heparin-treated mice to confirm systemic anticoagulation. Administration of intravenous heparin resulted in a marked increase in bleeding time and volume. LDI confirmed venous obstruction and ongoing arterial inflow. Venous obstruction resulted in severe visible edema that correlated with a significantly higher W/D ratio but was not associated with a significant decrease in muscle viability. GRO-1 and IL-6 protein and mRNA levels were significantly elevated in the venous occlusion group compared to sham. Heparin therapy significantly decreased TAT3 levels but did not alter the profile of GRO-1 or IL-6 protein levels seen with venous occlusion. Venous occlusion with partial ischemia induces a unique and potent local cytokine expression. Heparin therapy did not ameliorate the cytokine response. These data indicate that heparin therapy does not modulate the cytokine response to venous obstruction.

Hind limb ischemia-reperfusion in the leptin receptor deficient (db/db) mouse.

BACKGROUND: Diabetic patients have high incidence of peripheral vascular disease and limb loss after acute extremity injury. Experiments were designed to test the hypothesis that acute tissue injury in leptin receptor deficient (Db) diabetic (type2) mice would be more severe than in non-diabetic mice. METHODS: Db and wild type (Wt) mice were subjected to 3 h of ischemia followed by either 4 or 24 h of reperfusion (3/4 IR, 3/24 IR). Muscle analyzed for tissue viability (mitochondrial activity), cytokines (KC-murine equivalent of human IL-8, TNFalpha, IL-6), growth factor, and histological evaluation (neutrophils/uninjured muscle fibers). Tissue perfusion was detected during basal and reperfusion conditions using laser Doppler imaging. RESULTS: Mitochondrial activity and histological evaluation for tissue injury did not differ in the Db versus Wt mice at the time intervals studied. When compared with their respective sham animals, both Db and Wt mice had similarly increased levels of KC, IL-6, and VEGF after 3/24 IR. TNFalpha levels increased in Db but not Wt mice after IR. Although absolute increases in TNFalpha and KC were higher in Db mice, VEGF levels were actually lower in the Db mice. CONCLUSION: The patterns of tissue perfusion, cytokines, and growth factors were different in Db versus Wt mice. At the acute time intervals studied, these differences did not correlate with an expected greater degree of acute muscle injury in Db mice.

A novel model of acute murine hindlimb ischemia.

The McGivney hemorrhoidal ligator (MHL), a band designed to cause tissue necrosis, is the preferred experimental tool to create hindlimb ischemia-reperfusion (I/R) injury in rodents. This report defines and compares the ex vivo band tension exerted by MHL and orthodontic rubber bands (ORBs) along with select in vivo characteristics of I/R. As to method, ex vivo band tension was measured over relevant diameters using a tensiometer. In vivo assessment of murine limb perfusion during ischemia with ORB and MHL was compared using laser Doppler imaging and measurement of wet weight-to-dry weight ratio. Neuromuscular scoring and histological extent of muscle fiber injury after I/R with MHL and ORB were also compared. A dose-response curve, between the duration of ORB-induced I/R with both mitochondrial activity (methyl-thiazol-tetrazolium) or tail perfusion [laser Doppler imaging (LDI)], was generated. As a results, ex vivo measurements showed that ORB exerted significantly less force than the MHL. Despite less tension in ORB, in vivo testing of the ORB confirmed complete ischemia by both LDI and wet weight-to-dry weight ratio. After I/R, caused by ORB, there was significantly less neuromuscular dysfunction. Histological assessment confirmed similar degrees of muscle fiber injury after I/R with either the MHL or ORB. Increasing durations of ischemia created by the ORB followed by reperfusion significantly decreased mitochondrial activity and tail perfusion after 24 h of ischemia. In conclusions, ORB produced similar levels of tissue ischemia in murine models of limb I/R with fewer levels of nonspecific injury. ORB may be the preferred model for selected studies of limb I/R.

Local administration of the Poly ADP-Ribose Polymerase (PARP) inhibitor, PJ34 during hindlimb ischemia modulates skeletal muscle reperfusion injury.

BACKGROUND: PARP stabilizes DNA and modulates inflammation in murine models of sepsis, stroke, and myocardial infarction. Previous studies have shown that systemic PARP inhibition before hindlimb ischemia preserves tissue viability and modulates cytokine synthesis during reperfusion. The purpose of this study was to determine whether intra-muscular (IM) administration of PJ34, a potent inhibitor of PARP, after the onset of acute hindlimb ischemia (post hoc) modulates the local production of inflammatory mediators during ischemia/reperfusion (I/R). MATERIALS AND METHODS: The control tension tourniquet was used to establish unilateral hindlimb ischemia in mice for 3 h followed by 48 h I/R. The treatment group (PJ) received IM PJ34 (10 mg/kg) in the affected hindlimb 90 min into ischemia whereas the control group (UN) received IM saline (150 uL) at the same time point. Skeletal muscle viability (MTT mitochondrial activity), local neutrophil chemoattractant protein (KC), Interleukin 6 (IL-6), Interleukin 1beta (IL-1beta), and Myeloperoxidase (MPO) levels were measured in protein extracts after the reperfusion period. RESULTS: Muscle viability (102% +/- 10 PJ, 78% +/- 4 UN, P = 0.04), IL-B (21.1 +/- 1.3 PJ, 15.5 +/- 1.0 UN, P = 0.02), and IL-6 levels (16.3 +/- 1.2 PJ, 10.9 +/- 1.4 UN, P = 0.04) after 48 I/R were significantly higher in PJ. KC and MPO levels were higher in PJ but neither reached statistical significance. CONCLUSIONS: Post hoc PJ34 therapy appears to protect skeletal muscle from I/R injury despite increased levels of local cytokines. These initial findings support the role of local post hoc therapy in the treatment of acute limb threatening ischemia suggesting that further study of this novel therapy is warranted.

PJ34, a poly-ADP-ribose polymerase inhibitor, modulates renal injury after thoracic aortic ischemia/reperfusion.

BACKGROUND: These experiments sought to evaluate the effects of PJ34, a poly-ADP-ribose polymerase inhibitor, on molecular indices of renal injury, mitochondrial function, tissue thrombosis, and fibrinolysis after thoracic aortic ischemia/reperfusion (TAR). METHODS: Forty-three 129S1/SvImj mice were subjected to 11 minutes of TAR followed by 48 hours of reperfusion. Experimental groups included untreated normal saline (NS) controls (UC), (n=15, 0.5 mL NS i.p.) or PJ34 (PJ) (n=17, PJ34 10 mg/kg ip, 1 hour before and after TAR). Sham (SH) mice (n=11) underwent median sternotomy (heparin, NS i.p.) without TAR. Forty-eight hours after TAR or sham operation, kidney mitochondrial activity (using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium [MTT]), D-dimer, and thrombin-antithrombin III (TAT) complex levels were measured. Levels of messenger RNA for neutrophil gelatinase-associated lipocalin (NGAL), a marker for renal injury, were also measured by reverse transcriptase-polymerase chain reaction. RESULTS: PJ34 improves renal mitochondrial activity after 48 hours of TAR, compared with untreated control animals (UC, 87.6 +/- 2.2%; PJ, 151.4 +/- 9.5%; P < .001). PJ34 did not alter the increase in renal D-dimer levels by 48 hours reperfusion (UC, 1.37 +/- 0.09 U; PJ, 1.1 +/- 0.14 U; SH, 0.82 +/- 0.06 U; P < .05). TAR did not alter renal levels of TAT expression among groups (UC, 0.103 +/- 0.034; PJ, 0.067 +/- 0.008; SH, 0.106 +/- 0.027; P=.619). The incidence of significantly increased NGAL among UC mice was 1415 +/- 823.6 (n=12), compared with 29.6 +/- 20.8 (n=10) in the PJ34-treated group (P < .014). CONCLUSIONS: PJ34 preserves renal mitochondrial activity and decreases steady-state levels of NGAL after TAR. TAR did increase markers of fibrinolysis in renal tissue but their increase did not correlate with renal injury or PJ34 treatment. These studies indicate that PJ34 confers protection against TAR and suggest that PARP may represent a novel target for reducing perioperative renal injury.

Local inflammatory and thrombotic responses differ in a murine model of partial and complete hindlimb ischemia/reperfusion.

BACKGROUND: These experiments were designed to quantitatively compare the patterns of tissue thrombosis, cytokine response, and tissue viability in a murine model of partial (PI) versus complete hindlimb ischemia (CI), alone or with reperfusion (RE). METHODS: The control tension tourniquet was used to establish either PI or CI in the unilateral mouse hindlimb for 3 hours followed by 0, 4, and 24 hours of RE. Muscle viability, local neutrophil chemoattractant protein, interleukin 6, interleukin 1beta, D-dimer, thrombin-antithrombin III complex, plasminogen activator inhibitor 1, and tissue plasminogen activator levels were measured in protein extracts for each experimental interval. RESULTS: Tissue viability after CI and 24 hours of RE was significantly less than tissue subjected to PI and 24 hours of RE (96% +/- 16 PI, 64% +/- 4 CI, P=.02). The local cytokine response was initially elevated in the PI group but dissipated by 24RE. In contrast, the local cytokine response to CI alone was small but greatly increased by 24RE. The thrombotic response to PI was increased throughout ischemia/reperfusion. While thrombosis during CI alone was negligible, reperfusion led to a significant thrombotic response. CONCLUSIONS: Biochemical markers for tissue viability, thrombosis, and cytokine-mediated inflammation differ significantly in mice subjected to moderate and severe hindlimb ischemia/reperfusion. These biochemical markers may facilitate stratification of patients in clinical trials for treatment of ischemia/reperfusion injury and contribute to interpretation of their outcomes.

CXC chemokine expression and synthesis in skeletal muscle during ischemia/reperfusion.

BACKGROUND: The chemokines keratinocyte-Derived Cytokine (KC) and macrophage inflammatory protein (MIP)-2, murine equivalents of human interleukin 8, have been implicated in remote injury after acute hind limb ischemia/reperfusion (I/R). These studies were designed to determine whether the cytokines responsible for remote tissue injury are also synthesized and accumulate in the ischemic or reperfused hind limb. METHODS: B6, 129SF2/J mice were subjected to either 3 hours of unilateral hind limb ischemia alone (IA) or 3 hours of ischemia followed by 4 or 24 hours of reperfusion (I/R). After IA or I/R, experimental and control (nonischemic) contralateral hind limbs were harvested for analysis of protein content, messenger RNA (mRNA), tissue edema, and viability. RESULTS: IA did not increase KC or MIP-2 mRNA or protein levels. In contrast, I/R resulted in a 15- and 10-fold increase in KC mRNA after 4 and 24 hours of reperfusion, respectively. KC protein levels were increased 10-fold after 4 hours of reperfusion and 30-fold after 24 hours (vs IA or sham; P < .001). MIP-2 mRNA transiently increased 42-fold after 4 hours of reperfusion but decreased to basal levels after 24 hours of reperfusion. Despite the relative increase in MIP-2 mRNA by 4 hours of reperfusion, significantly increased (8- to 10 fold) MIP-2 protein levels were not detected until 24 hours of reperfusion only in the reperfused limbs. Tissue edema was increased significantly (P < .01) compared with sham after just 4 hours of reperfusion and remained increased at 24 hours. Tissue viability decreased 52% after 4 hours of reperfusion and did not change significantly by 24 hours. CONCLUSIONS: Skeletal muscle is a site of significant ongoing chemokine synthesis during reperfusion. The persistent increase in muscle chemokine levels at 24 hours of reperfusion was not associated with increased edema or injury. The role of these chemokines during reperfusion may be further investigated by local or oral administration of chemokines or chemokine receptor antagonists. CLINICAL RELEVANCE: I/R injury remains an important clinical problem across a variety of surgical specialties. In the critical care arena, serum levels of proinflammatory cytokines have been useful in predicting the mortality associated with acute respiratory distress syndrome and sepsis. In this article, the data presented indicate that murine skeletal muscle produces potent proinflammatory neutrophil and macrophage chemokines during reperfusion, but not during ischemia. These findings suggest that measurement of tissue and/or serum levels of chemokines during reperfusion may be an important adjunct to predicting tissue injury along with ongoing inflammation during the clinical course of reperfusion injury. Within the vascular system, severe inflammatory responses are usually associated with thrombotic events. New techniques to noninvasively image thrombin activation (by using magnetic resonance imaging) in reperfused limbs may coincide with the pattern of murine skeletal muscle chemokine expression in humans. The data suggest that reperfusion is when chemokine mRNA and protein synthesis increase. Within the time periods studied in these experiments, the chemokine component of the inflammatory response remained in the reperfused, rather than the systemic nonreperfused, tissue. This observation may underestimate the degree of the systemic response to ischemia because the single mouse hind limb represents only 7% of the mouse total body area, whereas the human limb represents nearly 18% of the adult body area. Despite this shortcoming, these data provide potential temporal and quantitative information regarding the location and magnitude of chemokine synthesis in skeletal muscle during reperfusion.

Polyadenosine diphosphate-ribose polymerase inhibition modulates skeletal muscle injury following ischemia reperfusion.

HYPOTHESIS: Polyadenosine diphosphate-ribose polymerase (PARP) has been implicated as a mediator of inflammation and tissue necrosis in murine models of human stroke and myocardial infarction. This study was designed to determine whether PARP modulates skeletal muscle injury and cytokine-growth factor levels during ischemia-reperfusion. DESIGN: Prospective controlled animal study. SETTING: Medical school-affiliated university hospital. INTERVENTIONS: Mice were divided into 2 groups-treated (PJ) and untreated; all mice were subjected to unilateral hind limb tourniquet ischemia followed by 4 or 48 hours of reperfusion. In treated mice, PJ34, an ultrapotent-specific PARP inhibitor was given immediately before ischemia and prior to reperfusion. A group of PARP-1 knockout mice (PARP-/-) were also subjected to hind limb ischemia followed by 48 hours of reperfusion. MAIN OUTCOME MEASURES: After ischemia-reperfusion, muscle was harvested for measurement of edema, viability, cytokine, and vascular endothelial growth factor content. RESULTS: The PJ34-treated mice had increased skeletal muscle viability when compared with the untreated mice after 4 and 48 hours of reperfusion (P<.01). Viability between PARP-/- and PJ34-treated mice were similar at 48 hours of reperfusion (P>.05), and it exceeded that of untreated mice (P<.01). Tissue edema was unaltered by PARP inhibition. Tissue levels of cytokine were only different (P<.05) in PJ34-treated vs untreated mice at 48 hours of reperfusion. Vascular endothelial growth factor levels in PJ34-treated mice were markedly reduced when compared with untreated mice only after 4 hours of reperfusion (P<.01), and in PARP-/- mice (P<.01) at 48 hours of reperfusion. CONCLUSIONS: Polyadenosine diphosphate-ribose polymerase modulates skeletal muscle viability, cytokine and vascular endothelial growth factor synthesis during reperfusion. Polyadenosine diphosphate-ribose polymerase inhibition may represent a novel method to modulate skeletal muscle ischemia-reperfusion injury.