A hydrogen-sulfide derivative of mesalamine reduces the severity of intestinal and lung injury in necrotizing enterocolitis through endothelial nitric oxide synthase.

Necrotizing enterocolitis (NEC) remains a devastating disease that affects preterm infants. Hydrogen sulfide (H2S) donors have been shown to reduce the severity of NEC, but the optimal compound has yet to be identified. We hypothesized that oral H2S-Mesalamine (ATB-429) would improve outcomes in experimental NEC, and its benefits would be dependent on endothelial nitric oxide synthase (eNOS) pathways. NEC was induced in 5-day-old wild-type (WT) and eNOS knockout (eNOSKO) pups by formula feeding and stress. Four groups were studied in both WT and eNOSKO mice: 1) breastfed controls, 2) NEC, 3) NEC + 50 mg/kg mesalamine, and 4) NEC + 130 mg/kg ATB-429. Mesalamine and ATB-429 doses were equimolar. Pups were monitored for sickness scores and perfusion to the gut was measured by Laser Doppler Imaging (LDI). After euthanasia of the pups, intestine and lung were hematoxylin and eosin-stained and scored for injury in a blind fashion. TLR4 expression was quantified by Western blot and IL-6 expression by ELISA. P < 0.05 was significant. Both WT and eNOSKO breastfed controls underwent normal development and demonstrated milder intestinal and pulmonary injury compared with NEC groups. For the WT groups, ATB-429 significantly improved weight gain, reduced clinical sickness score, and improved perfusion compared with the NEC group. In addition, WT ATB-429 pups had a significantly milder intestinal and pulmonary histologic injury when compared with NEC. ATB-429 attenuated the increase in TLR4 and IL-6 expression in the intestine. When the experiment was repeated in eNOSKO pups, ATB-429 offered no benefit in weight gain, sickness scores, perfusion, intestinal injury, pulmonary injury, or decreasing intestinal inflammatory markers. An H2S derivative of mesalamine improves outcomes in experimental NEC. Protective effects appear to be mediated through eNOS. Further research is warranted to explore whether ATB-429 may be an effective oral therapy to combat NEC.

Human Mesenchymal Stem Cell Hydrogen Sulfide Production Critically Impacts the Release of Other Paracrine Mediators After Injury.

BACKGROUND: The use of mesenchymal stem cells (MSCs) for treatment during ischemia is novel. Hydrogen sulfide (H2S) is an important paracrine mediator that is released from MSCs to facilitate angiogenesis and vasodilation. Three enzymes, cystathionine-beta-synthase (CBS), cystathionine-gamma-lyase (CSE), and 3-mercaptopyruvate-sulfurtransferase (MPST), are mainly responsible for H2S production. However, it is unclear how these enzymes impact the production of other critical growth factors and chemokines. We hypothesized that the enzymes responsible for H2S production in human MSCs would also critically regulate other growth factors and chemokines. MATERIALS AND METHODS: Human MSCs were transfected with CBS, MPST, CSE, or negative control small interfering RNA. Knockdown of enzymes was confirmed by polymerase chain reaction. Cells were plated in 12-well plates at 100,000 cells per well and stimulated with tumor necrosis factor-α (TNF-α; 50 ng/mL), lipopolysaccharide (LPS; 200 ng/mL), or 5% hypoxia for 24 h. Supernatants were collected, and cytokines measured by multiplex beaded assay. Data were compared with the Mann-Whitney U-test, and P < 0.05 was significant. RESULTS: TNF-α, LPS, and hypoxia effectively stimulated MSCs. Granulocyte colony-stimulating factor (GCSF), epidermal growth factor, fibroblast growth factor, granulocyte/monocyte colony-stimulating factor (GMCSF), vascular endothelial growth factor, and interferon gamma-inducible protein 10 were all significantly elevated when CSE was knocked down during TNF-α stimulation (P < 0.05). Knockdown of MPST during LPS stimulation more readily increased GCSF and epidermal growth factor but decreased GMCSF (P < 0.05). CBS knockdown decreased production of GCSF, fibroblast growth factor, GMCSF, and vascular endothelial growth factor (P < 0.05) after hypoxia. CONCLUSIONS: The enzymes that produce H2S in MSCs are also responsible for the production of other stem cell paracrine mediators under stressful stimuli. Therefore, reprogramming MSCs to endogenously produce more H2S as a therapeutic intervention could also critically impact other paracrine mediators, which may alter the desired beneficial effects.

Sildenafil as a Rescue Agent Following Intestinal Ischemia and Reperfusion Injury.

BACKGROUND: Acute mesenteric ischemia carries a significant morbidity. Measures to improve blood flow parameters to the intestine may ameliorate the disease. Sildenafil, a phosphodiesterase 5 inhibitor, increases cyclic guanosine monophosphate and has been shown to prevent the effects of ischemia when given before injury. However, its effects as a rescue agent have not been established. We therefore hypothesized that sildenafil, when given as a rescue agent for intestinal ischemia, would improve mesenteric perfusion, limit intestinal epithelial injury, and decrease intestinal leukocyte chemoattractants. METHODS: Eight to 12 wk-old-male C57BL/6J mice underwent laparotomy and temporary occlusion of the superior mesenteric artery for 60 min. Following ischemia, reperfusion was permitted, and before closing the abdomen, sildenafil was injected intraperitoneally in a variety of concentrations. After 24 h, reperfusion was reassessed. Animals were euthanized and intestines evaluated for histologic injury and leukocyte chemoattractants. RESULTS: Postischemic administration of sildenafil did not improve mesenteric perfusion following intestinal ischemia and reperfusion injury. However, sildenafil did improve histologic injury scores in dose ranges of 0.01 to 10 mg/kg. No difference was noted in histological injury with 100 mg/kg dose, and all members of the 1000 mg/kg group died within 24 h of injury. Epithelial protection was not facilitated by the leukocyte chemoattractants Regulated on Activation, Normal T Cell Expressed, and Secreted, macrophage inflammatory protein 1 alpha, monocyte chemoattractant protein, neutrophil activating protein, or granulocyte colony stimulating factor. CONCLUSIONS: Administration of sildenafil following intestinal ischemia may limit intestinal mucosal injury but does not appear to alter mesenteric perfusion or leukocyte chemoattractant influx. TYPE: Basic science. LEVEL OF EVIDENCE: N/A.

Mesenchymal stem cells promote mesenteric vasodilation through hydrogen sulfide and endothelial nitric oxide.

Mesenteric ischemia is a devastating process that can result in intestinal necrosis. Mesenchymal stem cells (MSCs) are becoming a promising treatment modality. We hypothesized that 1) MSCs would promote vasodilation of mesenteric arterioles, 2) hydrogen sulfide (H2S) would be a critical paracrine factor of stem cell-mediated vasodilation, 3) mesenteric vasodilation would be impaired in the absence of endothelial nitric oxide synthase (eNOS) within the host tissue, and 4) MSCs would improve the resistin-to-adiponectin ratio in mesenteric vessels. H2S was measured with a specific fluorophore (7-azido-3-methylcoumarin) in intact MSCs and in cells with the H2S-producing enzyme cystathionine ß synthase (CBS) knocked down with siRNA. Mechanical responses of isolated second- and third-order mesenteric arteries (MAs) from wild-type and eNOS knockout (eNOSKO) mice were monitored with pressure myography, after which the vessels were snap frozen and later analyzed for resistin and adiponectin via multiplex beaded assay. Addition of MSCs to the myograph bath significantly increased vasodilation of norepinephrine-precontracted MAs. Knockdown of CBS in MSCs decreased H2S production by MSCs and also decreased MSC-initiated MA dilation. MSC-initiated vasodilation was further reduced in eNOSKO vessels. The MA resistin-to-adiponectin ratio was higher in eNOSKO vessels compared with wild-type. These results show that MSC treatment promotes dilation of MAs by an H2S-dependent mechanism. Furthermore, functional eNOS within the host mesenteric bed appears to be essential for maximum stem cell therapeutic benefit, which may be attributable, in part, to modifications in the resistin-to-adiponectin ratio.NEW & NOTEWORTHY Stem cells have been shown to improve survival, mesenteric perfusion, and histological injury scores following intestinal ischemia. These benefits may be due to the paracrine release of hydrogen sulfide. In an ex vivo pressure myography model, we observed that mesenteric arterial dilation improved with stem cell treatment. Hydrogen sulfide release from stem cells and endothelial nitric oxide synthase within the vessels were critical components of optimizing stem cell-mediated mesenteric artery dilation.

Long-term outcomes after pediatric peripheral revascularization secondary to trauma at an urban level I center.

OBJECTIVE: The purpose of this investigation was to determine our limb-related contemporary pediatric revascularization perioperative and follow-up outcomes after major blunt and penetrating trauma. METHODS: A retrospective review was performed of a prospectively maintained pediatric trauma database spanning January 2010 to December 2017 to capture all level I trauma activations that resulted in a peripheral arterial revascularization procedure. All preoperative, intraoperative, and postoperative continuous variables are reported as a mean ± standard deviation; categorical variables are reported as a percentage of the population of interest. RESULTS: During the study period, 1399 level I trauma activations occurred at a large-volume, urban children's hospital. The vascular surgery service was consulted in 2.6% (n = 36) of these cases for suspected vascular injury based on imaging or physical examination. Our study population included only patients who received an arterial revascularization, which was performed in 23 of the 36 consultations (1.6% of total traumas; median age, 11 years). These injuries were localized to the upper extremity in 60.9% (n = 14), lower extremity in 30.4% (n = 7), and neck in 8.7% (n = 2). The mean Injury Severity Score in the revascularized cohort was 14.0 (±7.6). Bone fractures were associated with 39.1% of the vascular injuries (90% of blunt injuries). Restoration of in-line flow was achieved by an endovascular solution in one patient and open surgery in the remainder, consisting of arterial bypass in 59.1% and direct repair in 40.9%. Within 30 days of the operation, we observed no deaths, no infections of the arterial reconstruction, and no major amputations. One patient required perioperative reintervention by the vascular team secondary to the development of a superficial seroma without evidence of graft involvement. Mean follow-up in our cohort was 43.3 (±35.4) months. During this phase, no additional deaths, amputations, chronic wounds, or limb length discrepancies were observed. All vascular repairs were patent, and all but one patient reported normal function of the affected limb at the latest clinic visit. CONCLUSIONS: Traumatic peripheral vascular injury is rare in the pediatric population but is often observed secondary to a penetrating force or after long bone fracture. However, contemporary perioperative and long-term outcomes after surgical revascularization are excellent as demonstrated in this institutional case series.

Hydrogen Sulfide Donor GYY4137 Acts Through Endothelial Nitric Oxide to Protect Intestine in Murine Models of Necrotizing Enterocolitis and Intestinal Ischemia.

BACKGROUND: Necrotizing enterocolitis (NEC) in premature infants is often a devastating surgical condition with poor outcomes. GYY4137 is a long-acting donor of hydrogen sulfide, a gasotransmitter that is protective against intestinal injury in experimental NEC, likely through protection against injury secondary to ischemia. We hypothesized that administration of GYY4137 would improve mesenteric perfusion, reduce intestinal injury, and reduce inflammatory responses in experimental NEC and ischemia-reperfusion injury, and that these benefits would be mediated through endothelial nitric oxide synthase-dependent pathways. METHODS: NEC was induced in C57BL/6 wild-type (WT) and endothelial nitric oxide synthase (eNOS) knockout (eNOSKO) pups via maternal separation, formula feeding, enteral lipopolysaccharide, and intermittent hypoxic and hypothermic stress. Pups received daily intraperitoneal injections of 50 mg/kg GYY4137 or phosphate buffered saline vehicle. In separate groups, adult male WT and eNOSKO mice underwent superior mesenteric artery occlusion for 60 min. Before abdominal closure, 50 mg/kg GYY4137 or phosphate buffered saline vehicle was administered into the peritoneal cavity. Laser doppler imaging was used to assess mesenteric perfusion of pups at baseline and on postnatal day 9, and the adult mice at baseline and 24 h after ischemic insult. After euthanasia, the terminal ileum of each animal was fixed, paraffin embedded, sectioned, and stained with hematoxylin and eosin. Sections were blindly graded using published injury scores. Intestinal tissue was homogenized and cytokines measured by ELISA. Data were compared using Mann-Whitney U test, and P-values <0.05 were significant. RESULTS: After NEC and ischemia reperfusion (I/R) injury, GYY4137 improved perfusion in WT mice compared to vehicle, but this effect was lost in the eNOSKO animals. Histologic injury followed a similar pattern with reduced intestinal injury in WT mice treated with GYY4137, and no significant improvement in the eNOSKO group. Cytokine expression after GYY4137 administration was altered by the ablation of eNOS in both NEC and I/R injury groups, with significant differences noted in Interleukin 6 and vascular endothelial growth factor. CONCLUSIONS: GYY4137, a long-acting donor of hydrogen sulfide, has potential as a therapeutic compound for NEC. It improves mesenteric perfusion and intestinal injury in experimental NEC and intestinal I/R injury, and these benefits appear to be mediated through eNOS-dependent pathways.

Interleukin-6 Therapy Improves Intestinal Recovery Following Ischemia.

BACKGROUND: Interleukin-6 (IL6) has both proinflammatory and anti-inflammatory pathways, but its effects on intestinal recovery following ischemia are unknown. We hypothesized that administration of IL6 following intestinal ischemia would improve mesenteric perfusion and mucosal injury. METHODS: Adult male C57Bl6J mice were anesthetized, and a laparotomy was performed. Baseline intestinal perfusion was assessed by laser Doppler imaging. Intestinal ischemia was induced for 60 min by temporarily occluding the superior mesenteric artery. After ischemia, treatments were administered intraperitoneally before closure (Vehicle: 250 µL phosphate-buffered-saline, IL6 low dose (20 ng), IL6 medium dose (200 ng), or IL6 high dose (2 µg)). Animals were allowed to recover for 24 h, were reanesthetized, and their mesenteric perfusion was reassessed. Perfusion was expressed as percentage of baseline. Animals were then sacrificed, and the intestines were explanted for histological analysis. Separate frozen samples were homogenized and analyzed by ELISA for vascular endothelial growth factor (VEGF) and interferon gamma-induced protein 10. RESULTS: IL6 increased mesenteric perfusion in low dose groups only, whereas it improved postischemic mucosal injury scores in both low and medium dose groups. No differences in perfusion or histology were seen when high dose IL6 was utilized. Intestinal VEGF was higher in the low dose IL6 group compared to vehicle, whereas IP-10 levels were lower in low and medium dose groups compared to vehicle. No differences were noted compared to vehicle in intestinal VEGF and IP-10 with high dose IL6 therapy. CONCLUSIONS: Lower doses of IL6 may serve as effective therapy to decrease intestinal injury after ischemia. Further studies are needed to elucidate the downstream mechanisms before widespread clinical use.

Procedural Complexity of TransCarotid Artery Revascularization Is Not Increased in Irradiated and Reoperative Necks.

BACKGROUND: TransCarotid Revascularization (TCAR) with dynamic flow reversal using the ENROUTE Neuroprotection System (ENPS) is a Food and Drug Administration-approved alternative carotid revascularization modality. The purpose of this investigation was to determine whether TCAR in a hostile (fibrotic) surgical field increases procedural complexity and postoperative complications. METHODS: Perioperative variables for all institutional TCARs performed between December 2015 and April 2019 were prospectively captured. Procedures performed as part of the ongoing ROADSTER-2 registry were excluded. Univariate analysis, consisting of Student's T and Fisher's exact testing, comparing virgin and hostile neck TCAR, was performed at an alpha of 0.05. RESULTS: During the study period, 149 total procedures (n = 30, hostile ipsilateral necks) qualified for inclusion. Both hostile and virgin neck groups were comparable with respect to preoperative comorbidities and medication profiles. The ipsilateral hostile neck cohort consisted of ten patients who underwent previous ipsilateral neck radiation and 23 who were status after neck dissection (3 had both). Intraoperatively, there were no differences with respect to estimated blood loss (47.2 vs. 44.8 mL, P = 0.81), operative time (69.5 vs. 74.5 min, P = 0.38), reverse flow time (12.4 vs. 10.4 min, P = 0.34), radiation exposure (217.7 vs. 226.2 mGy, P = 0.88), fluoroscopy time (5.4 vs. 5.0 min, P = 0.65), contrast usage (23.5 vs. 25.0 mL, P = 0.55), and ability to achieve technical success (96.7% vs. 100%, P = 0.58) between virgin and hostile necks, respectively. Perioperative (30-day) ipsilateral stroke and death rate was 2.5% vs. 0% (P = 1.0) and 2.5% vs. 0% (P = 1.0), respectively, between virgin and hostile necks. We observed one postoperative cranial nerve injury in any of our TCAR patients (hostile neck, P = 0.20). Finally, a total of 3 hematomas (requiring washout) occurred in our (2 in virgin necks and one in a hostile neck) surgical cohort (P = 0.49). CONCLUSIONS: Based on this limited, small series, TCAR in hostile surgical fields is not associated with an increase in case complexity and maintains a similar perioperative risk to virgin field procedures.

Rationale and design of the Clinical and Histologic Analysis of Mesenchymal Stromal Cells in AmPutations (CHAMP) trial investigating the therapeutic mechanism of mesenchymal stromal cells in the treatment of critical limb ischemia.

OBJECTIVE: Currently, there are no accepted nonsurgical therapies that improve the delivery of blood-derived nutrients to patients with critical limb ischemia. Here, we describe the ongoing phase 1/2 Clinical and Histologic Analysis of Mesenchymal Stromal Cells in AmPutations (CHAMP) trial, which will provide crucial evidence of the safety profile of mesenchymal stromal cells (MSCs) and explore their therapeutic mechanisms in the setting of critical limb ischemia requiring below-knee amputation (BKA). METHODS: In the CHAMP and the parallel marrowCHAMP trials (hereafter grouped together as CHAMP), a total of 32 extremities with rest pain or tissue loss requiring BKA will be enrolled to receive intramuscular injections of allogeneic MSCs (CHAMP; n = 16) or autogenous concentrated bone marrow aspirate (marrowCHAMP; n = 16) along the distribution of the BKA myocutaneous flap and proximal tibialis anterior. After treatment, subjects are randomized to BKA at four time points after injection (days 3, 7, 14, and 21). At the time of amputation, skeletal muscle is collected at 2-cm increments from the tibialis injection site and used to determine proangiogenic cytokine description, MSC retention, quantification of proangiogenic hematopoietic progenitor cells, and histologic description. Clinical limb perfusion before and after treatment will be quantified using transcutaneous oximetry, toe-brachial index, ankle-brachial index, and indocyanine angiography. Additional clinical end points include all-cause mortality, need for amputation revision, and gangrene incidence during the 6-month post-treatment follow-up. RESULTS: Enrollment is under way, with 10 patients treated per protocol thus far. We anticipate full conclusion of follow-up within the next 24 months. CONCLUSIONS: CHAMP will be pivotal in characterizing the safety, efficacy, and, most important, therapeutic mechanism of allogeneic MSCs and autogenous concentrated bone marrow aspirate in ischemic skeletal muscle.

Results of nonoperative management of acute limb ischemia in infants.

OBJECTIVE: Acute limb ischemia (ALI) in infants poses a challenge to the clinician secondary to poor operative outcomes, limb loss risk, and lifelong morbidity. This retrospective study reviewed a 10-year institutional experience with the nonoperative management of ALI in infants. METHODS: Infants (aged ≤12 months) diagnosed with ALI by duplex ultrasound and treated with initial nonoperative management at a tertiary care children's hospital were identified through vascular laboratory arterial duplex ultrasound records and International Classification of Diseases and Current Procedural Terminology codes associated with ALI. Demographics of the patients, injury characteristics, treatment administered, and outcomes were abstracted by chart review and presented using descriptive statistics. RESULTS: During the study period, a total of 25 (28% female) infant patients were diagnosed with ALI. The average age for this cohort was 3.5 ± 3.2 months (standard deviation). Most cases were secondary to iatrogenic injury (88%) from arterial cannulation. Injury sites were more concentrated to the lower extremities (84%) compared with the upper. Absence of Doppler signals was noted in 64% of infants, whereas limb cyanosis was observed in 60% at the time of presentation. Infants were initially treated with anticoagulation (80%) when possible. Two patients failed to respond to nonoperative management and required thrombolysis secondary to progression of thrombus burden while anticoagulated. There were no major (above-ankle) amputations at 30 days. Three deaths occurred within 30 days; all were unrelated to limb ischemia. In the 30-day survivors, overall duration of follow-up was 53.5 ± 38.5 months. One infant required above-knee amputation 6 weeks after diagnosis, resulting in an overall limb salvage rate of 96% on follow-up. Long-term morbidity included two patients with a chronic wound of the affected limb and one patient with limb length discrepancy. No subjects reported claudication at the latest follow-up appointment. In addition, all patients were independently ambulatory except for one adolescent girl who was using a walker with leg braces. CONCLUSIONS: In contrast to the adult population, ALI in infants can be managed with anticoagulation alone with good results. Long-term follow-up continues to demonstrate excellent functional results and minimal disability.

Use of the Zenith Fenestrated platform to rescue failing endovascular and open aortic reconstructions is safe and technically feasible.

OBJECTIVE: Proximal neck dilation is a serious long-term complication directly causing the failure of endovascular aneurysm repair (EVAR) and open surgical repair (OSR) of abdominal aortic aneurysms. However, the implantation of a fenestrated device presents the opportunity for proximal extension of the aortic reconstruction into a healthy segment while maintaining patency of the visceral vessels. The objective of this investigation was to report perioperative and follow-up outcomes using the Zenith Fenestrated (ZFEN; Cook Medical, Bloomington, Ind) aortic stent system in salvaging previous aortic repairs undergoing type IA endoleak or aneurysmal degeneration of the proximal neck. METHODS: We performed a retrospective review of a prospectively maintained institutional database capturing all fenestrated EVAR (FEVAR) cases with the ZFEN platform. Fenestrated cases were classified as primary FEVAR or reoperative FEVAR (rFEVAR) after previous EVAR or OSR. Cohort comparisons were performed using Fisher exact tests and Student t-tests for categorical and continuous variables, respectively. RESULTS: Between October 2012 and March 2017, a total of 103 patients diagnosed with abdominal aortic aneurysm with an inadequate proximal seal zone for traditional EVAR were treated with ZFEN. In 12 patients, FEVAR was performed as a reoperation after previous EVAR (n = 6) or OSR (n = 6). The indications for rFEVAR were proximal neck dilation (>55 mm) after OSR (n = 6), type IA endoleak after EVAR (n = 5), and proximal neck dilation after EVAR without endoleak (n = 1). No difference in ability to achieve technical success was observed between primary FEVAR and rFEVAR (97.8% vs 100%; P = 1.00). In addition, there were no differences in estimated blood loss (363 vs 500 mL; P = .25) and intraoperative use of contrast material (97.3 vs 104.0 mL; P = .55). However, a significant increase in fluoroscopy time (61.1 vs 79.8 minutes; P = .04), radiation exposure (415.9 vs 606.3 rad; P = .02), and operative time (228.4 vs 287.6 minutes; P = .03) in the rFEVAR cohort was observed. In the 30-day perioperative period, there were no significant differences with regard to mortality (2.2% vs 0%; P = 1.0), major adverse cardiovascular events (5.5% vs 0%, P = 1.0), and stent-related adverse events (2.2% vs 0%; P = 1.0). There were no differences in rates of perioperative (5.5% vs 0%; P = 1.0) or follow-up reintervention after a mean follow-up duration of 20.8 months (18.6% vs 25.0%; P = .70). CONCLUSIONS: FEVAR with the ZFEN platform of failed and failing aortic reconstructions due to disease progression is safe and feasible without increased morbidity and mortality in select patients. These preliminary results support the inclusion of ZFEN as a treatment option for aortic reintervention.

Adjunctive visceral artery chimney in patients undergoing Zenith Fenestrated aortic repair.

OBJECTIVE: Visceral artery chimneys have been employed as an adjunct to endovascular aneurysm repair (EVAR) to treat short-neck infrarenal and juxtarenal aortic aneurysms for more than two decades. With the widespread introduction of fenestrated endovascular aneurysm repair by the Food and Drug Administration-approved Zenith Fenestrated endograft (ZFEN; Cook Medical, Bloomington, Ind) to the United States in 2012, clinicians gained the ability to apply the chimney technique to these custom devices for difficult anatomy. The purpose of this report was to demonstrate feasibility and to provide evidence on the performance of chimneys for the treatment of complex juxtarenal aneurysms that could not be adequately treated with ZFEN alone. METHODS: A retrospective analysis was performed of a prospectively maintained institutional ZFEN database capturing 110 fenestrated endovascular aneurysm repairs from October 2012 to January 2018 to identify patients undergoing a concomitant visceral artery chimney. All patients with <12 months of follow-up were excluded from further analysis. Demographic, anatomic, intraoperative, perioperative, and follow-up characteristics were tabulated and analyzed. RESULTS: Six patients met criteria and were included in this investigation. They were universally male with a mean age of 76.2 years at the time of ZFEN/chimney. Chimneys were placed in a total of six visceral arteries (n = 1 per patient) consisting of three renal arteries, two celiac arteries, and one accessory renal artery. Mean estimated blood loss and operative time were 283 mL and 298 minutes, respectively. Technical success was achieved in all cases. Two small type IA "gutter" endoleaks were detected early; both spontaneously resolved on follow-up. We observed no instances of chimney migration, stenosis, or thrombosis perioperatively or on follow-up. Two reinterventions were performed in these six patients; these consisted of a repeated renal stent for ostial stenosis at a main body fenestration and a common femoral artery endarterectomy and patch angioplasty for an access-related common femoral artery occlusion. CONCLUSIONS: Use of ZFEN in conjunction with a singular chimney is safe, feasible, and durable in patients with difficult anatomy who do not meet instructions for use as demonstrated in this limited series.

Ethnic minorities with critical limb ischemia derive equal amputation risk reduction from autologous cell therapy compared with whites.

OBJECTIVE: Ethnic minorities (nonwhites) with critical limb ischemia (CLI) have historically performed worse compared with whites with regard to major amputation risk reduction and amputation-free survival (AFS) after peripheral vascular intervention. This post hoc analysis was completed to determine whether this precedent also extended to treatment of CLI without a suitable revascularization option with intramuscular injections of concentrated bone marrow aspirate (cBMA). METHODS: The treatment arm of the randomized, double-blind, multicenter MarrowStim PAD Kit for the Treatment of Critical Limb Ischemia in Subjects with Severe Peripheral Arterial Disease (MOBILE) trial was stratified by ethnicity and evaluated for demographics, comorbidities, and outcomes. The primary and therapeutic end point was 1-year AFS and major amputation, respectively. Noninferiority analysis was performed with the margin set at historically reported hazard ratios. RESULTS: Thirty-seven minority (African American, Hispanic, other) CLI patients (9 placebo, 28 cBMA) with no suitable revascularization option were randomized to cBMA or placebo at a 3:1 ratio during the MOBILE trial. At 1-year follow-up for the treatment group, overall AFS was 80%. Of the 28 minority patients randomized to cBMA intervention, an 89% AFS rate was observed compared with 77% in whites. Specifically, 22 of 24 (92%) African Americans survived amputation free at 1-year follow-up. Noninferiority testing confirmed no difference between whites and the ethnic minority treated with cBMA with respect to major amputation reduction; however, noninferiority could not be confirmed with regard to AFS. No significant differences favoring whites treated with cBMA were noted in the secondary end points of vascular quality of life, limb pain, ankle-brachial index, toe-brachial index, transcutaneous oximetry, and 6-minute walk testing. CONCLUSIONS: This post hoc analysis of the MOBILE trial demonstrates noninferiority of cBMA intervention in minorities with no-option CLI for the therapeutic end point of major amputation prevention. cBMA represents a novel treatment paradigm and should be explored for minorities with poor revascularization options who face impending amputation secondary to progressive CLI.

Umbilical mesenchymal stromal cells provide intestinal protection through nitric oxide dependent pathways.

BACKGROUND: Umbilical-derived mesenchymal stromal cells (USCs) have shown promise in the protection of ischemic organs. We hypothesized that USCs would improve mesenteric perfusion, preserve intestinal histological architecture, and limit inflammation by nitric oxide-dependent mechanisms following intestinal ischemia/reperfusion (IR) injury. METHODS: Adult wild-type C57BL/6J (WT) and endothelial nitric oxide synthase knock out (eNOS KO) mice were used: (1) WT IR + vehicle, (2) WT IR + USC, (3) eNOS KO IR + vehicle, and (4) eNOS KO IR + USC. Mice were anesthetized, and a midline laparotomy was performed. The superior mesenteric artery was clamped with a nonoccluding clamp for 60-min. Following IR, mice were treated with an injection of 250 µL phosphate buffered saline or 2 × 106 USCs suspended in 250-µL phosphate buffered saline solution. Mesenteric perfusion images were acquired using laser Doppler imaging. Perfusion was analyzed as a percentage of baseline. At 24 h, mice were euthanized, and intestines were harvested. Intestines were evaluated for injury, and data were analyzed using the Mann-Whitney or Kruskal-Wallis tests. RESULTS: Intestinal mesenteric perfusion was significantly improved in WT mice treated with USC therapy compared with eNOS KOs. Intestinal histological architecture was preserved with USC therapy in WT mice. However, in eNOS KO mice, this benefit was abolished. Finally, the presence of several cytokines and growth factors were significantly improved in WT mice compared with eNOS KO mice treated with USCs. CONCLUSIONS: The benefits of USC-mediated therapy following intestinal IR injury likely occur via nitric oxide-dependent pathways. Further studies are required to define the molecular mechanisms by which USCs activate endothelial nitric oxide synthase to bring about their protective effects.

Rationale and Design of the ARREST Trial Investigating Mesenchymal Stem Cells in the Treatment of Small Abdominal Aortic Aneurysm.

BACKGROUND: Abdominal aortic aneurysms (AAAs) are a major source of morbidity and mortality despite continuing advances in surgical technique and care. Although the inciting factors for AAA development continue to be elusive, accumulating evidence suggests a significant periaortic inflammatory response leading to degradation and dilation of the aortic wall. Previous human trials have demonstrated safety and efficacy of mesenchymal stem cells (MSCs) in the treatment of inflammation-related pathologies such as rheumatoid arthritis, graft versus host disease, and transplant rejection. Therefore, herein, we describe the Aortic Aneurysm Repression with Mesenchymal Stem Cells (ARREST) trial, a phase I investigation into the safety of MSC infusion for patients with small AAA and the cells' effects on modulation of AAA-related inflammation. METHODS: ARREST is a phase I, single-center, double-blind, randomized controlled trial (RCT) investigating infusion both dilute and concentrated MSCs compared to placebo in 36 small AAA (35-45 mm) patients. Subjects will be followed by study personnel for 12 months to ascertain incidence of adverse events, immune cell phenotype expression, peripheral cytokine profile, and periaortic inflammation. Maximum transverse aortic diameter will be assessed regularly for 5 years by a combination of computed tomography and duplex sonography. RESULTS: Four patients have thus far been enrolled, randomized, and treated per protocol. We anticipate the conclusion of the treatment phase within the next 24 months with ongoing long-term follow-up. CONCLUSIONS: ARREST will be pivotal in assessing the safety of MSC infusion and provide preliminary data on the ability of MSCs to favorably modulate the pathogenic AAA host immune response. The data gleaned from this phase I trial will provide the groundwork for a larger, phase III RCT which may provide the first pharmaceutical intervention for AAA.

Perioperative Outcomes are Adversely Affected by Poor Pretransfer Adherence to Acute Limb Ischemia Practice Guidelines.

BACKGROUND: The accepted treatment for acute limb ischemia (ALI) is immediate systemic anticoagulation and timely reperfusion to restore blood flow. In this study, we describe the retrospective assessment of pretransfer management decisions by referring hospitals to an academic tertiary care facility and its impact on perioperative adverse events. METHODS: A retrospective analysis of ALI patients transferred to us via our Level I Vascular Emergency Program from 2010 to 2013 was performed. Patient demographics, comorbidities, Rutherford ischemia classification, time to anticoagulation, and time to reperfusion were tabulated and analyzed for correlation to incidence of major adverse limb events (MALEs), mortality, and bypass patency in the perioperative period (30-day postoperative). All intervals were calculated from the onset of symptoms and categorized into 3 subcohorts (<6 hr, 6-48 hr, and >48 hr). RESULTS: Eighty-seven patients with an average age of 64.0 (±16.2) years presented to outlying hospitals and were transferred to us with lower extremity ALI. The mean delay from symptom onset to initial referring physician evaluation was 18.3 hr. At that time of evaluation, 53.8% had Rutherford class IIA ischemia and 36.3% had class IIB ischemia. Seventy-six patients (87.4%) were started on heparin previous to transfer. However, only 44 patients (57.9%) reached therapeutic levels as measured by activated partial thromboplastin time before definitive revascularization. A delay of anticoagulation initiation >48 hr from symptom onset was associated with increased 30-day reintervention rates compared with the <6 hr group (66.7% vs. 23.5%; P < 0.05). However, time to reperfusion had no statistically significant impact on MALE, 30-day mortality, or 30-day interventional patency in our small cohorts. Additionally, patients with a previous revascularization had a higher 30-day reintervention rate (46.5%; P < 0.05). CONCLUSIONS: The practice of timely therapeutic anticoagulation of patients referred for ALI from community facilities occurs less frequently than expected and is associated with an increased perioperative reintervention rate.

Cryopreserved Homografts in Infected Infrainguinal Fields Are Associated with Frequent Reinterventions and Poor Amputation-Free Survival.

BACKGROUND: Single-length saphenous vein continues to be the conduit of choice in infected-field critical limb ischemia. However, half of these individuals have inadequate vein secondary to previous use or chronic venous disease. We reviewed our outcomes of infected-field infrainguinal bypasses performed with cryopreserved homografts (CHs), a widely accepted alternative to autogenous vein in this setting. METHODS: This is a retrospective, institutional descriptive analysis of infected-field infrainguinal revascularizations between 2012 and 2015. RESULTS: Twenty-four operations were performed in the same number of patients for limb ischemia with signs of active infection. The mean age of the cohort examined was 62.5 ± 14.4 (standard deviation) years. Mean Society of Vascular Surgery risk score was 3.9 with a baseline Rutherford's chronic ischemia score of 4.3 at presentation. Emergent procedures constituted 29% of cases, and the remainder cases were urgent procedures. The CH bypass captured was a reoperative procedure in all but one of the patients. Culture positivity was present in 75% of cases with Staphylococcus aureus (29%), the most commonly isolated organism. Thirty-day mortality and major adverse cardiovascular events were both 4%. Amputation-free survival (AFS) was 75% at 30 days. Similarly, 30-day reintervention was 38% with debridement (43%) and bleeding (29%), the most common indications. Average duration of follow-up was 27.9 ± 20.4 months (range: 0.5-60.4). Mean length of stay was 14.8 days. Reinfection requiring an additional procedure or antibiotic regimen separate from the index antibiotic course was 13%. Primary patency and AFS at 1 year was 50% and 58%, respectively. Primary patency and AFS at 2 years was 38% and 52%, respectively. Limb salvage at 1 and 2 years was 70% and 65%, respectively. Fifteen patients (63%) required reintervention during the follow-up period with 40% of those subjects undergoing multiple procedures. CONCLUSIONS: CHs remain a marginal salvage conduit in the setting of infection and no autogenous choices. Therefore, clinicians should individualize usage of this high-cost product in highly selected patients only.

Physical Examination is the Best Predictor of the Need for Abdominal Surgery in Children Following Motor Vehicle Collision.

BACKGROUND: Exploratory laparotomy in children after motor vehicle collision (MVC) is rare. In the absence of definitive hemorrhage or free abdominal air on radiographic imaging, predictors for operative exploration are conflicting. OBJECTIVE: The purpose of this study was to explore objective findings that may aid in determining which children require operative abdominal exploration after MVC. METHODS: Data from 2010-2014 at an American College of Surgeons-certified level 1 pediatric trauma center were retrospectively reviewed. Demographics, vital signs, laboratory data, radiologic studies, operative records, associated injuries, and outcomes were analyzed and p < 0.05 was considered statistically significant. RESULTS: Eight hundred sixty-two patients 0-18 years of age presented to the hospital after an MVC during the study period. Seventeen patients (2.0%) required abdominal exploration and all were found to have intraabdominal injuries. Respiratory rate was the only vital sign that was significantly altered (p = 0.04) in those who required abdominal surgery compared with those who did not. Physical examination findings, such as the seat belt sign, abdominal bruising, abdominal wound, and abdominal tenderness, were present significantly more frequently in those requiring abdominal surgery (p < 0.0001). Each finding had a negative predictive value for the need for operative exploration of at least 0.98. There were no significant differences in trauma laboratory values or radiographic findings between the 2 groups. CONCLUSION: Data from this study solidify the relationship between specific physical examination findings and the need for abdominal exploration after MVC in children. In addition, these data suggest that a lack of the seat belt sign, abdominal bruising, abdominal wounds, or abdominal tenderness are individually predictive of patients who will not require surgical intervention.

Macrophage Migration Inhibitory Factor-CXCR4 Receptor Interactions: EVIDENCE FOR PARTIAL ALLOSTERIC AGONISM IN COMPARISON WITH CXCL12 CHEMOKINE.

An emerging number of non-chemokine mediators are found to bind to classical chemokine receptors and to elicit critical biological responses. Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine that exhibits chemokine-like activities through non-cognate interactions with the chemokine receptors CXCR2 and CXCR4, in addition to activating the type II receptor CD74. Activation of the MIF-CXCR2 and -CXCR4 axes promotes leukocyte recruitment, mediating the exacerbating role of MIF in atherosclerosis and contributing to the wealth of other MIF biological activities. Although the structural basis of the MIF-CXCR2 interaction has been well studied and was found to engage a pseudo-ELR and an N-like loop motif, nothing is known about the regions of CXCR4 and MIF that are involved in binding to each other. Using a genetic strain of Saccharomyces cerevisiae that expresses a functional CXCR4 receptor, site-specific mutagenesis, hybrid CXCR3/CXCR4 receptors, pharmacological reagents, peptide array analysis, chemotaxis, fluorescence spectroscopy, and circular dichroism, we provide novel molecular information about the structural elements that govern the interaction between MIF and CXCR4. The data identify similarities with classical chemokine-receptor interactions but also provide evidence for a partial allosteric agonist compared with CXCL12 that is possible due to the two binding sites of CXCR4.