Publications by authors named "Michael T Watkins"

84 Publications

The impact of race on choice of location for elective surgical care in New York city.

Am J Surg 2020 04 24;219(4):557-562. Epub 2020 Jan 24.

Massachusetts General Hospital, Department of Surgery, 55 Fruit St, Boston, MA, 02114, USA; Massachusetts General Hospital, Codman Center for Clinical Effectiveness in Surgery, Charles River Plaza, Suite 403, 165 Cambridge Street, Boston, MA, 02114, USA.

Background: The "white-flight" phenomenon of the mid-20th century contributed to the perpetuation of residential segregation in American society. In light of recent reports of racial segregation in our healthcare system, could a contemporary "white-flight" phenomenon also exist?

Methods: The New York Statewide Planning and Research Cooperative System was used to identify all Manhattan and Bronx residents of New York city who underwent elective cardiothoracic, colorectal, general, and vascular surgeries from 2010 to 2016. Primary outcome was borough of surgical care in relation to patient's home borough. Multivariable analyses were performed.

Results: White patients who reside in the Bronx are significantly more likely than racial minorities to travel into Manhattan for elective surgical care, and these differences persist across different insurance types, including Medicare.

Conclusions: Marked race-based differences in choice of location for elective surgical care exist in New York city. If left unchecked, these differences can contribute to furthering racial segregation within our healthcare system.
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http://dx.doi.org/10.1016/j.amjsurg.2020.01.033DOI Listing
April 2020

Risk score for nonhome discharge after lower extremity bypass.

J Vasc Surg 2020 03 10;71(3):889-895. Epub 2019 Sep 10.

Division of Vascular and Endovascular Surgery, Department of Surgery, Massachusetts General Hospital, Boston, Mass.

Objective: Patients undergoing lower extremity bypass (LEB) for peripheral artery disease require intensive health care resource utilization including rehabilitation and skilled nursing facilities. However, few studies have evaluated factors that lead to nonhome discharge (NHD) in this population of patients. This study sought to predict NHD by preoperative risk factors in patients undergoing LEB for peripheral artery disease using a novel risk score.

Methods: The Vascular Study Group of New England database was queried for elective LEB for peripheral artery disease including claudication and critical limb ischemia from 2003 to 2017. Patients were excluded if the procedure was not elective, if they were not admitted from home, if they were bedridden, or if they died during the index admission. Only preoperative factors were considered in the analysis. The primary end point was NHD including rehabilitation and skilled nursing facilities. Data were split two-thirds for model derivation and one-third for validation. In the derivation cohort, bivariate analysis assessed the association of preoperative factors with NHD. A parsimonious manual stepwise binary logistic regression for NHD aimed at maximizing the C statistic while maintaining model simplicity was performed. A risk score was developed using the β coefficients and applied to the validation data set. The risk score performance was assessed using a C statistic and Hosmer-Lemeshow test for model fit.

Results: There were 10,145 cases included with an overall NHD rate of 26.4% (n = 2676). Mean age was 66 years (range, 41-90 years). NHD patients were older (72 years vs 64 years; P < .01) and more frequently male (57.2% vs 42.8%; P < .01) and nonwhite (16.1% vs 9.9%; P < .01); they more frequently had tissue loss (54.2% vs 23.0%; P < .01), anemia (16.0% vs 5.3%; P < .01), severe cardiac comorbidity (21.8% vs 10.5%; P < .01), and insulin-dependent diabetes (33.3% vs 18.2%; P < .01). On multivariable analysis, factors associated with NHD included age, sex, nonwhite race, tissue loss, cardiac comorbidity, partial ambulatory deficit, and insulin-dependent diabetes. The C statistic was 0.78 in the derivation group and 0.79 in the validation group, with Hosmer-Lemeshow P > .999. The risk score ranged from 0 to 18, with a mean score of 4 (standard deviation ±3.5). The risk score was divided into low risk (0-4 points; n = 5272 [52%]; NHD = 10.1%]), moderate risk (5-9 points; n = 3663 [36.7%]; NHD = 36.7%), and high risk (≥10 points; n = 1210 [11.9%]; NHD = 66.1%).

Conclusions: This novel risk score was highly predictive for NHD after LEB for peripheral artery disease using only preoperative comorbidities. High-risk patients account for 12% of LEB but nearly a third of all patients requiring NHD. This risk score can be used preoperatively to determine high-risk patients for NHD, which may help improve preoperative counseling and hospital efficiency by allocating resources appropriately.
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http://dx.doi.org/10.1016/j.jvs.2019.07.053DOI Listing
March 2020

Systemically Administered Hemostatic Nanoparticles for Identification and Treatment of Internal Bleeding.

ACS Biomater Sci Eng 2019 May 2;5(5):2563-2576. Epub 2019 May 2.

Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.

Internal bleeding is an injury that can be difficult to localize and effectively treat without invasive surgeries. Injectable polymeric nanoparticles have been developed that can reduce clotting times and blood loss, but they have yet to incorporate sufficient diagnostic capabilities to assist in identifying bleeding sources. Herein, polymeric nanoparticles were developed to simultaneously treat internal bleeding while incorporating tracers for visualization of the nanoparticles by standard clinical imaging modalities. Addition of 1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine perchlorate (DiD; a fluorescent dye), biotin functionality, and gold nanoparticles to hemostatic polymeric nanoparticles resulted in nanoparticles amenable to imaging with near-infrared (NIR) imaging, immunohistochemistry, and X-ray computed tomography (CT), respectively. Following a lethal liver resection injury, visualization of accumulated nanoparticles by multiple imaging methods was achieved in rodents, with the highest accumulation observed at the liver injury site, resulting in improved survival rates. Tracer addition to therapeutic nanoparticles allows for an expansion of their applicability, during stabilization by first responders to diagnosis and identification of unknown internal bleeding sites by clinicians using standard clinical imaging modalities.
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http://dx.doi.org/10.1021/acsbiomaterials.9b00054DOI Listing
May 2019

Inhaled nitric oxide prevents systemic and pulmonary vasoconstriction due to hemoglobin-based oxygen carrier infusion: A case report.

J Crit Care 2019 06 30;51:213-216. Epub 2019 Jan 30.

Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA. Electronic address:

Hemoglobin-based oxygen carriers (HBOCs) are used in extreme circumstances to increase hemoglobin concentration and improve oxygen delivery when allogenic red blood cell transfusions are contraindicated or not immediately available. However, HBOC-induced severe pulmonary and systemic vasoconstriction due to peripheral nitric oxide (NO) scavenging has stalled its implementation in clinical practice. We present a case of an 87 year-old patient with acute life-threatening anemia who received HBOC while breathing NO gas. This case shows that inhaled NO allows for the safe use of HBOC infusion by preventing HBOC-induced pulmonary and systemic vasoconstriction.
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http://dx.doi.org/10.1016/j.jcrc.2018.04.008DOI Listing
June 2019

Variation in Amputation Risk for Black Patients: Uncovering Potential Sources of Bias and Opportunities for Intervention.

J Am Coll Surg 2018 04 31;226(4):641-649.e1. Epub 2018 Jan 31.

Department of Surgery, Massachusetts General Hospital, Boston, MA.

Background: Differences in amputation rates for limb ischemia between white and black patients have been extensively studied. Our goal was to determine whether biases in provider decision-making contribute to the disparity. We hypothesized that the magnitude of the disparity is affected by surgeon and hospital factors.

Study Design: Analysis of the New York Statewide Planning and Research Cooperative System database was performed for 1999 to 2014. Black and white patients with ICD9 codes for peripheral vascular disease, who received either an amputation or salvage procedure, were included. The primary endpoint was treatment choice.

Results: We analyzed 215,480 inpatient admissions. The overall amputation rate was 38.0%, and blacks were significantly more likely to receive amputations than whites on unadjusted (42.6% vs 28.6%, p < 0.001), and multivariable analyses (odds ratio [OR] 1.45, 95% CI 1.31 to 1.60, p < 0.001). This difference was more pronounced among high total vascular volume surgeons (OR 1.74, 95% CI 1.50 to 2.00, p < 0.001), but not among those with low total vascular volume (OR 1.06, 95% CI 0.90 to 1.24, p = 0.49); high volume hospitals (OR 1.57, 95% CI 1.39 to 1.78, p < 0.001), but not among those with low amputation volume (OR 0.96, 95% CI 0.73 to 1.27, p < 0.80); and surgeons who treat fewer black patients (OR 1.58, 95% CI 1.44 to 1.73, p < 0.001) vs surgeons who see more black patients (OR 1.43, 95% CI 1.30 to 1.57, p < 0.0.001).

Conclusions: Black patients are significantly more likely to receive an amputation than a salvage procedure when presenting with significant peripheral vascular diseases. High procedural volume does not seem to reduce unequal treatment; diversity of surgeon practice does.
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http://dx.doi.org/10.1016/j.jamcollsurg.2017.12.038DOI Listing
April 2018

Skin regeneration with all accessory organs following ablation with irreversible electroporation.

J Tissue Eng Regen Med 2018 01 23;12(1):98-113. Epub 2017 May 23.

Center for Engineering in Medicine, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, and the Shriners Burns Hospital, Boston, MA, 02114, USA.

Skin scar formation is a complex process that results in the formation of dense extracellular matrix (ECM) without normal skin appendages such as hair and glands. The absence of a scarless healing model in adult mammals prevents the development of successful therapies. We show that irreversible electroporation of skin drives its regeneration with all accessory organs in normal adult rats. Pulsed electric fields at 500 V, with 70 μs pulse duration and 1000 pulses delivered at 3 Hz, applied through two electrodes separated by 2 mm lead to massive cell death. However, the ECM architecture of the skin was preserved. Six months after the ablation, the epidermis, sebaceous glands, panniculus carnosus, hair follicles, microvasculature and arrector pili muscle were altogether re-formed in the entire ablated area. These results suggest a key role of the ECM architecture in the differentiation, migration and signalling of cells during scarless wound healing. Copyright © 2016 John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/term.2374DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5555830PMC
January 2018

Ethyl pyruvate modulates delayed paralysis following thoracic aortic ischemia reperfusion in mice.

J Vasc Surg 2016 Nov;64(5):1433-1443

Division of Vascular and Endovascular Surgery, Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Mass. Electronic address:

Objective: Delayed paralysis is an unpredictable problem for patients undergoing complex repair of the thoracic/thoracoabdominal aorta. These experiments were designed to determine whether ethyl pyruvate (EP), a potent anti-inflammatory and antioxidant agent, might ameliorate delayed paralysis following thoracic aortic ischemia reperfusion (TAR).

Methods: C57BL6 mice were subjected to 5 minutes of thoracic aortic ischemia followed by reperfusion for up to 48 hours. Mice received either 300 mg/kg EP or lactated ringers (LR) at 30 minutes before ischemia and 3 hours after reperfusion. Neurologic function was assessed using an established rodent scale. Spinal cord tissue was analyzed for markers of inflammation (keratinocyte chemoattractant [KC], interleukin-6 [IL-6]), microglial activation (ionized calcium-binding adapter molecule-1 [Iba-1]), and apoptosis (Bcl-2, Bax, and terminal deoxynucleotidyl transferase dUTP nick end labeling [TUNEL] staining) at 24 and 48 hours after TAR. Nissl body stained motor neurons were counted in the anterior horns sections from L1-L5 segments.

Results: Ninety-three percent of the LR mice developed dense delayed paralysis between 40 and 48 hours after TAR, whereas only 39% of EP mice developed delayed paralysis (P < .01). Bcl-2 expression was higher (P < .05) and Iba-1 expression was lower (P < .05) in the EP group only at 24 hours reperfusion. At 48 hours, the number of motor neurons was higher (P < .01) and the number and TUNEL-positive cells was lower (P < .001) in the EP-treated mice. EP decreased the expression of KC (P < .01) and IL-6 (P < .001) at 48 hours after TAR.

Conclusions: The protection provided by EP against delayed paralysis correlated with preservation of motor neurons, higher expression of antiapoptotic molecules, decreased microglial cell activation, and decreased spinal cord inflammation. EP may be a treatment for humans at risk for delayed paralysis.
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http://dx.doi.org/10.1016/j.jvs.2015.06.214DOI Listing
November 2016

Photochemical Tissue Passivation Attenuates AV Fistula Intimal Hyperplasia.

Ann Surg 2018 Jan;267(1):183-188

Department of Surgery, Division of Plastic and Reconstructive Surgery, Harvard Medical School, Massachusetts General Hospital, Boston, MA.

Objective: We hypothesized that decreasing vein compliance would protect the vein against stretch injury and reduce intimal hyperplasia (IH).

Background: Although arteriovenous fistulas (AVFs) are the criterion standard for vascular access, their effectiveness is limited by poor patency with 40% to 60% failing due to IH. Venous stretch injury from exposure to arterial pressure induces IH. Photochemical tissue passivation (PTP) crosslinks adventitial collagen, decreasing vein compliance to resemble that of an artery.

Methods: AVFs were created between the femoral artery and epigastric vein in rats (n = 29). PTP was performed on the vein immediately before vessel anastomosis. AVFs were harvested after four weeks. Venous diameter was measured at the initial procedure and harvest. Intimal area was measured for each segment. Ultrasound was performed at harvest to measure AVF flow.

Results: Following AVF construction, venous diameter increased by 10% ± 18% for PTP-treated vessels and 78% ± 27% for controls (P ≤ 0.0001). At one month, PTP reduced AVF dilation by 71% compared to control (69% ± 29% vs 241% ± 78%; P ≤ 0.0001). Both juxta-anastomotic intimal area and total intimal area were reduced in PTP-treated vessels compared to control vessels. Specifically, intimal area was 0.024 ± 0.018 and 0.095 ± 0.089 mm for PTP-treated juxta-anastomotic segments of AVF and control, respectively (P < 0.05). Mean total intimal area for PTP-treated and control AVF were 0.080 ± 0.042 and 0.190 ± 0.110 mm, respectively (P < 0.03). AVF flow was 46.9 ± 35.3 and 19.1 ± 10.1 mL/min for PTP-treated and control AVF, respectively (P < 0.109).

Conclusions: These data demonstrate that PTP represents a promising therapy for the prevention of AVF IH, a process that might improve surgical outcomes for patients receiving hemodialysis.
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http://dx.doi.org/10.1097/SLA.0000000000002046DOI Listing
January 2018

Effect of DNase I treatment and neutrophil depletion on acute limb ischemia-reperfusion injury in mice.

J Vasc Surg 2016 Aug 15;64(2):484-493. Epub 2015 Dec 15.

Department of Surgery, Division of Vascular and Endovascular Surgery, Massachusetts General Hospital, Boston, Mass; Harvard Medical School, Boston, Mass.

Objective: Extracellular traps (ETs) consisting of DNA-protein complexes formed after tissue injury contribute to the inflammatory and thrombosis cascades, thereby exacerbating injury. Exogenous DNase I has been suggested as a therapeutic strategy to limit injury in the brain and myocardium. These studies were designed to evaluate the effects of exogenous DNase I treatment on skeletal muscle injury after acute hindlimb ischemia-reperfusion (IR) injury in mice and to determine whether neutrophils are a major source of ETs in postischemic muscle tissue.

Methods: C57BL6 mice were subjected to 1.5 hours of tourniquet ischemia and 24 hours of reperfusion with and without human recombinant DNase I treatment. A separate set of mice was subjected to neutrophil depletion (ND), followed by the same intervals of IR. Laser Doppler imaging and tissue harvesting were done at 24 hours for assessment of limb perfusion, muscle fiber injury, adenosine triphosphate (ATP) level, markers of inflammation, thrombosis, and formation of ETs.

Results: DNase I treatment significantly reduced detection of ETs in postischemic muscle but did not alter skeletal muscle fiber injury, levels of proinflammatory molecules, or ATP level. DNase I treatment did enhance postischemic hindlimb perfusion, decreased infiltrating inflammatory cells, and reduced the expression of thrombin-antithrombin III. ND resulted in a significant yet small reduction in ETs in the postischemic muscle. ND did not alter skeletal muscle fiber injury, hindlimb perfusion, or ATP levels.

Conclusions: These data suggest that neither DNase I treatment nor ND was protective against IR injury, even though both decreased detection of ETs in skeletal muscle after IR. Neutrophils are not the only source of ETs after IR.
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http://dx.doi.org/10.1016/j.jvs.2015.01.031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4909598PMC
August 2016

Revascularization and muscle adaptation to limb demand ischemia in diet-induced obese mice.

J Surg Res 2016 09 8;205(1):49-58. Epub 2016 Jun 8.

Division of Vascular and Endovascular Surgery, Department of Surgery, Massachusetts General Hospital, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.

Background: Obesity and type 2 diabetes are major risk factors for peripheral arterial disease in humans, which can result in lower limb demand ischemia and exercise intolerance. Exercise triggers skeletal muscle adaptation including increased vasculogenesis. The goal of this study was to determine whether demand ischemia modulates revascularization, fiber size, and signaling pathways in the ischemic hind limb muscles of mice with diet-induced obesity (DIO).

Materials And Methods: DIO mice (n = 7) underwent unilateral femoral artery ligation and recovered for 2 wks followed by 4 wks with daily treadmill exercise to induce demand ischemia. A parallel sedentary ischemia (SI) group (n = 7) had femoral artery ligation without exercise. The contralateral limb muscles of SI served as control. Muscles were examined for capillary density, myofiber cross-sectional area, cytokine levels, and phosphorylation of STAT3 and ERK1/2.

Results: Exercise significantly enhanced capillary density (P < 0.01) and markedly lowered cross-sectional area (P < 0.001) in demand ischemia compared with SI. These findings coincided with a significant increase in granulocyte colony-stimulating factor (P < 0.001) and interleukin-7 (P < 0.01) levels. In addition, phosphorylation levels of STAT3 and ERK1/2 (P < 0.01) were increased, whereas UCP1 and monocyte chemoattractant protein-1 protein levels were lower (P < 0.05) without altering vascular endothelial growth factor and tumor necrosis factor alpha protein levels. Demand ischemia increased the PGC1α messenger RNA (P < 0.001) without augmenting PGC1α protein levels.

Conclusions: Exercise-induced limb demand ischemia in the setting of DIO causes myofiber atrophy despite an increase in muscle capillary density. The combination of persistent increase in tumor necrosis factor alpha, lower vascular endothelial growth factor, and failure to increase PGC1α protein may reflect a deficient adaption to demand ischemia in DIO.
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http://dx.doi.org/10.1016/j.jss.2016.06.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5021992PMC
September 2016

Insulin Downregulates the Transcriptional Coregulator CITED2, an Inhibitor of Proangiogenic Function in Endothelial Cells.

Diabetes 2016 Dec 25;65(12):3680-3690. Epub 2016 Aug 25.

Joslin Diabetes Center and Harvard Medical School, Boston, MA

In patients with atherosclerotic complications of diabetes, impaired neovascularization of ischemic tissue in the myocardium and lower limb limits the ability of these tissues to compensate for poor perfusion. We identified 10 novel insulin-regulated genes, among them Adm, Cited2, and Ctgf, which were downregulated in endothelial cells by insulin through FoxO1. CBP/p300-interacting transactivator with ED-rich tail 2 (CITED2), which was downregulated by insulin by up to 54%, is an important negative regulator of hypoxia-inducible factor (HIF) and impaired HIF signaling is a key mechanism underlying the impairment of angiogenesis in diabetes. Consistent with impairment of vascular insulin action, CITED2 was increased in cardiac endothelial cells from mice with diet-induced obesity and from db/db mice and was 3.8-fold higher in arterial tissue from patients with type 2 diabetes than control subjects without diabetes. CITED2 knockdown promoted endothelial tube formation and endothelial cell proliferation, whereas CITED2 overexpression impaired HIF activity in vitro. After femoral artery ligation, induction of an endothelial-specific HIF target gene in hind limb muscle was markedly upregulated in mice with endothelial cell deletion of CITED2, suggesting that CITED2 can limit HIF activity in vivo. We conclude that vascular insulin resistance in type 2 diabetes contributes to the upregulation of CITED2, which impairs HIF signaling and endothelial proangiogenic function.
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http://dx.doi.org/10.2337/db16-0001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5127242PMC
December 2016

Spinal Cord Inflammation: Molecular Imaging after Thoracic Aortic Ischemia Reperfusion Injury.

Radiology 2017 Jan 10;282(1):202-211. Epub 2016 Aug 10.

From the Department of Surgery, Division of Vascular and Endovascular Surgery (H.A., J.D.M., R.P.C., M.T.W.), and Center for System Biology and Institute for Innovation in Imaging, Department of Radiology (J.W.C., Y.W., G.W., B.P.), Massachusetts General Hospital, Harvard Medical School, 70 Blossom St, Edwards 301, Boston, MA 02114; and Department of Radiology, Division of Vascular and Interventional Radiology, Mayo Clinic, Scottsdale, Ariz (R.O.).

Purpose To evaluate whether noninvasive molecular imaging technologies targeting myeloperoxidase (MPO) can reveal early inflammation associated with spinal cord injury after thoracic aortic ischemia-reperfusion (TAR) in mice. Materials and Methods The study was approved by the institutional animal care and use committee. C57BL6 mice that were 8-10 weeks old underwent TAR (n = 55) or sham (n = 26) surgery. Magnetic resonance (MR) imaging (n = 6) or single photon emission computed tomography (SPECT)/computed tomography (CT) (n = 15) studies targeting MPO activity were performed after intravenous injection of MPO sensors (bis-5-hydroxytryptamide-tetraazacyclododecane [HT]-diethyneletriaminepentaacetic acid [DTPA]-gadolinium or indium 111-bis-5-HT-DTPA, respectively). Immunohistochemistry and flow cytometry were used to identify myeloid cells and neuronal loss. Proinflammatory cytokines, keratinocyte chemoattractant (KC), and interleukin 6 (IL-6) were measured with enzyme-linked immunosorbent assay. Statistical analyses were performed by using nonparametric tests and the Pearson correlation coefficient. P < .05 was considered to indicate a significant difference. Results Myeloid cells infiltrated into the injured cord at 6 and 24 hours after TAR. MR imaging confirmed the presence of ischemic lesions associated with mild MPO-mediated enhancement in the thoracolumbar spine at 24 hours compared with the sham procedure. SPECT/CT imaging of MPO activity showed marked MPO-sensor retention at 6 hours (P = .003) that continued to increase at 24 hours after TAR (P = .0001). The number of motor neurons decreased substantially at 24 hours after TAR (P < .01), which correlated inversely with in vivo inflammatory changes detected at molecular imaging (r = 0.64, P = .0099). MPO was primarily secreted by neutrophils, followed by lymphocyte antigen 6 complex monocytes and/or macrophages. There were corresponding increased levels of proinflammatory cytokines KC (P = .0001) and IL-6 (P = .0001) that mirrored changes in MPO activity. Conclusion MPO is a suitable imaging biomarker for identifying and tracking inflammatory damage in the spinal cord after TAR in a mouse model. RSNA, 2016 Online supplemental material is available for this article.
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http://dx.doi.org/10.1148/radiol.2016152222DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5207124PMC
January 2017

Photochemical Tissue Passivation Reduces Vein Graft Intimal Hyperplasia in a Swine Model of Arteriovenous Bypass Grafting.

J Am Heart Assoc 2016 07 27;5(8). Epub 2016 Jul 27.

Division of Plastic and Reconstructive Surgery, Harvard Medical School, Massachusetts General Hospital, Boston, MA

Background: Bypass grafting remains the standard of care for coronary artery disease and severe lower extremity ischemia. Efficacy is limited by poor long-term venous graft patency secondary to intimal hyperplasia (IH) caused by venous injury upon exposure to arterial pressure. We investigate whether photochemical tissue passivation (PTP) treatment of vein grafts modulates smooth muscle cell (SMC) proliferation and migration, and inhibits development of IH.

Methods And Results: PTP was performed at increasing fluences up to 120 J/cm(2) on porcine veins. Tensiometry performed to assess vessel elasticity/stiffness showed increased stiffness with increasing fluence until plateauing at 90 J/cm(2) (median, interquartile range [IQR]). At 90 J/cm(2), PTP-treated vessels had a 10-fold greater Young's modulus than untreated controls (954 [IQR, 2217] vs 99 kPa [IQR, 63]; P=0.03). Each pig received a PTP-treated and untreated carotid artery venous interposition graft. At 4-weeks, intimal/medial areas were assessed. PTP reduced the degree of IH by 66% and medial hypertrophy by 49%. Intimal area was 3.91 (IQR, 1.2) and 1.3 mm(2) (IQR, 0.97; P≤0.001) in untreated and PTP-treated grafts, respectively. Medial area was 9.2 (IQR, 3.2) and 4.7 mm(2) (IQR, 2.0; P≤0.001) in untreated and PTP-treated grafts, respectively. Immunohistochemistry was performed to assess alpha-smooth muscle actin (SMA) and proliferating cell nuclear antigen (PCNA). Objectively, there were less SMA-positive cells within the intima/media of PTP-treated vessels than controls. There was an increase in PCNA-positive cells within control vein grafts (18% [IQR, 5.3]) versus PTP-treated vein grafts (5% [IQR, 0.9]; P=0.02).

Conclusions: By strengthening vein grafts, PTP decreases SMC proliferation and migration, thereby reducing IH.
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http://dx.doi.org/10.1161/JAHA.116.003856DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5015302PMC
July 2016

Extracellular matrix remodelling in response to venous hypertension: proteomics of human varicose veins.

Cardiovasc Res 2016 06 11;110(3):419-30. Epub 2016 Apr 11.

King's British Heart Foundation Centre, King's College London, 125 Coldharbour Lane, London SE5 9NU, UK

Aims: Extracellular matrix remodelling has been implicated in a number of vascular conditions, including venous hypertension and varicose veins. However, to date, no systematic analysis of matrix remodelling in human veins has been performed.

Methods And Results: To understand the consequences of venous hypertension, normal and varicose veins were evaluated using proteomics approaches targeting the extracellular matrix. Varicose saphenous veins removed during phlebectomy and normal saphenous veins obtained during coronary artery bypass surgery were collected for proteomics analysis. Extracellular matrix proteins were enriched from venous tissues. The proteomics analysis revealed the presence of >150 extracellular matrix proteins, of which 48 had not been previously detected in venous tissue. Extracellular matrix remodelling in varicose veins was characterized by a loss of aggrecan and several small leucine-rich proteoglycans and a compensatory increase in collagen I and laminins. Gene expression analysis of the same tissues suggested that the remodelling process associated with venous hypertension predominantly occurs at the protein rather than the transcript level. The loss of aggrecan in varicose veins was paralleled by a reduced expression of aggrecanases. Chymase and tryptase β1 were among the up-regulated proteases. The effect of these serine proteases on the venous extracellular matrix was further explored by incubating normal saphenous veins with recombinant enzymes. Proteomics analysis revealed extensive extracellular matrix degradation after digestion with tryptase β1. In comparison, chymase was less potent and degraded predominantly basement membrane-associated proteins.

Conclusion: The present proteomics study provides unprecedented insights into the expression and degradation of structural and regulatory components of the vascular extracellular matrix in varicosis.
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http://dx.doi.org/10.1093/cvr/cvw075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4872879PMC
June 2016

Prevention of vein graft intimal hyperplasia with photochemical tissue passivation.

J Vasc Surg 2017 Jan 8;65(1):190-196. Epub 2016 Apr 8.

Division of Plastic and Reconstructive Surgery, Department of Surgery, Harvard Medical School, Massachusetts General Hospital, Boston, Mass. Electronic address:

Objective: Saphenous vein is the conduit of choice for bypass grafting. Saphenous vein grafts have poor long-term patency rates because of intimal hyperplasia (IH) and subsequent accelerated atherosclerosis. One of the primary triggers of IH is endothelial injury resulting from excessive dilation of the vein after exposure to arterial pressures. Photochemical tissue passivation (PTP) is a technology that cross-links adventitial collagen by a light-activated process, which limits dilation by improving vessel compliance. The objective of this study was to investigate whether PTP limits the development of IH in a rodent venous interposition graft model.

Methods: PTP is accomplished by coating venous adventitia with a photosensitizing dye and exposing it to light. To assess the degree of collagen cross-linking after PTP treatment, a biodegradation assay was performed. Venous interposition grafts were placed in the femoral artery of Sprague-Dawley rats. Rats were euthanized after 4 weeks, and intimal thickness was measured histologically. Vein dilation at the time of the initial procedure was also measured.

Results: Time to digestion was 63 ± 7 minutes for controls, 101 ± 2.4 minutes for rose bengal (RB), and 300 ± 0 minutes for PTP (P < .001 PTP vs control). A total of 37 animals underwent the procedure: 12 PTP, 12 RB only, and 13 untreated controls. Dilation of the graft after clamp release was 99% for control, 65% for RB only, and 19% for PTP-treated (P < .001 PTP vs control). Intimal thickness was 77 ± 59 μm in controls, 60 ± 27 μm in RB only, and 33 ± 28 μm in PTP-treated grafts. There was a statistically significant 57% reduction in intimal thickness after treatment with PTP compared with untreated controls (P = .03).

Conclusions: PTP treatment of venous interposition grafts in a rat model resulted in significant collagen cross-linking, decreased vessel compliance, and significant reduction in IH.
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http://dx.doi.org/10.1016/j.jvs.2015.11.049DOI Listing
January 2017

Hemodialysis arteriovenous fistula as first option not necessary in elderly patients.

J Vasc Surg 2016 May 7;63(5):1326-32. Epub 2016 Jan 7.

Division of Interventional Radiology, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Mass. Electronic address:

Objective: Kidney Disease Outcomes Quality Initiative guidelines recommend arteriovenous fistulas as the preferred access for hemodialysis patients. However, this may not hold across all populations of patients, especially the elderly, given their comorbidities and relatively reduced life expectancy. Therefore, we investigated whether fistulas held benefit over arteriovenous grafts as hemodialysis access in elderly patients.

Methods: We retrospectively searched a vascular access database to compare the outcomes for 138 fistulas and 44 grafts that were placed in elderly patients (≥75 years old) during a 4-year period at a tertiary medical center.

Results: The primary failure rate was higher for the fistulas compared with the grafts (odds ratio, 2.89; P = .008), and more fistulas required one or more interventions before their successful use compared with grafts (31% vs 10%, respectively; P = .03). In addition, the time to catheter-free dialysis was longer for fistulas than for grafts (P < .001). However, the primary and secondary patency rates were comparable between the fistulas and grafts and between the different access locations. The all-cause mortality rates were also comparable between the fistula and graft groups.

Conclusions: Despite the Fistula First Initiative recommendations, grafts need not be discounted as a first-line hemodialysis access option in select elderly patients.
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http://dx.doi.org/10.1016/j.jvs.2015.11.036DOI Listing
May 2016

Skin rejuvenation with non-invasive pulsed electric fields.

Sci Rep 2015 May 12;5:10187. Epub 2015 May 12.

1] Center for Engineering in Medicine, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, and Shriners Burns Hospital, Boston, MA, 02114 [2] Department of Biomedical Engineering, Rutgers University, Piscataway, NJ 08854.

Degenerative skin diseases affect one third of individuals over the age of sixty. Current therapies use various physical and chemical methods to rejuvenate skin; but since the therapies affect many tissue components including cells and extracellular matrix, they may also induce significant side effects, such as scarring. Here we report on a new, non-invasive, non-thermal technique to rejuvenate skin with pulsed electric fields. The fields destroy cells while simultaneously completely preserving the extracellular matrix architecture and releasing multiple growth factors locally that induce new cells and tissue growth. We have identified the specific pulsed electric field parameters in rats that lead to prominent proliferation of the epidermis, formation of microvasculature, and secretion of new collagen at treated areas without scarring. Our results suggest that pulsed electric fields can improve skin function and thus can potentially serve as a novel non-invasive skin therapy for multiple degenerative skin diseases.
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http://dx.doi.org/10.1038/srep10187DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4428072PMC
May 2015

Effect of limb demand ischemia on autophagy and morphology in mice.

J Surg Res 2015 Oct 9;198(2):515-24. Epub 2015 Apr 9.

Division of Vascular and Endovascular Surgery, Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.

Background: Obesity is a major risk factor for diabetes and peripheral arterial disease, which frequently leads to lower limb demand ischemia. Skeletal muscle autophagy and mitochondrial biogenesis are important processes for proper oxidative capacity and energy metabolism, which are compromised in diabetes. This study compares autophagy, mitochondrial biogenesis, energy metabolism, and morphology in the hind limbs of obese diabetic mice subjected to demand or sedentary ischemia.

Materials And Methods: Unilateral hind limb demand ischemia was created in a group of diet-induced obese mice after femoral artery ligation and 4 wk of daily exercise. A parallel group of mice underwent femoral artery ligation but remained sedentary for 4 wk. Hind limb muscles were analyzed for markers of autophagy, mitochondrial biogenesis, adenosine triphosphate, and muscle tissue morphology.

Results: At the end of the 4-wk exercise period, demand ischemia increased the autophagy mediator Beclin-1, but it did not alter the autophagy indicator, LC3B-II/I ratio, or markers of mitochondrial biogenesis, optic atrophy/dynamin-related protein. In contrast, exercise significantly increased the level of mitochondrial protein-succinate dehydrogenase subunit-A and reduced adipocyte accumulation and the percentage of centrally nucleated myofibers in the demand ischemia limb. In addition, demand ischemia resulted in decreased uncoupling protein-3 levels without altering muscle adenosine triphosphate or pS473-Akt levels.

Conclusions: Limb demand ischemia markedly decreased adipocyte accumulation and enhanced muscle regeneration in obese mice, but it did not appear to enhance autophagy, mitochondrial biogenesis, energy metabolism, or insulin sensitivity. Future studies aimed at evaluating novel therapies that enhance autophagy and mitochondrial biogenesis in diabetes with peripheral arterial disease are warranted.
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http://dx.doi.org/10.1016/j.jss.2015.04.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4560984PMC
October 2015

Percutaneous interventions in aortic disease.

Circulation 2015 Apr;131(14):1291-9

From Division of Vascular and Endovascular Surgery, Department of Surgery, Massachusetts General Hospital, Boston.

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http://dx.doi.org/10.1161/CIRCULATIONAHA.114.006512DOI Listing
April 2015

Popliteal venous aneurysms: characteristics, management strategies, and clinical outcomes--a modern single-center series.

Ann Vasc Surg 2014 Nov 7;28(8):1816-22. Epub 2014 Jul 7.

Institute for Heart, Vascular and Stroke Care, Massachusetts General Hospital and Harvard Medical School, Boston, MA. Electronic address:

Background: Popliteal vein aneurysm (PVA) may be an incidental finding on imaging, but often presents in the context of acute venous thromboembolism (VTE). The role of anticoagulation with or without surgical excision versus expectant management is ill defined.

Methods: In this single-center, retrospective, cohort study, patient records from January 2002 to December 2013 were queried for terminology consistent with PVA. Demographic data and clinical outcomes were extracted via chart review.

Results: A total of 21 patients with PVA were identified (57% male). Mean follow-up was 38 ± 31 months. Mean PVA diameter was 2.5 ± 1.1 cm; 67% were saccular (with the remainder being fusiform), 19% contained thrombus, 67% were left sided, and bilateral PVA was present in 24% of cases. At the time of PVA diagnosis, 14% had pulmonary embolism. Treatment consisted of observation only (62%), anticoagulation (19%), surgery (5%), or both anticoagulation and surgery (14%). There were no recurrences of VTE once treated, although there was 1 acute deep venous thrombosis in a patient who was managed conservatively. Two patients had recurrent PVA after surgery, and there were 2 surgical complications (transient foot drop and hematoma).

Conclusions: PVA is associated with VTE. Based on our series, it is unclear if incidentally discovered PVA (without VTE) warrants treatment with anticoagulation and/or surgical repair. Further multicenter studies are needed to establish the indications for safety and durability of surgery.
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http://dx.doi.org/10.1016/j.avsg.2014.06.065DOI Listing
November 2014

Non-thermal, pulsed electric field cell ablation: A novel tool for regenerative medicine and scarless skin regeneration.

Technology (Singap World Sci) 2013 Sep;1(1):1-8

High voltage, short pulsed electric fields (PEF) is a non-thermal ablation method, in which defined PEF irreversibly destabilize cell membranes, while preserving other tissue components such as the extracellular matrix (ECM). In the present report, we show that PEF ablated rat skin retains its microvascular blood supply and ECM structure. Complete regeneration of epidermis, hair follicles, sebaceous glands, and the panniculus carnosusis observed two months after the ablation. Our results clearly indicate that non-thermal PEF has the potential to be a powerful and novel tool for scarless tissue regeneration.
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http://dx.doi.org/10.1142/S233954781320001XDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4078877PMC
September 2013

Hind limb ischemia-reperfusion injury in diet-induced obese mice.

J Surg Res 2014 Aug 17;190(2):683-91. Epub 2014 Jan 17.

Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts; Division of Vascular and Endovascular Surgery, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.

Background: Obesity is a major risk factor for the development of diabetes. Limb ischemia-reperfusion injury (IR) is a common clinical problem in diabetics who have compromised lower extremity perfusion. This study compared the histologic, metabolic, and functional outcomes after hind limb IR in diet-induced obese (DIO) and non-diabetic (ND) mice during the acute and the regenerative phases of IR.

Methods: DIO and ND mice were subjected to 1.5 h unilateral hind limb ischemia followed by 1- or 28-d IR. Muscle morphology, metabolic, and genomic stress were evaluated at days 1 and 28 IR; Acute inflammation and thrombosis were only measured at day-1 IR. At day 28, IR, skeletal muscle contractility, and maturation were also assessed.

Results: At day-1 IR, similar levels of acute muscle fiber necrosis were seen in both groups. DIO mice demonstrated substantially greater inflammatory, prothrombotic, and genomic stress responses, which were also associated with a greater reduction in energy substrates and Akt phosphorylation. At 28d, there was no difference in the peak forces generated in the hind limbs for the two groups. DIO mice had reduced fatigue resistance compared with ND and larger areas of fat accumulation although there was no significant difference in muscle fiber maturation.

Conclusions: DIO mice had an exacerbated acute response to IR with enhanced metabolic deficit, fat accumulation, and defective functional recovery during the regenerative phase of IR. These changes in fatigue resistance reflect compromised functional recovery after IR injury and have relevance for the functional recovery of patients with metabolic syndrome and insulin resistance.
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http://dx.doi.org/10.1016/j.jss.2014.01.020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4096585PMC
August 2014

Extracellular traps in lipid-rich lesions of carotid atherosclerotic plaques: implications for lipoprotein retention and lesion progression.

J Vasc Interv Radiol 2014 Apr 26;25(4):631-4. Epub 2014 Feb 26.

Department of Surgery, Division of Vascular Surgery, Massachusetts General Hospital, 290 Gray/Bigelow, 55 Fruit Street, Boston, MA 02114; Harvard Medical School, Boston, Massachusetts.

Purpose: To investigate the presence and location of extracellular traps (ETs) in atherosclerotic plaques and to determine whether they are spatially associated with inflammatory cells and the lipid core.

Materials And Methods: Human carotid atherosclerotic plaques were collected from seven patients after surgical endarterectomy. Sequential tissue sections were stained with hematoxylin-eosin or subjected to immunohistochemistry to detect ETs, neutrophils and macrophages or apolipoprotein B (ApoB). To demonstrate the specificity of the antibody used to detect ETs, the adjacent tissue section was pretreated with deoxyribonuclease-1 (DNase-1) before immunostaining for ETs.

Results: All seven carotid plaques demonstrated advanced atherosclerotic lesions. Extensive ET and ApoB immunostaining was detected predominantly within the acellular lipid core. Along the edges of the lipid core, confocal microscopy revealed areas suggestive of active release of ETs from MPO-positive cells. Pretreatment of tissue sections with DNase-1 abolished ET signal in the extracellular matrix, but not the signal within the cells along the margins of the core.

Conclusions: The localization of ETs to the lipid core suggests a possible binding site for lipoproteins, which may further promote lesion progression and inflammation.
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http://dx.doi.org/10.1016/j.jvir.2013.12.567DOI Listing
April 2014

Impact of severe chronic kidney disease on outcomes of infrainguinal peripheral arterial intervention.

J Vasc Surg 2014 Feb 28;59(2):368-75. Epub 2013 Oct 28.

Division of Vascular and Endovascular Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Mass.

Objective: Patients with severe chronic kidney disease (CKD) and peripheral vascular disease are at increased risk of major adverse limb events (MALEs) and death; however, patients with end-stage renal disease have been excluded in current objective performance goals. We evaluated the effect of severe (class 4 and 5) CKD on outcomes after infrainguinal endovascular arterial interventions.

Methods: All primary peripheral vascular interventions (PVIs) performed at a single institution (January 2002 through December 2009) were included. End points were defined by Society for Vascular Surgery objective performance goals for critical limb ischemia (CLI), which include all-cause mortality, reintervention, and composite end points of death or amputation and MALEs (reintervention or amputation). Univariate and multivariable analysis was used to examine the effect of severe CKD on study end points.

Results: A total of 879 PVIs were performed, with severe CKD in 125 (14%). Severe CKD patients were significantly (P < .05) more likely to have diabetes (64% vs 46%), CLI (72% vs 11%), and need a multilevel PVI (34% vs 19%) or tibial intervention (35% vs 20%) compared with the remainder of the cohort. Distribution of TransAtlantic Inter-Society Consensus C and D lesions were similar (19% severe CKD vs 15%; P = .2). Severe CKD predicted perioperative (30-day) reintervention (odds ratio [OR], 2.3; 95% confidence interval [CI], 1.5-4; P = .05), amputation or death (OR, 3.1; 95% CI, 1.1-9; P = .04), and MALEs (OR, 2.8; 95% CI, 1.3-6.1; P = .04), which was independent of CLI in multivariable regression analysis. On Kaplan-Meier analysis, severe CKD was significantly (log-rank P < .05) associated with death (31% ± 4% vs 7% ± 1%), amputation (14% ± 3% vs 3% ± 1%), and MALEs (40% ± 5% vs 26% ± 2%) at 1 year. Freedom from reintervention was similar at 1 year (70% ± 5% severe CKD vs 75% ± 2%; P = .23). Risk-adjusted (age, CLI, diabetes, coronary artery disease) Cox proportional hazards regression showed that severe CKD increased the risk of late mortality (hazard ratio [HR], 2.4; 95% CI, 1.8-3.2; P < .01), amputation (HR, 2.1; 95% CI, 1.1-3.9; P = .02), and death or amputation (HR, 1.8; 95% CI, 1.3-2.4; P = .04), without increasing the risk of late reinterventions or MALEs.

Conclusions: CKD independently predicts early and late adverse events after a PVI, in particular, excessive mortality. CKD should figure prominently in clinical decision making for patients with peripheral vascular disease.
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http://dx.doi.org/10.1016/j.jvs.2013.09.006DOI Listing
February 2014

Altered vascular activation due to deficiency of the NADPH oxidase component p22phox.

Cardiovasc Pathol 2014 Jan-Feb;23(1):35-42. Epub 2013 Sep 12.

Center for Systems Biology, Massachusetts General Hospital and Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.

Background: Reactive oxygen species generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase play important roles in vascular activation. The p22(phox) subunit is necessary for the activity of NADPH oxidase complexes utilizing Nox1, Nox2, Nox3, and Nox4 catalytic subunits.

Methods: We assessed p22(phox)-deficient mice and human tissue for altered vascular activation.

Results: Mice deficient in p22(phox) were smaller than their wild-type littermates but showed no alteration in basal blood pressure. The wild-type littermates were relatively resistant to forming intimal hyperplasia following carotid ligation, and the intimal hyperplasia that developed was not altered by p22(phox) deficiency. However, at the site of carotid artery ligation, the p22(phox)-deficient mice showed significantly less vascular elastic fiber loss compared with their wild-type littermates. This preservation of elastic fibers was associated with a reduced matrix metallopeptidase (MMP) 12/tissue inhibitor of metalloproteinase (TIMP) 1 expression ratio. A similar decrease in the relative MMP12/TIMP1 expression ratio occurred in human coronary artery smooth muscle cells upon knockdown of the hydrogen peroxide responsive kinase CK1αLS. In the ligated carotid arteries, the p22(phox)-deficient mice showed reduced expression of heterogeneous nuclear ribonucleoprotein C (hnRNP-C), suggesting reduced activity of CK1αLS. In a lung biopsy from a human patient with p22(phox) deficiency, there was also reduced vascular hnRNP-C expression.

Conclusions: These findings indicate that NADPH oxidase complexes modulate aspects of vascular activation including vascular elastic fiber loss, the MMP12/TIMP1 expression ratio, and the expression of hnRNP-C. Furthermore, these findings suggest that the effects of NADPH oxidase on vascular activation are mediated in part by protein kinase CK1αLS.
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http://dx.doi.org/10.1016/j.carpath.2013.08.003DOI Listing
July 2014

Reduced hind limb ischemia-reperfusion injury in Toll-like receptor-4 mutant mice is associated with decreased neutrophil extracellular traps.

J Vasc Surg 2013 Dec 14;58(6):1627-36. Epub 2013 May 14.

Division of Vascular Imaging and Intervention, Harvard Medical School, Massachusetts General Hospital, Boston, Mass.

Objective: Ischemia-reperfusion (IR) injury is a significant problem in the management of patients with acute limb ischemia. Despite rapid restoration of blood flow after technically successful open and endovascular revascularization, complications secondary to IR injury continue to occur and limit clinical success. Our aim was to create a murine model of hind limb IR injury to examine the role of Toll-like receptor-4 (TLR4) and to determine whether inactive TLR4 led to a decrease in the detection of neutrophil extracellular traps (NETs), which are known to be highly thrombogenic and may mediate microvascular injury.

Methods: A calibrated tension tourniquet was applied to unilateral hind limb of wild-type (WT) and TLR4 receptor mutant (TLR4m) mice for 1.5 hours to induce ischemia and then removed to initiate reperfusion. At the end of 48 hours of reperfusion, mice were euthanized and hind limb tissue and serum specimens were collected for analysis. Hematoxylin and eosin-stained sections of hind limb skeletal muscle tissue were examined for fiber injury. For immunohistochemistry, mouse monoclonal antihistone H2A/H2B/DNA complex antibody to detect NETs and rabbit polyclonal antimyeloperoxidase antibody were used to identify infiltrating cells containing myeloperoxidase. Muscle adenosine triphosphate levels, nuclear factor (NF)-κB activity, the α-subunit of inhibitor of NF-κB light polypeptide gene enhancer, poly (adenosine diphosphate-ribose) polymerase activity, and inducible nitric oxide synthase expression were measured. Systemic levels of keratinocyte-derived chemokine, monocyte chemotactic protein-1, and vascular endothelial growth factor in the serum samples were also examined.

Results: IR injury in the hind limb of WT mice demonstrated significant levels of muscle fiber injury, decreased energy substrates, increased NF-κB activation, decreased levels of α-subunit of inhibitor of NF-κB light polypeptide gene enhancer, increased inducible nitric oxide synthase expression, and increased poly (adenosine diphosphate-ribose) polymerase activity levels compared with the TLR4m samples. Additionally, there was marked decrease in the level of neutrophil and monocyte infiltration in the TLR4m mice, which corresponded to similar levels of decreased NET detection in the interstitial space and in microvascular thrombi. In situ nuclease treatment of WT tissue sections significantly diminished the level of NET immunostaining, demonstrating the specificity of the antibody to detect NETs and suggesting a potential role for nuclease treatment in IR injury.

Conclusions: These results suggest a pivotal role for TLR4 in mediating hind limb IR injury and suggest that NETs may contribute to muscle fiber injury.
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http://dx.doi.org/10.1016/j.jvs.2013.02.241DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3825746PMC
December 2013

Poly-ADP-ribose-polymerase inhibition ameliorates hind limb ischemia reperfusion injury in a murine model of type 2 diabetes.

Ann Surg 2013 Dec;258(6):1087-95

*Division of Vascular and Endovascular Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, and The University of Tennessee Medical Center, Knoxville, TN †Department of Surgery, The University of Tennessee Graduate School of Medicine, Knoxville, TN ‡Department of Surgery, Sinai Hospital, Baltimore, MD §Division of Vascular Imaging and Intervention, Massachusetts General Hospital, Harvard Medical School, Boston, MA, and The University of Tennessee Medical Center, Knoxville, TN; and ¶Division of Vascular and Endovascular Surgery, Massachusetts General Hospital, Boston, MA.

Introduction: Diabetes is known to increase poly-ADP-ribose-polymerase (PARP) activity and posttranslational poly-ADP-ribosylation of several regulatory proteins involved in inflammation and energy metabolism. These experiments test the hypothesis that PARP inhibition will modulate hind limb ischemia reperfusion (IR) in a mouse model of type-II diabetes and ameliorate the ribosylation and the activity/transnuclear localization of the key glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH).

Methods: db/db mice underwent 1.5 hours of hind limb ischemia followed by 1, 7, or 24 hours of reperfusion. The treatment group received the PARP inhibitor PJ34 (PJ34) over a 24-hour period; the untreated group received Lactated Ringer (LR) at the same time points. IR muscles were analyzed for indices of PARP activity, fiber injury, metabolic activity, inflammation, GAPDH activity/intracellular localization, and poly-ADP-ribosylation of GAPDH.

Results: PARP activity was significantly lower in the PJ34-treated groups than in the Lactated Ringer group at 7 and 24 hours of reperfusion. There was significantly less muscle fiber injury in the PJ34-treated group than in the Lactated Ringer-treated mice at 24 hours of reperfusion. PJ34 lowered levels of select proinflammatory molecules at 7 hours and 24 hours of IR. There were significant increases in metabolic activity only at 24 hours of IR in the PJ34 group, which temporally correlated with increase in GAPDH activity, decreased GAPDH poly-ADP-ribosylation, and nuclear translocation of GAPDH.

Conclusions: PJ34 reduced PARP activity, GAPDH ribosylation, and GAPDH translocation; ameliorated muscle fiber injury; and increased metabolic activity after hind limb IR injury in a murine model of type-II diabetes. PARP inhibition might be a therapeutic strategy after IR in diabetic humans.
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http://dx.doi.org/10.1097/SLA.0b013e31828cced3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3773522PMC
December 2013

Divergent systemic and local inflammatory response to hind limb demand ischemia in wild-type and ApoE-/- mice.

J Surg Res 2013 Aug 15;183(2):952-62. Epub 2013 Mar 15.

Division of Vascular and Endovascular Surgery, Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.

Background: We designed studies to determine whether the ApoE-/- phenotype modulates the local skeletal muscle and systemic inflammatory (plasma) responses to lower extremity demand ischemia. The ApoE-/- phenotype is an experimental model for atherosclerosis in humans.

Methods: Aged female ApoE-/- and C57BL6 mice underwent femoral artery ligation, then were divided into sedentary and demand ischemia (exercise) groups on day 14. We assessed baseline and postexercise limb perfusion and hind limb function. On day 14, animals in the demand ischemia group underwent daily treadmill exercise through day 28. Sedentary mice were not exercised. On day 28, we harvested plasma and skeletal muscle from ischemic limbs from sedentary and exercised mice. We assayed muscle for angiogenic and proinflammatory proteins, markers of skeletal muscle regeneration, and evidence of skeletal muscle fiber maturation.

Results: Hind limb ischemia was similar in ApoE-/- and C57 mice before the onset of exercise. Under sedentary conditions, plasma vascular endothelial cell growth factor and interleukin-6, but not keratinocyte chemoattractant factor (KC) or macrophage inflammatory protein-2 (MIP-2), were higher in ApoE (P < 0.0001). After exercise, plasma levels of vascular endothelial cell growth factor, KC, and MIP-2, but not IL-6, were lower in ApoE (P < 0.004). The cytokines KC and MIP-2 in muscle were greater in exercised ApoE-/- mice compared with C57BL6 mice (P = 0.01). Increased poly-ADP-ribose activity and mature muscle regeneration were associated with demand ischemia in the C57BL6 mice, compared with the ApoE-/- mice (P = 0.01).

Conclusions: Demand limb ischemia in the ApoE-/- phenotype exacerbated the expression of select systemic cytokines in plasma and blunted indices of muscle regeneration.
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http://dx.doi.org/10.1016/j.jss.2013.02.042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3713180PMC
August 2013

Factors predicting resource utilization and survival after major amputation.

J Vasc Surg 2013 Mar 9;57(3):784-90. Epub 2013 Jan 9.

Division of Vascular and Endovascular Surgery, Center for Surgery and Public Health, Brigham and Women's Hospital, Boston, MA, USA.

Objective: Major amputation is associated with increased short-term healthcare resource utilization (RU), early mortality, and socioeconomic status (SES) disparities. Our objective is to study patient-specific and SES-related predictors of long-term RU and survival after amputation.

Methods: This retrospective analysis identified 364 adult patients who underwent index major amputation for critical limb ischemia from January 1995 through December 2000 at two tertiary centers with outcomes through December 2010. Age, gender, SES (race, income, insurance, and marital status), comorbidities (congestive heart failure [CHF], diabetes, diabetes with complications, and renal failure [RF]), subsequent procedures, cumulative length of stay (cLOS), and mortality were analyzed. Bivariate and multivariate Poisson regression for subsequent procedures and cLOS and Cox proportional hazard modeling for all-cause mortality were undertaken.

Results: During a mean follow-up of 3.25 years, amputation patients had mean cLOS of 71.2 days per person-year (median, 17.6), 19.5 readmissions per person-year (median, 2.1), 0.57 amputation-related procedures (median, 0), and 0.31 cardiovascular procedures (median, 0). Below-knee amputation as the index procedure was performed in 70% of patients, and 25% had additional amputation procedures. Of readmissions at ≤ 30 days, 52% were amputation-related. Overall mortality during follow-up was 86.9%; 37 patients (10.2%) died within 30 days. Among patients surviving >30 days, multivariate Poisson regression demonstrated that younger age (incidence rate ratio [IRR], 0.98), public insurance (IRR, 1.63), CHF (IRR, 1.60), and RF (IRR, 2.12) were associated with increased cLOS. Diabetes with complications (IRR, 1.90) and RF (IRR, 2.47) affected subsequent amputation procedures. CHF (IRR, 1.83) and RF (IRR, 3.67) were associated with a greater number of cardiovascular procedures. Cox proportional hazard modeling indicated older age (hazard ratio [HR], 1.04), CHF (HR, 2.26), and RF (HR, 2.60) were risk factors for decreased survival. Factors associated with SES were not significantly related to the outcomes.

Conclusions: This study found that RU is high for amputees, and increased RU persists beyond the perioperative period. Results were similar across SES indices, suggesting higher SES may not be protective against poor outcomes when limb salvage is no longer attainable. These findings support the hypothesis that SES disparities may be more modifiable during earlier stages of care for critical limb ischemia.
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http://dx.doi.org/10.1016/j.jvs.2012.09.035DOI Listing
March 2013