Mohamed A. Zayed

Phase I study of eptifibatide in patients with sickle cell anaemia

The αIIbβ3 antagonist eptifibatide is an effective treatment for patients with acute coronary syndromes (ACS). Platelet reactivity and CD40 ligand (CD40L) may play a role in the pathophysiology of sickle cell anaemia (SCA) similar to that in ACS, suggesting that inhibition of platelet aggregation and CD40L release by eptifibatide may benefit patients with SCA. Following eptifibatide infusion, safety and pharmacodynamic data were obtained from four SCA patients in their non‐crisis, steady states. Eptifibatide was well tolerated, with no adverse changes in the haematological, biochemical or coagulation parameters studied. Eptifibatide did not increase plasma levels of platelet factor 4 or beta‐thromboglobulin, P‐selectin exposure or platelet:leucocyte aggregate formation. Moreover, decreases in platelet aggregation and soluble CD40L (sCD40L) levels achieved in SCA patients were comparable to those observed in the treatment of ACS. Finally, indicators of inflammation, macrophage inflammatory protein‐1α, tumour necrosis factor‐α and myoglobin were reduced following eptifibatide infusion, while vasodilation correlatives, matrix metalloproteinases (MMP‐2 and MMP‐9) and leptin were increased. Based on these phase I results, eptifibatide may benefit SCA patients by inhibiting platelet aggregation, decreasing sCD40L levels and favourably altering plasma levels of inflammatory mediators.

CIB1 Regulates Endothelial Cells and Ischemia-Induced Pathological and Adaptive Angiogenesis

Pathological angiogenesis contributes to various ocular, malignant, and inflammatory disorders, emphasizing the need to understand this process on a molecular level. CIB1 (calcium- and integrin-binding protein), a 22-kDa EF-hand–containing protein, modulates the activity of p21-activated kinase 1 in fibroblasts. Because p21-activated kinase 1 also contributes to endothelial cell function, we hypothesized that CIB1 may have a role in angiogenesis. We found that endothelial cells depleted of CIB1 by either short hairpin RNA or homologous recombination have reduced migration, proliferation, and tubule formation. Moreover, loss of CIB1 in these cells decreases p21-activated kinase 1 activation, downstream extracellular signal-regulated kinase 1/2 activation, and matrix metalloproteinase 2 expression, all of which are known to contribute to angiogenesis. Consistent with these findings, tissues derived from CIB1-deficient (CIB1−/−) mice have reduced growth factor–induced microvessel sprouting in ex vivo organ cultures and in vivo Matrigel plugs. Furthermore, in response to ischemia, CIB1−/− mice demonstrate decreased pathological retinal and adaptive hindlimb angiogenesis. Ischemic CIB1−/− hindlimbs also demonstrate increased tissue damage and significantly reduced p21-activated kinase 1 activation. These data therefore reveal a critical role for CIB1 in ischemia-induced pathological and adaptive angiogenesis.

Exploiting macrophage autophagy-lysosomal biogenesis as a therapy for atherosclerosis

Macrophages specialize in removing lipids and debris present in the atherosclerotic plaque. However, plaque progression renders macrophages unable to degrade exogenous atherogenic material and endogenous cargo including dysfunctional proteins and organelles. Here we show that a decline in the autophagy–lysosome system contributes to this as evidenced by a derangement in key autophagy markers in both mouse and human atherosclerotic plaques. By augmenting macrophage TFEB, the master transcriptional regulator of autophagy–lysosomal biogenesis, we can reverse the autophagy dysfunction of plaques, enhance aggrephagy of p62-enriched protein aggregates and blunt macrophage apoptosis and pro-inflammatory IL-1β levels, leading to reduced atherosclerosis. In order to harness this degradative response therapeutically, we also describe a natural sugar called trehalose as an inducer of macrophage autophagy–lysosomal biogenesis and show trehaloses ability to recapitulate the atheroprotective properties of macrophage TFEB overexpression. Our data support this practical method of enhancing the degradative capacity of macrophages as a therapy for atherosclerotic vascular disease.

Development and Implementation of an Introductory Endovascular Training Course for Medical Students

BACKGROUND Endovascular simulation has been promoted as an educational tool for trainees to practice procedures in a safe environment and improve basic technical skills. We sought to determine whether an established endovascular training course for medical students could increase technical proficiency, enhance interest in vascular surgery, and be implemented at another academic institution. METHODS At Center A, medical students participated in an eight-week elective course with a structured curriculum comprised of weekly mentored simulator sessions and didactic teachings. A similar course was developed at Center B to train a similar cohort of students using the same high-fidelity simulator. Demographics and survey data, including interest in vascular surgery, were obtained, and pre- and postcourse graded simulator sessions on renal stent or iliac/superficial femoral artery stent modules were conducted. Performance was assessed by expert observers using a standardized global endovascular rating scale and objective procedural metrics collected from the simulator. RESULTS Seventy-seven medical students (41 at Center A and 36 at Center B; 56 men and 21 women) completed the course from 2007 to 2009. Parameters measured on the standardized global endovascular rating scale, including angiography skills, wire handling, and interventional criteria as well as simulator-generated metrics, significantly improved from pre- to postcourse values for both groups of medical students at the two institutions (p < 0.05). More than 94% of the students agreed or strongly agreed that the simulation course increased their interest in vascular surgery. CONCLUSION A simulation-based endovascular course provides an educational tool that improves basic technical performance and increases interest in vascular surgery among medical students. This simple educational module appears to be transferable and adaptable at another institution with minimal modification to produce similar results.

A comparison between one- and two-stage brachiobasilic arteriovenous fistulas

OBJECTIVES Brachiobasilic arteriovenous fistulas (BBAVF) can be performed in one or two stages. We compared primary failure rates, as well as primary and secondary patency rates of one- and two-stage BBAVF at two institutions. METHODS Patients undergoing one- and two-stage BBAVF at two institutions were compared retrospectively with respect to age, sex, body mass index, use of preoperative venous duplex ultrasound, diabetes, hypertension, and cause of end-stage renal disease. Categorical variables were compared using chi-square and Fishers exact test, whereas the Wilcoxon rank-sum test was used to compare continuous variables. Patency rates were assessed using the Kaplan-Meier survival analysis and the Cox proportional hazards model with propensity analysis to determine hazard ratios. RESULTS Ninety patients (60 one-stage and 30 two-stage) were identified. Mean follow-up was 14.2 months and the mean time interval between the first and second stage was 11.2 weeks. Although no significant difference in early failure existed (one-stage, 22.9% vs two-stage, 9.1%; P = .20), the two-stage BBAVF showed significantly improved primary functional patency at 1 year at 88% vs 61% (P = .047) (hazard ratio, 0.2 (95% confidence interval [CI], .04-.80; P = .03). Patency for one-stage BBAVF markedly decreased to 34% at 2 years compared with 88% for the two-stage procedure (P = .047). Median primary functional patency for one-stage BBAVF was 31 weeks (interquartile range [IQR], 11-54) vs 79 weeks (IQR, 29-131 weeks) for the two-stage procedure, respectively (P = .0015). Two-year secondary functional patency for one- and two-stage procedures were 41% and 94%, respectively (P = .015). CONCLUSIONS Primary and secondary patency at 1 and 2 years as well as functional patency is improved with the two-stage BBAVF when compared with the one-stage procedure. Lower primary failure rates prior to dialysis with the two-stage procedure approached, but did not reach statistical significance. While reasons for these finding are unclear, certain technical aspects of the procedure may play a role.

Tumor growth and angiogenesis is impaired in CIB1 knockout mice

BackgroundPathological angiogenesis contributes to various ocular, malignant, and inflammatory disorders, emphasizing the need to understand this process more precisely on a molecular level. Previously we found that CIB1, a 22 kDa regulatory protein, plays a critical role in endothelial cell function, angiogenic growth factor-mediated cellular functions, PAK1 activation, MMP-2 expression, and in vivo ischemia-induced angiogenesis. Since pathological angiogenesis is highly dependent on many of these same processes, we hypothesized that CIB1 may also regulate tumor-induced angiogenesis.MethodsTo test this hypothesis, we allografted either murine B16 melanoma or Lewis lung carcinoma cells into WT and CIB1-KO mice, and monitored tumor growth, morphology, histology, and intra-tumoral microvessel density.ResultsAllografted melanoma tumors that developed in CIB1-KO mice were smaller in volume, had a distinct necrotic appearance, and had significantly less intra-tumoral microvessel density. Similarly, allografted Lewis lung carcinoma tumors in CIB1-KO mice were smaller in volume and mass, and appeared to have decreased perfusion. Intra-tumoral hemorrhage, necrosis, and perivascular fibrosis were also increased in tumors that developed in CIB1-KO mice.ConclusionsThese findings suggest that, in addition to its other functions, CIB1 plays a critical role in facilitating tumor growth and tumor-induced angiogenesis.

New-Onset Maternal Gestational Hypertension and Risk of Retinopathy of Prematurity

PURPOSE To evaluate associations between conditions of maternal new-onset gestational hypertension (mHTN) and the features imparting risk of severe retinopathy of prematurity (ROP) in preterm infants. METHODS Hospital databases and charts of all preterm inborn infants at the University of North Carolina from 1996 to 2007 were retrospectively reviewed. The presence or absence of mHTN (e.g., pre-eclampsia) and infant factors (birthweight, gestational age, erythropoietin use, and zone and stage of ROP) were analyzed for independence of association. RESULTS Of the 5143 infants, 323 had ROP and 76 had mothers with mHTN. Infants with ROP were more likely to have mothers with mHTN and to be younger and smaller at birth. At initial examination, more infants of mothers with mHTN had vascularization into the lower zones than did infants of mothers without mHTN (P < 0.001). However, at the examination in which the most severe ROP was present, there was no association between mHTN and ROP stage (P = 0.2342). Analysis of stage and zone together showed that infants born to mothers with mHTN were more likely to have ROP at initial examination, after adjustment for gestational age, but not for birth weight. The use of erythropoietin was not associated with ROP zone or stage, even after adjustment for maternal condition, infant birth weight, or gestational age. CONCLUSIONS Although larger avascular areas or higher severity scores were associated with mHTN after adjustment for gestational age at initial examination, no associations were found between mHTN and ROP severity score at the examination when ROP was most severe. There were no associations between ROP severity and treatment with erythropoietin.

Ethnic differences in arm vein diameter and arteriovenous fistula creation rates in men undergoing hemodialysis access

OBJECTIVE The National Kidney Foundation recommends that arteriovenous fistulas (AVFs) be placed in at least 65% of hemodialysis patients. Some studies suggest that African American patients are less likely to receive a first-time AVF than patients of other ethnicities, although the reason for this disparity is unclear. The purpose of our study is to determine (1) whether there are ethnic differences in AVF creation, (2) whether this may be related to differences in vein diameters, and (3) whether AVF patency rates are similar between African American and non-African American male patients. METHODS Consecutive male patients undergoing first-time hemodialysis access from 2006 to 2010 at two institutions were retrospectively reviewed. Data collected included age, ethnicity, weight, height, body mass index, diabetes, hypertension, congestive heart failure, smoking history, intravenous drug abuse, need for temporary access placement, and preoperative venous ultrasound measurements. Categoric variables were compared using χ(2) analysis, and the Wilcoxon rank-sum test was used to compare continuous variables. RESULTS Of 249 male patients identified, 95 were African American. Median age in African American and non-African American patients was 63 years. Hypertension and hyperlipidemia were statistically significantly greater in African American patients. The need for temporary access before hemoaccess was similar between the cohorts. African American patients demonstrated significantly smaller median basilic and cephalic vein diameters at most measured sites. Overall, 221 of 249 (88.8%) underwent AVF first. An AV graft was created in 17.9% of African American patients vs in only 7.1% of non-African Americans (odds ratio, 2.8; 95% confidence interval, 1.3-6.4; P = .009). The difference between median vein diameters used for autologous fistula creation in African American and non-African American patients was not significant. There was no significant difference in the primary patency (80.8% vs 76.2%; P = .4), primary functional patency (73.1% vs 69.2%; P = .5), or secondary functional patency rates (91.0% vs 96.5%; P = .1). Average primary fistula survival time was 257 days in African American and 256 in non-African American patients (P = .2). CONCLUSIONS African American patients are less likely than non-African American patients to undergo AVF during first-time hemodialysis access surgery. This ethnic discrepancy appears to be due to smaller arm vein diameters in African American patients. In African American patients with appropriate vein diameters who do undergo AVF, primary and functional patencies are equivalent to non-African American patients.

Intravascular ultrasound as a clinical adjunct for carotid plaque characterization

OBJECTIVE Virtual histology intravascular ultrasound (VH IVUS) is valuable for estimating minimal lumen diameter and plaque characterization. The clinical use of IVUS in carotid intervention is not well characterized. We aim to evaluate the role of IVUS in carotid plaque characterization and determine whether it could be predictive of procedure-related microemboli. METHODS From July 2010, patients with severe carotid stenosis who underwent elective carotid stenting procedures were prospectively enrolled. IVUS evaluation was performed before stent placement. Patient demographics, comorbidities, and preoperative images were recorded. Comparison of pre- and postoperative diffusion-weighted magnetic resonance images was used to identify the number of procedure-related microemboli. IVUS-derived minimal lumen diameter and vessel wall plaque characteristics were collected. Univariate and multivariate logistic regressions were used to search for associations between IVUS-derived VH data and incidence of microemboli. RESULTS A total of 38 high-risk patients receiving carotid stenting were enrolled. Among them, 25 patients had type I aortic arches and 17 of the patients were symptomatic (preoperative stroke or transient ischemic attack). VH IVUS data did not show strong associations with microemboli, however, a trend was found between the area of fibrous tissue and median or more incidence of microemboli (P = .099). IVUS-defined vessel diameter maximum was associated with median or more incidence of microemboli (P = .042). In addition, median or more incidence of microemboli showed trends with proximal common carotid artery calcification (P = .056) and with being over the age of 80 (P = .06). Contralateral carotid occlusion or high-grade stenosis was associated with postoperative contralateral microemboli (P = .036). CONCLUSIONS We demonstrate that periprocedural carotid IVUS is clinically feasible. VH IVUS may be helpful in better understanding plaque morphology and determining optimal stent placement. However, its use in predicting microembolization remains limited.

A comparison of 0 + 5 versus 5 + 2 applicants to vascular surgery training programs.

OBJECTIVE The new integrated 0 + 5 vascular surgery (VS) training paradigm introduced in 2007 required program directors and faculty to reconsider recruiting methods and exposure of medical students to VS. As a means to identify variables important for recruitment of 0 + 5 VS applicants, we sought to analyze national 0 + 5 VS residency application trends and to compare medical school demographics of applicants to both our 0 + 5 residency and 5 + 2 fellowship programs. METHODS Electronic Residency Application Service and National Resident Matching Program online public databases were queried to evaluate nationwide trends in the number of applicants to integrated VS residency programs between 2007 and 2010. Demographic data from Electronic Residency Application Service applications submitted to our institutions 0 + 5 and 5 + 2 VS training programs during the same time period were reviewed. RESULTS From 2008 to 2011, there were 190 applicants to our 0 + 5 VS residency program and 161 applicants to our 5 + 2 fellowship program, with 127 (66.8%) and 122 (75.8%) being United States medical graduates, respectively. Annual application volume to our programs over these years remained stable for both training pathways (range, 39-49 for 0 + 5 integrated; range, 39-43 for 5 + 2 traditional). Nationally, applications to 0 + 5 programs increased sixfold over the same time period (52 in 2007 to 340 applicants in 2010; P < .001), far exceeding the available training positions. Compared with applicants to the 5 + 2 VS fellowships, medical students applying to the 0 + 5 programs are more likely to be female, be slightly older, have additional postgraduate degrees and publications, have higher United States Medical Licensure Examination test scores, and are more likely to be in the top quartile of their medical school class. CONCLUSIONS Nationwide interest in the 0 + 5 vascular surgery residency training paradigm continues to significantly increase. Significant differences exist between the cohorts of 0 + 5 residency and 5 + 2 fellowship program applicants at the completion of medical school, suggesting that 0 + 5 VS residency programs are attracting a different medical student population to the VS specialty. VS program directors should continue to foster interest in this new applicant pool through early exposure, mentorship, and extracurricular research activities.