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Biomedical subjects

Alan Dardik

Publications and source records attributed to Alan Dardik.

At least 19 recordsLinked to original sources
PubMed2007

Construction of an autologous tissue-engineered venous conduit from bone marrow-derived vascular cells: optimization of cell harvest and seeding techniques.

BACKGROUND: Currently available vascular grafts for pediatric cardiovascular operations are limited by their inability to grow. Tissue-engineering techniques can be used to create vascular grafts with the potential for repair, remodeling, and growth. This study demonstrates the feasibility of constructing an autologous tissue-engineered venous conduit from bone marrow-derived vascular cells (BMVCs) in the ovine animal model. METHODS: Ovine mononuclear cells were isolated from the bone marrow, cultured in endothelial growth medium, and characterized with immunocytochemistry. Biodegradable tubular scaffolds were constructed from polyglycolic acid mesh coated with a copolymer of poly[epsilon-caprolactone-L-lactide]. Scaffolds were seeded at various cell concentrations and incubation times to optimize seeding conditions for the construction of an autologous venous conduit. Using optimized conditions, 6 tissue-engineered vascular grafts were implanted as inferior vena cava interposition grafts in juvenile lambs. Grafts were assessed for patency at days 1 to 30 postoperatively and explanted for histological and immunohistochemical analysis. RESULTS: A mixed cell population of BMVCs consisting of smooth muscle cells and endothelial cells was cultured from ovine sternal bone marrow. A seeding concentration of 2 x 10(6) cells/cm2 and 7 days of postseeding incubation were optimal for creating a confluent cellular layer on the polyglycolic acid/poly[epsilon-caprolactone-L-lactide]) scaffold. Grafts were explanted up to 4 weeks postoperatively. All grafts were patent without evidence of thrombosis. Histological evaluation of the explanted grafts demonstrated neo-endothelialization. Graft wall was composed of neo-tissue made up of residual polymer matrix, mesenchymal cells, and extracellular matrix without evidence of calcification. CONCLUSIONS: Bone marrow-derived vascular cells, containing endothelial and smooth muscle cells, can be isolated and cultured from ovine sternal bone marrow and used as a cell source for vascular tissue engineering. Our optimized techniques for BMVC harvest and seeding onto biodegradable scaffolds can be used for studying autologous tissue-engineered vascular grafts in the ovine animal model.

Animals↗
PubMed2006

Evidence supporting changes in Nogo-B levels as a marker of neointimal expansion but not adaptive arterial remodeling.

Both neointimal hyperplasia and inward remodeling contribute to restenosis and lumen loss. Nogo-B has been recently described as an inhibitor of vascular injury and neointimal hyperplasia. To determine whether Nogo-B expression may be a mediator of inward remodeling, we examine the localization of expression of Nogo-B in an in vivo model that examines both neointimal hyperplasia and inward remodeling. The rabbit carotid artery was subjected to balloon injury, outflow branch ligation to reduce flow, or both balloon injury and reduction in flow. In balloon injury-induced neointimal hyperplasia Nogo-B expression was reduced in the intima and media but stimulated in the adventitia. In low flow-induced inward remodeling medial Nogo-B expression was not reduced and adventitial Nogo-B expression was not stimulated. Low flow significantly augmented balloon injury-induced neointimal hyperplasia and was accompanied by reduced intimal and medial Nogo-B expression, and increased adventitial Nogo-B expression in both smooth muscle cells and macrophages. Low flow-induced inward remodeling is not associated with changes in medial Nogo-B expression and is distinct from injury-induced neointimal hyperplasia. Pharmacological strategies to inhibit neointimal hyperplasia and restenosis using normal flow models may only partially account for lumen loss and therefore may not accurately predict responses in patients with extensive outflow disease.

Animals↗
PubMed2006

Safety of carotid endarterectomy in a high-risk population: lessons from the VA and Connecticut.

BACKGROUND: The safety and efficacy of carotid endarterectomy (CEA) have been demonstrated in randomized trials, but these studies excluded patients thought to be at higher risk for poor outcomes. We sought to determine whether patients undergoing CEA in Veteran Affairs Hospitals (VA) were at higher risk and had different outcomes, compared with patients in nonfederal hospitals. STUDY DESIGN: Records of all CEA performed in the VA Connecticut Healthcare System between October 1997 and September 2002 were examined and compared with CEA performed in all nonfederal Connecticut hospitals (CT). RESULTS: There were 7,089 CEAs performed (VA, 140; CT, 6,949). VA patients had increased comorbidity scores and symptomatic presentation (39% versus 14%; p < 0.0001). Perioperative mortality rates were 1.4% (VA) and 0.3% (CT) (p = 0.06). Perioperative stroke (VA, 1.4% versus CT, 0.9%; p = 0.15) and cardiac complication (VA, 2.9% versus CT, 2.1%; p = 0.54) rates were similar. Multivariate analysis demonstrated that perioperative mortality correlated with symptomatic presentation (odds ratio 11.7, p < 0.0001), but not performance, in a VA hospital (p = 0.23); patients treated at the VA were also not at higher risk for stroke (p = 0.94) or cardiac complications (p = 0.90). CONCLUSIONS: Despite increased severity of illness and symptomatic presentation, VA patients had similar perioperative outcomes compared with patients undergoing CEA in nonfederal hospitals in the state of Connecticut. These results suggest not only that patients undergoing vascular surgery at the VA may form a higher-risk population compared with patients receiving care in non-VA hospitals, but that these high-risk patients can undergo CEA safely.

Comorbidity↗
PubMed2006

Hospital-based factors predict outcome after carotid endarterectomy.

OBJECTIVE: Patient, hospital, and surgeon factors affect outcome after carotid endarterectomy (CEA). The nature and importance of hospital-specific factors, especially those unrelated to procedural volume, that affect post-CEA outcome remains poorly defined. We used a statewide database to determine the impact of several hospital-associated factors on outcome after CEA. METHODS: Hospital factors were established by telephone survey and validated by repeated survey as well as by the Connecticut Hospital Association, Connecticut state, and individual hospital internet Websites. All CEA in Connecticut non-federal hospitals between 1991 and 2002 were examined, including perioperative mortality, stroke, and cardiac complications. Multivariable logistic regression was used to analyze data. RESULTS: There were 14,288 CEAs performed with 0.5% mortality, 1.3% stroke, and 2.4% cardiac complications. The only hospital factor independently predictive of perioperative mortality was few number of hospital beds (less than 132 beds; odds ratio (OR) 2.78, P = 0.032). Factors predictive of perioperative stroke included few number of beds (OR 1.96, P = 0.001) and absence of a critical pathway (OR 1.39, P = 0.038). Factors predictive of perioperative cardiac complications included few number of beds (OR 3.01, P = 0.003), absence of a critical pathway (OR 1.50, P = 0.001), and absence of dedicated vascular recovery beds (OR 1.35, P = 0.03). Combined mortality, stroke, or cardiac complications were independently predicted by few hospital beds (OR 4.58, P = 0.002), absence of a critical pathway (OR 1.81, P < or = 0.0001), or inability to perform cardiac angiography (OR 3.92, P = 0.024). CONCLUSIONS: Hospital-based factors, such as greater bed capacity, use of critical pathways, ability to perform cardiac angiography, or presence of a dedicated vascular recovery unit predict reduced perioperative mortality, stroke and cardiac complications from CEA. These results suggest that hospital-associated factors do impact surgical outcome and that surgeons need to optimize these factors, extrinsic to the patient and surgeon, to provide maximal quality of care.

Endarterectomy, Carotid↗
PubMed2006

Malnutrition after vascular surgery: are patients with chronic renal failure at increased risk?

BACKGROUND: The deleterious effects of perioperative malnutrition on recovery after general surgery are established. Since the effects of perioperative malnutrition on recovery after vascular surgery are not known, we examined the effects of nutritional status, and risk factors predictive of malnutrition, on outcome after vascular surgery. METHODS: The records of all open index vascular cases (abdominal aortic aneurysm [AAA] repair, carotid endarterectomy [CEA], lower extremity bypass) performed at the Veterans Affairs (VA) Connecticut between July 2004 and June 2005 were reviewed. The primary outcome was mortality; secondary outcomes included infection and nutritional risk index (NRI) scores. RESULTS: Sixty-eight open vascular cases were performed during the study period. Nutritional depletion developed in 55% of patients and was more likely in patients undergoing AAA (85%) or bypass (77%) than CEA (30%; P = .0005). Patients who developed malnutrition had similar mortality as patients who did not develop postoperative malnutrition (6.1% vs. 3.7%; P = .68); however, malnourished patients had higher rates of postoperative infection (24.2% vs. 3.7%; P = .03). Chronic renal failure was the only patient-associated risk factor predictive of postoperative nutritional depletion (odds ratio 5.9, confidence interval 1.0 to 33.6; P = .04). CONCLUSIONS: Patients undergoing major open vascular surgery have high rates of postoperative malnutrition, with patients undergoing AAA repair having the highest rates of postoperative malnutrition and infection. Patients with chronic renal failure undergoing vascular surgery are associated with increased risk for postoperative malnutrition and may be a group to target for perioperative risk factor modification and nutritional supplementation.

Aortic Aneurysm, Abdominal↗
PubMed2006

Catheter-direct thrombolysis versus pharmacomechanical thrombectomy for treatment of symptomatic lower extremity deep venous thrombosis.

BACKGROUND: Rheolytic mechanical thrombectomy using the AngioJet catheter (Possis Medical, Minneapolis, MN) has been shown to be effective in the treatment of deep venous thrombosis (DVT). Additional infusion of thrombolytic agents via the device creates a novel treatment strategy of pharmacomechanical thrombectomy (PMT), which further enhances thrombectomy efficacy. The purpose of the current study was to compare the treatment outcome in patients with symptomatic DVT who underwent either catheter-directed thrombolysis (CDT) or PMT intervention. METHODS: During a recent 8-year period, clinical records of all patients with symptomatic lower leg DVT undergoing catheter-directed interventions were evaluated. Patients were divided into 2 treatment groups: CDT or PMT. Comparisons were made with regards to the treatment outcome between the 2 groups. RESULTS: A total of 93 patients who underwent 98 catheter-directed interventions for DVT were included in the study. Among them, CDT or PMT was performed in 46 (47%) and 52 (53%) procedures, respectively. In the CDT group, complete or partial thrombus removal was accomplished in 32 (70%) and 14 (30%) cases, respectively. In the PMT cohort, complete or partial thrombus removal was accomplished in 39 (75%) and 13 (25%) cases, respectively. Venous balloon angioplasty and/or stenting in the CDT or PMT groups was necessary in 36 (78%) and 43 (82%), respectively (difference not significant [NS]). Patients in the CDT groups underwent a mean of 2.5 venograms during the hospital course, in contrast to 0.4 venograms per patient in PMT cohorts (P < .001). Immediate (<24 hours) improvement in clinical symptoms in CDT and PMT groups was achieved in 33 (72%) and 42 (81%) cases, respectively (NS). Significant reductions in the intensive care unit (ICU) and hospital lengths of stay was noted in the PMT group (0.6 and 4.6 days) when compared to the CDT group (2.4 and 8.4 days). During follow-up visits, the primary patency rates at 1 year of CDT and PMT groups were 64% and 68%, respectively (NS). Hospital cost analysis showed significant cost reduction in the PMT group compared to the CDT group (P < .01). CONCLUSIONS: PMT with adjunctive thrombolytic therapy is an effective treatment modality in patients with significant DVT. When compared to CDT, this treatment provides similar treatment success with reduced ICU, total hospital length of stay, and hospital costs.

Adult↗
PubMed2006

Development of a model system for preliminary evaluation of tissue-engineered vascular conduits.

BACKGROUND/PURPOSE: The ability to construct tissue-engineered neovessels for use as arterial or venous grafts holds great promise for the advancement of pediatric surgical disciplines. Although the feasibility of tissue engineering vascular grafts has been demonstrated, the long-term function, safety, and efficacy of these grafts as well as their capacity to grow and adapt remain largely unknown. In an attempt to further characterize and develop this technology, we used severe combined immunodeficiency beige (SCID/bg) mouse recipients, chosen because such animals accept xenogenic human cells, to create a small animal model that would allow a rapid and cost-effective preliminary evaluation of the function of tissue-engineered vascular grafts. METHODS: Eight CB-17 SCID/bg female mice underwent vascular graft placement. Four of these mice received aortic interposition grafts, 1 mouse received an inferior vena cava interposition graft, and 3 mice underwent aortocaval graft insertion. All grafts were fashioned from decellularized ovine arteriole tissue engineering scaffolds. Grafts were evaluated for patency using clinical examination, ultrasound interrogation, and micro-computed tomography. Animals were killed at various time points after implantation, and grafts were harvested and analyzed histologically using standard hematoxylin and eosin staining. RESULTS: All grafts were patent based on clinical examination for up to 35 days. Patency was confirmed in 5 grafts using ultrasound interrogation. Patency was confirmed in 4 grafts using micro-computed tomography. One animal that underwent arteriovenous grafting had to be euthanized secondary to high-output cardiac failure on postoperative day 2. The remaining animals were killed between postoperative days 12 and 35. Histologic evaluation of the specimens demonstrated patent grafts with cellular ingrowth into the tissue engineering scaffold. CONCLUSIONS: From these results, we conclude that the use of the SCID/bg mouse model for preliminary evaluation of new tissue engineering methodologies for construction of vascular conduits is feasible. Use of this model has the added advantage of evaluating nonautologous and even xenograft tissues, including human cells.

Animals↗
PubMed2006

In situ reconstruction with cryopreserved arterial allografts for management of mycotic aneurysms or aortic prosthetic graft infections: a multi-institutional experience.

We designed this study to evaluate a multi-institutional experience regarding the efficacy of cryopreserved aortic allografts in the treatment of infected aortic prosthetic grafts or mycotic aneurysms. We reviewed clinical data of all patients from 4 institutions who underwent in situ aortic reconstruction with cryopreserved allografts for either infected aortic prosthetic graft or mycotic aneurysms from during a 6-year period. Relevant clinical variables and treatment outcomes were analyzed. A total of 42 patients (37 men; overall mean age 63 +/- 13 years, range 41-74 years) were identified during this study period. Treatment indications included 34 primary aortic graft infections (81%), 6 mycotic aneurysms (22%), and 2 aortoenteric erosions (5%). Transabdominal and thoracoabdominal approaches were used in 38 (90%) and 4 patients (10%), respectively. Staphylococcus aureus was the most commonly identified organism (n=27, 64%). Although there was no intraoperative death, the 30-day operative mortality was 17% (n=7). There were 21 (50%) nonfatal complications, including local wound infection (n=8), lower-extremity deep venous thrombosis (n=5), amputation (n=6), and renal failure requiring hemodialysis (n=2). The average length of hospital stay was 16.4 +/- 7 days. During a mean follow-up period of 12.5 months, reoperation for allograft revision was necessary in 1 patient due to graft thrombosis (6%). The overall treatment mortality rate was 21% (n=9). In situ aortic reconstruction with cryopreserved allografts is an acceptable treatment method in patients with infected aortic prosthetic graft or mycotic aneurysms. Our study showed that mid-term graft-related complications such as reinfection or aneurysmal degeneration were uncommon.

Adult↗
PubMed2005

Hyperplastic cellular remodeling of the media in ascending thoracic aortic aneurysms.

BACKGROUND: Progressive medial degeneration and atrophy is thought to be a cause of ascending thoracic aortic aneurysms in the elderly. Extensive apoptosis of vascular smooth muscle cells (VSMCs) has been demonstrated in the media of abdominal aortic aneurysms. We investigated whether medial atrophy from loss of VSMCs occurs in primary ascending thoracic aortic aneurysms. METHODS AND RESULTS: Morphometric analysis of 28 nonaneurysmal ascending thoracic aortas and 29 ascending thoracic aortic aneurysms was performed by directly measuring the thickness of their vascular layers and by indirectly calculating the area of their vascular compartments. The cellular and matrix composition of the media was assessed at the structural, protein, and transcript levels. Despite thinning of the media secondary to vascular dilatation, there was an overall increase in the medial area of aneurysms. VSMC density was preserved, implying cellular hyperplasia as a result of the increased medial mass. There was decreased expression of matrix proteins, despite sustained synthesis of these molecules, which was associated with evidence of increased matrix degradation. The remodeling and expansion of the media was most evident in comparisons between nonaneurysmal aortas versus smaller aneurysms and did not evolve further in larger aneurysms. CONCLUSIONS: The mechanisms for luminal enlargement in thoracic and abdominal aortic aneurysms differ significantly with regard to the survival of VSMCs and atrophy of the media but share common pathophysiology involving degeneration of the matrix. Hyperplastic cellular remodeling of the media in ascending thoracic aortic aneurysms may be an initial adaptive response to minimize increased wall stress resulting from vascular dilatation.

Aorta↗
PubMed2005

Transmural inflammation by interferon-gamma-producing T cells correlates with outward vascular remodeling and intimal expansion of ascending thoracic aortic aneurysms.

Arterial pathology manifests as aneurysmal or obstructive disease depending on changes in lumen size due to vascular remodeling (change in vessel external diameter) and/or intimal expansion. Recent clinical and experimental observations in abdominal aortic aneurysms have led to the emerging dogma that Th2-dominant immune responses result in expansive vascular remodeling and luminal ectasia, whereas Th1 immune responses cause intimal hyperplasia and luminal stenosis. We tested this hypothesis by descriptive analyses of 31 non-aneurysmal and 29 aneurysmal ascending thoracic aortic specimens. Approximately half the aneurysms were distinguished by transmural inflammation. The remaining aneurysms and all the non-aneurysmal aortas had a similar leukocytic infiltrate that spared the inner media. Aneurysm tissue had increased expression of the prototypical Th1 cytokine, interferon (IFN)-gamma, and undetectable Th2 cytokines. Specimens with inner media infiltration displayed robust production of IFN-gamma, induction of the IFN-gamma-inducible chemokines IP-10 and Mig, and recruitment of lymphocytes bearing their cognate receptor CXCR3. Transmural inflammation and IFN-gamma production were associated with increased aortic external diameter, intimal thickening, preserved vascular smooth muscle cell density, and decreased matrix proteins. Th1, but not Th2, immune responses have a positive correlation with both outward vascular remodeling and intimal expansion of ascending thoracic aortic aneurysms.

Adolescent↗
PubMed2005

Differential responsiveness of early- and late-passage endothelial cells to shear stress.

BACKGROUND: The incidence of vascular disease increases with age. Because atherosclerosis and neointimal hyperplasia colocalize in areas of disturbed shear stress, the effects of orbital shear stress (SS) on endothelial cell proliferation, protein kinase B (Akt) activation, and functional activity were analyzed using a senescence model. METHODS: Early- (p3 to 7) and late- (p28 to 32) passage bovine aortic endothelial cells were exposed to orbital SS (210 rpm) or static conditions (0 to 5 days). Cell proliferation was directly counted and confirmed with proliferating cell nuclear antigen reactivity. Phosphorylated and total Akt were assessed with Western blotting. Endothelial cell-induced smooth muscle cell migration was assessed with a Boyden chamber. RESULTS: Late-passage endothelial cells demonstrated no increase in orbital SS stimulated proliferation compared with early-passage cells (P = .42). Late-passage endothelial cells demonstrated decreased Akt phosphorylation in response to SS compared with early passage cells (n = 6, P = .01). Late-passage cells induced 26% less smooth muscle cell migration than early-passage cells (n = 3, P = .03). CONCLUSIONS: Late-passage endothelial cells demonstrate decreased proliferation, Akt phosphorylation, and secretion of smooth muscle cell chemoattractants in response to orbital SS compared with early passage cells. These results suggest that late-passage endothelial cells respond to SS differently than early-passage cells and confirm the utility of the in vitro senescence model.

Aging↗
PubMed2005

Safety of carotid endarterectomy in 2,443 elderly patients: lessons from nonagenarians--are we pushing the limit?

BACKGROUND: Elderly patients are a rapidly expanding segment of the population. Recent studies suggest that octogenarians have mortality and morbidity after carotid endarterectomy (CEA) similar to that in their younger cohort. Outcomes of CEA performed in nonagenarians have not been commonly reported; this study seeks to determine the safety of CEA in nonagenarians in general practice. STUDY DESIGN: All patients in nonfederal Connecticut hospitals undergoing CEA between 1990 and 2002 were identified using the state discharge database (Chime Inc; ). RESULTS: A total of 14,679 procedures were performed during the 12 study years. Sixty-four patients were nonagenarians (0.4%). Perioperative mortality was higher among nonagenarians (3.1%) compared with younger patients, including the 2,379 octogenarians (0.6%; p = 0.008, chi-square; odds ratio = 9.1, p = 0.006). No statistically significant difference was noted in perioperative stroke rates between nonagenarians (3.1%) and octogenarians (1.2%; p = 0.35, chi-square; odds ratio 2.3, p = 0.28). Nonagenarians had longer hospital lengths of stay (7.3 days, p < 0.0001), intensive care unit lengths of stay (1.2 days, p = 0.0013), and greater hospital charges ($17,967 +/- $1,907, p < 0.0001) than younger patients. Nonagenarians underwent operative procedures more frequently in an emergent setting (22%) compared with octogenarians (11%, p < 0.001) and had a greater percentage of symptomatic presentations (stroke: 14% versus 11%, p = 0.04; transient ischemic attack: 8% versus 5%, p = 0.04, respectively). All perioperative deaths and strokes occurred in symptomatic nonagenarians (15% versus 0%, p = 0.038; 15% versus 0%, p = 0.038; respectively). CONCLUSIONS: Carotid endarterectomy is performed in nonagenarians, as a group, with greater rates of perioperative mortality and morbidity than in younger patients, including octogenarians. But nonagenarians have a greater rate of symptomatic and emergent presentations than younger patients, which may account for their increased mortality, morbidity, length of stay, and incurred charges. Asymptomatic nonagenarians have similar outcomes after carotid endarterectomy compared with younger patients, including octogenarians, with low rates of mortality and morbidity.

Age Factors↗
PubMed2005

Shear stress-stimulated endothelial cells induce smooth muscle cell chemotaxis via platelet-derived growth factor-BB and interleukin-1alpha.

OBJECTIVE: Vascular smooth muscle cell (SMC) migration is critical to the development of atherosclerosis and neointimal hyperplasia. Hemodynamic forces such as shear stress and cyclic strain stimulate endothelial cell signal-transduction pathways, resulting in the secretion of several factors, including SMC chemoattractants such as platelet-derived growth factor (PDGF). We hypothesized that mechanical forces stimulate endothelial cells to secrete SMC chemoattractants to induce migration via the mitogen-activated protein kinase (MAPK) pathway. METHODS: Bovine aortic endothelial cells were exposed to shear stress, cyclic strain, or static conditions for 16 hours. The resulting conditioned medium was used as a SMC chemoattractant in a Boyden chamber. Activation of SMC extracellular signal-regulated protein kinase 1/2 (ERK1/2) was assessed by Western blot analysis. Pathways were inhibited with anti-PDGF-BB or anti-interleukin-1alpha (IL-1alpha) antibodies, or the ERK1/2 upstream pathway inhibitor PD98059. RESULTS: Conditioned medium from endothelial cells exposed to shear stress corresponding to arterial levels of shear stress stimulated SMC migration but lower levels of shear stress or cyclic strain did not. Both PDGF-BB and IL-1alpha were secreted into the conditioned medium by endothelial cells stimulated with shear stress. Both PDGF-BB and IL-1alpha stimulated SMC chemotaxis but were not synergistic, and both stimulated SMC ERK1/2 phosphorylation. Inhibition of PDGF-BB or IL-1alpha inhibited SMC chemotaxis and ERK1/2 phosphorylation. CONCLUSION: Shear stress stimulates endothelial cells to secrete several SMC chemoattractants, including PDGF-BB and IL-1alpha; both PDGF-BB and IL-1alpha stimulate SMC chemotaxis via the ERK1/2 signal-transduction pathway. These results suggest that the response to vascular injury may have a common pathway amenable to pharmacologic manipulation. CLINICAL RELEVANCE: One difficulty in the pharmacologic treatment of atherosclerosis or neointimal hyperplasia leading to restenosis is the multiplicity of activated pathways and thus potential treatment targets. This study demonstrates that shear stress, a hemodynamic force that may be a biologically relevant stimulus to induce vascular pathology, stimulates endothelial cells to secrete PDGF-BB and IL-1alpha. Both of these mediators stimulate the SMC ERK1/2 pathway to induce migration, a critical event in the pathogenesis of atherosclerosis and neointimal hyperplasia. Therefore, this study suggests a relevant common target pathway in SMC that is amenable to manipulation for clinical treatment.

Animals↗
PubMed2005

Differential effects of orbital and laminar shear stress on endothelial cells.

OBJECTIVE: Laminar shear stress is atheroprotective for endothelial cells (ECs), whereas nonlaminar, disturbed, or oscillatory shear stress correlates with development of atherosclerosis and neointimal hyperplasia. The effects of orbital and laminar shear stress on EC morphology, proliferation, and apoptosis were compared. METHODS: ECs were exposed to orbital shear stress with an orbital shaker (210 rpm) or laminar shear stress (14 dyne/cm 2) with a parallel plate. Shear stress in the orbital shaker was measured with optical velocimetry. Cell proliferation was assessed with direct counting and proliferating cell nuclear antigen staining; apoptosis was assessed with transferase-mediated deoxyuridine triphosphate nick end labeling staining. Cell surface E-selectin and intercellular adhesion molecule expression were assessed with fluorescence-activated cell sorting. Akt phosphorylation was assessed with Western blotting. RESULTS: Orbital shear stress increased EC proliferation by 29% and 3 [H]thymidine incorporation two-fold compared to 16% and 38% decreases, respectively, in ECs treated with laminar shear stress (P < .0001 and P = .03, analysis of variance). Cells in the periphery of the culture well aligned to the direction of shear stress similar to the shape change seen with laminar shear stress, whereas ECs in the center of the well appeared unaligned similar to ECs not exposed to shear stress. Shear stress at the bottom surface of the culture well was reduced in the center of the well (5 dyne/cm 2) compared to the periphery (11 dyne/cm 2); the Reynolds' number was 2066. ECs were seeded differentially in the center and periphery of the wells. ECs in the center of the well had increased proliferation, increased apoptosis, reduced Akt phosphorylation, increased intercelluar adhesion molecule expression, and reduced E-selectin down-regulation, compared with ECs in the periphery of the well. CONCLUSION: Although the orbital shaker does not apply uniform shear stress throughout the culture well, arterial magnitudes of shear stress are present in the periphery of the well. ECs cultured in the center of the well exposed to low magnitudes of orbital shear stress might be a model of the "activated" EC phenotype. CLINICAL RELEVANCE: The perfect in vitro model to study and assess treatments for atherosclerosis and neointimal hyperplasia does not exists. An extensive body of literature describing effects of laminar shear stress on endothelial cells has contributed to our understanding of the interactions between shear stress and blood vessels. Laminar shear stress is atheroprotective, whereas oscillatory or disturbed shear stress correlates with areas of atherosclerosis and neointimal hyperplasia in vivo. This study describes the orbital shear stress model, its effects on endothelial cell proliferation and apoptosis, and suggests that activation of the intracellular Akt pathway is associated with these differing effects of laminar and orbital shear stress on endothelial cells.

Animals↗
PubMed2005

Sustained orbital shear stress stimulates smooth muscle cell proliferation via the extracellular signal-regulated protein kinase 1/2 pathway.

OBJECTIVE: Nonlaminar shear stress stimulates smooth muscle cell (SMC) proliferation and migration in vivo, especially after an endothelial-denuding injury. To determine whether sustained shear stress directly stimulates SMC proliferation in vitro, the effect of orbital shear stress on SMC proliferation, phenotype, and extracellular signal-regulated protein kinase 1/2 (ERK1/2) phosphorylation was examined. METHODS: Bovine SMCs were exposed to orbital shear stress (210 rpm) for up to 10 days, with and without the ERK1/2 upstream pathway inhibitor PD98059 (10 microM) or the p38 pathway inhibitor SB203580 (10 microM). Proliferation was directly counted and assessed with proliferation cell nuclear antigen. Western blotting was used to assess activation of SMC ERK1/2 and SMC phenotype markers. RESULTS: SMCs exposed to sustained orbital shear stress (10 days) had 75% increased proliferation after 10 days compared with static conditions. Expression of markers of the contractile phenotype (alpha-actin, calponin) was decreased, and markers of the synthetic phenotype (vimentin, beta-actin) were increased. ERK1/2 was phosphorylated in the presence of orbital shear stress, and orbital shear-stress-stimulated SMC proliferation was inhibited in the presence of PD98059 but sustained in the presence of SB203580. Orbital shear-stress-induced changes in SMC phenotype were also inhibited in the presence of PD98059. CONCLUSION: Orbital shear stress directly stimulates SMC proliferation in long-term culture in vitro and is mediated, at least partially, by the ERK1/2 pathway. The ERK1/2 pathway may also mediate the orbital shear-stress-stimulated switch from SMC contractile to synthetic phenotype. These results suggest that shear-stress-stimulated SMC proliferation after vascular injury is mediated by a pathway amenable to pharmacologic manipulation.

Animals↗
PubMed2005

Arterial thrombosis associated with heterozygous factor V Leiden disorder, hyperhomocysteinemia, and peripheral arterial disease: importance of synergistic factors.

A 47-year-old man with heterozygous factor V Leiden disorder and intermittent hyperhomocysteinemia developed spontaneous acute popliteal artery thrombosis. Homocysteine levels were above normal limits at presentation. Intra-arterial thrombolysis was used successfully to treat the acute thrombosis; long-term treatment included anticoagulation, folic acid, and risk factor modification. Although factor V Leiden is strongly associated with deep venous thrombosis, additional cofactors such as hyperhomocysteinemia may predispose to an increased risk of acute arterial thrombosis in areas of pre-existing peripheral arterial disease.

Acute Disease↗
PubMed2004

Inhibition of accelerated graft arteriosclerosis by gene transfer of soluble fibroblast growth factor receptor-1 in rat aortic transplants.

OBJECTIVE: Because increased fibroblast growth factor-1 (FGF-1) and FGF receptor (FGFR) expression correlate with the development of accelerated graft arteriosclerosis in transplanted human hearts, this study sought to determine whether local gene transfer of soluble FGFR-1, capable of binding both FGF-1 and FGF-2, could blunt the development of accelerated graft arteriosclerosis in the rat aortic transplant model. METHODS AND RESULTS: A construct encoding the FGFR-1 ectodomain, capable of neutralizing FGF-2 action, was expressed in rat aortic allografts, using adenoviral gene transfer at the time of transplantation. Neointima formation was inhibited in aortic allografts transduced with soluble FGFR-1, compared with allografts transduced with Null virus. CONCLUSIONS: FGFs play a causal role in the development of accelerated graft arteriosclerosis in the rat aortic transplant model. Targeted interruption of FGF function could potentially reduce neointima formation in patients with heart and kidney transplants.

Adenoviridae↗