A thrombolytic therapy using diagnostic ultrasound combined with RGDS-targeted microbubbles and urokinase in a rabbit model.

This study aimed to explore thrombolysis therapy based on ultrasound combined with urokinase and Arg-Gly-Asp sequence (RGDS)-targeted microbubbles by evaluating the histological changes in a thrombotic rabbit model. Forty-two New Zealand rabbits featuring platelet-rich thrombi in the femoral artery were randomized to (n = 6/group): ultrasound alone (US); urokinase alone (UK); ultrasound plus non-targeted microbubbles (US + M); ultrasound plus RGDS-targeted microbubbles (US + R); RGDS-targeted microbubbles plus urokinase (R + UK); ultrasound, non-targeted microbubbles and urokinase (US + M + UK); and ultrasound, RGDS-targeted microbubbles and urokinase (US + R + UK) groups. Diagnostic ultrasound was used transcutaneously over the thrombus for 30 min. We evaluated the thrombolytic effect based on ultrasound thrombi detection, blood flow, and histological observations. Among all study groups, complete recanalization was achieved in the US + R + UK group. Hematoxylin and eosin staining showed that the thrombi were completely dissolved. Scanning electron microscopy examination demonstrated that the fiber network structure of the thrombi was damaged. Transmission electron microscopy showed that the thrombus was decomposed into high electron-dense particles. Histology for von Willebrand factor and tissue factor were both negative in the US + R + UK group. This study revealed that a thrombolytic therapy consisting of diagnostic ultrasound together with RGDS-targeted and urokinase coupled microbubbles.

Bright quantum dots emitting at ∼1,600 nm in the NIR-IIb window for deep tissue fluorescence imaging.

With suppressed photon scattering and diminished autofluorescence, in vivo fluorescence imaging in the 1,500- to 1,700-nm range of the near-IR (NIR) spectrum (NIR-IIb window) can afford high clarity and deep tissue penetration. However, there has been a lack of NIR-IIb fluorescent probes with sufficient brightness and aqueous stability. Here, we present a bright fluorescent probe emitting at ∼1,600 nm based on core/shell lead sulfide/cadmium sulfide (CdS) quantum dots (CSQDs) synthesized in organic phase. The CdS shell plays a critical role of protecting the lead sulfide (PbS) core from oxidation and retaining its bright fluorescence through the process of amphiphilic polymer coating and transferring to water needed for imparting aqueous stability and compatibility. The resulting CSQDs with a branched PEG outer layer exhibited a long blood circulation half-life of 7 hours and enabled through-skin, real-time imaging of blood flows in mouse vasculatures at an unprecedented 60 frames per second (fps) speed by detecting ∼1,600-nm fluorescence under 808-nm excitation. It also allowed through-skin in vivo confocal 3D imaging of tumor vasculatures in mice with an imaging depth of ∼1.2 mm. The PEG-CSQDs accumulated in tumor effectively through the enhanced permeation and retention effect, affording a high tumor-to-normal tissue ratio up to ∼32 owing to the bright ∼1,600-nm emission and nearly zero autofluorescence background resulting from a large ∼800-nm Stoke's shift. The aqueous-compatible CSQDs are excreted through the biliary pathway without causing obvious toxicity effects, suggesting a useful class of ∼1,600-nm emitting probes for biomedical research.

Investigation of the Effects and Mechanisms of Mai Tong Formula on Lower Limb Macroangiopathy in a Spontaneous Diabetic Rat Model.

A new Chinese herbal formula called Mai Tong Formulae (MTF) has recently been used to treat lower limb macroangiopathy in type 2 diabetes mellitus (T2DM) patients. In this study, we investigated the effect of MTF on lower limb macroangiopathy in a spontaneous diabetic rat model (GK rats). We found that MTF treatment significantly reduced serum fasting blood glucose (FBG), triglycerides (TG), total cholesterol (TC), IL6, and VEGF and increased serum insulin in this model. Histological and ultrastructural observations showed that MTF treatment significantly reduced vascular endothelial cell shedding and improved endothelium injuries. We further detect proteome alteration following MTF treatment. 25 differential proteins (DPs) abnormally expressed in GK rats were normalized by MTF treatment. These DPs significantly are enriched in biological processes and pathways that regulate muscle contraction and cGMP-PKG signaling pathway and so on. Additional protein-protein interaction (PPI) network analyses of the DPs showed that Fasn and Prkar2a are involved in the AMPK signaling pathway, and Gnas, Myh11, and Myh6 are involved in vascular smooth muscle contraction; these 5 DPs were validated by Western blotting. These results indicate that MTF treatment effectively treats lower limb macroangiopathy by regulating key proteins involved in AMPK signaling pathway and vascular smooth muscle contraction.

Direct Evidence for P2Y2 Receptor Involvement in Vascular Response to Injury.

OBJECTIVES: Extracellular nucleotide release at the site of arterial injury mediates the proliferation and migration of vascular smooth muscle cells. Our aim was to investigate the role of the P2Y2 nucleotide receptor (P2Y2R) in neointimal hyperplasia. Approach and Results: Vascular injury was induced by the implantation of a polyethylene cuff around the femoral artery in wild-type and P2Y2R-deficient mice (P2Y2R-/-). Electron microscopy was used to analyze monocyte and lymphocyte influx to the intima 36 h after injury. Compared to wild-type littermates, P2Y2R-/- mice exhibited a 3-fold decreased number of mononuclear leukocytes invading the intima (p < 0.05). Concomitantly, the migration of smooth muscle cells was decreased by more than 60% (p < 0.05), resulting in a sharp inhibition of intimal thickening formation in P2Y2R-/- mice (n = 15) 14 days after cuff placement. In vitro, loss of P2Y2R significantly impaired monocyte migration in response to nucleotide agonists. Furthermore, transgenic rats overexpressing the P2Y2R developed accelerated intimal lesions resulting in more than 95% luminal stenosis (p < 0.05, n = 10). CONCLUSIONS: Loss- and gain-of-function approaches established direct evidence for P2Y2R involvement in neointimal hyperplasia. Specific anti-P2Y2R therapies may be used against restenosis and bypass graft failure.

Mechanical, biological and structural characterization of human atherosclerotic femoral plaque tissue.

The failure of endovascular treatments of peripheral arterial disease represents a critical clinical issue. Specialized data are required to tailor such procedures to account for the mechanical response of the diseased femoral arterial tissue to medical device deployment. The purpose of this study is to characterize the mechanical response of atherosclerotic femoral arterial tissue to large deformation, the conditions typical of angioplasty and stenting, and also to determine the mechanically induced failure properties and to relate this behaviour to biological content and structural composition using uniaxial testing, Fourier transform infrared spectroscopy and scanning electron microscopy. Mechanical and biological characterization of 20 plaque samples obtained from femoral endarterectomy identified three distinct classifications. "Lightly calcified" samples display linear mechanical responses and fail at relatively high stretch. "Moderately calcified" samples undergo an increase in stiffness and ultimate strength coupled with a decrease in ductility. Structural characterization reveals calcified nodules within this group that may be acting to reinforce the tissue matrix, thus increasing the stiffness and ultimate strength. "Heavily calcified" samples account for the majority of samples tested and exhibit significantly reduced ultimate strength and ductility compared to the preceding groups. Structural characterization of this group reveals large areas of calcified tissue dominating the failure cross-sections of the samples. The frequency and structural dominance of these features solely within this group offers an explanation as to the reduced ultimate strength and ductility and highlights the need for modern peripheral endovascular devices to account for this behaviour during novel medical device design.

Contemporary management of critical lower limb ischemia in TASC D lesions with subintimal angioplasty in femoro-popliteal lesions, tibial angioplasty and sequential compression biomechanical device for infra-inguinal arterial occlusion. Experience and quality of life outcome learned over 25 years.

AIM: Patients with end-stage critical limb ischemia (CLI) survive on borrowed time and amputation is inevitable if an aggressive management stratagem is not instigated. Our primary aim was to equate effectiveness of subintimal angioplasty (SIA) and tibial balloon angioplasty (TBA) in sustaining clinical improvement and amputation free survival (AFS) in patients with CLI TASD II D. Moreover, patients with severe CLI, who were not suitable for revascularization and who were offered therapy with a sequential compression biomechanical device (SCBD) were scrutinised as part of a comprehensive lower limb salvage program. METHODS: From 2002-2012, 5876 patients were referred with peripheral vascular disease (PVD); 987 presented with CLI and 798 had intervention; 189 patients presenting with CLI were not candidates for revascularisation, out of which 171 were offered SCBD. We formed a prospective observational group study of 441 patient who had TASC D disease. All of these patients presented as emergencies and were allocated to the next available treatment list. Duplex ultrasound arterial mapping (DUAM) was the sole preoperative investigation tool in 92% of all cases. Of the 441 patients studied, 190 patients (206 procedures) has SIA for TASC D femero-popliteal occlusions, 80 patients (89 procedures) had TBA and cool eximer laser angioplasty (CELA) for tibial artery occlusions and 171 patients with severe CLI were not suitable for revascularization and joined the SCBD program. Mean age (SIA 73±13 years vs. TBA/CELA 74±8 years vs. SCBD 75±13 years), and comorbidity severity scores (P>0.05) were similar between groups. RESULTS: Perioperative mortality within the SIA group was 1.6% vs. 0% within the TBA group and 0.6% in SCBD. Length of hospital stay within the TBA group was 3.8±2 days vs. SIA 14±16 days, P<0.0001. The 5-year freedom from major adverse events (MAE) for the SIA group was 68% that was comparable to the results obtained for both the TBA group; 59%, and SCBD group: 62.5% (P=0.1935). Five-year freedom from target lesion revascularization was 85.9% within the SIA group and 79% within the TBA group. A sustained clinical improvement was seen in 82.8% of primary SIA and 68% of TBA, which mimics the outcome of SCBD at 68% at one year. A total of 83% SCBD patients had no rest pain within one week of starting the program and gangrene remained dry and non-progressive. Ulceration healed in all but 12 patients. There were no device-related complications. Limb salvage was 94% at 5 years. All-cause survival was 69%. Quality time spent without symptoms of disease or toxicity of treatment (Q-TWiST) was 24.7 months for SIA and 8.5 months for TBA and was 38.13 for SCBD for a total of 708 months of usage. Cost per quality adjusted-life years (QALY) for SIA was € 5662.79, € 12,935.18 for TBA and € 2943.56 for SCBD. CONCLUSION: All treatment pathways augmented patient-specific Q-TWiST with substantial cost reduction. SIA, TBA and SCBD expand AFS and symptom-free survival. All treatment modalities are minimally invasive and allow for a high patient turnover without compromising limb salvage, once they are performed by experienced vascular surgeons in high deliberate practice volume centers.

Pycnogenol® and Centella Asiatica for asymptomatic atherosclerosis progression.

AIM: The aim of the study was to evaluate the effect of the nutritional supplements Pycnogenol and TECA (total triterpenic fraction of Centella Asiatica) on atherosclerosis progression in low-risk asymptomatic subjects with carotid or femoral non-stenosing plaques. METHODS: This was an observational pilot substudy of the San Valentino epidemiological cardiovascular study. The study included 1363 subjects aged 45-60 without any conventional risk factors who had non stenosing atherosclerotic plaques (<50%) in at least one carotid or common femoral bifurcation, allocated into 6 groups: Group 1 (CONTROLS): management was based on education, exercise, diet and lifestyle changes. This same management plan was used in all groups; Group 2 Pycnogenol 50 mg/day; Group 3 Pycnogenol 100 mg/day; Group 4 Aspirin 100 mg/day or Ticlopidine 250 mg/day if intolerant to aspirin; Group 5 Aspirin 100 mg/day and Pycnogenol 100 mg/day; Group 6 Pycnogenol 100 mg/day plus TECA (total triterpenic fraction of Centella Asiatica) 100 mg/day. There was a six monthly follow-up up to 30 months. Plaque progression was assessed using the ultrasonic arterial score based on the arterial wall morphology and the number of plaques that progressed from the non-stenotic to the stenotic group. A secondary endpoint was to evaluate the changes in oxidative stress at baseline and at 30 months. RESULTS: The ultrasonic score increased significantly in groups 1, 2 and 4 but not in groups 3, 5 and 6 suggesting a beneficial effect of Pycnogenol 100 mg. The percentage of plaques that progressed from class IV to class V was 8.4% in group 2, 5.3% in group 3, 4% in group 5 and 1.1% in group 6 (P<0.0001) compared with 16.6% in group 4 (aspirin) and 21.3% in the control group suggesting a beneficial effect of Pycnogenol. The lowest rate of progression was in group 6 (Pycnogenol plus TECA). At 30 months, the oxidative stress in all the Pycnogenol groups was less than in the control group. The oxidative stress was lower in the Pycnogenol 100 mg group than the Pycnogenol 50 mg group (P<0.0001). In the combined group of Pycnogenol and TECA the oxidative stress was less than the Pycnogenol alone (P<0.001). CONCLUSION: Pycnogenol and the combination of Pycnogenol+TECA appear to reduce the progression of subclinical arterial lesions in low-risk asymptomatic subjects. The reduction in plaque progression was associated with a reduction in oxidative stress. The results justify a large randomized controlled study to demonstrate the efficacy of the combined Pycnogenol and TECA prophylactic therapy in subclinical atherosclerosis.

Preclinical evaluation of second-generation everolimus- and zotarolimus-eluting coronary stents.

OBJECTIVES: This study was designed to evaluate the pharmacokinetic and vascular healing of a second-generation everolimus-eluting stent (EES) and slow-release zotarolimus-eluting stent (R-ZES). BACKGROUND: Second-generation DESs have alleviated the safety concerns of late stent thrombosis by addressing issues of polymer biocompatibility and stent design, and optimizing drug loads and release kinetics. No preclinical comparison study exists between these stents. METHODS: Rabbit iliac artery stent implantation was performed using Xience Prime EES and Resolute R-ZES. Histomorphometric evaluation was performed at 28 and 60 days after implantation in an induced atheroma model. Endothelial coverage and maturation were assessed by scanning electron microscopy and immuno-labeling at 14 and 28 days following deployment. For pharmacokinetic studies, arterial tissue and stents were retrieved at 3, 14, 28, and 90 days, and blood samples were obtained during the first 24 hours. RESULTS: Vascular remodeling (percent stenosis, neointimal thickness) was similar in arteries implanted with either stent group. At 28 days, inflammation was significantly less in the EES group as compared to the R-ZES group (inflammation score: 1.59 ± 0.52 vs 2.22 ± 0.69, respectively; P=.044), with no differences observed at 60 days. Endothelial coverage was similar between both groups; however, endothelial maturation above stent struts was significantly higher in the EES group vs R-ZES group at 28 days (33 ± 20% vs 22 ± 21%, respectively; P=.040). Arterial drug level concentrations were also shown to be significantly less in the EES group vs the R-ZES group (P<.0001). CONCLUSIONS: Overall, EES and R-ZES displayed similar remodeling properties with lower arterial drug levels observed in the EES group vs the R-ZES group, which may have led to more rapid endothelial maturation.

Bedside ultrasound diagnosis of acute embolic femoral artery occlusion.

BACKGROUND: Acute limb ischemia is both a limb-threatening and life-threatening disease process. Nontraumatic acute peripheral arterial occlusion is most commonly caused by a thrombosis or an embolism. OBJECTIVES: There is limited evidence on the use of bedside ultrasound for the detection of acute limb ischemia, but duplex ultrasonography is standard in the diagnosis and operative planning in chronic limb ischemia. Emergency physicians may use bedside ultrasound in the evaluation of patients with symptoms and signs suggestive of this disease entity. CASE REPORT: A 64-year-old man with a past medical history of hypertension and an ischemic stroke presented to the Emergency Department with <2 h of severe upper left leg pain that radiated down to his foot. A bedside ultrasound of the left lower extremity was emergently performed. On B-mode ultrasound evaluation, echogenic material was visualized in the left common femoral artery, the artery was noncompressible, and there was an absence of Doppler flow signal. He was then directly taken to the operating room for an emergent limb-saving procedure. CONCLUSION: A focused examination of the aorta, iliac vessels, and femoral artery bifurcation with bedside ultrasonography may help to localize peripheral arterial occlusions and can assist the emergency physician in seeking timely surgical consultation and management.

Biocompatibility and biodegradability of Mg-Sr alloys: the formation of Sr-substituted hydroxyapatite.

Magnesium is an attractive material for use in biodegradable implants due to its low density, non-toxicity and mechanical properties similar to those of human tissue such as bone. Its biocompatibility makes it amenable for use in a wide range of applications from bone to cardiovascular implants. Here we investigated the corrosion rate in simulated body fluid (SBF) of a series of Mg-Sr alloys, with Sr in the range of 0.3-2.5%, and found that the Mg-0.5 Sr alloy showed the slowest corrosion rate. The degradation rate from this alloy indicated that the daily Sr intake from a typical stent would be 0.01-0.02 mg day⁻¹, which is well below the maximum daily Sr intake levels of 4 mg day⁻¹. Indirect cytotoxicity assays using human umbilical vascular endothelial cells indicated that Mg-0.5 Sr extraction medium did not cause any toxicity or detrimental effect on the viability of the cells. Finally, a tubular Mg-0.5 Sr stent sample, along with a WE43 control stent, was implanted into the right and left dog femoral artery. No thrombosis effect was observed in the Mg-0.5 Sr stent after 3 weeks of implantation while the WE43 stent thrombosed. X-ray diffraction demonstrated the formation of hydroxyapatite and Mg(OH)2 as a result of the degradation of Mg-0.5 Sr alloy after 3 days in SBF. X-ray photoelectron spectroscopy further showed the possibility of the formation of a hydroxyapatite Sr-substituted layer that presents as a thin layer at the interface between the Mg-0.5 Sr alloy and the corrosion products. We believe that this interfacial layer stabilizes the surface of the Mg-0.5 Sr alloy, and slows down its degradation rate over time.

Nonsuture anastomosis of arteries and veins using the magnetic pinned-ring device: a histologic and scanning electron microscopic study.

BACKGROUND: The goal of this study was to evaluate the performance of the magnetic pinned-ring device for nonsuture vascular anastomosis. METHODS: The magnetic pinned-ring device consists of paired magnetic rings that are coated with titanium nitride and embedded in a polypropylene shell; the rings are equipped with alternately spaced holes and titanium pins. The vascular anastomosis procedure using the novel magnetic pinned-ring device was performed on 14 mongrel dogs, and the traditional hand-sewing technique was used on 14 additional dogs. In situ end-to-end anastomoses were performed in the femoral artery and the inferior vena cava. Patency was confirmed through ultrasonographic scans at different time points as late as 24 weeks after surgery. Gross observation, histological staining, and scanning electron microscopy were used to evaluate the results at 24 weeks postoperatively. RESULTS: The time required to perform the vascular anastomosis was significantly shorter for the magnetic device than for hand sewing. A continuity of re-endothelialization was confirmed in all anastomotic stomas after 24 weeks, and neither formation of aneurysms nor thickening of the vascular wall was noted. The re-endothelialization was smooth at the anastomotic site of the magnetic device, whereas hand sewing resulted in rough and uneven re-endothelialization and the presence of visible sutures. Moreover, the endothelial cells were regularly arranged at the anastomotic site of the magnetic device, whereas different-sized and irregularly aligned endothelial cells were present at the hand-sewn anastomotic site. Use of the magnetic device was associated with significantly decreased deposition of fibrotic collagen and depressed infiltration of inflammatory cells compared with use of the hand-sewing technique. CONCLUSIONS: The magnetic pinned-ring device offers a simple, fast, reliable, and efficacious technique for nonsuture vascular anastomosis. Use of this device shortens operation time, maintains a high patency rate, and improves the healing of vascular tissue.

The emerging issue of human resident arterial progenitors: the contribution of organ culture.

Human femoral arteries were cultured up to 56 days. Samples were processed for light, immunohistochemical, and transmission electron microscopy. Arteries became rapidly depopulated; at day 42, an endothelial lining (CD31(+), Weibel-Palade bodies) developed on the intima; endothelium was in continuity with mesenchymal stromal cells (CD44(+), CD90(low), CD105(low)) placed on adventitia. The media-adventitia area showed heterogeneous cell populations. In long-term organ culture, femoral artery develops a continuous cell coverage that differentiates to endothelium on the intima exclusively. This suggests that distinct topographical factors, such as resident progenitors and/or matrix signals, are able to regulate vascular homeostasis in adult life.

New biodegradable small-diameter artificial vascular prosthesis: a feasibility study.

An in-house built instrument was used to fabricate a small internal diameter (2 mm) artificial vascular prosthesis from biodegradable chitosan. This new artificial vascular prosthesis has shown a good biocompatibility based on the studies of its cell compatibility, inflammatory reaction, and platelet adhesion. In an animal test, the prosthesis was used to replace a 4-cm-long section of femoral artery in each of the seven tested dogs. The patency of the replacement was monitored at regular intervals using Doppler ultrasound diagnostics. Nine months after the implantation, hematoxylin and eosin staining, immunohistochemical study, and scanning electron microscope observation were carried out. Complete decomposition of the prosthesis and replacement by a natural blood vessel were observed. The results suggests that the artificial vascular prosthesis displays many characteristics of the "ideal" small-diameter artificial vascular, and have the biocompatibility that can be tailored to match those desired in vascular replacement application.

Knitted nitinol represents a new generation of constrictive external vein graft meshes.

OBJECTIVE: Constriction of vein grafts with braided external nitinol meshes had previously led to the successful elimination of neointimal tissue formation. We investigated whether pulse compliance, smaller kink-free bending radius, and milder medial atrophy can be achieved by knitting the meshes rather than braiding, without losing the suppressive effect on intimal hyperplasia. METHODS: Pulse compliance, bending stiffness, and bending radius, as well as longitudinal-radial deformation-coupling and radial compression, were compared in braided and knitted nitinol meshes. Identical to previous studies with braided mesh grafts, a senescent nonhuman primate model (Chacma baboons; bilateral femoral interposition grafts/6 months) mimicking the clinical size mismatch between vein grafts and runoff arteries was used to examine the effect of knitted external meshes on vein grafts: nitinol mesh-constricted (group 1); nitinol mesh-constricted and fibrin sealant (FS) spray-coated for mesh attachment (group 2); untreated control veins (group 3), and FS spray-coated control veins (group 4). RESULTS: Compared with braided meshes, knitted meshes had 3.8-times higher pulse compliance (3.43 ± 0.53 vs 0.94 ± 0.12%/100 mm Hg; P = .00002); 30-times lower bending stiffness (0.015 ± 0.002 vs 0.462 ± 0.077 Nmm(2); P = .0006); 9.2-times narrower kink-free bending radius (15.3 ± 0.4 vs 140.8 ± 22.4 mm; P = .0006), and 4.3-times lower radial narrowing caused by axial distension (18.0% ± 1.0% vs 77.0% ± 3.7%; P = .00001). Compared with mesh-supported grafts, neointimal tissue was 8.5-times thicker in group I (195 ± 45 µm) vs group III (23.0 ± 21.0 µm; P < .001) corresponding with a 14.3-times larger neointimal area in group I (4330 ± 957 × 103 µm(2)) vs group III (303 ± 221× 103 µm(2); P < .00004). FS had no significant influence. Medial muscle mass remained at 43.4% in knitted meshes vs the 28.1% previously observed in braided meshes. CONCLUSION: Combining the suppression of intimal hyperplasia with a more physiologic remodeling process of the media, manifold higher kink-resistance, and lower fraying than in braided meshes makes knitted nitinol an attractive concept in external vein graft protection.

Vascular pathological changes in rat lower extremity and timing of microsurgery after electrical trauma.

The purpose of this study was to form a standard electrical trauma model in rat, to investigate the pathological changes in vessels, and to determine the best day for performing microsurgery. In the preliminary study, 20 rats were divided into five groups. One was control, and the rats in the other four groups were exposed to 240 V electrical potential for 5, 10, 15, and 20 seconds, respectively. Femoral vessels from each group were biopsied for electron and light microscopy. In the study group, 36 rats were subjected to 240 V electrical trauma for 18 seconds. The rats in the study group were divided into three groups. On days 3, 7, and 21, the femoral artery of nine rats in each group were cut and anastomosed. The anastomoses were followed for thrombus formation. Visible, respectively increasing necroses were seen in all animals in the second, third, and fourth preliminary study groups. Light and electron microscopy revealed degeneration of vessel walls and loss of endothelium. Second and third microsurgery study groups had statistically significantly more thrombus. Although after electrical trauma major vessels seem normal, they have pathological changes, and microsurgery success rates are decreased shortly after electrical trauma.

Effect of anastomotic length on the development of intimal hyperplasia in the distal anastomosis of bypass graft.

Many hemodynamic factors have been shown to be associated with increased intimal hyperplasia at the distal anastomosis of arterial bypass graft. However, the relationship between the length of anastomosis and the development of such a complication has not been studied before. The aim of this study was to assess this relationship at the distal anastomosis with a Dacron graft. Iliofemoral bypass using 6 mm Dacron grafts was performed in 10 German shepherd dogs. In accordance with preoperative randomization to individual animal legs, distal anastomoses were reconstructed using four different groups (A, B, C, and D), depending on the length of the arteriotomy: 3.0, 3.5, 4.0, and 4.5 times the internal diameter of the artery, respectively. The vessels were harvested 6 months after the operation, and specimens were processed for histologic and transmission electron microscopic (TEM) studies. Quantitative analysis was performed to assess the extent of intimal hyperplasia at three zones (heel, toe, and midzone of the arterial bed) of the distal anastomosis. Sixteen arterial bypasses were included in this study. Both light and TEM studies revealed evidence of intimal hyperplasia in the four groups. Quantitative analysis showed a significant decrease in intimal hyperplasia with increasing the length of the anastomosis at the heel, toe, or midzone of the arterial bed. Mean (mum +/- SD) intimal hyperplasia of the three zones together was significantly higher in group A than group B (585 +/- 106 vs 423 +/- 8.6, p < .001) and in group B than group C (423 +/- 8.6 vs 202 +/- 15, p < .001). However, the difference between group C and group D (202 +/- 15 vs 162 +/- 8.6; p = .13) was statistically insignificant. The present study showed that the length of the anastomosis is one of the hemodynamic factors involved in the development of intimal hyperplasia. Anastomotic techniques that resulted in the least intimal hyperplasia were end to side, with length 4 or 4.5 times the internal diameter of the artery.

Dose-dependent ultrastructural and morphometric alterations after erythropoietin treatment in rat femoral artery vasospasm model.

PURPOSE: Cerebral vasospasm is the common cause of poor outcome after aneurysmal subarachnoid hemorrhage (aSAH). Although many agents are experimentally and clinicaly used to protect or recover from vasospasm, an effective neurotherapeutic drug is still missing. Erythropoietin (EPO) is recently a promising candidate. The aim of this study is to investigate the dose-dependent effects of recombinant human EPO (rhEPO) on arterial wall in a rat femoral artery vasospasm model. METHODS: Thirty two animals were divided into four groups: vasospasm without any treatment (group A), vasospasm +250 IU/kg rhEPO group (group B), vasospasm +500 IU/kg rhEPO group (group C), and control group (group D). Rat femoral artery vasospasm model was used. For groups B and C, 7 days of 250 IU/kg and 500 IU/kg intraperitoneal rhEPO in 0.3 ml saline were administered respectively; and for groups A and D, 0.3 ml saline were administered intraperitoneally without any treatment. After 7 days, histological and morphometric analyses were carried out. RESULTS: Vasospasm alone group demonstrated the highest vessel wall thicknesses, comparing to other groups (p < 0.001). While for groups B and C, vessel wall thickness values were significantly higher than the control group (p < 0.001), between these two groups, there was no significant difference achieved (p > 0.05). CONCLUSION: In our study, there was no significant difference between the two rhEPO treatment groups, but rhEPO treatment was shown to be histologically and morphometrically effective in vasospasm. However, if dosage of EPO treatment is augmented, successful results may be achieved.

The connective tissue of the adductor canal--a morphological study in fetal and adult specimens.

The adductor canal is a conical or pyramid-shaped pathway that contains the femoral vessels, saphenous nerve and a varying amount of fibrous tissue. It is involved in adductor canal syndrome, a claudication syndrome involving young individuals. Our objective was to study modifications induced by aging on the connective tissue and to correlate them to the proposed pathophysiological mechanism. The bilateral adductor canals and femoral vessels of four adult and five fetal specimens were removed en bloc and analyzed. Sections 12 microm thick were obtained and the connective tissue studied with Sirius Red, Verhoeff, Weigert and Azo stains. Scanning electron microscopy (SEM) photomicrographs of the surfaces of each adductor canal were also analyzed. Findings were homogeneous inside each group. The connective tissue of the canal was continuous with the outer layer of the vessels in both groups. The pattern of concentric, thick collagen type I bundles in fetal specimens was replaced by a diffuse network of compact collagen bundles with several transversal fibers and an impressive content of collagen III fibers. Elastic fibers in adults were not concentrated in the thick bundles but dispersed in line with the transversal fiber system. A dynamic compression mechanism with or without an evident constricting fibrous band has been proposed previously for adductor canal syndrome, possibly involving the connective tissue inside the canal. The vessels may not slide freely during movement. These age-related modifications in normal individuals may represent necessary conditions for this syndrome to develop.

Visualization of activated platelets by targeted magnetic resonance imaging utilizing conformation-specific antibodies against glycoprotein IIb/IIIa.

Ruptured atherosclerotic plaques, lined with activated platelets, constitute an attractive target for magnetic resonance imaging (MRI). This study evaluated whether microparticles of iron oxide (MPIO) targeting ligand-induced binding sites (LIBS) on the activated conformation of glycoprotein IIb/IIIa could be used to image platelets. MPIO (size: 1 microm) were conjugated to anti-LIBS or control single-chain antibody. Following guidewire injury to mouse femoral artery, platelet adhesion was present after 24 h. Mice were perfused with anti-LIBS-MPIO (or control MPIO) via the left ventricle and 11.7-tesla MRI was performed on femoral arteries ex vivo. A 3D gradient echo sequence attained an isotropic resolution of 25 microm. MPIO binding, quantified by MRI, was 4-fold higher with anti-LIBS-MPIO in comparison to control MPIO (p < 0.01). In histological sections, low signal zones on MRI and MPIO correlated strongly (R(2) = 0.72; p < 0.001), indicating accurate MR quantification. In conclusion, anti-LIBS-MPIO bind to activated platelets in mouse arteries, providing a basis for the use of function-specific single-chain antibody-MPIO conjugates for molecular MRI, and represent the first molecular imaging of a conformational change in a surface receptor. This presents an opportunity to specifically image activated platelets involved in acute atherothrombosis with MRI.

In vitro study of endothelial cells lining vascular grafts grown within the recipient's peritoneal cavity.

A living-tissue conduit with strong mechanical properties was used to produce small-diameter vessels. To improve blood compatibility, a shear-resistant confluent monolayer endothelium was formed on the luminal surface of the conduit. Under mechanical stimulation induced by pulsatile flow in a bioreactor, abrupt high-flow shear stress of 15.3 +/- 4.6 dynes/cm2 was applied to endothelial cells (ECs) seeded onto the lumen of a living-tissue conduit after 2 days of static culture. Scanning electron microscopy images revealed that most of the ECs were washed off after 3 days of dynamic culture. When shear stress was increased stepwise from 1.5 +/- 0.8 to 15.3 +/- 4.6 dynes/cm2 and applied to the ECs, scanning electron microscopy images of the luminal surface revealed that the confluent monolayer ECs were highly elongated and oriented to the flow direction, similar to findings in natural arteries in vivo. The results indicated that in vitro flow conditions played a key role in determining the durability of the EC layer. Careful design of the bioreactor and careful selection of the culture conditions will greatly improve the chances of producing a useful anti-thrombogenic surface for tissue-engineered small-diameter vessels.