Biomedical subjects

W R Wagner

Publications and source records attributed to W R Wagner.

At least 19 recordsLinked to original sources

PubMed2000

Assessing acute platelet adhesion on opaque metallic and polymeric biomaterials with fiber optic microscopy.

The degree of platelet adhesion and subsequent thrombus formation is an important measure of biocompatibility for cardiovascular biomaterials. Traditional methods of quantifying platelet adhesion often are limited by the need for direct optical access, limited spatial resolution, or the lack of temporal resolution. We have developed a new imaging system that utilizes fiber optics and fluorescence microscopy for the quantification of platelet adhesion. This fiber optic remote microscope is capable of imaging individual fluorescently labeled platelets in whole blood on opaque surfaces. Using this method, platelet adhesion was quantified on a series of metallic [low-temperature isotropic carbon (LTIC); titanium alloy (Ti); diamond-like carbon (DLC); oxidized titanium alloy (TiO); and polycrystalline diamond (PCD)] and polymeric [woven Dacron (WD)] collagen-impregnated Dacron (HEM), expanded polytetrafluoroethylene (ePTFE), and denucleated ePTFE (dePTFE)] biomaterials designed for use in cardiovascular applications. These materials were perfused with heparinized whole human blood in an in vitro parallel plate flow chamber. Platelet adhesion after 5 min of perfusion ranged from 3.7 +/- 1.0 (dePTFE) to 16.8 +/- 1.5 (WD) platelets/1000 micrometer. The temporal information revealed by these studies provides a comparative measure of the acute thrombogenicity of these materials as well as some insight into their long-term hemocompatibilities. Also studied here were the effects of wall shear rate and axial position on platelet adhesion. A predicted increase in platelet adhesion with increased wall shear rate and a trend toward a decrease in platelet adhesion with increased axial distance was observed with the fiber optic microscope. Future applications for this imaging technique may include the long-term evaluation of thrombosis in blood-contacting devices in vitro and, in animal models, in vivo.

Alloys↗

PubMed2000

Treatment of rat pancreatic islets with reactive PEG.

Covalent attachment of polymers to cells and tissues could be used to solve a variety of problems associated with cellular therapies. Insulin-dependent diabetes mellitus is a disease resulting from the autoimmune destruction of the beta cells of the islets of Langerhans in the pancreas. Transplantation of islets into diabetic patients would be an attractive form of treatment, provided that the islets could be protected from the host's immune system in order to prevent graft rejection. If reaction of polyethylene glycol (PEG) segments with the islet surface did not damage function, the immunogenicity and cell binding characteristics of the islet could be altered. To determine if this process damages islets, rat islets have been isolated and treated with protein-reactive PEG-isocyanate (MW 5000) under mild reaction conditions. An assessment of cell viability using a colorimetric mitochondrial activity assay showed that treatment of the islets with PEG-isocyanate did not reduce cell viability. Insulin release in response to secretagogue challenge was used to evaluate islet function after treatment with the polymer. The insulin response of the PEG-treated islets was not significantly different than untreated islets in a static incubation secretagogue challenge. In addition, PEG-isocyanate-treated islets responded in the same manner as untreated islets in a glucose perifusion assay. Finally, the presence of PEG on the surface of the islets after treatment with the amine-reactive N-hydroxysuccinimide-PEG-biotin (not PEG-isocyanate) was confirmed by indirect fluorescence staining. These results demonstrate the feasibility of treating pancreatic islets with reactive polymeric segments and provide the foundation for further investigation of this novel means of potential immunoisolation.

Animals↗

PubMed2000

Modeling flow effects on thrombotic deposition in a membrane oxygenator.

The hypothesis that regions of low blood velocity in a membrane oxygenator, as predicted by computational fluid dynamics (CFD), would correspond with regions of clinical thrombotic deposition was investigated. Twenty heparin-coated oxygenators were sectioned following use in adult extracorporeal membrane oxygenation. The activated clotting time (ACT) was maintained at approximately 180 s via heparin infusion throughout the support period. Cross-sections were systematically photographed, and slides made to allow image projection upon a digitizing pad. Thrombotic deposition was traced to allow creation of a device cross-section image with an overlaid color scale representing thrombotic deposition frequency. A two-dimensional CFD model was developed to predict blood velocities throughout the oxygenator cross-section. Direct spatial comparisons were made between maps of CFD modeled blood speed and thrombotic deposition. Theoretical oxygenator design modification was performed within the CFD model to investigate flow paths which might minimize regions of low blood velocity. CFD results demonstrated that low velocity regions qualitatively matched regions with a high incidence of thrombotic deposition. Thrombotic deposition was also correlated to longer perfusion periods. This technique of coupling clinical data and CFD offers the potential to relate flow characteristics to thrombotic deposition and represents a potentially powerful new methodology for the optimization of oxygenator flow-related biocompatibility.

Adult↗

PubMed2000

Evaluation of platelet activation in depressed patients with ischemic heart disease after paroxetine or nortriptyline treatment.

This study investigated the effects of antidepressant treatment on platelet activation in depressed patients with ischemic heart disease (IHD). Plasma levels of platelet alpha-granule release products beta-thromboglobulin (BTG) and platelet factor 4 (PF4) were measured in 17 depressed patients with IHD who were treated in a 6-week, double-blind trial with either paroxetine (10 patients) or nortriptyline (7 patients). Baseline measurements of BTG and PF4 were significantly elevated in both drug treatment groups before the initiation of antidepressant therapy compared with those of healthy control subjects. In the paroxetine group, mean PF4 and BTG levels significantly decreased from these elevated baseline values within 1 week of treatment and remained low at 3- and 6-week measurements. In contrast, the nortriptyline group did not exhibit a significant decrease in PF4 or BTG plasma levels after 1, 3, or 6 weeks of treatment. Therefore, platelet activation in depressed patients with IHD seems to be inhibited by the selective serotonin reuptake inhibitor paroxetine. The effect of paroxetine on PF4 and BTG plasma levels suggests that it may reduce platelet aggregation in vivo and may positively impact IHD-related mortality in this population.

Antidepressive Agents, Second-Generation↗

PubMed2000

Cocaine activates platelets and increases the formation of circulating platelet containing microaggregates in humans.

OBJECTIVE: To determine whether there is evidence of platelet activation following in vivo cocaine administration in humans, as cocaine abuse is associated with myocardial infarction and stroke, and platelet activation leading to thrombosis is a possible mechanism. SETTING: University hospital. DESIGN AND SUBJECTS: Following a randomised, double blind crossover design, 14 healthy volunteers were studied twice, receiving cocaine (2 mg/kg intranasally) once and placebo once. Flow cytometric analysis of P-selectin expression (an alpha granule membrane protein found on the surface of activated platelets), quantification of the platelet specific proteins platelet factor 4 and beta thromboglobulin, and measurement of platelet containing microaggregate and platelet microparticle (fragment) formation were used to assess platelet activation. Circulating von Willebrand factor antigen (vWF) was measured to evaluate a possible role of endothelial stimulation concurrent with platelet activation. RESULTS: There was an increase in both platelet factor 4 (mean (SD), 16 (7) to 39 (22) IU/ml, p = 0. 04) and beta thromboglobulin (70 (20) to 98 (26) IU/ml, p < 0.01) at 120 minutes following cocaine administration. Platelet containing microaggregate formation was increased at 40 minutes (from 47 (3.2)% to 54 (2.0)%, p < 0.001) and 80 minutes (55 (2.5)%, p = 0.04). Bleeding time decreased following cocaine from 10 (1) to 9 (1) minutes (p = 0.07). No changes in any of the measured variables were noted following placebo administration. CONCLUSIONS: Cocaine exposure causes platelet activation, alpha granule release, and platelet containing microaggregate formation. These data support the view that cocaine, even at the relatively low doses commonly self administered by occasional abusers, may promote thrombosis and predispose healthy individuals to ischaemic events. Platelet inhibitors should be considered early in any patient with suspected cocaine related ischaemia.

Adult↗

PubMed2000

Blood biocompatibility analysis in the setting of ventricular assist devices.

Ventricular assist devices (VADs) are increasingly applied to support patients with advanced cardiac failure. While the benefit of VADs in supporting this patient group is clear, substantial morbidity and mortality occur during the VAD implant period due to thromboembolic and infective complications. Efforts at the University of Pittsburgh aimed at evaluating the blood biocompatibility of VADs in the clinical, animal, and in vitro setting over the past decade are summarized. Emphasis is placed on understanding the mechanisms of thrombosis and thromboembolism associated with these devices.

Biocompatible Materials↗

PubMed2000

Effect of the previously gravid uterine horn and postpartum interval on follicular diameter and conception rate in beef cows treated with estradiol benzoate and progesterone.

An experiment was performed to evaluate the effect of the side of ovulation with respect to the previously gravid uterine horn on fertility of cows inseminated at one of two periods postpartum. All cows were treated with an intravaginal progesterone insert for 7 d and received estradiol benzoate (2 mg, i.m.) at the time of device insertion, prostaglandin F2alpha (25 mg, i.m.) at the time of device removal, and estradiol benzoate (1 mg, i.m.) 30 h after device removal. All cows were inseminated 28 to 30 h after the second treatment with estradiol benzoate, regardless of observed estrus. Cows treated in Period 1 received inserts at 16 to 20 d postpartum and were inseminated at 25 to 29 d postpartum. Cows treated in Period 2 received inserts at 26 to 30 d postpartum and were inseminated at 35 to 39 d postpartum. Diameter of the largest follicle at insert removal was greater in cows treated in Period 2 (10.1 +/- 0.3; mm +/- SEM) than in cows treated in Period 1 (9.1 +/- 0.3; P < .05). Diameter did not differ with the side of ovulation in respect to the previously gravid uterine horn. Diameter was greater in cows 5 to 9 (10.3 +/- 0.3) than in cows 3 to 4 (9.0 +/- 0.3) or 10 to 13 (9.4 +/- 0.6) yr of age (P < .01). The proportion of cows that ovulated from the ovary contralateral to the previously gravid uterine horn was greater (P < .05) than of those that ovulated from the ipsilateral ovary, and the incidence of ovulation was reduced in cows 3 to 4 yr of age (P < .01). Conception rate tended to be greater for ovulation from the ipsilateral compared with the contralateral ovary, relative to the previously gravid uterine horn (P < .10) and for ovulation from the right than the left ovary (P < .06). Conception rate was less if cows ovulated a follicle that was < 9 mm than a follicle > or = 9 mm in diameter at insert removal (P < .01) and was greater in cows inseminated in June than in April or May (P < .05). In conclusion, in cows in which estrus was synchronized at 25 to 39 d postpartum, ovulation from either the ovary ipsilateral to the previously gravid uterine horn, or the right ovary, tended to increase fertility.

Animals↗

PubMed1999

In vitro stability of a highly crystalline hydroxylapatite coating in a saturated citric acid solution.

A novel pressurized hydrothermal post-plasma-spray process has been developed to convert the crystalline non-HA and amorphous components of plasma-sprayed hydroxylapatite coatings back into crystalline HA. The process, known commercially as MP-1, was used to produce coatings comprising approximately 96% crystalline HA. The in vitro solubility of the coating in saturated citric acid solution has been measured to simulate the effect of implant detoxification procedures, which use citric acid as a cleaning medium. The MP-1 coating solubility in saturated citric acid solution (pH = 1) was compared to that of coatings with crystalline HA contents ranging from 37.5-82%. All coatings showed an initial sharp rise in coating dissolution, which correlated with crystalline HA content, followed by a steady state dissolution rate. After 60 s at 25 degrees C, the MP-1 coating showed a 65% decrease in solubility compared to a highly amorphous coating (AM-2). All coatings showed very similar steady state dissolution rates, except for AM-2, which was significantly higher. SEM analysis showed that the AM-2 coating surface was degraded substantially more than the other coatings, resulting in partial coating exfoliation. A mechanism of coating dissolution is proposed, in which the initial rapid leaching of soluble phases from the coating leaves behind a porous layer of highly crystalline HA at the coating surface. The stability of this porous crystalline layer leads to steady state, diffusion-limited dissolution of the remainder of the coating. The observed two-regime dissolution profile can be accurately represented by a 2-parameter model, which predicts the initial sharp rise in coating dissolution followed by a slower, steady state loss in coating mass. Model parameters were determined from experimental solubility data, and were shown to correlate with the percentage of crystalline HA in the coatings. The present data suggest that the treated coating is significantly more resistant to degradation from aggressive detoxification procedures such as citric acid burnishing.

Citric Acid↗

PubMed1999

Targeting and ultrasound imaging of microbubble-based contrast agents.

Preparation and characterization of targeted microbubbles (ultrasound contrast agents) is described. Specific ligands were attached to the microbubble shell, and ligand-coated microbubbles were selectively attached to various targets, using either an avidin biotin model system or an antigen-antibody system for targeting to live activated endothelial cells. Firm attachment of microbubbles to the target was achieved. Forces necessary to detach microbubbles from the target were estimated to exceed dozens of pN. Microbubbles were bound to the target even in the rapidly moving stream of the aqueous medium. Down to 20 ng of the ultrasound contrast material on the target surface could be detected by the ultrasound imaging with a commercial medical imaging system. At high bubble density on the target surface, strong ultrasound image attenuation was observed.

Antigen-Antibody Reactions↗

PubMed1999

Follicular growth, estrus and pregnancy after fixed-time insemination in beef cows treated with intravaginal progesterone inserts and estradiol benzoate.

An experiment was performed to compare the effects of 3 short-term treatments with progesterone and estradiol benzoate (EB) on follicular growth, synchrony of estrus and pregnancy rate after fixed-time insemination in lactating postpartum beef cows. In Treatment 1 (n = 46), each cow received a progesterone-containing intravaginal insert for 7 d with injection of EB (2 mg, i.m.) at the time of device insertion. In Treatment 2 (n = 46), the insert was used for only 5 d with injection of EB (2 mg, i.m.) at the time of insertion. Cows in Treatment 3 (n = 47) received an insert for 5 d with no EB at the time of insertion. Each cow in the 3 groups received PGF2 alpha (25 mg, i.m.) at the time of insert removal, followed by EB (1 mg, i.m.) 30 h later. The cows were then inseminated 28 to 30 h after treatment with EB (58 to 60 h after insert removal). Treatment with 2 mg EB terminated the growth of the largest ovarian follicle (> 5 mm in diameter) at device insertion in 16/16 and 14/15 cows in Treatments 1 and 2, respectively. Estrus was detected within an 8-h target period (48 to 56 h after insert removal) in 93, 87 and 81% of cows in Treatments 1, 2 and 3, respectively (P > 0.05). Pregnancy rates at 39 d post insemination were 60, 50 and 51% for Treatments 1, 2 and 3, respectively (P > 0.05). The pregnancy rates did not differ between cows that were anovulatory or those that had ovulated before the initiation of treatments (54%), or among cows that were 28 to 40, 41 to 60 or > 60 days post partum at insemination (43, 59 and 54%, respectively). Treatment with progesterone inserts for 5 or 7 d, PGF2 alpha at the time of insert removal and 1 mg EB 30 h later induced the high degree of synchrony of estrus and ovulation necessary for fixed-time insemination.

Administration, Intravaginal↗

PubMed1999

Molecular barriers to biomaterial thrombosis by modification of surface proteins with polyethylene glycol.

For cardiovascular biomaterials, thrombosis, thromboembolism and vascular graft occlusion are believed to be precipitated by the adsorption of proteins containing adhesive ligands for platelets. Polyethylene-glycol-diisocyanate(PEG-diisocyanate, 3400 MW) may potentially react with protein amines to form molecular barriers on adsorbed proteins on biomaterials, thereby masking adhesive ligands and preventing acute surface thrombosis. To test this notion, PE, PTFE, and glass microconduits were pre-adsorbed with fibrinogen and treated with PEG-diisocyanate, non-reactive PEG-dihydroxyl, or remained untreated. Following perfusion of 111In-labeled platelets in whole human blood for 1 min (wall shear rate = 312 s(-1)), PEG-diisocyanate treated surfaces experienced 96%(PE), 97%(PTFE) and 94% (glass) less platelet deposition than untreated surfaces. Similar reductions were seen for PEG-diisocyanate versus PEG-dihydroxyl treatment. Low shear perfusions of plasma for one hour prior to blood contact did not reduce the inhibitory effect of PEG-diisocyanate. Platelet adhesion onto collagen coated glass coverslips and platelet deposition onto preclotted Dacron was also reduced by treatment with PEG-diisocyanate (93 and 91%, respectively). Protein-reactive PEG may thus have utility in forming molecular barriers on surface associated proteins to inhibit acute thrombosis on cardiovascular biomaterials.

Adsorption↗

PubMed1999

Effects of hydroxylapatite coating crystallinity on biosolubility, cell attachment efficiency and proliferation in vitro.

A hydroxylapatite (HA) coating with approximately 97% crystalline HA content (MP-1 treated HA coating, MP-HA) was tested in vitro for its biosolubility and cellular biocompatibility. The MP-HA coating was compared with a standard HA coating with approximately 63% crystallinity (SHA) and an amorphous HA coating with approximately 25% crystallinity (AHA), as well as a titanium (Ti) surface without HA coating as a control. The topographic study with scanning electron microscopy indicated that MP-HA appeared more coarse, with projected nodules which altered the shape of cells attached to the substrate. Biosolubility study indicated that MP-HA had the least effect on the culture medium pH, while AHA (P < 0.01) and SHA (P < 0.05) significantly raised the medium pH up to 8.2 and 7.75, respectively. X-ray diffraction (XRD) analysis showed essentially unchanged levels of the total soluble phases of all coatings after incubation with culture medium, except that the CaO phase was rapidly dissolved from AHA coatings and completely eliminated from SHA coatings. Cultures of human gingival fibroblasts on these HA coatings showed that MP-HA and SHA had about the same cell attachment efficiency which was relatively lower than that of AHA coatings. MP-HA generated significant higher cell proliferation rate relative to AHA (P < 0.01) and SHA (P < 0.05). This study indicated that surface chemistry and topography of lower crystallinity might be favorable to cell attachment, but that elevated medium pH might result in a cytotoxic effect that inhibits the proliferation of attached cells on coating surfaces.

Biocompatible Materials↗

PubMed1999

Highly crystalline MP-1 hydroxylapatite coating. Part I: In vitro characterization and comparison to other plasma-sprayed hydroxylapatite coatings.

A novel pressurized hydrothermal post-plasma-spray process, referred to as MP-1, has been developed to convert the crystalline non-HA and amorphous components of plasma-sprayed hydroxylapatite coating back into crystalline HA. No detrimental effects are observed on the strength of either the base metal or the coating. X-ray diffraction (XRD) and FTIR analysis, surface roughness, shear adhesion strength and calcium solubility testing were conducted on Calcitite coated samples before and after treatment with this process. Other commercially available coatings were also studied using XRD and solubility testing. Quantitative XRD data show that the MP-1 treatment increases the average crystalline HA content of the Calcitite coating from 77% to 96%, while the amorphous content decreases from 21% to 4%. Other commercially available dental implant coatings ranged in crystalline HA content from 45% to 73%, with amorphous phase content ranging from 29% to 62%. FTIR spectra for treated coatings were significantly more well defined, and showed an increase in peak separation and intensity. Surface roughness and shear adhesion strength were not affected by the treatment. In vitro solubility testing revealed that for all coatings there is an initial introduction of calcium into solution over the first 2 h of testing; however, the amount of calcium dissolved was significantly lower for the MP-1 coating. Under a pH and temperature representative of normal physiologic conditions, the rate of calcium dissolution for the MP-1 coating was significantly lower than that of the other commercial HA coatings. In increasingly acidic conditions, the MP-1 coating was compared to the Calcitite coating and was found to have a significantly slower rate of calcium release. The MP-1 treatment enhances typical HA coatings by increasing the crystalline HA content at the expense of the plasma-spray-induced soluble phases without a reduction in the strength of the coating. The resulting coatings exhibit significantly decreased in vitro solubility over a wide range of pH. The results of this solubility testing suggest that the treated coating may show significantly enhanced in vivo stability, even under the extreme conditions encountered during periods of infection or rigorous detoxification procedures. The significant differences between plasma-sprayed HA coatings reported here underscore the need for industry and academic researchers to raise the level of discourse and understanding of HA coatings. By offering consistent and accurate descriptions of coating compositions and methods of analysis, meaningful comparisons between different HA coatings can be made.

Adhesiveness↗

PubMed1999

Highly crystalline MP-1 hydroxylapatite coating. Part II: In vivo performance on endosseous root implants in dogs.

The in vivo integration strength and degree of bone apposition were compared for oral endosseous implants with different plasma-sprayed hydroxylapatite (HA) coatings. Pullout strength measurements and histological analysis were used to compare two different commercially available coating from the same manufacturer. One coating does not receive a post-plasma-spray treatment and contains about 75% crystalline HA. The other coating is treated with the MP-1 process, a pressurized hydrothermal post-plasma-spray process, which increases the coating composition to approximately 95% crystalline HA without changing the coating's adhesive or cohesive strength. Comparisons were made in dogs after healing times of 3 and 15 weeks in the mandible. No significant differences were found in either case between the two coatings. Two different methods were used to determine the degree of bone apposition at 15 weeks. Both methods confirmed that the MP-1 process does not affect the osseointegration rate of plasma-sprayed HA coatings. Qualitative histology data suggest that the treated coating is more stable than the control coating, especially in cases of direct soft tissue attachment to the implant. The present data suggest that extensive dissolution of calcium phosphate components into surrounding tissue is not a necessary precursor for direct apposition of bone to HA-coated implants.

Animals↗

PubMed1999

Measurement of hemostatic indexes in conjunction with transcranial doppler sonography in patients with ventricular assist devices.

BACKGROUND AND PURPOSE: Clinical thromboembolism (TE) remains an impediment to the chronic application of ventricular assist devices (VADs). Microembolic signals (MES) have been detected by transcranial Doppler ultrasound (TCD) in patients with VADs, although their origin and relation to TE remain undefined. We have investigated the hypothesis that hemostatic alterations are related to MES and that MES are associated with TE in a group of 27 VAD patients. METHODS: Indexes of coagulation, fibrinolysis, and cellular activation and aggregation were measured before and during the VAD implantation period in conjunction with TCD. Groups were defined on the basis of presence of MES, degree of MES showering, and incidence of TE. RESULTS: MES were observed in 67 (58%) of 115 of individual postoperative TCD measurements and in 21 (78%) of 27 patients. Of patients with TE, 10 (83%) of 12 had detectable MES compared with 11 (73%) of 15 patients without TE (P=0.66). MES were significantly associated with elevated thrombin generation during the implantation period, as reflected by plasma prothrombin fragment F1.2. Elevations in indexes of coagulation, platelet activation, and fibrinolysis relative to normal control subjects were found for patients with VADs with and without detected MES. CONCLUSIONS: Although no significant relation between MES and TE in VAD patients was found, the data support the hypothesis that MES are related to increased hemostatic activity in this patient group despite aggressive anticoagulant therapy.

Adolescent↗

PubMed1999

Effects of long-term estrogen implants in beef heifers.

Crossbred beef heifers (n = 78) were assigned randomly to one of three treatments. Heifers received either no implant, one estradiol-releasing implant (Compudose), or two estradiol-releasing implants. Heifers were implanted at birth and then reimplanted every 150 d. Calves were maintained with the cows until weaning at approximately 200 d of age. Heifers were placed in the feedlot as one group and fed a growing diet for 56 d. Following the growing phase, heifers were segregated into their respective treatment groups and fed until selected by industry buyers for harvest. Beginning at 1 yr of age and continuing every 14 d until puberty or harvest, heifers were palpated per rectum, and blood samples were collected for determination of ovarian activity and attainment of puberty. Serum progesterone of > or =1 ng/mL and(or) palpation of a detectable corpus luteum were criteria of puberty. At weaning and again at harvest, an x-ray was taken of the left front leg of six heifers selected randomly from each group. Metacarpal bones III and IV from the same animals were collected at harvest and transected for determination of epiphyseal plate closure. The x-ray scores and the actual measurements had a correlation of .94. Epiphyseal plate closure occurred in a dose-related manner, with heifers on the higher dose of estrogen having earlier plate closure than heifers on the lower dose. At harvest, reproductive tissues and carcass data were collected for all heifers. Eighteen of 25 untreated control heifers (P < .05), 6 of 26 heifers treated with one implant, and 2 of 26 heifers treated with two implants attained puberty by the end of the experiment. No differences (P > .10) were detected among treatment groups for carcass traits. These data suggest that early and continuous treatment of heifers with estradiol implants can retard reproductive function.

Animals↗

PubMed1999

Directions in cardiovascular tissue engineering.

The generation of tissue replacements or supplements for diseased tissue within the cardiovascular system has been the target of recent tissue engineering efforts. While clinically applicable methodologies remain to be achieved, important foundational experimentation has been performed in recent years to begin the move toward engineered tissue replacement therapy. Inadequacies of current valve, vessel, and other heart prostheses are reviewed briefly, followed by the discussion of selected progress in the supplementation or replacement of each cardiovascular component with tissue constructs. Topics addressed include the endothelialization of bio-prosthetic valves and synthetic vascular grafts, the generation of tissue valve leaflets and vascular conduits, the genetic manipulation of endothelial cells with implications for graft endothelialization, and cardiomyoplasty achieved through cellular and genetic means.

Animals↗

PubMed1998

Microbubbles targeted to intercellular adhesion molecule-1 bind to activated coronary artery endothelial cells.

BACKGROUND: Preclinical atherosclerosis is associated with increased endothelial cell (EC) expression of leukocyte adhesion molecules (LAMs), which mediate monocyte adhesion during atherogenesis. Identification of cell-surface LAMs may uniquely allow assessment of endothelial function, but there are no in vivo methods for detecting LAMs. We tested a new microbubble designed to bind to and allow specific ultrasound detection of intercellular adhesion molecule-1 (ICAM-1). METHODS AND RESULTS: A perfluorobutane gas-filled lipid-derived microsphere with monoclonal antibody to ICAM-1 covalently bound to the bubble shell was synthesized. Bubbles with either nonspecific IgG or no protein on the shell were synthesized as controls. Coverslips of cultured human coronary artery ECs were placed in a parallel-plate perfusion chamber and exposed to 1 of the 3 microbubble species, followed by perfusion with culture medium. Experiments were performed with either normal or interleukin-1beta-activated ECs overexpressing ICAM-1, and bubble adherence was quantified with epifluorescent videomicroscopy. There was limited adherence of control bubbles to normal or activated ECs, whereas a 40-fold increase in adhesion occurred when anti-ICAM-1-conjugated bubbles were exposed to activated ECs compared with normal ECs (8.1+/-3.5 versus 0.21+/-0.09 bubbles per cell, respectively, P<0.001). Although diminished, this difference persisted even after perfusion at higher wall shear rates. CONCLUSIONS: A gas-filled microbubble with anti-ICAM-1 antibody on its shell specifically binds to activated ECs overexpressing ICAM-1. Diagnostic ultrasound in conjunction with targeted contrast agents has the unique potential to characterize cell phenotype in vivo.

Antibodies, Monoclonal↗