RESUMEN
Alemtuzumab infusion is rarely associated with serious cardiac toxicity. We report a case of acute troponin-negative chest pain with dynamic T-wave changes, immediately following first infusion of alemtuzumab in a patient with multiple sclerosis. The chest pain and ECG (electrocardiogram) changes improved with cessation of alemtuzumab and conservative management. The presumed cause was infusion-associated cytokine release, but the precise mechanism is unknown.
Asunto(s)
Alemtuzumab/efectos adversos , Cardiotoxicidad/etiología , Factores Inmunológicos/efectos adversos , Esclerosis Múltiple Recurrente-Remitente/tratamiento farmacológico , Electrocardiografía , Femenino , Humanos , Infusiones Intravenosas , Adulto JovenRESUMEN
The zygapophysial joint, a diarthrodial joint commonly referred to as the facet joint, plays a pivotal role in back pain, a condition that has been a leading cause of global disability since 1990. Along with the intervertebral disc, the facet joint supports spinal motion and aids in spinal stability. Highly susceptible to early development of osteoarthritis, the facet is responsible for a significant amount of pain in the low-back, mid-back, and neck regions. Current noninvasive treatments cannot offer long-term pain relief, while invasive treatments can relieve pain but fail to preserve joint functionality. This review presents an overview of the facet in terms of its anatomy, functional properties, problems, and current management strategies. Furthermore, this review introduces the potential for regeneration of the facet and particular engineering strategies that could be employed as a long-term treatment.
Asunto(s)
Osteoartritis/fisiopatología , Regeneración , Columna Vertebral/fisiopatología , Articulación Cigapofisaria/fisiopatología , Animales , Dolor de Espalda/fisiopatología , Cartílago Articular/fisiopatología , Comorbilidad , Humanos , Inyecciones Intraarticulares , Rodilla/anatomía & histología , Terminaciones Nerviosas , Ortopedia , Escoliosis/complicaciones , Estenosis Espinal/complicaciones , Columna Vertebral/fisiología , Espondilolistesis/complicaciones , Membrana Sinovial/patología , Articulación Cigapofisaria/anatomía & histología , Articulación Cigapofisaria/cirugíaRESUMEN
Astrocytic necrosis is a prominent pathological feature of neuromyelitis optica (NMO) lesions and is clinically relevant. We report 5 NMO-related cases, all with longitudinally extensive lesions in the upper cervical cord, who underwent cervical cord (1) H-magnetic resonance spectroscopy. Lower myo-inositol/creatine values, suggesting astrocytic damage, were consistently found within the NMO lesions when compared with healthy controls and patients with multiple sclerosis (MS), who showed at least 1 demyelinating lesion at the same cord level. Therefore, the in vivo quantification of myo-inositol may distinguish NMO from MS. This is an important step toward developing imaging markers for clinical trials in NMO.
Asunto(s)
Astrocitos/patología , Inositol/metabolismo , Neuromielitis Óptica/patología , Médula Espinal/patología , Adulto , Astrocitos/metabolismo , Biomarcadores , Vértebras Cervicales/patología , Diagnóstico Diferencial , Femenino , Humanos , Inositol/deficiencia , Masculino , Persona de Mediana Edad , Esclerosis Múltiple/diagnóstico , Esclerosis Múltiple/metabolismo , Esclerosis Múltiple/patología , Neuromielitis Óptica/diagnóstico , Neuromielitis Óptica/metabolismo , Médula Espinal/metabolismoRESUMEN
Human articular chondrocytes (hACs) are scarce and lose their chondrogenic potential during monolayer passaging, impeding their therapeutic use. This study investigated (a) the translatability of conservative chondrogenic passaging and aggregate rejuvenation on restoring chondrogenic properties of hACs passaged up to P9; and (b) the efficacy of a combined treatment of transforming growth factor-beta 1 (TGF-ß1) (T), chondroitinase-ABC (C), and lysyl oxidase-like 2 (L), collectively termed TCL, on engineering functional human neocartilage via the self-assembling process, as a function of passage number up to P11. Here, we show that aggregate rejuvenation enhanced glycosaminoglycan (GAG) content and type II collagen staining at all passages and yielded human neocartilage with chondrogenic phenotype present up to P7. Addition of TCL extended the chondrogenic phenotype to P11 and significantly enhanced GAG content and type II collagen staining at all passages. Human neocartilage derived from high passages, treated with TCL, displayed mechanical properties that were on par with or greater than those derived from low passages. Conservative chondrogenic passaging and aggregate rejuvenation may be a viable new strategy (a) to address the perennial problem of chondrocyte scarcity and (b) to successfully rejuvenate the chondrogenic phenotype of extensively passaged cells (up to P11). Furthermore, tissue engineering human neocartilage via self-assembly in conjunction with TCL treatment advances the clinical use of extensively passaged human chondrocytes for cartilage repair.
Asunto(s)
Cartílago Articular , Condrocitos , Diferenciación Celular , Células Cultivadas , Condrogénesis , Humanos , Rejuvenecimiento , Ingeniería de TejidosRESUMEN
BACKGROUND: This pilot study was designed to investigate the efficacy of a cognitive behavioral treatment for anger. METHOD: Twelve (5 men and 7 women) outpatient adults completed 2-hour group sessions for 16 sessions. Participants were diagnosed with 29 Axis I and 34 Axis II disorders with high rates of comorbidity. Empirically supported techniques of skills training, cognitive restructuring, and relaxation were utilized. In this protocol, cognitive restructuring emphasized the use of the ABC model to understand anger episodes and the Rational Emotive Behavior Therapy (REBT) techniques of disputing irrational beliefs and rehearsing rational coping statements, but additional cognitive techniques were used, e.g. self-instructional training (SIT). Skills training included problem-solving and assertiveness. Relaxation training was paced respiration. Motivational interviewing, imaginal exposure with coping, and relapse prevention were also included. RESULTS: Significant improvements were found from pre- to post-treatment on the following measures: the Trait Anger Scale of the State-Trait Anger Expression Inventory-II; and Anger Disorder Scale total scores; idiosyncratic anger measurements of situational intensity and symptom severity; and the Beck Depression Inventory-II. CONCLUSIONS: In order to extend the significant research findings of this pilot study, future investigations should involve larger sample sizes, populations drawn from various settings, and contact control groups.
Asunto(s)
Ira , Terapia Cognitivo-Conductual/métodos , Trastornos Mentales/terapia , Psicoterapia Racional-Emotiva/métodos , Adaptación Psicológica , Agresión/psicología , Asertividad , Terapia Combinada , Femenino , Hostilidad , Humanos , Masculino , Trastornos Mentales/diagnóstico , Trastornos Mentales/psicología , Inventario de Personalidad/estadística & datos numéricos , Proyectos Piloto , Solución de Problemas , Psicometría , Terapia por Relajación , Resultado del TratamientoRESUMEN
The immunosuppressive tumor microenvironment constitutes a significant hurdle to immune checkpoint inhibitor responses. Both soluble factors and specialized immune cells, such as regulatory T cells (Treg), are key components of active intratumoral immunosuppression. Inducible costimulatory receptor (ICOS) can be highly expressed in the tumor microenvironment, especially on immunosuppressive Treg, suggesting that it represents a relevant target for preferential depletion of these cells. Here, we performed immune profiling of samples from tumor-bearing mice and patients with cancer to demonstrate differential expression of ICOS in immune T-cell subsets in different tissues. ICOS expression was higher on intratumoral Treg than on effector CD8 T cells. In addition, by immunizing an Icos knockout transgenic mouse line expressing antibodies with human variable domains, we selected a fully human IgG1 antibody called KY1044 that bound ICOS from different species. We showed that KY1044 induced sustained depletion of ICOShigh T cells but was also associated with increased secretion of proinflammatory cytokines from ICOSlow effector T cells (Teff). In syngeneic mouse tumor models, KY1044 depleted ICOShigh Treg and increased the intratumoral TEff:Treg ratio, resulting in increased secretion of IFNγ and TNFα by TEff cells. KY1044 demonstrated monotherapy antitumor efficacy and improved anti-PD-L1 efficacy. In summary, we demonstrated that using KY1044, one can exploit the differential expression of ICOS on T-cell subtypes to improve the intratumoral immune contexture and restore an antitumor immune response.
Asunto(s)
Anticuerpos Monoclonales/farmacología , Proteína Coestimuladora de Linfocitos T Inducibles/metabolismo , Linfocitos T Reguladores/inmunología , Microambiente Tumoral/efectos de los fármacos , Animales , Anticuerpos Monoclonales/inmunología , Antígeno B7-H1/inmunología , Línea Celular Tumoral , Citocinas/metabolismo , Femenino , Humanos , Tolerancia Inmunológica/efectos de los fármacos , Proteína Coestimuladora de Linfocitos T Inducibles/inmunología , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BLRESUMEN
Strategies to overcome the limited availability of human articular chondrocytes and their tendency to dedifferentiate during expansion are required to advance their clinical use and to engineer functional cartilage on par with native articular cartilage. This work sought to determine whether a biochemical factor (transforming growth factor-ß1 [T]), a biophysical agent (chondroitinase-ABC [C]), and a collagen crosslinking enzyme (lysyl oxidase-like 2 [L]) are efficacious in forming three-dimensional human neocartilage from expanded human articular chondrocytes. Among the treatment regimens, the combination of the three stimuli (TCL treatment) led to the most robust glycosaminoglycan content, total collagen content, and type II collagen production. In particular, TCL treatment synergistically increased tensile stiffness and strength of human neocartilage by 3.5-fold and 3-fold, respectively, over controls. Applied to two additional donors, the beneficial effects of TCL treatment appear to be donor independent; tensile stiffness and strength were increased by up to 8.5-fold and 3-fold, respectively, over controls. The maturation of human neocartilage in response to TCL treatment was examined following 5 and 8 weeks of culture, demonstrating maintenance or further enhancement of functional properties. The present study identifies a novel strategy for engineering human articular cartilage using serially passaged chondrocytes.
Asunto(s)
Aminoácido Oxidorreductasas/farmacología , Cartílago/metabolismo , Condrocitos/metabolismo , Condroitina ABC Liasa/farmacología , Ingeniería de Tejidos , Factor de Crecimiento Transformador beta1/farmacología , Adulto , Cartílago/citología , Condrocitos/citología , Humanos , Masculino , Resistencia a la TracciónRESUMEN
About 10-15% of patients with multiple sclerosis (MS) present with gradually increasing neurological disability, a disorder known as primary-progressive multiple sclerosis (PPMS). Compared with relapse-onset multiple sclerosis, people with PPMS are older at onset and a higher proportion are men. Inflammatory white-matter lesions are less evident but diffuse axonal loss and microglial activation are seen in healthy-looking white matter, in addition to cortical demyelination, and quantitative MRI shows atrophy and intrinsic abnormalities in the grey matter and the white matter. Spinal cord atrophy corresponds to the usual clinical presentation of progressive spastic paraplegia. Although neuroaxonal degeneration seems to underlie PPMS, the pathogenesis and the extent to which immune-mediated mechanisms operate is unclear. MRI of the brain and spinal cord, and examination of the CSF, are important investigations for diagnosis; conventional immunomodulatory therapies, such as interferon beta and glatiramer acetate, are ineffective. Future research should focus on the clarification of the mechanisms of axonal loss, improvements to the design of clinical trials, and the development of effective neuroprotective treatments.
Asunto(s)
Esclerosis Múltiple Crónica Progresiva/diagnóstico , Esclerosis Múltiple Crónica Progresiva/tratamiento farmacológico , Encéfalo/patología , Diagnóstico Diferencial , Humanos , Imagen por Resonancia Magnética , Esclerosis Múltiple Crónica Progresiva/genética , Esclerosis Múltiple Crónica Progresiva/fisiopatologíaRESUMEN
The facet joint, a synovial joint located on the posterior-lateral spine, is highly susceptible to degenerative changes and plays a significant role in back-related morbidities. Despite its significance, the facet is rarely studied and thus current treatment strategies are lacking. This study aimed to characterize, for the first time, the properties of human, pig, monkey, and rabbit lumbar facet cartilage providing much-needed design criteria for tissue engineering approaches. In this study, where possible, the facet's morphological, histological, mechanical, and biochemical properties were evaluated. Comparisons between the properties of the inferior and superior facet surfaces, as well as among spinal levels were performed within each species. In addition, interspecies comparisons of the properties were determined. The human facet joint was found to be degenerated; 100% of joint surfaces showed signs of pathology and approximately 71% of these were considered to be grade 4. Joint morphology varied among species, demonstrating that despite the mini-pig facet being closest to the human in terms of width and length, it was far more curved than the human or any of the other species. No notable differences were found in the mini-pig, monkey, and rabbit mechanical and biochemical properties, suggesting that these species, despite morphological differences, may serve as suitable animal models for studying structure-function relationships of the human facet joint. The characterization data reported in this study may increase our understanding of this ill-described joint as well as provide the foundation for the development of new treatments such as tissue engineering. STATEMENT OF SIGNIFICANCE: This work provides the first comprehensive description of the properties of lumbar facet joint cartilage. Importantly, this work establishes that histological, biochemical, and mechanical properties are comparable between bipedal and quadrupedal animals, helping to guide future selection of appropriate animal models. This work also suggests that the human facet joint is highly susceptible to pathology. The mechanical properties of facet cartilage, found to be inferior to those of other synovial joints, provide a greater understanding of the joint's structure-function relationships as well as the potential etiology of facet joint pathology. Lastly, this work will serve as the foundation for the development of much-needed facet joint treatments, especially those based on tissue engineering approaches.
Asunto(s)
Cartílago/química , Articulación Cigapofisaria/química , Animales , Cartílago/patología , Femenino , Humanos , Macaca mulatta , Masculino , Conejos , Especificidad de la Especie , Porcinos , Articulación Cigapofisaria/patologíaAsunto(s)
Factores Inmunológicos/uso terapéutico , Esclerosis Múltiple Recurrente-Remitente/tratamiento farmacológico , Péptidos/uso terapéutico , Progresión de la Enfermedad , Acetato de Glatiramer , Humanos , Interferón beta/uso terapéutico , Imagen por Resonancia Magnética , Esclerosis Múltiple Recurrente-Remitente/diagnóstico , Pronóstico , Ensayos Clínicos Controlados Aleatorios como Asunto , SíndromeRESUMEN
Approximately 10% of patients with multiple sclerosis (MS) run a primary progressive course characterised by an accumulation of neurological deficits without relapse or remission. Designing therapeutic trials in primary progressive MS (PPMS) has presented several problems. Patient recruitment may be difficult because of the relative rarity of PPMS and historically has been hindered by the lack of specific diagnostic criteria. There has been a limited choice of validated outcome measures, although, in recent studies, the MS functional composite measure and magnetic resonance imaging measures of lesion load and atrophy have been widely used. Despite these problems, several trials have been designed specifically for PPMS, including exploratory randomised controlled trials of interferon-beta-1a and interferon-beta-1b and mitoxantrone, a phase III trial of glatiramer acetate, and an open-label study of riluzole. Patients with PPMS have also been included in randomised controlled trials of azathioprine, methotrexate, cladribine, intravenous immunoglobulin and cyclophosphamide, and open-label studies of haematopoietic stem cell transplantation and pirfenidone in progressive MS. However, no treatment has been proven definitively to modify the course of the disease. Looking to the future, therapeutic agents should aim to target the underlying pathogenic mechanisms in PPMS. As a result of the relative lack of inflammation in PPMS, neuroprotective agents that target neuronal loss directly, rather than inflammation, may be more worthwhile. However, further investigation into the pathogenic mechanisms in PPMS is required to guide the development of future therapeutic agents.
Asunto(s)
Factores Inmunológicos/uso terapéutico , Esclerosis Múltiple Crónica Progresiva/tratamiento farmacológico , Progresión de la Enfermedad , Humanos , Interferón beta/uso terapéutico , Resultado del TratamientoRESUMEN
Varying degrees of calcification are present in most abdominal aortic aneurysms (AAAs). However, their impact on AAA failure properties and AAA rupture risk is unclear. The aim of this work is evaluate and compare the failure properties of partially calcified and predominantly fibrous AAA tissue and investigate the potential reasons for failure. Uniaxial mechanical testing was performed on AAA samples harvested from 31 patients undergoing open surgical repair. Individual tensile samples were divided into two groups: fibrous (n=31) and partially calcified (n=38). The presence of calcification was confirmed by fourier transform infrared spectroscopy (FTIR). A total of 69 mechanical tests were performed and the failure stretch (λf), failure stress (σf) and failure tension (Tf) were recorded for each test. Following mechanical testing, the failure sites of a subset of both tissue types were examined using scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) to investigate the potential reasons for failure. It has been shown that the failure properties of partially calcified tissue are significantly reduced compared to fibrous tissue and SEM and EDS results suggest that the junction between a calcification deposit and the fibrous matrix is highly susceptible to failure. This study implicates the presence of calcification as a key player in AAA rupture risk and provides further motivation for the development of non-invasive methods of measuring calcification.
Asunto(s)
Aneurisma de la Aorta Abdominal/patología , Aneurisma de la Aorta Abdominal/fisiopatología , Rotura de la Aorta/patología , Rotura de la Aorta/fisiopatología , Calcificación Fisiológica , Fenómenos Mecánicos , Anciano , Fenómenos Biomecánicos , Femenino , Humanos , MasculinoRESUMEN
BACKGROUND: Interferon- beta (IFNbeta) acts by a variety of mechanisms in relapsing-remitting multiple sclerosis (MS). One of these is a cellular down-regulation of gelatinase B or matrix metalloproteinase-9 (MMP-9), which is known from biochemical, biological and immunohistochemical evidences to play a disease-promoting role in MS. AIMS: a) To investigate the influence of IFNbeta-1a (30 or 60 micro g I. M./week) on serum MMP-9 levels in patients with primary progressive MS (PPMS). b) To correlate serum MMP-9 levels with clinical and magnetic resonance imaging (MRI) findings. METHODS: Serial blood samples were collected every 3 months from 49 patients participating in a phase II trial of IFNbeta-1a in PPMS. Serum MMP-9 was quantified by ELISA and correlations with clinical (EDSS) as well as MRI findings (brain and spinal cord atrophy, ventricular volume, T1 and T2 lesion load) were calculated. RESULTS: No significant differences were found between serial serum MMP-9 levels in IFNbeta-treated versus placebo-treated patients. MMP-9 levels did not differ between patients who progressed or did not progress during the study interval. Although mean absolute serum MMP-9 levels over the study period correlated with an increase in T2 lesion load (relative T2 change: r=0.51, p<0.001; absolute T2 change: r=0.30, p=0.038), absolute increase in brain ventricular volume (r=0.29, p=0.05) and increased brain atrophy (r=0.35, p=0.02), only the correlation with T2 lesion load was sustained throughout the study period. No correlations were found between MMP-9 levels and relative changes in ventricular volume or with relative/absolute changes in T1 lesion load and in spinal cord atrophy. None of the MRI measures correlated with MMP-9 changes between baseline levels and those on treatment. CONCLUSION: Although some evidence suggests a down-regulating effect of IFNbeta on MMP-9, this was not confirmed for a once weekly intramuscular dose of IFNbeta-1a in patients with PPMS. The sustained correlation between serum MMP-9 and changes in T2 volumes, and the lack of correlation with clinical or MRI measures of disease progression may suggest that MMP-9 is more directly related to non-specific central nervous system damage than to axonal loss.
Asunto(s)
Interferón beta/uso terapéutico , Metaloproteinasa 9 de la Matriz/sangre , Esclerosis Múltiple Crónica Progresiva/sangre , Esclerosis Múltiple Crónica Progresiva/tratamiento farmacológico , Adulto , Femenino , Humanos , Interferón beta-1a , Imagen por Resonancia Magnética/métodos , Masculino , Persona de Mediana Edad , Esclerosis Múltiple Crónica Progresiva/patologíaRESUMEN
There is currently no disease-modifying treatment proven to be of efficacy in primary progressive multiple sclerosis (PPMS). However, a number of therapeutic trials have recently been specifically designed for this group. These include a randomised controlled trial of interferon beta-1a which is discussed here. It is hoped that therapeutics in primary progressive multiple sclerosis will continue to expand and effective therapeutic agents will be developed.
Asunto(s)
Adyuvantes Inmunológicos/uso terapéutico , Interferón beta/uso terapéutico , Esclerosis Múltiple Crónica Progresiva/tratamiento farmacológico , Adolescente , Adulto , Antineoplásicos/uso terapéutico , Evaluación de la Discapacidad , Progresión de la Enfermedad , Relación Dosis-Respuesta a Droga , Estudios de Seguimiento , Acetato de Glatiramer , Humanos , Interferón beta-1a , Interferon beta-1b , Imagen por Resonancia Magnética , Persona de Mediana Edad , Mitoxantrona/uso terapéutico , Fármacos Neuroprotectores/uso terapéutico , Péptidos/uso terapéutico , Riluzol/uso terapéutico , Resultado del TratamientoRESUMEN
Quantitative electroencephalographic (qEEG) profiles were studied in cocaine dependent patients in response to cocaine cue exposure. Using neurometric analytical methods, the spectral power of each primary bandwidth was computed and topographically mapped. Additional measures of cue-reactivity included cocaine craving, anxiety and related subjective ratings, and physiological measures of skin conductance, skin temperature, heart rate, and plasma cortisol and HVA levels. Twenty-four crack cocaine-dependent subjects were tested for their response to tactile, visual and audio cues related to crack cocaine or neutral items. All measures were analyzed for significant difference by comparing cocaine versus neutral cue conditions. An increase in cocaine craving, anxiety and related subjective ratings, elevated plasma cortisol levels, and a decrease in skin temperature, were induced by cocaine cue exposure. Distinct qEEG profiles were found during the paraphernalia handling and video viewing (eyes-open), and guided imagery (eyes-closed), phases of cocaine cue exposure. During paraphernalia handling and video viewing, there was an increase in beta activity accompanied by a drop in delta power in the frontal cortex, and an increase in beta mean frequency in the occipital cortex. In contrast, during guided imagery there was an increase in theta and delta power in the frontal cortex, and an increase in beta power in the occipital cortex. Correlation analyses revealed that cue-induced anxiety during paraphernalia handling and video viewing was associated with reduced high frequency and enhanced low frequency EEG activity. These findings demonstrated that EEG activation during cue-induced cocaine craving may be topographically mapped and subsequently analyzed for functional relevance.
Asunto(s)
Conducta Adictiva/diagnóstico , Conducta Adictiva/fisiopatología , Trastornos Relacionados con Cocaína/diagnóstico , Trastornos Relacionados con Cocaína/fisiopatología , Condicionamiento Psicológico , Señales (Psicología) , Diagnóstico por Computador/métodos , Electroencefalografía/métodos , Adolescente , Adulto , Anciano , Conducta Adictiva/complicaciones , Conducta Adictiva/psicología , Mapeo Encefálico/métodos , Trastornos Relacionados con Cocaína/complicaciones , Trastornos Relacionados con Cocaína/psicología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estimulación Luminosa/métodos , Valor Predictivo de las Pruebas , Estadística como AsuntoRESUMEN
S100B belongs to a family of calcium-binding proteins implicated in intracellular and extracellular regulatory activities. This study of serum S100B in primary progressive multiple sclerosis (PPMS) is based on data obtained from a randomized, controlled trial of Interferon beta-1a in subjects with PPMS. The key questions were whether S100B levels were associated with either disability or MRI findings in primary progressive MS and whether Interferon beta-1a has an effect on their S100B levels. Serial serum S100B levels were measured using an ELISA method. The results demonstrated that serum S100B is not related to either disease progression or MRI findings in subjects with primary progressive MS given Interferon beta-1a. Furthermore there is no correlation between S100B levels and the primary and secondary outcome measures.
Asunto(s)
Interferón beta/uso terapéutico , Esclerosis Múltiple Crónica Progresiva/sangre , Esclerosis Múltiple Crónica Progresiva/tratamiento farmacológico , Factores de Crecimiento Nervioso/sangre , Proteínas S100/sangre , Adulto , Estudios de Casos y Controles , Femenino , Humanos , Interferón beta-1a , Imagen por Resonancia Magnética , Masculino , Factores de Crecimiento Nervioso/metabolismo , Subunidad beta de la Proteína de Unión al Calcio S100 , Proteínas S100/metabolismoRESUMEN
BACKGROUND: Preservation of the native artery׳s functionality can be important in both clinical and experimental applications. Although, simple cryopreservation techniques offer an attractive solution to this problem, the extent to which freezing affects the tissue׳s properties is widely debated. Earlier assessments of the mechanical properties post-freezing have been limited by one or more of the following: small sample numbers, uncontrolled inter-specimen/animal variability, failure to account for the impact of potential errors in thickness measurements, short storage times and uniaxial test methods. MATERIAL AND METHODS: Biaxial mechanical tests were performed on porcine aortic samples (n=89) extracted from superior, middle and inferior regions of five aortas, stored in isotonic saline at -20°C for 1 day, 1 week, 1, 6 and 12 months, thawed and retested. The sample׳s weight and thickness were also measured pre and post-freezing. A total of 178 tests were performed and elastic modulus was assessed by calculating the slope of the Cauchy stress-stretch curve at the low and high stretch regions in both the circumferential (θ) and longitudinal (L) directions. RESULTS: The weight of the samples increased post-freezing. However, in general, no significant difference was found between the elastic modulus of porcine aortic tissue before and after freezing at -20°C and was unaffected by storage time. Although more accurate measuring instruments are warranted to confirm this finding, minor changes to the elastic modulus as a result of freezing were negatively correlated with regional variances i.e. changes in the elastic modulus decreased from the superior to the inferior region. CONCLUSIONS: These results indicate that for applications which require preservation of the gross mechanical properties, storing the tissue at -20°C in isotonic saline, for an extended period of time, is acceptable.
Asunto(s)
Aorta/citología , Criopreservación , Fenómenos Mecánicos , Porcinos , Animales , Fenómenos Biomecánicos , Ensayo de MaterialesRESUMEN
Intraluminal thrombus (ILT) is present in 75% of clinically-relevant abdominal aortic aneurysms (AAAs) yet, despite much research effort, its role in AAA biomechanics remains unclear. The aim of this work is to further evaluate the biomechanics of ILT and determine if different ILT morphologies have varying mechanical properties. Biaxial mechanical tests were performed on ILT samples harvested from 19 patients undergoing open surgical repair. ILT were separated into luminal, medial and medial/abluminal layers. A total of 356 tests were performed and the Cauchy stress (σ) and tangential modulus (TM) at a stretch ratio (λ) of 1.14 were recorded for each test in both the circumferential (θ) and longitudinal (L) directions. Our data revealed three distinct types of ILT morphologies, each with a unique set of mechanical properties. All ILT layers were found to be isotropic and inhomogeneous. Type 1 (n=10) was a multi-layered ILT (thick medial/abluminal layer) whose strength and stiffness decreased gradually from the luminal to the medial/abluminal layer. Type 2 (n=6) was a multi-layered ILT (thin/highly degraded medial/abluminal layer) whose strength and stiffness decreased abruptly between the luminal and medial/abluminal layer and Type 3 (n=3) is a single layered ILT with a lower strength and stiffness than Types 1 and 2. In a sub-study, we found the luminal layer to be stronger and stiffer in the posterior than the anterior region. This work provides further insights to the biomechanical behaviour of ILT and the use of our ILT classification may be useful in future studies.
Asunto(s)
Aneurisma de la Aorta Abdominal/fisiopatología , Trombosis/fisiopatología , Anciano , Anisotropía , Fenómenos Biomecánicos , Simulación por Computador , Femenino , Humanos , Masculino , Persona de Mediana Edad , Modelos Teóricos , Estrés Mecánico , Resistencia a la Tracción , Tomografía Computarizada por Rayos XRESUMEN
Rupture of the abdominal aortic aneurysm (AAA) occurs when the local wall stress exceeds the local wall strength. Knowledge of AAA wall mechanics plays a fundamental role in the development and advancement of AAA rupture risk assessment tools. Therefore, the aim of this study is to evaluate the biaxial mechanical properties of AAA tissue. Multiple biaxial test protocols were performed on AAA samples harvested from 28 patients undergoing open surgical repair. Both the Tangential Modulus (TM) and stretch ratio (λ) were recorded and compared in both the circumferential (Ï´) and longitudinal (L) directions at physiologically relevant stress levels, the influence of patient specific factors such as sex, age AAA diameter and status were examined. The biomechanical response was also fit to a hyperplastic material model. The AAA tissue was found to be anisotropic with a greater tendency to stiffen in the circumferential direction compared to the longitudinal direction. An anisotropic hyperelastic constitutive model represented the data well and the properties were not influenced by the investigated patient specific factors however, a future study utilizing a larger cohort of patients is warranted to confirm these findings. This work provides further insights on the biomechanical behavior of AAA and may be useful in the development of more reliable rupture risk assessment tools.