The focal mechanical properties of normal and diseased porcine aortic valve tissue measured by a novel microindentation device.

Cells sense and respond to the heterogeneous mechanical properties of their tissue microenvironment, with implications for the development of many diseases, including cancer, fibrosis, and aortic valve disease. Characterization of tissue mechanical heterogeneity on cellular length scales of tens of micrometers is thus important for understanding disease mechanobiology. In this study, we developed a low-cost bench-top microindentation system to readily map focal microscale soft tissue mechanical properties. The device was validated by comparison with atomic force microscopy nanoindentation of polyacrylamide gels. To demonstrate its utility, the device was used to measure the focal microscale elastic moduli of normal and diseased porcine aortic valve leaflet tissue. Consistent with previous studies, the fibrosa layer of intact leaflets was found to be 1.91-fold stiffer than the ventricularis layer, with both layers exhibiting significant heterogeneity in focal elastic moduli. For the first time, the microscale compressive moduli of focal proteoglycan-rich lesions in the fibrosa of early diseased porcine aortic valve leaflets were measured and found to be 2.44-fold softer than those of normal tissue. These data provide new insights into the tissue micromechanical environment in valvular disease and demonstrate the utility of the microindentation device for facile measurement of the focal mechanical properties of soft tissues.

Clinico-Hematological Findings of Acute Pediatric Visceral Leishmaniasis Referred to the Northeast of Iran during 2005-2015.

BACKGROUND: To characterize the epidemiological, clinical, hematological and biochemical features of 33 cases hospitalized with pediatric visceral leishmaniasis (PVL) in North Khorasan Province of Iran from 2005 to 2015. METHODS: The serological, hematological and biochemical tests were employed in 33 children between 8 months to 6 yr with a final diagnosis of acute visceral leishmaniasis (VL). The diagnosis of VL was established by microscopic demonstration of Leishmania spp. amastigotes inactive bone marrow aspiration (BMA). RESULTS: The most common presenting features were anemia (82.5%), fever (75%), and hepatosplenomegaly (45.4%). Various hematological parameters showed that most patients were suffering from moderate to severe microcytic hypochromic anemia (78.8% had RBC count less than 4 million cells/ul, 67.7% Hb less than 8 fl). 66.7% of them were leukopenic (WBC: less than 5× 10 3 /µL) and 24.2% had decreased platelet counts. Pancytopenia was observed in 18.2% of cases. MCV, MCH, and MCHC levels were below the reference range in 88%, 90% and 85.1% of the patients respectively. Moreover, aspartate transaminase (AST) and alanine transaminase (ALT) levels were increased in 53.33% and 6.66% of the patients respectively. 92.9% of cases were C-reactive protein (CRP) positive. Bone marrow was found hyper-cellular in all of them, and myeloid to erythroid ratio (M/E) was more than 4 in 39.1% of cases. Plasma cells slightly were increased in 60% of patients and megakaryocytes were decreased in thrombocytopenic patients. CONCLUSION: Bone marrow/splenic aspiration still remains the gold standard test despite its risk and pain for patients.

Association between carotid intima-media thickness and ulcerative colitis: a systematic review and meta-analysis.

BACKGROUND: Early detection of atherosclerosis is an essential means of decreasing cardiovascular events and its associated mortality. Systemic inflammatory diseases such as ulcerative colitis (UC), are thought to be a contributing factor to atherosclerosis due to the rise of inflammatory cytokines. OBJECTIVE: The aim of this systematic review and meta-analysis was to assess the association between atherosclerosis and UC. METHODS: This systematic review and meta-analysis was performed in February 2017 with no date restrictions. PubMed, Cochrane Library and Embase were searched to discover all available observational studies on atherosclerosis among UC patients. The STROBE criteria were used to assess the quality of the included articles. Heterogeneity was assessed by the I-square statistic and publication bias with funnel plot and Egger's regression test. Overall summary mean difference was calculated as study effect size using random effect model. Comprehensive Meta-Analysis Software version 2.2 was used to perform analyses. RESULTS: A total of 5 articles met our eligibility criteria. We included a sum of 206 UC patients and 229 non-UC individuals in our review with a mean difference of c-IMT ranged from 0.03±0.0 to 0.16±0.03 mm, and a pooled mean difference of 0.127 mm (95% CI 0.058-0.195: I2 =90.266%). Potential publication bias did not exist for the UC. CONCLUSION: Our findings showed significant differences in carotid intima-media thickness among UC and Non-UC groups, making c-IMT a viable choice as a predicting marker for atherosclerosis. Thus, we suggest that policy makers assess and consider its application in future protocols for the follow up and management of UC patients.

Microdevice arrays with strain sensors for 3D mechanical stimulation and monitoring of engineered tissues.

Native and engineered tissue development are regulated by the integrative effects of multiple microenvironmental stimuli. Microfabricated bioreactor array platforms can efficiently dissect cue-response networks, and have recently integrated critical 2D and 3D mechanical stimulation for greater physiological relevance. However, a limitation of these approaches is that assessment of tissue functional properties is typically limited to end-point analyses. Here we report a new deformable membrane platform with integrated strain sensors that enables mechanical stretching or compression of 3D cell-hydrogel arrays and simultaneous measurement of hydrogel construct stiffness in situ. We tested the ability of the integrated strain sensors to measure the evolution of the stiffness of cell-hydrogel constructs for two cases. First, we demonstrated in situ stiffness monitoring of degradable poly (ethylene glycol)-norbornene (PEG-NB) hydrogels embedded with mesenchymal stromal cells (MSCs) and cultured with or without cyclic tensile stimulation for up to 15 days. Whereas statically-cultured hydrogels degraded and softened throughout the culture period, mechanically-stimulated gels initially softened and then recovered their stiffness corresponding to extensive cell network and collagen production. Second, we demonstrated in situ measurement of compressive stiffening of MSC-seeded PEG-NB gels cultured statically under osteogenic conditions, corresponding to increased mineralization and cellularization. This measurement technique can be generalized to other relevant bioreactor and organ-on-a-chip platforms to facilitate online, non-invasive, and high-throughput functional analysis, and to provide insights into the dynamics of engineered tissue development that are otherwise not available.

Polyacrylamide gel substrates that simulate the mechanical stiffness of normal and malignant neuronal tissues increase protoporphyin IX synthesis in glioma cells.

Protoporphyrin IX (PPIX) produced following the administration of exogenous 5d-aminolevulinic acid is clinically approved for photodynamic therapy and fluorescence-guided resection in various jurisdictions around the world. For both applications, quantification of PPIX forms the basis for accurate therapeutic dose calculation and identification of malignant tissues for resection. While it is well established that the PPIX synthesis and accumulation rates are subject to the cell's biochemical microenvironment, the effect of the physical microenvironment, such as matrix stiffness, has received little attention to date. Here we studied the proliferation rate and PPIX synthesis and accumulation in two glioma cell lines U373 and U118 cultured under five different substrate conditions, including the conventional tissue culture plastic and polyacrylamide gels that simulated tissue stiffness of normal brain (1 kPa) and glioblastoma tumors (12 kPa). We found that the proliferation rate increased with substrate stiffness for both cell lines, but not in a linear fashion. PPIX concentration was significantly higher in cells cultured on tissue-simulating gels than on the much stiffer tissue culture plastic for both cell lines. These findings, albeit preliminary, suggest that the physical microenvironment might be an important determinant of tumor aggressiveness and PPIX synthesis in glioma cells.

Effect of Aortic Annulus Size and Prosthesis Oversizing on the Hemodynamics and Leaflet Bending Stress of Transcatheter Valves: An In Vitro Study.

BACKGROUND: There are few data about the patient- and prosthesis-related factors influencing the hemodynamics of transcatheter heart valves (THVs). The objective of this in vitro study was to assess the effect of aortic annulus size and prosthesis oversizing on the valve hemodynamics and estimated leaflet bending stress of the Edwards SAPIEN balloon-expandable THV (Edwards Lifesciences, Irvine, CA). METHODS: The effective orifice area (EOA) of the 23-mm and 26-mm SAPIEN THVs were measured by Doppler echocardiography in a pulse duplicator under the following experimental conditions: (1) stroke volume of 20, 30, 50, 70, and 80 mL and (2) aortic annulus size of 19, 20, 21, and 22 mm for the 23-mm SAPIEN and 22, 23, and 24, and 25 mm for the 26-mm SAPIEN. The percentage of valve oversizing was calculated as follows: % OS = 100 × [(prosthesis nominal area - aortic annulus area)/aortic annulus area], where % OS is the percentage of oversizing. The leaflet bending stress was measured by high-speed camera imaging of the THV leaflet opening. RESULTS: The 2 independent determinants of valve EOA were the aortic annulus diameter (R(2) = 0.33; P < 0.001) and the stroke volume (R(2) = 0.63; P < 0.001). The prosthesis size and % OS were not independently related to EOA. However, a larger % OS was independently associated with higher peak systolic leaflet bending stress (ΔR(2) = 0.11; P < 0.0001). CONCLUSIONS: The hemodynamic performance of THV is in large part determined by the aortic annulus diameter in which the valve is deployed. Oversizing (up to 20% in area) has no significant effect on valve EOA but is associated with higher leaflet bending stress, which might promote faster structural valve degeneration in the long term.

An in vitro model of aortic stenosis for the assessment of transcatheter aortic valve implantation.

A significant number of elderly patients with severe symptomatic aortic stenosis are denied surgical aortic valve replacement (SAVR) because of high operative risk. Transcatheter aortic valve implantation (TAVI) has emerged as a valid alternative to SAVR in these patients. One of the main characteristics of TAVI, when compared to SAVR, is that the diseased native aortic valve remains in place. For hemodynamic testing of new percutaneous valves and clinical training, one should rely on animal models. However, the development of an appropriate animal model of severe aortic stenosis is not straightforward. This work aims at developing and testing an elastic model of the ascending aorta including a severe aortic stenosis. The physical model was built based on a previous silicone model and tested experimentally in this study. Experimental results showed that the error between the computer-aided design (CAD) file and the physical elastic model was <5%, the compliance of the ascending aorta was 1.15 ml/mm Hg, the effective orifice area (EOA) of the stenotic valve was 0.86 cm2, the peak jet velocity was 4.9 m/s and mean transvalvular pressure gradient was 50 mm Hg, consistent with as severe. An EDWARDS-SAPIEN 26 mm valve was then implanted in the model leading to a significant increase in EOA (2.22 cm2) and a significant decrease in both peak jet velocity (1.29 m/s) and mean transvalvular pressure gradient (3.1 mm Hg). This model can be useful for preliminary in vitro testing of percutaneous valves before more extensive animal and in vivo tests.

A metric for the stiffness of calcified aortic valves using a combined computational and experimental approach.

Calcific aortic valve disease is the most common heart valve disease. It is associated with a significant increase in cardiovascular morbidity and mortality and independently increases the cardiovascular risk. It is then important to develop parameters that can estimate the stiffness of the valve. Such parameters may contribute to early detection of the disease or track its progression and optimize the timing for therapy. In this study, we introduce a metric representing the stiffness of the native aortic calcified valve over a wide range of stenosis severities. Our approach is based on three-dimensional structural finite-element simulations and in vitro measurements. The proposed method is developed first in a pulse duplicator; its clinical applicability is then evaluated in three patients with severe aortic stenosis. Our results indicate that the value of the proposed metric varies considerably between healthy valves and valves with very severe aortic stenosis, from 0.001 to 7.38 MPa, respectively. The method introduced in this study could give useful information regarding the stiffness of the valve leaflets with potential application to the evaluation of aortic sclerosis and aortic stenosis.