The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform

Spandan Maiti - One of the best experts on this subject based on the ideXlab platform.

  • computational modeling of the strength of the ascending thoracic Aortic Media tissue under physiologic biaxial loading conditions
    Journal of Biomechanics, 2020
    Co-Authors: Spandan Maiti, James Thunes, Ronald N. Fortunato, Thomas G. Gleason, David A. Vorp
    Abstract:

    Abstract Type A Aortic Dissection (TAAD) is a life-threatening condition involving delamination of ascending Aortic Media layers. While current clinical guidelines recommend surgical intervention for aneurysm diameter > 5.5 cm, high incidence of TAAD in patients below this diameter threshold indicates the pressing need for improved evidence-based risk prediction metrics. Construction of such metrics will require the knowledge of the biomechanical failure properties of the Aortic wall tissue under biaxial loading conditions. We utilized a fiber-level finite element based structural model of the Aortic tissue to quantify the relationship between Aortic tissue strength and physiologically relevant biaxial stress state for nonaneurysmal and aneurysmal patient cohorts with tricuspid Aortic valve phenotype. We found that the model predicted strength of the Aortic tissue under physiologic biaxial loading conditions depends on the stress biaxiality ratio, defined by the ratio of the longitudinal and circumferential components of the tissue stress. We determined that predicted biaxial tissue strength is statistically similar to its uniaxial circumferential strength below biaxiality ratios of 0.68 and 0.69 for nonaneurysmal and aneurysmal cohorts, respectively. Beyond this biaxiality ratio, predicted biaxial strength for both cohorts reduced drastically to a magnitude statistically similar to its longitudinal strength. We identified fiber-level failure mechanisms operative under biaxial stress state governing aforementioned tissue failure behavior. These findings are an important first step towards the development of mechanism-based TAAD risk assessment metrics for early identification of high-risk patients.

  • A structural finite element model for lamellar unit of Aortic Media indicates heterogeneous stress field after collagen recruitment
    Journal of Biomechanics, 2016
    Co-Authors: James Thunes, Ronald N. Fortunato, Julie A. Phillippi, Thomas G. Gleason, David A. Vorp, Spandan Maiti
    Abstract:

    Incorporation of collagen structural information into the study of biomechanical behavior of ascending thoracic Aortic (ATA) wall tissue should provide better insight into the pathophysiology of ATA. Structurally motivated constitutive models that include fiber dispersion and recruitment can successfully capture overall mechanical response of the arterial wall tissue. However, these models cannot examine local microarchitectural features of the collagen network, such as the effect of fiber disruptions and interaction between fibrous and non-fibrous components, which may influence emergent biomechanical properties of the tissue. Motivated by this need, we developed a finite element based three-dimensional structural model of the lamellar units of the ATA Media that directly incorporates the collagen fiber microarchitecture. The fiber architecture was computer generated utilizing network features, namely fiber orientation distribution, intersection density and areal concentration, obtained from image analysis of multiphoton microscopy images taken from human aneurysmal ascending thoracic Aortic Media specimens with bicuspid Aortic valve (BAV) phenotype. Our model reproduces the typical J-shaped constitutive response of the Aortic wall tissue. We found that the stress state in the non-fibrous matrix was homogeneous until the collagen fibers were recruited, but became highly heterogeneous after that event. The degree of heterogeneity was dependent upon local network architecture with high stresses observed near disrupted fibers. The magnitude of non-fibrous matrix stress at higher stretch levels was negatively correlated with local fiber density. The localized stress concentrations, elucidated by this model, may be a factor in the degenerative changes in aneurysmal ATA tissue.

Chunsheng Wang - One of the best experts on this subject based on the ideXlab platform.

  • LncRNA LOXL1-AS is up-regulated in thoracic Aortic aneurysm and regulated proliferation and apoptosis of Aortic smooth muscle cells
    Bioscience Reports, 2019
    Co-Authors: Ben Huang, Hao Lai, Yongxin Sun, Chunsheng Wang
    Abstract:

    Long non-coding RNA LOXL1-AS is up-regulated in several types of cancers. The present study was carried out to explore the potential interactions between LOXL1-AS and lncRNA Giver in thoracic Aortic aneurysm (TAA). We found that LOXL1-AS was up-regulated in TAA patients than in healthy controls in Aortic Media specimens. Altered expression levels of LOXL1-AS distinguished TAA patients from healthy controls. LncRNA Giver was also up-regulated in TAA patients than in healthy controls in Aortic Media specimens, and was positively correlated with LOXL1-AS. LOXL1-AS overexpression Mediated the up-regulation of Giver in human Aortic smooth muscle cells, while Giver overexpression failed to significantly affect LOXL1-AS. LOXL1-AS and Giver overexpression resulted in promoted proliferation and inhibited apoptosis of HAOSMC. Giver silencing played an opposite role and attenuated the effect of LOXL1-AS overexpression. Therefore, LOXL1-AS was up-regulated in TAA and regulated proliferation and apoptosis of LOXL1-AS by up-regulating Giver.

  • Isolation and culture of smooth muscle cells from human acute type A Aortic dissection
    Journal of cardiothoracic surgery, 2013
    Co-Authors: Xiaoning Sun, Tao Hong, Kai Song, Shouguo Yang, Chunsheng Wang
    Abstract:

    Background Acute type A Aortic dissection (TAAD) is a life-threatening vascular disease. Smooth muscle cells (SMCs) are the main composition of Aortic Media and dysfunction of SMCs may lead to acute TAAD. The aim of this work was to investigate whether the SMCs of acute TAAD could be isolated and cultured for further research.

David A. Vorp - One of the best experts on this subject based on the ideXlab platform.

  • computational modeling of the strength of the ascending thoracic Aortic Media tissue under physiologic biaxial loading conditions
    Journal of Biomechanics, 2020
    Co-Authors: Spandan Maiti, James Thunes, Ronald N. Fortunato, Thomas G. Gleason, David A. Vorp
    Abstract:

    Abstract Type A Aortic Dissection (TAAD) is a life-threatening condition involving delamination of ascending Aortic Media layers. While current clinical guidelines recommend surgical intervention for aneurysm diameter > 5.5 cm, high incidence of TAAD in patients below this diameter threshold indicates the pressing need for improved evidence-based risk prediction metrics. Construction of such metrics will require the knowledge of the biomechanical failure properties of the Aortic wall tissue under biaxial loading conditions. We utilized a fiber-level finite element based structural model of the Aortic tissue to quantify the relationship between Aortic tissue strength and physiologically relevant biaxial stress state for nonaneurysmal and aneurysmal patient cohorts with tricuspid Aortic valve phenotype. We found that the model predicted strength of the Aortic tissue under physiologic biaxial loading conditions depends on the stress biaxiality ratio, defined by the ratio of the longitudinal and circumferential components of the tissue stress. We determined that predicted biaxial tissue strength is statistically similar to its uniaxial circumferential strength below biaxiality ratios of 0.68 and 0.69 for nonaneurysmal and aneurysmal cohorts, respectively. Beyond this biaxiality ratio, predicted biaxial strength for both cohorts reduced drastically to a magnitude statistically similar to its longitudinal strength. We identified fiber-level failure mechanisms operative under biaxial stress state governing aforementioned tissue failure behavior. These findings are an important first step towards the development of mechanism-based TAAD risk assessment metrics for early identification of high-risk patients.

  • A structural finite element model for lamellar unit of Aortic Media indicates heterogeneous stress field after collagen recruitment
    Journal of Biomechanics, 2016
    Co-Authors: James Thunes, Ronald N. Fortunato, Julie A. Phillippi, Thomas G. Gleason, David A. Vorp, Spandan Maiti
    Abstract:

    Incorporation of collagen structural information into the study of biomechanical behavior of ascending thoracic Aortic (ATA) wall tissue should provide better insight into the pathophysiology of ATA. Structurally motivated constitutive models that include fiber dispersion and recruitment can successfully capture overall mechanical response of the arterial wall tissue. However, these models cannot examine local microarchitectural features of the collagen network, such as the effect of fiber disruptions and interaction between fibrous and non-fibrous components, which may influence emergent biomechanical properties of the tissue. Motivated by this need, we developed a finite element based three-dimensional structural model of the lamellar units of the ATA Media that directly incorporates the collagen fiber microarchitecture. The fiber architecture was computer generated utilizing network features, namely fiber orientation distribution, intersection density and areal concentration, obtained from image analysis of multiphoton microscopy images taken from human aneurysmal ascending thoracic Aortic Media specimens with bicuspid Aortic valve (BAV) phenotype. Our model reproduces the typical J-shaped constitutive response of the Aortic wall tissue. We found that the stress state in the non-fibrous matrix was homogeneous until the collagen fibers were recruited, but became highly heterogeneous after that event. The degree of heterogeneity was dependent upon local network architecture with high stresses observed near disrupted fibers. The magnitude of non-fibrous matrix stress at higher stretch levels was negatively correlated with local fiber density. The localized stress concentrations, elucidated by this model, may be a factor in the degenerative changes in aneurysmal ATA tissue.

James Thunes - One of the best experts on this subject based on the ideXlab platform.

  • computational modeling of the strength of the ascending thoracic Aortic Media tissue under physiologic biaxial loading conditions
    Journal of Biomechanics, 2020
    Co-Authors: Spandan Maiti, James Thunes, Ronald N. Fortunato, Thomas G. Gleason, David A. Vorp
    Abstract:

    Abstract Type A Aortic Dissection (TAAD) is a life-threatening condition involving delamination of ascending Aortic Media layers. While current clinical guidelines recommend surgical intervention for aneurysm diameter > 5.5 cm, high incidence of TAAD in patients below this diameter threshold indicates the pressing need for improved evidence-based risk prediction metrics. Construction of such metrics will require the knowledge of the biomechanical failure properties of the Aortic wall tissue under biaxial loading conditions. We utilized a fiber-level finite element based structural model of the Aortic tissue to quantify the relationship between Aortic tissue strength and physiologically relevant biaxial stress state for nonaneurysmal and aneurysmal patient cohorts with tricuspid Aortic valve phenotype. We found that the model predicted strength of the Aortic tissue under physiologic biaxial loading conditions depends on the stress biaxiality ratio, defined by the ratio of the longitudinal and circumferential components of the tissue stress. We determined that predicted biaxial tissue strength is statistically similar to its uniaxial circumferential strength below biaxiality ratios of 0.68 and 0.69 for nonaneurysmal and aneurysmal cohorts, respectively. Beyond this biaxiality ratio, predicted biaxial strength for both cohorts reduced drastically to a magnitude statistically similar to its longitudinal strength. We identified fiber-level failure mechanisms operative under biaxial stress state governing aforementioned tissue failure behavior. These findings are an important first step towards the development of mechanism-based TAAD risk assessment metrics for early identification of high-risk patients.

  • A structural finite element model for lamellar unit of Aortic Media indicates heterogeneous stress field after collagen recruitment
    Journal of Biomechanics, 2016
    Co-Authors: James Thunes, Ronald N. Fortunato, Julie A. Phillippi, Thomas G. Gleason, David A. Vorp, Spandan Maiti
    Abstract:

    Incorporation of collagen structural information into the study of biomechanical behavior of ascending thoracic Aortic (ATA) wall tissue should provide better insight into the pathophysiology of ATA. Structurally motivated constitutive models that include fiber dispersion and recruitment can successfully capture overall mechanical response of the arterial wall tissue. However, these models cannot examine local microarchitectural features of the collagen network, such as the effect of fiber disruptions and interaction between fibrous and non-fibrous components, which may influence emergent biomechanical properties of the tissue. Motivated by this need, we developed a finite element based three-dimensional structural model of the lamellar units of the ATA Media that directly incorporates the collagen fiber microarchitecture. The fiber architecture was computer generated utilizing network features, namely fiber orientation distribution, intersection density and areal concentration, obtained from image analysis of multiphoton microscopy images taken from human aneurysmal ascending thoracic Aortic Media specimens with bicuspid Aortic valve (BAV) phenotype. Our model reproduces the typical J-shaped constitutive response of the Aortic wall tissue. We found that the stress state in the non-fibrous matrix was homogeneous until the collagen fibers were recruited, but became highly heterogeneous after that event. The degree of heterogeneity was dependent upon local network architecture with high stresses observed near disrupted fibers. The magnitude of non-fibrous matrix stress at higher stretch levels was negatively correlated with local fiber density. The localized stress concentrations, elucidated by this model, may be a factor in the degenerative changes in aneurysmal ATA tissue.

Lin Han - One of the best experts on this subject based on the ideXlab platform.

  • brg1 expression is increased in thoracic Aortic aneurysms and regulates proliferation and apoptosis of vascular smooth muscle cells through the long non coding rna hif1a as1 in vitro
    European Journal of Cardio-Thoracic Surgery, 2015
    Co-Authors: Shuwei Wang, Xiwu Zhang, Yang Yuan, Mengwei Tan, Le Zhang, Xiang Xue, Yan Yan, Lin Han
    Abstract:

    OBJECTIVES: Brahma-related gene 1 (BRG1) and long non-coding RNAs (lncRNAs) play important roles in cellular processes. However, little is known regarding their roles in thoracic Aortic aneurysms. We investigated BRG1 expression in thoracic Aortic aneurysms and the roles of BRG1 and the lncRNA HIF 1 alpha-antisense RNA 1 in regulating the proliferation and apoptosis of Aortic smooth muscle cells in vitro. METHODS: BRG1 mRNA and protein expression in human Aortic Media specimens were examined by quantitative real-time polymerase chain reaction, immunohistochemical staining and western blot. BRG1 expression was up-regulated by lentiviral vectors. Vascular smooth muscle cell proliferation and apoptosis were studied using Cell Counting Kit-8 and terminal deoxynucleotidyl transferase dUTP nick-end labelling assays. We performed western blots to detect Caspase3 and Bcl2 protein expression. LncRNAs regulated by BRG1 were identified through microarray in BRG1 gain- and loss-of-function vascular smooth muscle cells. Finally, the expression of HIF 1 alpha-antisense RNA 1 was reduced by siRNA and cell proliferation and apoptosis was studied using Cell Counting Kit-8 assays, caspase-3 activity assays and western blot. RESULTS: BRG1 expression in the Aortic Media was significantly higher in thoracic Aortic aneurysms than in normal controls. Overexpression of BRG1 in human Aortic smooth muscle cells promoted apoptosis and reduced proliferation. The expression of HIF 1 alpha-antisense RNA 1 was significantly down- and up-regulated in BRG1 knock-down and overexpressing vascular smooth muscle cells, respectively. We further demonstrated that suppression of HIF 1 alpha-antisense RNA 1 by siRNA in vascular smooth muscle cells reduced apoptosis and promoted proliferation. CONCLUSIONS: BRG1 is overexpressed in the Aortic Media of thoracic Aortic aneurysms and the interaction between BRG1 and HIF 1 alpha-antisense RNA 1 plays a key role in the proliferation and apoptosis of vascular smooth muscle cells in vitro, which may contribute to the pathogenesis of thoracic Aortic aneurysms.