Endothelial and smooth muscle cell interactions with a PCL-PU composite vascular scaffold with potential for bioactive release

Paper discussing endothelial and smooth muscle cell interactions with a PCL-PU composite vascular scaffold with potential for bioactive release

The role of calcium in the organization of fibrillin microfibrils

AbstractThe microfibrillar glycoprotein fibrillin has a multidomain structure which contains forty-three epidermal growth factor-like motifs with calciumbinding consensus sequences. We have utilized intact microfibrils isolated from human dermal fibroblast cultures to investigate the putative influence of bound calcium on microfibrillar organization and integrity. Incubation with EDTA or EGTA rapidly resulted in gross disruption of microfibril morphology. The treatment induced disorganization of the interbead domains although the regular beaded arrangement was always apparent. These changes were readily reversible on replacing calcium, indicating that the treatment had not compromised microfibrillar integrity. The data localize calcium binding EGF-like repeats to the interbead domains and indicate that lateral packing of fibrillin monomers is calcium-dependent. This arrangement suggests how mutations in epidermal growth factor-like domains of fibrillin might cause the disruption in microfibril organization and interactions which underlies the clinical symptoms of some Marian syndrome patients

Vascular endothelial growth factor can signal through platelet-derived growth factor receptors

Vascular endothelial growth factor (VEGF-A) is a crucial stimulator of vascular cell migration and proliferation. Using bone marrow–derived human adult mesenchymal stem cells (MSCs) that did not express VEGF receptors, we provide evidence that VEGF-A can stimulate platelet-derived growth factor receptors (PDGFRs), thereby regulating MSC migration and proliferation. VEGF-A binds to both PDGFRα and PDGFRβ and induces tyrosine phosphorylation that, when inhibited, results in attenuation of VEGF-A–induced MSC migration and proliferation. This mechanism was also shown to mediate human dermal fibroblast (HDF) migration. VEGF-A/PDGFR signaling has the potential to regulate vascular cell recruitment and proliferation during tissue regeneration and disease

Adhesion to the extracellular matrix is required for interleukin-1 beta actions leading to reactive phenotype in rat astrocytes

The extracellular matrix (ECM) of the brain is essential for homeostasis and normal functions, but is rapidly remodelled during acute brain injury alongside the development of an inflammatory response driven by the cytokine interleukin (IL)-1. Whether the ECM regulates IL-1 actions in astrocytes is completely unknown. The aim of this study was to test the hypothesis that cellular attachment to the ECM is a critical mediator of IL-1β-induced signalling pathways and development of reactive phenotype in astrocytes. Primary rat astrocytes adhered to fibronectin, laminin and fibrillin-1 in an integrin-dependent manner. Attachment to these ECM molecules significantly increased IL-1β-induced activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and inhibition of RhoA and Rho kinase (ROCK), coincident with loss of focal adhesions and cellular morphological changes. Our data demonstrate that the ECM regulates IL-1 actions in astrocytes via cross-talk mechanisms between ERK1/2 and RhoA/ROCK, which could have important implications in brain inflammatory disorders

Fibrillin-Rich Microfibrils are Reduced in Photoaged Skin. Distribution at the Dermal–Epidermal Junction

Chronic sun exposure results in photoaged skin with deep coarse wrinkles and loss of elasticity. We have examined the distribution and abundance of fibrillin-rich microfibrils, key structural components of the elastic fiber network, in photoaged and photoprotected skin. Punch biopsies taken from photoaged forearm and from photoprotected hip and upper inner arm of 16 subjects with a clinical range of photoaging were examined for fibrillin-1 and fibrillin-2 expression and microfibril distribution. In situ hybridization revealed decreased fibrillin-1 mRNA but unchanged fibrillin-2 mRNA levels in severely photoaged forearm biopsies relative to photoprotected dermal sites. An immunohistochemical approach demonstrated that microfibrils at the dermal–epidermal junction were significantly reduced in moderate to severely photoaged forearm skin. Confocal microscopy revealed that the papillary dermal microfibrillar network was truncated and depleted in photoaged skin. These studies highlight that the fibrillin-rich microfibrillar network associated with the upper dermis undergoes extensive remodeling following solar irradiation. These changes may contribute to the clinical features of photoaging, such as wrinkle formation and loss of elasticity

Fibrillin-1 regulates the bioavailability of TGFβ1

We have discovered that fibrillin-1, which forms extracellular microfibrils, can regulate the bioavailability of transforming growth factor (TGF) β1, a powerful cytokine that modulates cell survival and phenotype. Altered TGFβ signaling is a major contributor to the pathology of Marfan syndrome (MFS) and related diseases. In the presence of cell layer extracellular matrix, a fibrillin-1 sequence encoded by exons 44–49 releases endogenous TGFβ1, thereby stimulating TGFβ receptor–mediated Smad2 signaling. This altered TGFβ1 bioavailability does not require intact cells, proteolysis, or the altered expression of TGFβ1 or its receptors. Mass spectrometry revealed that a fibrillin-1 fragment containing the TGFβ1-releasing sequence specifically associates with full-length fibrillin-1 in cell layers. Solid-phase and BIAcore binding studies showed that this fragment interacts strongly and specifically with N-terminal fibrillin-1, thereby inhibiting the association of C-terminal latent TGFβ-binding protein 1 (a component of the large latent complex [LLC]) with N-terminal fibrillin-1. By releasing LLC from microfibrils, the fibrillin-1 sequence encoded by exons 44–49 can contribute to MFS and related diseases

Cell-matrix biology in vascular tissue engineering

We are developing biocompatible small-calibre vascular substitutes based on polymeric scaffolds that incorporate cell-matrix signals to enhance vascular cell attachment and function. Our graft scaffold comprises an outer electrostatically spun porous polyurethane layer seeded with smooth muscle cells, and a luminal polycaprolactone layer for endothelial cell attachment. Vascular cell adhesion properties of three vascular elastic fibre molecules, tropoelastin, fibrillin-1 and fibulin-5, have been defined, and adhesion fragments optimized. These fragments are being used to coat the scaffolds to enhance luminal endothelial cell attachment, and to regulate smooth muscle cell attachment and function. Tropoelastin-based cell seeding materials are also being developed. In this way, vascular cell-matrix biology is enhancing graft design

The tight skin mouse: demonstration of mutant fibrillin-1 production and assembly into abnormal microfibrils

Mice carrying the Tight skin (Tsk) mutation harbor a genomic duplication within the fibrillin-1 (Fbn 1) gene that results in a larger than normal in-frame Fbn 1 transcript. In this study, the consequences of the Tsk mutation for fibrillin-containing microfibrils have been examined. Dermal fibroblasts from Tsk/+ mice synthesized and secreted both normal fibrillin (approximately 330 kD) and the mutant oversized Tsk fibrillin-1 (approximately 450 kD) in comparable amounts, and Tsk fibrillin-1 was stably incorporated into cell layers. Immunohistochemical and ultrastructural analyses of normal and Tsk/+ mouse skin highlighted differences in the gross organization and distribution of microfibrillar arrays. Rotary shadowing of high Mr preparations from Tsk/+ skin demonstrated the presence of abundant beaded microfibrils. Some of these had normal morphology and periodicity, but others were distinguished by diffuse interbeads, longer periodicity, and tendency to aggregate. The presence of a structurally abnormal population of microfibrils in Tsk/+ skin was unequivocally demonstrated after calcium chelation and in denaturating conditions. Scanning transmission electron microscopy highlighted the presence of more mass in Tsk/+ skin microfibrils than in normal mice skin microfibrils. These data indicate that Tsk fibrillin-1 polymerizes and becomes incorporated into a discrete population of beaded microfibrils with altered molecular organization

Les jeunes peu qualifiés : une diversité de positions sur le marché du travail

Le parcours de jeunes sortis depuis plusieurs années et sans diplôme du système scolaire fait l’objet d’une enquête qualitative et longitudinale. Prenant appui sur une typologie, cet article met en exergue la diversité des positions des jeunes par rapport au marché du travail secondaire. Il s’agit de mieux comprendre comment et pourquoi ces positions sont plus ou moins contraignantes et intégratives pour ces jeunes.The results of this qualitative and longitudinal research that we have to present in this paper are about the process of young people, without diploma, who has left scholar system few years ago. Bulding on a typology, this article compare their positions to understand how and why these same positions seem to be more or less expensive and integrative fort those young.Die Laufbahn junger Menschen, die seit mehreren Jahren ohne Abschluss das Schulsystem verlassen haben, ist Gegenstand einer qualitativen und einer Längsschnittstudie. Gestützt auf eine Typologie werden in diesem Artikel die vielfältigen Positionen in Bezug auf den sekundären Arbeitsmarkt herausgestellt. Es soll herausgefunden werden, wie und warum diese Positionen für die jungen Menschen mehr oder weniger zwingend und integrativ sind.El itinerario de jóvenes que salieron del sistema escolar hace algunos años sin título es el objeto de una investigación cualitativa y longitudinal. Sobre la base de una tipología, este artículo pone de relieve la diversidad de posiciones respecto del mercado de trabajo secundario. Se trata de comprender mejor cómo y por qué estas posiciones son más o menos restrictivas e integradoras para estos jóvenes