Hemodynamic regulation of MMP-2 and MMP-9: roles in angiogenesis and migration

Hemodynamic forces generated by the flow of blood are crucial in maintaining homeostasis within the blood vessel wall. These forces, namely cyclic strain and shear stress are intricately involved in vascular remodeling, a process which underlies the pathogenesis of cardiovascular diseases such as atherosclerosis and restenosis. Since degradation of the extracellular matrix scaffold enables reshaping of tissue, the role matrix metalloproteinases (MMPs) has become the object of intense recent interest in relation to physiological and pathological vascular remodeling. The culminating data indicates that hemodynamic forces are important regulators of MMP expression and activity. A more complete understanding of the hemodynamic regulation of MMPs may advance the understanding of pathological vascular remodeling. We have investigated the effect of cyclic strain on the endothelial cell migration and angiogenic activity and the role of gelatinases in mediating these responses We have shown that exposure of bovine aortic endothelial cells (BAEC) to cyclic strain promoted migration and tubule formation with concurrent increases in MMP-2 and MMP-9 activity. Additionally, we have revealed that cyclic strain-induced increases in migration and tube formation are dependent on Gi-protein and integrin signaling However, cyclic strain stimulated increases in MMP-2 expression involve different signaling mechanisms, which in part, stimulate both p38- and ERK-dependent pathways through activation of Gpy and tyrosine kinase in BAEC. The participation of gelatinases in strain-induced increases in BAEC migration and tube formation was determined by inhibition of MMP activity using either a broad spectrum MMP inhibitor (GM6001) or siRNA targeted specifically to MMP-2 or MMP-9 We have shown that cyclic straininduced increases in BAEC migration are independent of MMP activity. In addition, we have demonstrated that MMP-9 but not MMP-2 is the key angiogenic switch involved in evoking cyclic straininduced angiogenesis. In conclusion, we examined the role of BAEC derived factors in regulating bovine aortic smooth muscle cell (BASMC) migration. Our data has shown that exposure of BASMC to conditioned media from cyclically strained BAEC inhibits SMC migration compared to controls and that MMP-2 is an important factor in mediating this inhibition. These findings clearly demonstrate that increases in MMP expression and activity associated with cyclic strain are important in modulating both BAEC and BASMC phenotype

Management of synergistic knowledge alliances

Purpose: In this thesis the viable system model (VSM) is used as a framework to develop a model for the management of a business alliance that contains the necessary and sufficient conditions for maintaining synergy of its constituent organisations and for adapting to a changing environment so that it can remain a long-term viable alliance. In addition, a model is developed that makes explicit the inherent link between the VSM and the core elements of knowledge management theory. Based then on the alliance management model and the link established between the VSM and knowledge management, an application framework is developed to guide practitioners in defining necessary alliance management functions and relationships, the knowledge required by that management to fulfill those functions, and the processes that need to be in place to manage that knowledge. Design/strategy: The research has been divided into four phases: theoretical construction, refinement with practitioners, real-world application, and evaluation of test case and toolset. The researcher has worked closely with practitioners actively involved in the formation of a new international alliance to develop a VSM model and application framework for the alliance management. Formally, the research strategy has been defined as an action research and the research philosophy as one of pragmatism. Findings/limitations: The developed application framework, has been successfully used to identify absent and incomplete roles, actions, and interactions within the management of the specific alliance test case. This has helped to demonstrate how the application framework and VSM model can be used to diagnose and, most importantly, to articulate and visualise management deficiencies to facilitate clear and unambiguous discussions. The timing of this cross-sectional research did not allow the application framework to be utilised from the outset of the alliance formation as an organisational planning tool and also not to its full extent to support the development of knowledge processes for the alliance management. However, the step-by-step approach used in developing the toolset and then explaining its application will allow the reader to judge its credability and generalisability for other practical applications. Practical implications: The developed toolset consists of a VSM for an alliance management, job descriptions for that management (responsibilities, interfaces, and core competencies), a visual model illustrating the link between the VSM and knowledge management, and an application framework to guide the filling of the alliance management job descriptions in phases of recruitment, onboarding, and development (of interfaces and activities processes). Overall, one could say that the conditions prescribed by the VSM are rather obvious and yet, as seen by the specific alliance test case, many of these conditions have been completely overlooked by a management that was more than capable, willing, and empowered to enact those conditions. This gives a good indication that the toolset which has been compiled in a visual and tabular systematic fashion may well be useful to practitioners for the organisational planning of an alliance management. The visual representation of a management role in the VSM as a set of knowledge episodes put forward by this research is significant. It forces the express recognition that knowledge management is an integral part of every interaction that takes place and every action performed that, according to the VSM, are necessary and altogether are sufficient for viability. It means that knowledge management cannot be considered as some abstract topic or unnecessary overhead or afterthought – it is entirely necessary, practical and forms a natural course of events during design of action/interaction processes. In other words, if an organisation is viable then, by definition, it does knowledge management whether or not it is formally recognised as such. The VSM, by defining necessary and sufficient actions and interactions for its roles, therefore provides a focus for relevant knowledge and serves as a tool for structured knowledge management. Originality/value: This research addresses a general academic call for hands-on insights of VSM applications by sharing real-world insights, artifacts and reflections generated by a practical and relevant organisational management application. It also addresses the potential, recognised by academics, for VSM as a framework for knowledge management by developing an intuitive model linking those theories and then using that model as part of a framework to guide its application. The introduction to aspects of knowledge management theory relevant to the model developed as well as the meticulousness and comprehensive explanation of the VSM provides a solid theoretical foundation for practitioners. The developed toolset is based on existing theories from multiple fields of research that have been logically linked and extended in an original and novel manner with a strong focus on practical application. This researcher’s hope is that this will stimulate interest for future research and practical application from academics and practitioners alike

Investigating Metalloproteinases MMP-2 and MMP-9 Mechanosensitivity to Feedback Loops Involved in the Regulation of In Vitro Angiogenesis by Endogenous Mechanical Stresses

International audienceAngiogenesis is a complex morphogenetic process regulated by growth factors, but also by the force balance between endothelial cells (EC) traction stresses and extracellular matrix (ECM) viscoelastic resistance. Studies conducted with in vitro angiogenesis assays demonstrated that decreasing ECM stiffness triggers an angiogenic switch that promotes organization of EC into tubular cords or pseudo-capillaries. Thus, mechano-sensitivity of EC with regard to proteases secretion, and notably matrix metalloproteinases (MMPs), should likely play a pivotal role in this switching mechanism. While most studies analysing strain regulation of MMPs used cell cultured on stretched membranes, this work focuses on MMP expression during self-assembly of EC into capillary-like structures within fibrin gels, i.e. on conditions that mimics more closely the in vivo cellular mechanical microenvironment. The activity of MMP-2 and MMP-9, two MMPs that have a pivotal role in capillaries formation, has been monitored in pace with the progressive elongation of EAhy926 cells that takes place during the emergence of cellular cords. We found an increase of the zymogen proMMP-2 that correlates with the initial stages of EC cords formation. However, MMP-2 was not detected. ProMMP-9 secretion decreased, with levels of MMP-9 kept at a rather low value. In order to analyse more precisely the observed differences of EAhy926 response on fibrin and plastic substrates, we proposed a theoretical model of the mechano-regulation of proMMP-2 activation in the presence of type 2 tissue inhibitor of MMPs (TIMP-2). Using association/dissociation rates experimentally reported for this enzymatic network, the model adequately describes the synergism of proMMP-2 and TIMP-2 strain activation during pseudo-capillary morphogenesis. All together, these results provide a first step toward a systems biology approach of angiogenesis mechano-regulation by cell-generated extracellular stresses and strains

Alternatively spliced tissue factor induces angiogenesis through integrin ligation

The initiator of coagulation, full-length tissue factor (flTF), in complex with factor VIIa, influences angiogenesis through PAR-2. Recently, an alternatively spliced variant of TF (asTF) was discovered, in which part of the TF extracellular domain, the transmembrane, and cytoplasmic domains are replaced by a unique C terminus. Subcutaneous tumors produced by asTF-secreting cells revealed increased angiogenesis, but it remained unclear if and how angiogenesis is regulated by asTF. Here, we show that asTF enhances angiogenesis in matrigel plugs in mice, whereas a soluble form of flTF only modestly enhances angiogenesis. asTF dose-dependently upregulates angiogenesis ex vivo independent of either PAR-2 or VIIa. Rather, asTF was found to ligate integrins, resulting in downstream signaling. asTF-αVβ3 integrin interaction induces endothelial cell migration, whereas asTF-dependent formation of capillaries in vitro is dependent on α6β1 integrin. Finally, asTF-dependent aortic sprouting is sensitive to β1 and β3 integrin blockade and a TF-antibody that disrupts asTF-integrin interaction. We conclude that asTF, unlike flTF, does not affect angiogenesis via PAR-dependent pathways but relies on integrin ligation. These findings indicate that asTF may serve as a target to prevent pathological angiogenesis