Browsing by Author "Wyatt, Rachael A."

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    Mouse embryonic fibroblasts accumulate differentially on titanium surfaces treated with nanosecond laser pulses
    (AVS: Science & Technology of Materials, Interfaces, and Processing, 2016) Radmanesh, Mitra; Ektasabi, Amin M.; Wyatt, Rachael A.; Crawford, Bryan D.; Kiani, Amirkianoosh
    Biomaterial engineering, specifically in bone implant and osseointegration, is currently facing a critical challenge regarding the response of cells to foreign objects and general biocompatibility of the materials used in the production of these implants. Using the developing technology of the laser surface treatment, this study investigates the effects of the laser repetition rate (frequency) on cell distribution across the surface of the titanium substrates. The main objective of this research is building a fundamental understanding of how cells interact with treated titanium and how different treatments affect cell accumulation. Cells respond differently to surfaces treated with different frequency lasers. The results of this research identify the influence of frequency on surface topography properties and oxidation of titanium, and their subsequent effects on the pattern of cell accumulation on its surface. Despite increased oxidation in laser-treated regions, the authors observe that fibroblast cells prefer untreated titanium to laser-treated regions, except the regions treated with 25 kHz pulses, which become preferentially colonized after 72 h.
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    Patterns and mechanisms of post-translational regulation of Mmp2 in vivo during zebrafish development
    (University of New Brunswick, 2020) Wyatt, Rachael A.; Crawford, Bryan; Pulinilkunnil, Thomas
    In addition to cells, multicellular tissues are made up of context-specific complexes of secreted proteins that are assembled dynamically outside cells to produce the physical characteristics of the vertebrate body and organs. The resistive strength of tendons, the elasticity and impermeability of skin and the support structure of the skeleton are functional largely because of the extracellular matrix (ECM). The development and maintenance of these tissues requires careful orchestration between assembly and degradation of components. Matrix metalloproteinases (MMPs) are one of the enzyme families known to degrade ECM. Matrix metalloproteinase-2 (MMP-2), my enzyme of interest, is known to have roles in pathologies such as arthritis, where its function is protective, and cancer metastasis, where it is activated as part of the migration and invasion of metastatic cells. It is an enzyme that requires post-translational activation by proteolytic cleavage, and therefore its role cannot be fully described by either mmp2 transcript patterns or Mmp2 protein accumulation. Using a transgenic zebrafish line with the epitope-mediated MMP activation (EMMA) assay construct, for the first time we can localize activation of Mmp2 in vivo, and here I describe its presence and activation during embryonic development. Though endogenous Mmp2 is expressed ubiquitously during the development of a zebrafish embryo, I show here that it is proteolytically activated in a much smaller set of structures. It is most strongly activated in the notochord, epithelium, fin folds and neural tube. Active Mmp2 has a role during the morphogenesis of the notochord, a driving structure in vertebrate development, and in the fin folds where actinotrichia are collagen based ECM structures that form the basis for fin rays. Further, I show that the activation mechanisms of Mmp2 are tissue- and stage-dependent: mechanisms that require metalloproteases are required for the activation of Mmp2 during fin fold development, but mechanisms dependent upon serine proteases are involved in the activation of Mmp2 in the notochord during notochord elongation and straightening. This is the first description of activation patterns in vivo and offers a starting point from which to examine the requirement of metalloproteases during development and to interrogate their mechanisms of activation.