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<p> Downregulation of E-cadherin is a frequent event in epithelial cancers and it correlates with weakened cell-cell adhesion and the induction of an epithelial-to-mesenchymal transition (EMT). It is postulated that E-cadherin downregulation liberates the catenin p120 and allows p120's translocation to the nucleus where it interacts with and functionally regulates the novel BTB/POZ transcription factor, Kaiso. Kaiso mediates transcriptional repression of various tumourigenesis-associated genes via methylated CpG dinucleotides or a sequence-specific Kaiso binding site (KBS). The Kaiso/p120 interaction has been detected in E-cadherin expressing cells of various origins, but is seldom detected in N-cadherin expressing cells or cells that have undergone EMT. We hypothesize that p120 and Kaiso play a role in EMT by modulating the expression of EMT-associated genes. We demonstrated that TGF-β-induced EMT occurs in a dose- and time-dependent manner in NMuMG cells but not in FHL-124 cells. In both cells lines, the Kaiso/p120 interaction occurred irrelevant of EMT induction by TGF-β. In NMuMG cells, the expression of p120 increased with EMT induction, while the expression of Kaiso remained unchanged. Finally, misexpression of Kaiso and p120 in mammary epithelial cells affected TGF-β-mediated EMT induction by delaying the upregulation of the positive mesenchymal markers, N-cadherin and α-SMA.</p> / Thesis / Master of Science (MSc)

Keratins are a family of proteins found within human hair, skin and nails, as well as a broad variety of animal tissue. Prior research suggests hydrogel constructs of keratin and keratin derivatives exhibit several mechanical and biological properties that support their use for tissue engineering and regenerative medicine applications. Microparticle formulations of these hydrogels are an intriguing delivery vehicle for drugs and cellular payloads for tissue engineering purposes due to the ability to exploit size, surface area, loading potential and importantly, non-invasive delivery (i.e. injection) of cells and biologics. Here we examine the water-in-oil emulsion synthesis procedure to produce keratin microparticles using an oxidized keratin derivative, keratose (KOS). Analyses of particle size, microstructure, and other characterization techniques were performed. Drug loading characteristics, release kinetics, and feasibility of use in two different microparticles was subsequently investigated, first using a model-drug and later testing an antibiotic payload on bacterial cultures to validate antibacterial applications. A suspension culture technique was developed to load bone marrow-derived mesenchymyal stromal cells (BM-MSCs), testing the capacity to maintain viability and express key protein-based factors in cell growth and development. Finally, we tested the in vitro effects of cell-loaded microparticles on the L6 skeletal muscle cell line to determine potentially beneficial outcomes for skeletal muscle tissue regeneration. Largely spherical particles with a porous internal structure were obtained, displaying hydrogel properties and forming viscoelastic gels with small differences between synthesis components (solvents, crosslinkers), generating tailorable properties. The uniquely fibrous microstructure of KOS particles may lend them to applications in rapid drug release or other payload delivery wherein a high level of biocompatibility is desired. Data showed an ability to inhibit bacterial growth in the emulsion-generated system, and thereby demonstrated the potential for a keratin-based microparticle construct to be used in wound healing applications. Dense cell populations were loaded onto particles. Particles maintained cell viability, even after freeze-thaw cycling, and provided a material substrate that supported cell attachment through the formation of focal adhesions. Finally, in vitro studies show that both KOS and BM-MSCs support varying aspects of skeletal muscle development, with combinatorial treatments of cell-loaded particles conferring the greatest growth responses. / Doctor of Philosophy / Keratins and keratin hydrogels may exhibit several properties that support their use for tissue engineering and regenerative medicine applications. Microparticle formulations of these hydrogels are an intriguing delivery vehicle for payloads for tissue engineering purposes. Here we examine the water-in-oil emulsion synthesis procedure to produce keratin microparticles that were analyzed based on drug loading characteristics. A suspension culture technique was developed to load bone marrow-derived mesenchymyal stromal cells (BM-MSCs). Finally, we tested these products to determine potentially beneficial outcomes for skeletal muscle tissue regeneration. Particles with a porous structure were obtained. The microstructure of these particles may lend them to applications in drug release or other payload delivery. Data showed an ability to load and unload specific drug payloads. Dense cell populations were loaded onto particles. Finally, studies show that both keratin and BM-MSCs support skeletal muscle development, with combinatorial treatments of cell-loaded particles conferring the greatest growth responses.

Osteoarthritis (OA) is a degenerative disease of diarthrodial joints causing pain and loss of joint function. Etiology is heterogeneous, but commonly involves inflammation arising from impairment of normal tissue homeostasis and/or function. A cycle of low-grade inflammation and global tissue degradation causes alteration of tissue morphology and function via primary mechanisms or inability to withstand physiological forces. Current therapies variably ameliorate symptoms but do not modify progression. Mesenchymal stem cells (MSCs) have multi-modal properties but are ineffective in ameliorating equine OA. However, anti-inflammatory activities of bone marrow derived MSCs (BMSCs) are enhanced by three-dimensional spheroid culture so equine BMSC (eBMSC) spheroids could inhibit intra-articular inflammation. The overarching hypothesis is that eBMSCs can be enhanced to produce an allogeneic eBMSC therapy that inhibits intra-articular inflammation. In vitro experiments compared differences in anti-inflammatory phenotype between spheroid and traditionally cultured monolayer eBMSCs, the viability and health of eBMSC spheroids administered through needles, and the effects of allogeneic donor on the anti-inflammatory potential of eBMSC spheroids. A model of equine LPS induced synovitis was used to investigate anti-inflammatory efficacy of spheroid eBMSCs compared to placebo or monolayer eBMSCs in vivo. eBMSCs aggregate into spheroids that have stable stem cell marker expression with increased secretion and gene expression of IL-6 and PGE2, and gene expression of SDF-1 and TSG-6. IFN𝛾 and TNFα were not produced by eBMSC spheroids and IL-10 production varied between individuals. Spheroids maintain higher viability and lower senescence than monolayer eBMSCs after injection through a needle and form in high-throughput culture without detrimental effects on expression of TSG-6, IL-6 and PGE synthases that denote an anti-inflammatory phenotype. Additionally, there is significant variation in this phenotype depending on the eBMSC donor. eBMSC spheroids reduced total nucleated cell counts and objective lameness measurements at peak levels of intra-articular inflammation compared to monolayer cultured eBMSCs in vivo. In summary, spheroids increase anti-inflammatory potential of eBMSCs and are practical for clinical use. Increased anti-inflammatory efficacy was demonstrated in a model of in vivo inflammation. This dissertation provides an understanding of the anti-inflammatory activities of eBMSC spheroids that can be used to develop an OA therapy. / Ph. D.

Gap junctions, comprised of connexin proteins, are essential for direct intercellular electrical, metabolic, and immunological coupling. Connexin43 (Cx43, gene name GJA1) is the most ubiquitously expressed gap junction protein, and Cx43 gap junctions are altered in pathological states including cardiac disease and cancer. The GJA1 mRNA undergoes alternative translation initiation to yield a truncated Cx43 isoform, GJA1-20k, that can regulate gap junction formation. Using epithelial-mesenchymal transition (EMT) as a cellular model of gap junction remodeling, we have demonstrated altered translation initiation of Gja1 as a mechanism by which cellular Cx43 gap junctions can be dynamically regulated. Suppression of Gja1 alternative translation is necessary for Cx43 gap junction loss, and stable expression of GJA1-20k rescues gap junction formation during EMT. To identify regulatory factors acting on the Gja1 mRNA, an MS2 RNA aptamer tagging system was adapted to isolate Gja1 with associated RNA binding proteins. We find the RNA binding protein IMP1 is sensitive to hypoxic stress and complexes with Gja1 mRNA, where it is necessary for alternative translation to generate GJA1-20k. We have demonstrated alterations in translation initiation of the Gja1 mRNA as a critical mechanism by which cells modulate Cx43 gap junctional coupling in changing conditions and identified a novel regulator of this process in mammalian cells. / Doctor of Philosophy / Communication between cells is necessary for healthy function of organs throughout the body. Gap junctions form conduits through which signals can pass directly between neighboring cells. Many diseases, including cancer and heart disease, involve disturbances in gap junction communication. Connexin proteins are the building blocks of gap junctions, and it was recently demonstrated that smaller fragments of connexins are synthesized by cells by a poorly understood process called alternative translation. Importantly, levels of these connexins fragments can alter gap junction formation. We have used mammalian cells to delineate the mechanism by which this alternative protein translation regulates gap junction formation and generated insight into how such protein synthesis is dynamically regulated. Harnessing this knowledge will inform development of new therapeutics inducing alternative translation to rescue gap junctions, and restore normal communication in pathological conditions.

Eukaryotic cell chemotaxis, or directed cell migration in response to a chemoeffector gradient, plays a central role in many important biological process such as wound healing, cancer metastasis, and embryogenesis. In vivo, cells migrate on fibrous ECM, but chemotaxis studies are typically conducted on flat substrates which fail to recapitulate ECM or 3D gel environments with heterogeneous and poorly defined biophysical properties. To address these challenges, this thesis focused on developing a microfluidic assay device which utilizes a reductionist approach to study single cell chemotaxis on aligned, suspended ECM-mimicking nanofibers. The device is comprised of a network of microfluidic mixing channels which produce a temporally invariant, linear chemical gradient over nanofiber scaffolds in an observation channel. The microfluidic device design was guided by a numerical model and validated with experimental testing. This device was used to study mouse embryonic fibroblast NIH/3T3 response to platelet derived growth factor (PDGF) on flat polystyrene and suspended, polystyrene nanofibers with small (15 μm), and large (25 μm) spacing. Cell aspect ratio is lowest for flat polystyrene (spread morphology) and highest for large-spaced fibers (spindle morphology). Cells migrating on fibers begin to show a chemotaxis response to a PDGF gradient 10 times shallower than that required for chemotaxis response on a flat substrate. Furthermore, cells with spindle morphology maintain a robust and strong response over a broad range of chemoattractant concentration. These cells also had a 45% increase in speed and 26% increase in persistence over cells on flat polystyrene. The findings of this thesis suggest that 2D substrates may not be sufficient for studying physiologically relevant chemotaxis. / Master of Science