The primary olfactory pathway in adult mammals has retained a remarkable potential for self-repair. Olfactory ensheathing cells (OECs), specialized glial cells within the olfactory nerve, are thought to play an important role in the ongoing growth and replenishment of sensory connections in this system. To gain insight into novel molecules that could mediate OEC-supported growth of axons within the olfactory nerve, gene expression profiling experiments revealed very high expression of the fibulin-3 glycoprotein in OECs. To date, research on fibulin-3 has been limited and mainly focused on its involvement in Doyne honeycomb retinal dystrophy, vasculogenesis and tumor formation. As the extracellular matrix associated with OECs is thought to be an important contributor to a growth-permissive environment, the main aim of this thesis was to define a putative role for fibulin-3 during olfactory receptor neuron replacement and regeneration. This hypothesis was investigated in a series of in vitro and in vivo experiments that involved lentiviral vectors to manipulate fibulin-3 gene expression in OECs as well as the use of knock-out mice. Using genetically-modified OECs, experimental data showed that increased levels of fibulin-3 induced morphological changes in OECs and also impeded their migration. Lentiviral vector-mediated expression of fibulin-3 in OECs also had an inhibitory effect on neurite outgrowth from dorsal root ganglion explants. On the other hand, knock-down of fibulin-3 levels via siRNA technology resulted in reduced proliferation. Comparative lesioning experiments in fibulin-3 knock-out and wild-type mice allowed for further assessment of a role for fibulin-3 in olfactory nerve repair in vivo. Two experimental injury models, i.e. epithelial (Triton-X) lesioning and olfactory bulbectomy, were employed. The results obtained were in line with in vitro observations. A lack of fibulin-3 in knock-out mice resulted in a seemingly augmented regeneration of the olfactory epithelium at 10 days post-injury. However, at the latest recovery time point of 42 days post-injury, an impaired recovery of the olfactory epithelium from the experimental insults was observed. Although the precise mechanism for the latter phenomenon is not yet fully understood, our data point towards several factors which include vascular abnormalities and altered cell proliferation within the olfactory epithelium. Additionally, the precise protein distribution of another wide-spread family of extracellular matrix molecules, the laminins, was investigated in this thesis. It was of interest to investigate the spatiotemporal expression of laminin isoforms during iii olfactory nerve development and regeneration as these molecules may have distinct roles in promoting olfactory sensory neuron growth and patterning. In situ hybridization and immunohistochemical studies concluded that laminin-211 and laminin-411 were the most likely candidates to play such a role. In summary, this thesis provides new insights into the role of the extracellular matrix, fibulin-3 in particular, in regulating cell migration, division and axonal growth in the primary olfactory pathway. Such knowledge also gives a greater understanding of the molecular mechanisms by which OEC transplants may enhance axonal regeneration elsewhere in the CNS.

Includes bibliographical references (leaves 292-352) / xvi, 352 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Determines the role of matrix metalloproteinases, MMP-2 and MMP-9 in reperfusion injury following skeletal muscle ischaemia; and, whether inhibition of MMPs by doxycycline protects against tissue damage. / Thesis (M.D.)--University of Adelaide, Dept. of Surgery, 2002

<p>Granulocyte adhesion and release of their granule proteins are key steps during selective accumulation of a certain cell to an inflammatory site. Eosinophils are specifically recruited to sites of allergic inflammation and parasitic infection, whereas neutrophil influx predominates in bacterial infection and rheumatoid arthritis. </p><p>A simple, reliable and convenient method was developed for the measurement of granulocyte adhesion and release of granule proteins by using the normal population of granulocytes. The design allows simultaneous quantitative assessment of eosinophil and neutrophil adhesion to proteins and degranulation. </p><p>Using this method, manganese ions (Mn²⁺) induced a higher level of eosinophil adhesion to fibronectin, fibrinogen and albumin as compared with neutrophils. PMA induced comparable levels of eosinophil and neutrophil adhesion. F-MLP stimulated a rapid, short-term adhesion of neutrophils to fibrinogen. </p><p>In the same conditions PMA alone stimulated a dose-dependent release of ECP from cells that adhered to both fibronectin and fibrinogen. Meanwhile, Mn²⁺ amplified the release of ECP induced by PMA. Furthermore, release of ECP was shown to be associated with cell death.</p><p>PMA, in combination with Mn²⁺, induced a marked release of ~ 80%of the intracellular content of lactoferrin and HNL in neutrophils. PMA or f-MLP alone induced 30-40% release of lactoferrin and HNL. A maximal release of MPO of 15-20% was obtained from neutrophils stimulated by PMA and Mn²⁺. Release of lactoferrin and HNL showed a significant negative relationship to the viability of cells.</p><p>Stimulated by PMA, eosinophils from pollen-atopic patients during early pollen season displayed a markedly enhanced adhesion and release of ECP of eosinophils compared with eosinophils from the references. Priming with IL-5 caused a significantly higher adhesion and release of ECP by eosinophils in response to PMA. GM-CSF priming enhanced eosinophil adhesion in response to PAF and PMA plus Mn²⁺, but did not enhance the release of ECP.</p><p>In conclusion, the assay allows a simple quantification of eosinophil and neutrophil adhesion, as well as degranulation by using the normal population of granulocytes. Cellular adhesion plays an important role in the regulation of both eosinophil and neutrophil degranulation, but adhesion and degranulation can be induced separately.</p>

Mechanistic insights on molecular and cellular mechanisms whereby KSHV induces Kaposi?s sarcoma (KS) are key for our understanding of KS tumors and for the development of new therapies. We have previously developed an animal model for KSHV induced KS using murine bone marrow cells transfected with a KSHVBac36. We found that although these cells lacked attributes of transformed cells in vitro, they were able to cause KS-like tumors in vivo. In vivo tumorigenesis correlated with upregulation of both KSHV lytic genes and host angiogenesis suggesting that that cues provided from the microenvironment played a major role in regulating viral and host gene expression related with KSHV-induced tumorigenesis. Our goal thus, was to identify these molecular cues regulating pathogenic gene expression in KSHV infected cells in vivo. An important difference between cells kept in vitro versus in vivo is the lack of environmental extracellular matrix (ECM) signals. Therefore the mECK36 cells were cultured in vitro in matrigel, a basement membrane preparation rich in ECM proteins and its individual components, to discern the effect of host signaling by the ECM on KSHV infected cells. Investigation of gene expression through Real Time RT-PCR identified several viral and host genes associated with tumorigenesis such as KSHV vGPCR and angiogenesis associated VEGF and EGF- receptors were upregulated in response to this environment. Further analysis of the molecular activity of the cell indicated the change in transcription was due to the activation of integrin signaling, as assessed by phosphorylation of the Focal Adhesion Kinase (FAK) protein. Our results show that integrin signaling occurring in vivo through interaction with ECM serves to enhance the pathogenic viral and host gene expression of KSHV infected cells and that EGFR upregulation can be correlated with these conditions. These results points to the integrin signaling pathway or the EGF-Receptor as promising targets for therapy and prevention of KS tumors.

The goal of our work was to characterize more precisely the role of ADAMTS2 in physiological and pathological processes, in order to develop potential therapeutic applications. We confirmed that the function of ADAMTS2 is essential during embryogenesis and development, including by its major role in the processing of fibrillar collagens type I and III in skin and lung tissues. Its specific activity was also matched up with that of two other aminoprocollagen peptidases, ADAMTS3 and ADAMTS14. The impact of ADAMTS2 inhibition during pathological formation of scar fibrous tissue was determined in two murine models of hepatic fibrosis and granulomatous reaction. In this context, ADAMTS2 appears as a therapeutic target of interest for the treatment of all process characterized by the deposition of an excessive scar matrix, including liver fibrosis. Finally, the potential anti-angiogenic properties of ADAMTS2 were demonstrated both in vitro and in vivo. Its potent activity during angiogenesis results from its action onto several distinct steps participating to the formation of new blood vessels. Molecular mechanisms by which ADAMTS2 modulates the behaviour of endothelial cells and inhibits tumor growth remain to be confirmed. L'objectif de nos études était de caractériser de manière plus précise le rôle de l'ADAMTS2 dans des processus physiologiques et pathologiques, et d'en déduire d'éventuelles applications en thérapeutique clinique. Nous avons confirmé que l'ADAMTS2 détenait une fonction essentielle au cours de l'embryogenèse et du développement, notamment par son rôle majeur dans la maturation des procollagènes fibrillaires de type I et de type III dans la peau et le poumon. Son activité spécifique a également été mise en perspective avec celle des deux autres aminoprocollagène peptidases, les ADAMTS3 et 14. L'impact de l'inhibition de l'ADAMTS2 au cours de la formation pathologique de tissu fibreux cicatriciel a été démontré dans des modèles murins de fibrose hépatique et de réaction granulomateuse à corps étranger. A ce titre, l'ADAMTS2 apparaît comme une cible thérapeutique d'intérêt pour le traitement de toute affection caractérisée par le dépôt d'une trame cicatricielle excessive, dont la fibrose hépatique. Enfin, le potentiel anti-angiogène de l'ADAMTS2 a été démontré à la fois in vitro et in vivo. Son efficacité remarquable résulte de son action au cours de plusieurs étapes distinctes de la formation des néo-vaisseaux. Les mécanismes moléculaires précis par lesquels l'ADAMTS2 agit sur les cellules endothéliales et l'inhibition de la croissance tumorale restent à préciser.

Granulocyte adhesion and release of their granule proteins are key steps during selective accumulation of a certain cell to an inflammatory site. Eosinophils are specifically recruited to sites of allergic inflammation and parasitic infection, whereas neutrophil influx predominates in bacterial infection and rheumatoid arthritis. A simple, reliable and convenient method was developed for the measurement of granulocyte adhesion and release of granule proteins by using the normal population of granulocytes. The design allows simultaneous quantitative assessment of eosinophil and neutrophil adhesion to proteins and degranulation. Using this method, manganese ions (Mn2+) induced a higher level of eosinophil adhesion to fibronectin, fibrinogen and albumin as compared with neutrophils. PMA induced comparable levels of eosinophil and neutrophil adhesion. F-MLP stimulated a rapid, short-term adhesion of neutrophils to fibrinogen. In the same conditions PMA alone stimulated a dose-dependent release of ECP from cells that adhered to both fibronectin and fibrinogen. Meanwhile, Mn2+ amplified the release of ECP induced by PMA. Furthermore, release of ECP was shown to be associated with cell death. PMA, in combination with Mn2+, induced a marked release of ~ 80%of the intracellular content of lactoferrin and HNL in neutrophils. PMA or f-MLP alone induced 30-40% release of lactoferrin and HNL. A maximal release of MPO of 15-20% was obtained from neutrophils stimulated by PMA and Mn2+. Release of lactoferrin and HNL showed a significant negative relationship to the viability of cells. Stimulated by PMA, eosinophils from pollen-atopic patients during early pollen season displayed a markedly enhanced adhesion and release of ECP of eosinophils compared with eosinophils from the references. Priming with IL-5 caused a significantly higher adhesion and release of ECP by eosinophils in response to PMA. GM-CSF priming enhanced eosinophil adhesion in response to PAF and PMA plus Mn2+, but did not enhance the release of ECP. In conclusion, the assay allows a simple quantification of eosinophil and neutrophil adhesion, as well as degranulation by using the normal population of granulocytes. Cellular adhesion plays an important role in the regulation of both eosinophil and neutrophil degranulation, but adhesion and degranulation can be induced separately.

The growing incidences of coronary artery bypass graft surgeries have triggered a need to engineer a viable small diameter blood vessel substitute. An ideal tissue engineered vascular graft should mimic the microenvironment of a native blood vessel, while providing the adequate compliance post-implantation. Current vascular graft technologies lack the ability to promote vascular ECM deposition, leading to a compliance mismatch and ultimately, graft failure. Hence, in order to engineer suitable vascular grafts, this thesis describes the synthesis and characterization of novel elastin mimetic peptides, EM-19 and EM-23, capable of promoting vascular ECM deposition within a poly(ethylene glycol) diacrylate (PEG-DA) hydrogel. By combining the material properties of a synthetic and bio-inspired polymer, a suitable microenvironment for cell growth and ECM deposition can be engineered, leading to improved compliance. As such, characterization of EM-19 and EM-23 was conducted in human vascular smooth muscle cell (SMC) cultures, and the peptides self-assembled with a growing elastic matrix. After grafting the peptides onto the surface of PEG-DA hydrogels, EM-23 increased SMC adhesion by 6000% over PEG-RGDS hydrogels, which have been the gold standard of cell adhesive PEG scaffolds. Moreover, EM-23 grafted surfaces were able to promote elastin deposition that was comparable to tissue cultured polystyrene (TCPS) surface even though TCPS had roughly 4.5 times more SMCs adhered. Once translated to a 3D model, EM-23 also stimulated increased elastin deposition and improved the mechanical strength of the scaffold over time. Moreover, degradation studies suggested that EM-23 may serve as a template that not only promotes ECM deposition, but also allows ECM remodeling over time. The characterization studies in this thesis suggest that this peptide is an extremely promising candidate for improving vascular ECM deposition within a synthetic substrate, and that it may be beneficial to incorporate EM-23 within polymeric scaffolds to engineer compliant vascular grafts.

The genus Bartonella comprises emerging pathogens that are causative agents of a wide range of clinical manifestations such as cat scratch disease, bacillary angiomatosis, and Carrion’s disease. All species are transmitted by blood-sucking arthropods and infect erythrocytes and endothelial cells of hosts. Carrion’s disease is a bi-phasic infection caused by Bartonella bacilliformis which is characterized by hemolysis of infected erythrocytes followed by invasion of the vascular endothelium. This provokes pronounced cellular proliferation, angiogenesis and skin eruptions called verruga peruana. Endothelial cells are thought to be the primary niche wherein bacteria reside between inoculation and erythrocyte infection. This study aims to elucidate some of the endothelial factors involved during the verruga peruana phase of Carrion’s disease. In order to adhere to and invade human microvascular endothelial cells (HMEC-1), B. bacilliformis engages a family of cell receptors called integrins. We used anti-integrin antibodies to show that the primary integrin involved is the fibronectin receptor á5â1, although the vitronectin receptor áVâ3 also plays a minor role. We show B. bacilliformis invasion is also dependent on integrin ligands, fibronectin and vitronectin as antibodies against these proteins decreased invasion and attachment, whereas pre-treatment of the bacteria with these molecules enhanced infection of endothelial cells. Bacterial uptake requires various host cytoplasmic signaling pathways to work in tandem, and our study identified three mitogen activated protein kinases involved. Apart from MAPKs, phosphotidylinositol 3 kinase plays a role during invasion and cell survival. PI3K inhibitors blocked bacterial internalization and B. bacilliformis infected cells showed accelerated apoptosis. Lastly, microarray analysis was performed to study the gene expression profile of B. bacilliformis infected HMEC-1 cells. Numerous molecules of the integrin signaling pathways are involved, suggesting integrins as the major receptor recruited for the successful infection by B. bacilliformis. In summary this is the first study to demonstrate the role of integrins as B. bacilliformis receptors and integrin ligands as facilitators of infection. Gene expression analysis suggests the possibility that integrin mediated signaling pathways are the key modulators of cellular alterations during B. bacilliformis infection. This hypothesis is supported by the identification of some members of the integrin signaling pathway necessary for B. bacilliformis entry into endothelial cells.

Damage to synovial joints results in osteochondral defects that only heal with inferior fibrous repair tissue. Since mesenchymal stem cells (MSCs) play a vital role in the natural development, maintenance, and repair of cartilage and bone, tissue engineering strategies to enhance functional regeneration by modulating MSC differentiation are a promising alternative to the limitations and potential complications associated with current conventional therapies. In this work, signals present in the native microenvironment were utilized in fabricating polymer/extracellular matrix composite scaffolds to guide chondrogenic and osteogenic differentiation. In an osteochondral defect environment, interactions exist between bone marrow cell populations. Although MSCs have been extensively utilized for their ability to support hematopoietic stem and progenitor cells (HSPCs), the role of HSPCs in regulating the osteogenic differentiation of MSCs in the bone marrow niche is not well understood, and thus was explored via direct contact co-culture. HSPCs in a low dose with sustained osteogenic induction by dexamethasone accelerated osteogenesis and enhanced mineral deposition, whereas the lack of induction signals affected the spatial distribution of cell populations and minerals. Thus, HSPCs presumably play an active role in modulating the development and maintenance of the osteogenic niche. Since physical signals affect cellular activity, flow perfusion culture was employed to deposit mineralized extracellular matrix (ECM) with different maturity and composition on electrospun poly([varepsilon]-caprolactone) (PCL) microfibers in fabricating mineralized PCL/ECM composite scaffolds. The presence of mineralized matrix induced the osteogenic differentiation of MSCs even in the absence of dexamethasone, and a more mature matrix with higher quantities of collagen and minerals improved osteogenesis by accelerating alkaline phosphatase expression and matrix mineralization. To determine whether PCL/ECM scaffolds can be applied to support the chondrogenic differentiation of MSCs, cartilaginous PCL/ECM composite scaffolds were fabricated. The presence of cartilaginous matrix reduced fibroblastic phenotype and in combination with transforming growth factor-β1 (TGF-β1), further promoted chondrogenesis as evident in elevated levels of glycosaminoglycan synthetic activity. While further investigation is necessary to optimize and test these scaffolds to induce the regeneration of cartilage and bone, this work demonstrates the importance of harnessing signals present in the native microenvironment to modulate chondrogenic and osteogenic differentiation.

<p>Intervertebral disc (IVD) disorders are a major contributor to disability and health costs. Disc disorders and resulting pain may be preceded by changes which first occur in the nucleus pulposus (NP) region of the IVD, where significant alterations in tissue cellularity, composition, and structure begin early in human life and continue with increasing age and degeneration. These changes coincide with the loss of a distinct cell population, notochordally-derived immature NP cells, which may play a key role in the generation and maintenance of this tissue. These cells reside in a gelatinous, highly-hydrated extracellular matrix (ECM) environment and exhibit in situ cell-matrix and cell-cell interactions which are quite distinct from cells in other regions of the disc or in other cartilagenous, including expression of laminin cell-matrix receptors and cell-associated laminin proteins. The ECM environment is known to be a key regulator of cellular behaviors, with ECM ligands and elasticity modulating cell adhesion, organization, differentiation, and phenotype. The primary motivating hypothesis of this thesis is that the unique ECM environment of the NP plays a key role in modulating immature NP cell behaviors, and that laminin ligands, in combination with ECM elasticity, modulate immature NP cell behaviors including adhesion, organization, and phenotype.</p><p>To investigate this hypothesis, flow cytometric analyses were performed to examine IVD cell integrin receptor expression over time in culture, including assessment of key laminin-binding integrin subunits. The roles of specific integrin receptors modulating NP cell adhesion to ECM proteins were identified in studies utilizing function-blocking antibodies. NP cell adhesion, spreading, and relative cell adhesion strength was assessed on various ECM constituents, including specific isoforms of laminin. Additionally, studies were performed to examine the roles of ECM ligand and substrate stiffness in modulating NP cellular organization, utilizing polyacrylamide gel substrates with tunable mechanical properties and functionalized with different ECM ligands. Finally, the role of ECM environment was examined on one key measure of NP cell function, proteoglycan production, over time in culture.</p><p>NP cells isolated from immature NP tissues were found to express high levels of the laminin-binding integrin subunit alpha 6 ex situ and maintain this expression over time in culture. Function blocking studies revealed this receptor to be a key regulator of NP cell adhesion to laminin, in contrast to cells from the adjacent AF region, which did not express this receptor nor adhere to laminin. Cell adhesion studies demonstrated that NP cells preferentially interact with two laminin isoforms, LM-511 and LM-332, in comparison to other ECM proteins, with enhanced cell attachment, spreading, and adhesion strength on surfaces coated with these ligands. These findings correspond with laminin isoform and receptor expression patterns identified in immature NP tissues. Additionally, NP cell-cell interactions were found to be modulated by both ECM ligand and substrate stiffness, with soft, laminin-functionalized substrates promoting self-assembly of NP cells into cell clusters with morphologies similar to those identified in immature NP tissues. Finally, culture of immature NP cells on soft, laminin-rich substrates was found to promote a key measure of NP cell function, proteoglycan synthesis.</p><p>The studies presented here demonstrate that immature NP cells interact uniquely with laminin extracellular matrix proteins, and that laminin ligands and matrix elasticity are two key regulators of NP cell organization and phenotype in the IVD. These findings suggest that alterations in one or both of these factors during IVD aging or degeneration may contribute to the differentiation or loss of this unique cell population. Additionally, these results indicate that soft, laminin-functionalized biomaterials may be appropriate for in vitro culture and expansion of immature NP cells, as well as for use in NP tissue engineering strategies.</p> / Dissertation