The human endometrium is a dynamic, multi-cellular tissue that lines the inside of the uterine cavity. During a woman’s reproductive lifespan the endometrium is subjected to cyclical episodes of proliferation, angiogenesis, differentiation/decidualisation, shedding (menstruation), repair and regeneration in response to fluctuating levels of oestrogen and progesterone secreted by the ovaries. The endometrium displays unparalleled, tightly regulated, tissue remodelling resulting in a healed, scar-free tissue following menses or parturition. Mechanisms responsible for initiation of menses have been well documented: following progesterone withdrawal there is an increase in inflammatory mediators, focal hypoxia and induction and activation of matrix-degrading enzymes. In contrast, the molecular and cellular changes responsible for rapid, regulated, tissue repair at a time when oestrogen and progesterone are low are poorly understood. Histological studies using human menstrual phase endometrium have revealed that tissue destruction and shedding occur in close proximity to re-epithelialisation/repair. It has been proposed that re-epithelialisation involves proliferation of glandular epithelial cells in the remaining basal compartment; there is also evidence for a contribution from the underlying stroma. A role for androgens in the regulation of apoptosis of endometrial stromal cells has been proposed but the impact of androgens on tissue repair has not been investigated. Studies using human xenografts and primates have been used to model some aspects of the impact of progesterone withdrawal but simultaneous shedding (menses) and repair have not been modelled in mice; the species of choice for translational biomedical research. In the course of the studies described in this thesis, the following aims have been addressed: 1. To establish a model of menses in the mouse which mimics menses in women, namely; simultaneous breakdown and repair, overt menstruation, immune cell influx, tissue necrosis and re-epithelialisation. 2. To use this model to determine if the stromal cell compartment contributes to endometrial repair. 3. To examine the impact of androgens on the regulation of menses (shedding) and repair. An informative mouse model of endometrial breakdown that was characterised by overt menses, as well as rapid repair, was developed. Immunohistological evidence for extensive tissue remodelling including active angiogenesis, transient hypoxia, epithelial cell-specific proliferation and re-epithelialisation were obtained by examining uterine tissues recovered during an “early window of breakdown and repair” (4 to 24 hours after progesterone withdrawal). Novel data included identification of stromal cells that expressed epithelial cell markers, close to the luminal surface following endometrial shedding, suggesting a role for mesenchymal to epithelial transition (MET) in re-epithelialisation of the endometrium. In support of this idea, array and qRTPCR analyses revealed dynamic changes in expression of mRNAs encoded by genes known to be involved in MET during the window of breakdown and repair. Roles for hypoxia and tissue-resident macrophages in breakdown and tissue remodelling were identified. Treatment of mice with dihydrotestosterone to mimic concentrations of androgens circulated in women at the time of menses had an impact on the timing and duration of endometrial breakdown. Array analysis revealed altered expression of genes implicated in MET and angiogenesis/inflammation highlighting a potential, previously unrecognised role for androgens in regulation of tissue turnover during menstruation. In summary, using a newly refined mouse model new insights were obtained, implicating androgens and stromal MET in restoration of endometrial tissue homeostasis during menstruation. These findings may inform development of new treatments for disorders associated with aberrant repair such as heavy menstrual bleeding and endometriosis.

published_or_final_version / Orthopaedic Surgery / Doctoral / Doctor of Philosophy

published_or_final_version / Orthopaedics and Traumatology / Master / Master of Medical Sciences

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

No description available.

No description available.

No description available.

Zebrafish, in contrast to mammals, are capable of functional regeneration after complete transection of the spinal cord. In this system I asked: (1) Which spinal cell types regenerate in the lesioned spinal cord? (2) To what extent do the dopaminergic and 5-HT systems regenerate and (3) do dopaminergic axons from the brain influence cellular regeneration in the spinal cord? (1) Lost motor neurons are replaced by newly born motor neurons that mature and are integrated into the spinal circuitry after a spinal lesion in adult zebrafish. Using immunohistochemical and transgenic markers in combination with BrdU labeling, we showed that also 5-HT, parvalbuminergic, Pax2+ and Vsx1+ cells are newly born after lesion. Thus, my work shows that diverse cell types are newly generated in the lesioned spinal cord of adult zebrafish. (2) After spinal cord lesion, zebrafish completely recover locomotion within six weeks. Previous work suggested that axonal regeneration is crucial for functional recovery. Here I analyzed changes in the density of 5-HT and dopaminergic axon terminals in the lesioned spinal cord during recovery. Rostral to the lesion site, I observed die-back and sprouting of dopaminergic axons within two weeks post-lesion. Caudal of the lesion, axons are lost indicating Wallerian degeneration. At six weeks post-lesion I tested functional recovery with a behavioral swim test. In recovered fish, a third of the axonal density was restored just caudal of the lesion site, but not at far caudal levels. In contrast, in fish that had non-recovered, only few axons had bridged the lesion site. Thus dopaminergic axon regrowth correlates with functional recovery. Re-transection of the spinal cord in recovered animals abolished re-gained swimming capability, suggesting that behavioral recovery critically depends on axons that crossed the spinal lesion site and not on an intraspinal circuit. 5-HT axon terminals are of both intra- and supraspinal origin. The overall time course of changes in axon terminal density during recovery is similar to that of dopaminergic axon terminals and also correlates with functional recovery. Overall, the organization of the spinal dopaminergic and 5-HT systems, consisting of neuronal somata in the spinal cord and descending axons, differs significantly from their unlesioned organization. I observe sprouting rostral to the lesion site and limited innervation of the caudal spinal cord, as axons do not regrow into the far distal spinal cord. (3) We further hypothesized that signals released by descending axons are involved in cellular regeneration around the lesion site. Dopaminergic axons of supraspinal origin sprout rostral, but are almost completely absent caudal to the lesion site at two weeks post-lesion. Moreover, we observe that expression of the dopamine receptor drd4a is only increased rostral to the lesion site in the ventricular zone of progenitor cells, including olig2 expressing motor neuron progenitor cells. Correlated with these rostro-caudal differences, numbers of regenerating motor neurons are almost two-fold higher rostral than caudal of the lesion site. To functionally test whether dopamine is involved in motor neuron regeneration, we ablated tyrosine hydroxylase positive, mostly dopaminergic axons by injecting the toxin 6-hydroxydopamine. This treatment significantly reduced motor neuron numbers only rostral to the lesion site. As a gain-of-function experiment, we injected the dopamine agonist NPA after spinal lesion, which increased motor neuron numbers only rostral to the lesion site at two weeks post-lesion. These results suggest that dopamine released by descending axons, augments the generation of motor neurons in the lesioned spinal cord of adult zebrafish. In summary, during spinal cord regeneration I observe generation of various cell types and plastic changes of descending axonal projections. Dopamine released by descending axons is able to increase motor neuron regeneration, showing for the first time that signals from descending axons influence cellular regeneration in the spinal cord.

The addition of silicon ions (10-500 μM) to the culture medium of MG63 osteoblast-like cells showed no changes in cell viability, metabolic activity, proliferation or morphology. Silicon ions resulted in a concentration-dependent increase in the expression of vascular endothelial growth factor (VEGF) by the MG63 cells. Addition of magnesium ions (1-50 mM) to the culture medium of MG63 cells caused a dose-dependent decrease in cell viability, metabolic activity and proliferation at each time point. In general, silicon and magnesium ions had no effect on the viability of a human endothelial cell line (HUVEC). A slight decreasing trend to the metabolic activity of the HUVECs was observed with increasing concentrations of silicon ions at all time points, but this decreasing trend was more pronounced with the addition of magnesium ions. The highest magnesium ion concentration studied (50 mM) caused a change in HUVEC morphology from a typical cobblestone appearance to a fibroblast-like shape. Lastly, the effect of silicon ions on angiogenesis <i>in vitro</i> was studied using two different <i>in vitro</i> assays. The first, using Matrigel as an extracellular matrix coating for the guidance of endothelial cells to form tube-like structures (an indicator of angiogenesis), proved unreliable for studying the promotion of angiogenesis. Additionally, tube-like structures were also observed with osteoblasts cells, raising questions about the efficiency of this assay. The second assay, AngioKit, was a suitable model for studying stimulation and inhibition of tube-like formation. Results obtained using this assay showed that silicon ions alone (500 μM) did not stimulate tube-like formation, but a significant increase in tube-like formation was observed with MG63 cell-conditioned media, with (500 μM) and without silicon ions, when compared to the control medium.

Critical writing on public art in the late 20th century in the UK and USA either legitimized public art as an extension of studio art intended to widen its public, or implied a new relation to public space - as demonstrated in texts by Cork (1995) and Phillips (1988) respectively. This suggests a polarization of art's aesthetic and social dimensions. A deeper understanding of the relation between these dimensions is found in the work of Marcuse, Bloch and Adorno. Marcuse, in his early work, sees art as serving the needs of bourgeois society by displacing ideas of a better world to an independent aesthetic realm; Bloch sees art as giving form to hope, shaping a recurrent aspiration for a better world; Adorno sees the tension between the aesthetic and social dimensions of art as unresolvable, and, like Marcuse in his later work, sees art's autonomy as a space of criticality. But, as Bloch argues, conditions for change are noncontemporaneous, fostering culture which is both progressive and regressive. In this respect, Gablik's appropriations of other cultures may be seen as regressive, whilst Lippard's concern for locality offers art a basis for progressive intervention. The introduction of the local, as a point of reference alongside the aesthetic and social, leads to consideration of three cases of art practice: Common Ground's Parish Maps (1986-96), the Visions of Utopia Festival coordinated by the Artists Agency (1996-8), and 90% Crude (1996--), a project by PLATFORM in London. The originality of the thesis is in its investigation of these cases; and equally in making connections between them and the elements of art criticism and critical theory noted above.