Mechanobiology of the nucleus pulposus: The effect of hydrostatic pressure and glucose deprivation on nucleus pulposus cell sub‐populations

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dc.contributor.advisor McGlashan, S en
dc.contributor.advisor Thambyah, A en Saggese, Taryn en 2016-02-15T03:38:17Z en 2016 en
dc.identifier.citation 2016 en
dc.identifier.uri en
dc.description.abstract The nucleus pulposus of the intervertebral disc contains two cell types: notochordal (NC) and chondrocyte‐like mature nucleus pulposus (MNP) cells; the ratio of which changes with species, age and health. Intervertebral disc (IVDs) that contain predominantly MNP cells are susceptible to degeneration, while NC cell–rich discs remain healthy. Loss of NC cells is hypothesized to be initiated by mechanical stress and/or nutrient deprivation. This study aimed to investigate the phenotypic and functional differences between NC and MNP cells in response to a range of hydrostatic pressures and glucose concentrations. In this study a novel isolation method was developed that isolated single MNP cells and NC cell‐clusters from the same nucleus pulposus. Each cell type was cultured in 3D alginate beads, and assessed for phenotypic markers and extracellular matrix (ECM) expression on days 1 and 7 of culture. A custom‐built hydrostatic pressure chamber was used to expose each cell type to low/ physiological (0.6 MPa) and high/ pathological (2 MPa) pressure for 24 hours. To study the effect of nutrient deprivation, each cell type was cultured in either normal (5.5 mM) glucose media or glucose‐ deprived (0.55 mM) media. Finally, the combined effect of glucose deprivation and high pressure was examined. Following isolation, NC cells remained in cell clusters and expressed NC markers cytokeratin‐8 and brachyury. NC cells expressed significantly more aggrecan and GAG than MNP cells over the 7 day culture period. MNP cells responded to low pressure with an increase in total GAG while high pressure resulted in a significant decrease in aggrecan gene expression. NC cells showed no response in matrix gene expression or production to either loading regime. Glucose deprivation decreased the expression of the anti‐catabolic factor TIMP‐1 in NC cells but had no effect on MNP gene expression. However, the combination of glucose deprivation and high pressure resulted in a decrease in aggrecan, collagen II and ADAMTS‐5 gene expression in MNP cells. NC cells did not alter their gene expression response to the combined pathological insult. Together these findings show that NC cells are the major producers of proteoglycans, and are resistant to mechanical stress. In contrast, MNP cells produce relatively less proteoglycan and are susceptible to mechanical stress, which is exacerbated under glucose‐deprived conditions. This study has shown that NC and MNP cells from the same IVD have dramatically different responses to two key pathological stimuli, providing insight into the differential roles these cells play in the pathogenesis of disc degeneration. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA99264842514102091 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
dc.rights.uri en
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dc.title Mechanobiology of the nucleus pulposus: The effect of hydrostatic pressure and glucose deprivation on nucleus pulposus cell sub‐populations en
dc.type Thesis en Biomedical Science en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The Author en
dc.rights.accessrights en
pubs.elements-id 522832 en
pubs.record-created-at-source-date 2016-02-15 en

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