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Role of oxidative stress responses in clonal variations in dental pulp stem cell ageing and regenerative potential

Alaidaroos, Nadia Yousef A. 2019. Role of oxidative stress responses in clonal variations in dental pulp stem cell ageing and regenerative potential. PhD Thesis, Cardiff University.
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Human dental pulp stem cells (hDPSCs) are increasingly being recognised as a viable cell source in regenerative medicine. However, significant heterogeneity in their ex vivo expansion capabilities are well-established, which influences their multipotent differentiation and therapeutic potential. This is partly attributed to contrasting telomere lengths between individual DPSC sub-populations influencing their relative susceptibilities to replicative (telomere-dependent) senescence, which impairs cellular regenerative properties. This has significant implication for regenerative medicine, in terms of obtaining sufficient cell numbers for therapeutic use, whilst maintaining stem cell and multipotency characteristics. As DPSCs have no reverse transcriptase, human telomerase catalytic subunit (hTERT) expression, this suggests that other mechanisms are responsible for variations in telomere lengths and replicative senescence susceptibilities between high and low proliferative DPSCs. As oxidative stress is a well-established mediator of cellular senescence, this study investigated whether DPSCs also differed in their susceptibilities to oxidative stress (0-200µM H2O2)- induced (telomere-independent) senescence and bimolecular damage; and whether differences in enzymic antioxidant profiles contribute to contrasting oxidative stress responses in high and low proliferative DPSC sub-populations. Significant variations were shown in the susceptibilities of DPSC sub-populations to H2O2-induced senescence. Low proliferative DPSCs underwent accelerated senescence (<40PDs) with 0-200µM H2O2 treatments, accompanied by increased SAβ-galactosidase and senescence marker (p53, p21waf1, p16INK4a) detection. High proliferative DPSCs exhibited increased resistance to H2O2-induced senescence,reaching 80PDs (0-50µM H2O2) or 50-76PDs (100-200µΜ H2O2), prior to senescence marker detection. However, telomere lengths and stem cell marker expression were largely unaffected by increasing H2O2 treatment or culture expansion. Enhanced low proliferative DPSC susceptibility to H2O2-induced senescence was accompanied by increased oxidative stress-induced bimolecular damage at early PDs (2-10PDs), with elevated DNA (8-hydroxy-deoxy-guanosine), protein (carbonyl content) and lipid (peroxidation) detection, irrespective of H2O2 treatments. In contrast, high proliferative DPSCs exhibited limited oxidative biomolecular damage at early PDs (2-10PDs), only equivalent to low proliferative DPSCs at much later PDs (45-60PDs). In line with their resistance to H2O2-induced senescence and biomolecular damage, significant increases in superoxide dismutase (SOD2) and glutathione Stransferase ζ (GSTZ1) expression, in addition to significantly increased total SOD activities, were identified in high proliferative DPSCs at early PDs (10-25PDs). However, SOD1/GSTZ1 expression and total SOD activities significantly declined during culture expansion (45-60PDs). In contrast, low proliferative DPSCs at early PDs (2-10PDs) mostly exhibited low/negligible SOD1, SOD2, SOD3, catalase,GSTZ1 and other glutathione-related antioxidant expression/activities overall, implying that antioxidant mechanisms are impaired in these sub-populations.This study demonstrates that significant variations exist in the susceptibilities of high and low proliferative DPSC sub-populations to oxidative stress-induced senescence and biomolecular damage, contributed to by inherent differences in SOD2 and GSTZ1 antioxidant profiles, which help maintain the proliferative, stemness and multipotency capabilities of high proliferative DPSCs during ex vivo expansion. Thus, the identification of such contrasting enzymic antioxidant profiles between high and low proliferative DPSCs enhances our understanding of DPSC biology and its interrelationship with oxidative stress and cellular ageing overall.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Dentistry
Subjects: Q Science > Q Science (General)
Uncontrolled Keywords: dental pulp stem cells; oxidative stress; oxidative damage; premature senescence; SOD2; GSTZ1
Date of First Compliant Deposit: 8 July 2020
Last Modified: 05 Aug 2022 01:40

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