- Title
- Towards non-surgical sterilisation of feral horses: biomarkers of folliculogenesis and covalent modification of proteins using electrophilic aldehydes
- Creator
- Hall, Sally Elizabeth
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2017
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Feral horses currently require immediate population control in certain areas of Australia, and are a pest species across many regions of the world. Fertility control is considered the most suitable management strategy for control; however, agents currently available are largely non-sustainable for free-ranging feral horses. This is due to the difficulties associated with application of a fertility control agent, the ability to then identify animals which have been treated, and finally, the timely readministration of boosters. Consequently, there is an urgent need to develop a fertility control agent for feral horses that is easy to administer and will persist for the lifetime of the animal. While extensive research in the development of a non-surgical sterilisation method has been conducted in mouse models, little has been done in horses, creating a need for research to be undertaken investigating horse gamete biology. In this thesis, a fertility control agent for feral horse management was investigated from both a female and male perspective. Initial recruitment at the beginning of folliculogenesis, responsible for the activation of primordial follicles within the ovary, is considered the fundamental phase that determines the reproductive potential of a female. There is an abundance of evidence to indicate that if recruitment from the primordial follicle population is suppressed or if the primordial follicle population is depleted then a state of infertility is induced. Recent work has shown that interruption of normal follicular processes via irregularities in signalling pathways such as phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) can have irrevocable consequences, resulting in infertility. Consequently, investigation into mare ovarian anatomy and follicular signalling processes was the primary approach taken to determine whether manipulation of these pathways could be used in the future development of a non-surgical sterilisation method. Messenger RNA expression of signalling molecules within two signalling pathways essential for initial recruitment in folliculogenesis, PI3K/AKT and janus kinase/signal transducer and activator of transcription (JAK/STAT), significantly increased between gestation and adulthood, coincident with sexual maturity. Protein localisation was also largely conserved which suggests that signalling pathway inhibitors can indeed be used as a means of manipulating the rate of primordial follicle activation as an approach to fertility control in this species. Next we explored the impact of exogenous electrophilic aldehydes on stallion spermatozoa, as interruption of the delicate protein profile that exists within the plasma membrane has been demonstrated to cause infertility, often due to defective sperm-egg recognition and fusion. A significant increase in mitochondrial and cytosolic reactive oxygen species (ROS), lipid peroxidation and a commensurate loss of motility resulted following exposure to acrolein (ACR) and 4-hydroxynonenal (4HNE); partly due to perturbation of mitochondrial aldehyde dehydrogenase (ALDH2), a detoxification mechanism which is responsible for counteracting acute ROS formation. We identified proteins vulnerable to adduction and covalent modification, including: heat shock protein 90 alpha (cytosolic) class A member 1 (HSP90AA1) and arylsulfatase A (ARSA) by ACR and 4HNE, respectively. Zona pellucida binding competence was also lost following exposure to low levels of ACR and 4HNE. Exposure to electrophilic aldehydes such as ACR and 4HNE has been associated with the development of autoimmune disease. Consequently, following on from the findings in the previous study, we next performed a fertility trial within the mouse model, immunising mice with proteins that had previously been exposed to ACR and 4HNE. Females immunised with ACR-adducted sperm proteins and subsequently mated experienced a reduction in the number of pregnancies, while sperm from mice immunised with ACR-adducted sperm proteins had significantly reduced zona pellucida binding competence in vitro. Blood serum from males revealed antibodies against proteins that were covalently modified by ACR, which have been implicated in gamete interaction, including: heat shock protein 60 (HSP60) and arylsulfatase A (ARSA), izumo sperm-egg fusion 1 (IZUMO1) and protein disulfide isomerase A6 (PDIA6). Taken together, the studies within this thesis have significantly contributed to our understanding of mare and stallion gamete biology. We have identified a critical role for electrophilic aldehydes in the adduction and covalent modification of sperm proteins critical for sperm-egg recognition. The use of covalently modified sperm proteins in a species-specific vaccine for feral horses would provide a novel means of fertility control that may potentially offer long-term contraceptive protection.
- Subject
- antisperm antibodies; electrophilic aldehydes; feral horses; immunocontraceptive; primordial follicle activation
- Identifier
- http://hdl.handle.net/1959.13/1347466
- Identifier
- uon:30044
- Rights
- Copyright 2017 Sally Elizabeth Hall
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 6 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 272 KB | Adobe Acrobat PDF | View Details Download |