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Evaluation Of The Therapeutic Potential Of In Vitro-Derived Oocytes For Fertility Preservation.

PGR-P-163

Key facts

Type of research degree
4 year PhD
Application deadline
Ongoing deadline
Country eligibility
International (outside UK)
Funding
Non-funded
Supervisors
Dr John Huntriss and Professor Helen Picton
Schools
School of Medicine
Research groups/institutes
Leeds Institute of Cardiovascular and Metabolic Medicine
<h2 class="heading hide-accessible">Summary</h2>

In recent years improvements in the diagnosis, management and treatment of a range of solid and haematological malignancies has lead to a marked increase in the chances of long-term survival for a significant number of children and adolescents. Unfortunately germ cells, like the cancer cells that are their intended targets, are highly susceptible to damage by radiation and by the alkylating agents and platinum compounds that are commonly used in chemotherapy formulations. Thus the radiation and chemotherapy used to cure many cancers can render patients of either sex or any age temporarily or even permanently infertile.

<h2 class="heading hide-accessible">Full description</h2>

<p>&nbsp;The premature gonadal failure or total sterility that can occur as a consequence of cancer treatment is particularly relevant to young girls who, in the event of ovarian failure, are faced with the prospects of life long hormone replacement therapy. Healthcare professionals are therefore faced with the challenge of not only developing and improving the technologies that will treat cancer and protect the individual&rsquo;s wellbeing, but they must also implement strategies that will conserve the fertility of young patients.</p> <p>The current options available to preserve the fertility of young female cancer patients range from no medical intervention at all to the use of invasive procedures to harvest and freeze-store tissues or isolated cells. Assisted reproductive techniques can be used for the collection and storage of mature oocytes (eggs) and embryos. However these approaches are only suitable for patients of reproductive age and they are clearly not an option for most adolescents or for prepubertal girls. An alternative approach that is suitable for both children and adults is the cryopreservation of ovarian tissue.</p> <p>Ovarian tissue cryopreservation involves freezing the earliest staged primordial oocytes in situ either through freezing small pieces of the surface of the ovary or by freezing the whole ovary. The tissue fragments or ovary can then be transplanted back to the patient when she is in remission and wishes to start her family. Unfortunately, ovarian autografting is not suitable for patients with blood bourn diseases such as Leukaemia or steroid related cancers as these diseases carry a high risk of reintroducing the cancer to the body through the transplanted tissue. Where any such risk exists a safer alternative for the restoration of fertility is to grow the immature oocytes within the ovarian tissue to maturity in the laboratory through a process known as the in vitro growth (IVG) of eggs contained within ovarian follicles. Once the eggs are fully grown they can then be matured by in vitro maturation (IVM) and fertilised using in vitro fertilisation (IVF) technologies so that only embryos that are free from cancer cells are transferred back to the patient to establish a pregnancy.</p> <p>The development of technologies for the complete IVG of fertile oocytes from the most abundant primordial follicles holds many attractions for assisted conception, in humans and for animal production and animal conservation. Any culture strategy designed to support the complete IVG of oocytes must mimic the sequence of events seen by these cells in vivo in terms of growth rates, gene expression patterns, protein synthesis and metabolism. This legacy of development is required to support the production of a fertile oocyte and early post-fertilisation development of the zygote. The team at Leeds has recently developed a 3D culture strategy that supports the complete in vitro development of oocytes over extended periods of up to 3-4 months.</p> <p>The student will join a team of world class scientists working on human oocyte biology. He/she will be trained in a range of specialist laboratory methods including: ovarian tissue cryopreservation, follicle and oocyte harvest and culture, in vitro fertilisation and embryo culture; confocal and fluorescent microscopy; analysis of the oocytes&rsquo; metabolome (mitochondrial activity measurement, quantification of energy and protein turnover), transcriptome (real time PCR and RNA Sequencing), and epigenome (pyrosequencing methylation analysis); and bioinformatics. Due to the limited availability of human ovarian tissue for research, abattoir-derived sheep ovaries and oocytes will be used as a model for human ovary/oocytes throughout the course of this Ph.D project. The proposed experiments will grow follicles from the earliest primordial stages to maturity in the laboratory using our in-house, follicle culture system. The developmental capacity of in vitro grown oocytes from fresh and cryopreserved ovarian tissue will be tested. A series of cellular, metabolic and molecular assays will be used to evaluate the health and developmental capacity of oocytes derived using culture methods. Follicle and oocyte size will be measured and growth rates recorded. Follicle development and culture stress will be assessed by measuring follicle and oocyte metabolism and waste product production in samples of spent culture media. Molecular genetic and epigenetic indices of oocyte growth and health will be compared to in vivo derived cells. The capacity of in vitro-derived oocytes to complete meiotic maturation and produce a fertile gamete will ultimately be assessed using methods for IVM and IVF. Embryo developmental potential will be quantified by culturing embryos for up to 7 days to the blastocyst stage and recording embryo cleavage rates, blastocyst production, cell number, embryo metabolism and gene expression profiles. All of the technologies for IVG, IVM and IVF of sheep oocytes, together with analytical techniques used to assess growth and fertility are in routine use in the Leeds laboratory.</p> <p><strong>References</strong></p> <p>Picton HM, Kim S, &amp; Gosden RG (2000). Cryopreservation of gonadal tissue and cells. British Medical Bulletin 56(3), 603-615</p> <p>Picton HM, Harris SE, Muruvi W and Chambers EL (2008) Advances In In Vitro Follicle Development And Oocyte Maturation. Reproduction 136: 703-715.</p> <p>Huntriss J &amp; Picton HM (2008). Epigenetic consequences of assisted reproduction and infertility on human preimplantation embryos. Human Fertility (Camb).11(2):85-94.</p> <p>Chambers EL, Gosden RG, Yap C, Picton HM (2010) In situ identification of follicles in ovarian cortex as a tool to quantify follicle density, viability and developmental potential in strategies to preserve female fertility. Hum Reprod 25(10):2559-68</p> <p>Cotterill M, Catt SL, Picton HM (2012) Characterisation of the cellular and molecular responses of ovine oocytes to preovulatory levels of FSH and LH during in vitro maturation. Reproduction, 44:195-207.</p> <p>Hemmings KE, Maruthini D, Vyjayanthi S, Hogg JE, Balen AH, Campbell BK, Leese HJ, Picton HM (2013). Amino acid turnover by human oocytes is influenced by gamete developmental competence, patient characteristics and gonadotrophin treatment. Hum Reprod 28(4):1031-44</p> <p>Campbell BK*, Hernandez-Medrano J, Onions V, Pincott-Allen C, Aljaser F, Fisher J, McNeilly AS, Webb B, Picton HM (2014). Restoration of ovarian function and natural fertility following the cryopreservation and transplantation of whole adult ovaries. Human Reproduction August; 29(8): 1749&ndash;1763</p> <p>Newton HL, Glaser A, Picton HM (2017) The feasibility, safety and outcome of fertility preservation treatment options in pre-pubertal girls. Minerva Ginecol. 69(6):568-586. doi: 10.23736/S0026-4784</p> <p>Martinez F (2017) Update on fertility preservation from the Barcelona International Society for Fertility Preservation-ESHRE-ASRM 2015 expert meeting: Indications, results and future perspectives. Hum Reprod, 32(9): 1802-1811.</p> <p>Matthews SJ, Picton H, Ernst E, Andersen CY. (2018) Successful pregnancy in a woman previously suffering from &beta;-thalassaemia following transplantation of ovarian tissue cryopreserved before puberty. Minerva Ginecol 70(4):432-435.</p>

<h2 class="heading">How to apply</h2>

<p>Please note these are not standalone projects and applicants must apply to the PhD academy directly.</p> <p>Applications can be made at any time. To apply for this project applicants should complete a<a href="https://medicinehealth.leeds.ac.uk/downloads/download/129/faculty_graduate_school_-_application_form"> Faculty Application Form</a> and send this alongside a full academic CV, degree transcripts (or marks so far if still studying) and degree certificates to the Faculty Graduate School <a href="mailto:fmhpgradmissions@leeds.ac.uk">fmhpgradmissions@leeds.ac.uk</a></p> <p>We also require 2 academic references to support your application. Please ask your referees to send these <a href="https://medicinehealth.leeds.ac.uk/downloads/download/130/faculty_graduate_school_-_scholarship_reference_form">references</a> on your behalf, directly to <a href="mailto:fmhpgradmissions@leeds.ac.uk">fmhpgradmissions@leeds.ac.uk</a></p> <p>If you have already applied for other projects using the Faculty Application Form this academic session you do not need to complete this form again. Instead you should email fmhgrad to inform us you would like to be considered for this project.</p> <p>If English is not your first language, you must provide evidence that you meet the University&#39;s minimum English language requirements (below).</p>

<h2 class="heading heading--sm">Entry requirements</h2>

A degree in biological sciences, dentistry, medicine, midwifery, nursing, psychology or a good honours degree in a subject relevant to the research topic. A Masters degree in a relevant subject may also be required in some areas of the Faculty. For entry requirements for all other research degrees we offer, please contact us.

<h2 class="heading heading--sm">English language requirements</h2>

Applicants whose first language is not English must provide evidence that their English language is sufficient to meet the specific demands of their study. The Faculty of Medicine and Health minimum requirements in IELTS and TOEFL tests for PhD, MSc, MPhil, MD are: &acirc;&euro;&cent; British Council IELTS - score of 7.0 overall, with no element less than 6.5 &acirc;&euro;&cent; TOEFL iBT - overall score of 100 with the listening and reading element no less than 22, writing element no less than 23 and the speaking element no less than 24.

<h2 class="heading">Contact details</h2>

<p>For further information please contact the Graduate School Office<br /> e:<a href="mailto:fmhpgradmissions@leeds.ac.uk">fmhpgradmissions@leeds.ac.uk</a>, t: +44 (0)113 343 8221.</p>


<h3 class="heading heading--sm">Linked research areas</h3>