Developmental and meiotic potential of oocytes derived from human ovarian germ line stem cells (OSCs) in vitro.

For decades, scientists have believed that women were born with all the eggs they would ever have and that no new ones could ever be made. Recently a group of researchers in the USA isolated a primitive "stem" like cell from the ovaries of adult women. These cells were shown to be capable of forming what appeared to be new eggs (oocytes) when they were injected back into ovarian tissue. The implications of this are potentially enormous, but at the moment we know very little about what these cells may or may not be capable of. If we could make new eggs we could eventually help restore fertility in women who have become infertile for a variety of reasons, including chemotherapy, early menopause or just normal ageing. However, these findings have led to controversy and many questions remain as to whether these new eggs can develop normally. This project will determine whether these cells can be isolated from the ovaries of healthy women from a range of ages. Then using a system which we have developed where we can grow eggs outside the body (culture system), we will determine whether these cells can form new eggs and whether they are normal. The ultimate end point of this work would be to determine whether these cells were capable of forming eggs that could be fertilised and form embryos.

Cells with germ line potential have been isolated and purified from adult mouse ovary and from human ovarian tissue obtained from adult women. These cells, termed oogonial stem cells (OSCs) have been characterised in mice and after in vivo transplantation they form functional oocytes that can be matured, fertilised and form embryos. The equivalent human cells that have been isolated have been much less fully characterised. Yet the ability to develop these cells into mature oocytes would have many potential applications in assisted reproduction and fertility preservation as well being of huge value as a model for the study of human oogenesis. This project aims to confirm the isolation of this cell population from ovaries of adult women of varying ages and to determine the developmental potential of oocytes derived from human OSCs. To test the developmental potential of human OSCs we will combine them with a multistep culture system recently developed in our lab that supports development of human oocytes from the most immature stage (primordial) to fully developed stages with some being capable of undergoing meiotic maturation to Metaphase II. Using this system our preliminary data show that OSCs form follicles when injected into human ovary tissue, with confirmation that they can undergo the initial stages of folliculogenesis. By combining these two technologies we will be able to explore robustly the full meiotic and developmental potential of these cells, and provide a basis for future studies exploring their therapeutic potential.

This proposal is to study a newly identified cell type isolated from the ovaries of adult women that appears to have the potential to form new eggs (oocytes). This study will determine whether these newly formed oocytes are normal and viable. The beneficiaries of this proposal will be:
1) Researchers in Reproductive Sciences: Researchers will benefit from this work as it will provide a model to study the early processes of human egg development. It will provide tools to study processes such as meiosis which has previously been in accessible in humans.
2) Students and Scientists will benefit as this project will offer greater insight into a central tenet of mammalian female reproduction. These results could lead to new hypotheses to explain the process of ovarian ageing.
3) Fertility Preservation patients and practitioners would benefit if positive results are obtained. This work could lead to the process of isolating this stem cell population as a method for fertility preservation. This would affect a range of patient groups from cancer sufferers to those with Premature Ovarian Failure and genetic conditions such as Turners syndrome.
4) Assisted Reproductive Technologies; healthcare providers, clinical practitioners and patients. If the results of this project are positive then we will be in a position to develop methodologies for novel approaches to assisted reproduction. These could potentially a) negate the need for hormonal stimulation of the patient, b) avoid multiple surgical procedures to harvest the resultant eggs, c) implement a series of quality control measures to optimise egg selection for subsequent fertilisation and d) improve success rates particularly in older women, and most importantly provide options for women who have no options currently available. All these are highly desirable outcomes for improving the treatment and management of infertile women.
5) Commercial companies. Assisted reproduction is an area of high commercial interest. With any new potential therapies comes the development of a range of techniques to facilitate it. This work would impact on the development of techniques to isolate, store and culture these cells.