The development of technologies to grow oocytes from the most abundant primordial follicles to maturity in vitro holds many attractions for clinical practice, animal production technology and research. The production of fertile oocytes and live offspring has been achieved in mice following the long-term culture of oocytes in primordial follicles from both fresh and cryopreserved ovarian tissue. In contrast, in non-rodent species advances in follicle culture are centred on the growth of isolated preantral follicles. As a functional unit, mammalian preantral follicles are well-suited to culture but primordial and primary follicles do not grow well after isolation from the ovarian stroma. The current challenges for follicle culture are numerous and include: optimisation of culture media and the tailoring of culture environments to match the physiological needs of the cell in vivo; the maintenance of cell-cell communication and signalling during culture; and the evaluation of the epigenetic status, genetic health and fertility of in vitro derived mature oocytes. In large animals and humans, the complete in vitro growth and maturation of oocytes is only likely to be achieved following the development of a multistage strategy that closely mimics the ovary in vivo. In this approach, primordial follicle growth will be initiated in situ by the culture of ovarian cortex. Isolated preantral follicles will then be grown to antral stages before steroidogenic function is induced in the somatic cells. Finally, cytoplasmic and nuclear maturation will be induced in the in vitro derived oocytes with the production of fertile metaphase II gametes.

NR predicts viable follicle density in situ in slices of ovine and human ovarian cortex. Furthermore incubation of tissue in NR prior to culture does not compromise subsequent follicle survival in vitro, indicating the potential suitability of this approach in fertility preservation regimes.

Please cite this paper as: Balen A, Harris S, Chambers E, Picton H. Conservation of fertility and oocyte genetics in a young woman with mosaic Turner syndrome. BJOG 2010;117:238-242. Case reportWe report a case of oocyte cryopreservation and ovarian tissue cryopreservation in a woman with mosaic Turner syndrome in whom, for the first time in the literature, a detailed assessment was made of the genetic composition of the oocytes. The aim was to preserve fertility in a woman considered at high risk of premature ovarian failure.The patient presented at the age of 12 years with short stature. Her parents had been concerned about her rate of growth compared with her contemporaries. She had no other stigmata of Turner syndrome, but investigations confirmed mosaicism with 45,X/46,XX, with only two of the 30 cells examined being 46,XX and the remainder being 45,X. All other investigations were normal and, in particular, an ultrasound scan revealed a prepubertal uterus with ovaries clearly visualised and of normal volume.Treatment was commenced with growth hormone under the care of a paediatric endocrinologist. This produced a good response with a final height of 1.55 m. Puberty occurred naturally and menarche was achieved at the age of 15 years and 0 months, followed by a regular menstrual cycle. There was fluctuating thyroid function and, eventually, the girl became hypothyroid and is now on thyroxine replacement.The patient consulted at the age of 17 years to talk about the possibility of ovarian cryopreservation. At that stage, we were undertaking research into ovarian tissue cryopreservation for women about to undergo chemotherapy. 1,2 Therefore, counselling was provided with regard to the risks and limitations of this process. 3 The patient continued to have a regular menstrual cycle with normal gonadotrophin concentrations and, therefore, in February 1998, laparoscopy was performed and bilateral ovarian biopsies were taken. Both ovaries appeared to be of normal size and appearance. Multiple samples of ovarian cortical tissue were collected laparoscopically using punch biopsy and the tissue was cryopreserved by slow freezing following equilibration in 1.5 m dimethylsulphoxide and 0.5 m sucrose, according to the protocol described by Newton et al., 1 and stored under liquid nitrogen. A specimen from each ovary was karyotyped. The analysis of cultures from the left ovarian biopsy showed 16 cells with a normal female pattern and 14 cells with only a single X chromosome. From the right ovary, eight cells had a normal female pattern and 22 cells had a single X chromosome. Therefore, these ovarian tissue biopsies showed a significantly higher proportion of cells with a normal female pattern. The patient was reviewed annually and continued to have a fairly regular 28-30-day menstrual cycle with normal serum gonadotrophin concentrations.At the age of 25 years, the serum follicle-stimulating hormone concentration was 3.3 iu/l with a luteinising hormone level of 1.3 iu/l. A measurement of inhibin B yielded 176 pg/ml. These ...

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