Growing human eggs in the lab

“Fertility hope for cancer patients,” is the headline in The Times . An advance in the method of growing human eggs in the laboratory could “help women and girls to preserve their fertility during treatment for cancer,” the newspaper says. Other newspapers also carry the story. The Daily Mail reports that the technology could also be used for women who are infertile and suggests that it will “allow thousands more women to wait until middle age to have children”.

The stories are based on a laboratory study using ovarian cells from six women. The researchers were able to harvest very immature eggs and grow them outside the body. The findings from this study may one day translate into technologies to treat human infertility. For now, though, this application is a long way off. More research is needed to determine whether the cells that are being cultured outside of the body are “normal” cells, and whether they can go on to further development and specialisation to a degree that will allow fertilisation. The technology is in its infancy and will no doubt feature in future human reproductive research.

Where did the story come from?

Dr Evelyn Telfer and colleagues from the University of Edinburgh carried out this research. The study was funded by the Medical Research Council (MRC), the Biotechnology and Biological Sciences Research Council (BBRSC) and the Edinburgh Assisted Conception Unit Endowment Fund. It was published in Human Reproduction , a peer-reviewed medical journal.

What kind of scientific study was this?

The study was a laboratory study. The researchers were interested in whether they could harvest immature ovarian follicles (the precursors to eggs) from women’s ovaries and allow them to grow and mature in a cell culture outside of the body. If they could, this would offer a solution to problems often encountered during assisted reproduction techniques, for example that there are usually only a few mature, harvestable eggs available. It would also help women who have had chemotherapy for cancer and whose eggs are unavailable; up to now, fertility has depended on the use of stored ovarian tissue.

Ovarian biopsies were taken from six women aged between 26 and 40 years while they were undergoing caesarean sections. The researchers took a small piece of ovarian tissue (measuring about 5mm x 4mm) from the cortical cells, the part of the ovary that produces female eggs. They made sure there were no eggs present. They then grew these strips of cells in a cell culture for six days at 37C in a special medium that they developed. After six days, they transferred the strips to another medium and removed 74 immature follicles. These immature follicles were placed on separate culture plates for four days at 37C to see how they would grow and mature.

Thirty-eight of the culture plates contained a chemical called activin, which has been shown to be important in growing and maturing eggs from sheep and cattle. The researchers then examined the eggs using a microscope to see what stage of development they had reached.

What were the results of the study?

The researchers noted that follicles were growing while the strips of ovarian tissue were being cultured. Over time, the stage of development of these follicles changed. After six days, there were more “developed” eggs and fewer ”immature” ones. This indicated that the cells were maturing in the culture. The majority of those grown in the medium containing activin showed an increase in size during the first two days of being in the culture. More of the follicles grown with activin were “healthy” compared with those grown without it.

What interpretations did the researchers draw from these results?

The researchers conclude that their study has shown that human “pre-antral follicles” (i.e. eggs at an early stage of development) that have developed in culture from even more immature cells can be “isolated and have the potential to grow” to the antral stage of development (the stage where eggs grow rapidly in a process that is dependent on hormones and growth factors). They also found that the growth was more accelerated in the presence of activin.

What does the NHS Knowledge Service make of this study?

This laboratory study will be of interest to the scientific and medical communities, which are always seeking ways to enhance assisted reproduction techniques. The researchers have shown that culture techniques which have been successful with sheep and cattle can be used to grow and develop human female eggs. As they say, it was difficult for them to isolate all the eggs that were present by day six of the culture of ovarian tissue, but they did get a good harvest: 74 intact pre-antral follicles from six biopsies. The accelerated growth and development of the follicles that they have achieved outside the body is much quicker than these processes take inside the human female. This makes the technique a potentially attractive approach to addressing infertility in women, i.e. by harvesting very immature cells from women’s ovaries and developing and growing them outside the body. The technique could also improve fertility treatments for women undergoing chemotherapy.

This technology is in its very early stages. Any application to fertility treatments for women is a long way off. Most importantly, this study did not determine whether the developing eggs were “normal”, though the researchers say that they appeared to be “intact”. It is not clear whether further development of these cells, i.e. to the point where the cells are ready for fertilisation, and the subsequent formation of an embryo would proceed without problems. This, of course, cannot be assumed. The research into this technology remains in a developmental phase itself.

Sir Muir Gray adds...

This is a good example of evaluating a new technology before widespread introduction.