Implanting ovarian tissue from women into mice could be a more successful alternative to freezing eggs for those facing cancer treatment that could effect fertility, scientists report.

The tissue, and the eggs it contains, would be kept alive in the mouse muscle until it was needed.

Then, by giving fertility drugs to the mouse, eggs could be harvested and potentially used in IVF treatment.

A team of scientists from Toronto, Canada, has been able to thaw frozen ovarian tissue, implanting that into mice and then producing eggs.

Although ovarian tissue has been directly grafted into humans and stimulated to produce hormones, no-one has managed to produce eggs this way.

Attempt next year

The scientists believe that the eggs they have harvested so far could well be useable, and are now carrying out laboratory tests to check this.

They hope that the extraordinary technique might be used as early as next year to try for a child.

However, stronger restrictions on the use of fertility techniques are likely to delay its introduction in the UK for some time.

UK Clinics have only just been given permission to thaw out and use frozen eggs, years after the technique began to be used by women elsewhere.

Powerful cancer treatments, along with those for other conditions such as endometriosis, can threaten a woman's future fertility.

Many opt to have eggs removed and stored for use at a later date.

While the thawing process appears not to cause health problems for babies born using the method, the conception rate is low - so fertility experts may be interested if the mouse method yields a higher success rate.

Dr Ariel Revel, from the Samuel Luenfield Research Institute at Mount Sinai Hospital in Toronto, said their research could have found a viable alternative to the standard egg freezing process.

Planted in muscle

"The fact that we have within the last few weeks also managed to retrieve eggs from frozen and thawed tissue is a vital and further step."

The team took fresh tissue from the ovarian cortex - the surface area of the ovary where most egg-producing "follicles" are found.

This was transplanted into muscle on the back of "nude" mice - a species which has no immune system, and cannot therefore reject the graft.

The graft achieves a good blood supply within the muscle.

In theory, women - or even children, facing treatment which could render them infertile could have ovarian tissue removed, frozen, and then the mice could be used to help it to generate eggs when the woman wants to use the tissue to have children.

Dr Revel said that using the muscle tissue as a "nursery" was ideal, as it was very difficult to mature the eggs in culture in a laboratory.

However, ovarian transplant expert Dr Yves Aubard says that it would be ethically unsound to use a mouse to "store" the ovarian tissue.

He said: "To ever use this technique clinically would be a huge problem - the best option is to transplant it back into the person it was taken from."