When ovaries from young mice were transplanted into aging females, the old mice lived longer and changed their reproductive behaviour, scientists from Japan have found. The findings raise the question of whether a similar effect may be seen in women receiving ovarian transplants.
Dr Noriko Kawaga from the Kato Ladies' Clinic in Tokyo and his colleagues transplanted either one or two ovaries from young donor females into older mice who were no longer fertile. In both experiments, all the recipient animals became fertile again and resumed the behaviour of young mice.
'They showed interest in male mice, mated and some had pups', explained Dr Kagawa. 'Old mice stay in the corner of the cage and don't move much, but the activity of the mice that had ovarian transplants was transformed'.
Surprisingly, the old mice who received young ovaries also lived more than 40 per cent longer than the control animals - an average of 877 or 915 days respectively, compared to an average normal lifespan of 548 days. Although the reason for this increased longevity is not yet known, the researchers think it may be because the transplants prompt normal hormonal functions to continue.
'The completely unexpected extra benefit of fertility-preserving procedures in our mouse studies indicates that there is a possibility that carrying out similar procedures in women could lengthen their lifespans in general', Dr Kagawa said.
Ovarian transplant operations are currently performed to preserve fertility after cancer therapy, which can leave some women infertile. Ovarian tissue can be removed and frozen before beginning treatment, and transplanted back a few years later when the woman is cured.
The new findings indicate that, by producing the hormones usually seen in younger women, the transplanted ovaries could also protect these older women from skin, heart, bone and brain problems and extend their lifespan. However, Dr Kagawa stressed that a lot more research is needed to investigate whether ovarian transplants could have the same effect in humans, particularly as it would involve waiting until the women reached old age.
Dr Sherman Silber from St Luke's Hospital in St Louis, US, has successfully performed ovarian transplants in a number of women and has been collaborating with Dr Kagawa for the past six years.
'Latest data shows that after menopause in humans similar changes occur as in mice and all other mammals', he said.
'The problem is that our hormone replacement regimes for humans have been very distorted…with the correct HRT (hormone replacement therapy) this study indicates that we can prevent this deterioration in the physical condition of women and lengthen their lives significantly… transplantation of a young ovary provides the right physiological hormone replacement to solve this problem'.