A recent study has unveiled promising results in the quest to extend women's fertility, suggesting that softening the ovaries could play a crucial role. Researchers found that an experimental drug designed to reduce ovarian stiffness significantly improved conception rates and litter sizes in older mice and rats, raising hopes for potential human applications.
Women's fertility typically begins to decline in their mid-thirties, a trend that contrasts with the increasing number of women in countries like England and Wales who are choosing to have children later in life. While the number and quality of immature eggs naturally decrease with age, there is also growing evidence that ovaries themselves become stiffer over time, which may further impede egg development and quality.
The research, conducted by Shixuan Wang and colleagues at Huazhong University of Science and Technology in China, investigated the underlying mechanisms of ovarian stiffness. Their findings revealed that a protein called interleukin-11 increases in human ovaries with age. This protein activates fibroblasts, cells in connective tissue responsible for producing collagen, which in turn contributes to ovarian stiffness. By genetically modifying mice to be unresponsive to interleukin-11, the team observed reduced ovarian stiffness and increased ovulation rates as the animals aged.
In a further significant step, the researchers tested an experimental drug that blocks the production of interleukin-11. When injected into 36-week-old mice, an age equivalent to a person in their late 30s or early 40s, the drug reduced ovarian stiffness by 36 per cent. Crucially, it doubled their conception rate from 25 per cent to 50 per cent and increased their average litter size from three to five pups. Similar positive effects were observed in rats, with conception rates rising from 20 per cent to 50 per cent and litter sizes increasing fivefold, from one to five pups.
While these results are encouraging, experts caution that further research is essential. Francesca Duncan from Northwestern University in Illinois notes that while interleukin-11 also increases with age in human ovaries, the human data in this study came from women with a history of gynaecological cancer, meaning the same trend might not apply universally. The drug's safety is also a key concern, as interleukin-11 is expressed in many human tissues, necessitating a high safety bar for any intervention targeting the ovary. Additionally, the optimal duration of treatment for humans remains unclear, as does the long-term impact on ovarian health.