As women age, their fertility typically starts to decline in their mid-thirties, partly because the number and quality of their eggs decrease. However, research suggests another factor might be at play: ovaries tend to become stiffer over time, which can negatively affect egg development. Now, a new study in rodents has raised hopes that making ovaries softer could help extend the fertility window.
A research team led by Shixuan Wang at the Huazhong University of Science and Technology in Wuhan, China, investigated this stiffness. They analyzed protein levels in healthy ovaries removed from women of various ages. The researchers discovered that a protein called interleukin-11 (IL-11) increases in ovaries as women age. This protein triggers cells in the connective tissue to produce collagen, a structural protein that causes the ovaries to stiffen.
To see if they could reverse this process, the team genetically modified mice so they could not respond to IL-11. As these mice aged, their ovaries remained softer, and they ovulated more eggs compared to normal mice.
Next, the researchers tested an experimental drug designed to block the gene that produces IL-11. They injected this drug twice a week for four weeks into 36-week-old mice, which is roughly equivalent to a human in their late 30s or early 40s. The treatment reduced ovarian stiffness by 36 percent. More importantly, the mice's conception rate doubled from 25 percent to 50 percent, and their average litter size grew from three to five pups. Similar positive results were observed in rats, where the conception rate rose from 20 percent to 50 percent and litter sizes increased fivefold.
While the findings are promising, experts urge caution. Francesca Duncan at Northwestern University in Illinois pointed out that the human ovarian tissues used in the study came from women with a history of gynecological cancer, so it remains unclear if the same IL-11 increase occurs in women without such conditions. Furthermore, because IL-11 is found throughout the human body, targeting the ovaries specifically is crucial to avoid potentially dangerous side effects.
Nevertheless, if the drug proves safe and effective in humans, it could have benefits beyond fertility. Barbara Vanderhyden from the University of Ottawa in Canada noted that prolonging ovarian function could delay the onset of menopause, potentially reducing the risk of associated health issues like osteoporosis and heart disease.