PRDX4 Alleviates Ovarian Aging by Suppressing Endoplasmic Reticulum Stress‑Related Ferroptosis in Granulosa Cells

The ovaries are the body's engine for reproduction, a complex organ that produces eggs and the hormones necessary for pregnancy. Like all biological systems, this engine wears down over time. In women, this process of ovarian aging begins noticeably after age thirty and leads to menopause around age fifty. When the ovaries age, the cells that support egg development—known as granulosa cells—lose their ability to function properly, making conception difficult and increasing the risk of age-related health issues. Scientists have long sought to understand the specific molecular breakdown that causes these cells to fail. One emerging culprit is a form of cell death called ferroptosis. Unlike other types of cell death that involve the cell simply shutting down or bursting, ferroptosis is a process where the cell's internal machinery becomes overwhelmed by rust-like damage. This happens when iron builds up inside the cell and triggers a chain reaction that destroys the cell's protective fats, effectively causing the cell to corrode from the inside out. Another key player in this story is a protein called PRDX4, which acts as a shield against stress within the cell's internal factory, the endoplasmic reticulum. The question researchers have been trying to answer is whether this protective protein can stop the rusting process and keep the ovaries functioning longer.

A team of researchers at the First Affiliated Hospital with Nanjing Medical University set out to investigate exactly how PRDX4 interacts with this rusting process in aging ovaries. They began by looking at the ovaries of mice that had naturally aged, comparing them to younger mice. Using powerful microscopes, they observed that the mitochondria—the tiny power plants inside the cells—of the older mice were shrunken and damaged, lacking the internal folds that generate energy. They also found that the older ovaries contained more than twice the amount of iron compared to the younger ones. Chemical tests confirmed that the older cells were suffering from high levels of oxidative stress and lipid peroxidation, the specific type of damage that defines ferroptosis. The researchers measured the levels of key proteins and found that the cells had lost their main defense against this rusting, while simultaneously increasing the machinery that brings iron into the cell. This confirmed that as ovaries age, their cells become highly vulnerable to this corrosive form of death.

To understand how to stop this, the scientists turned to a laboratory model of human granulosa cells. They aged these cells in a dish using a chemical that mimics the stress of aging. In these aging cells, the levels of the protective protein PRDX4 dropped significantly. The researchers then used a viral vector to force the cells to produce extra PRDX4. The result was immediate and clear: the cells with high levels of PRDX4 looked and acted much younger. They contained far less iron and oxidative damage, and their mitochondria remained healthy. The cells also stopped producing the chemical signals that usually mark them as old and worn out. By boosting PRDX4, the researchers effectively turned off the rusting process, proving that this protein is a powerful guardian against ferroptosis in ovarian cells.

However, the team wanted to know exactly how PRDX4 achieved this protection. They suspected the answer lay in the endoplasmic reticulum, the cell's protein-folding factory. When this factory gets overwhelmed, it sends out a distress signal known as endoplasmic reticulum stress. The researchers found that in aging cells, this stress signal was loud and constant, and it was this signal that was telling the cell to start the rusting process. To test this, they used a drug called 4-PBA, which is known to calm down endoplasmic reticulum stress. When they treated the aging cells with 4-PBA, the rusting stopped, even if the cells did not have extra PRDX4. Conversely, when they used a different drug to artificially create stress in the factory, the protective effect of PRDX4 disappeared, and the cells began to rust again. This experiment revealed the precise mechanism: PRDX4 works by keeping the endoplasmic reticulum calm. When the factory is not stressed, it does not send the signal that triggers the iron buildup and cell death.

The study concludes that the decline of PRDX4 is a critical factor in ovarian aging because it allows endoplasmic reticulum stress to rise, which in turn triggers ferroptosis. By keeping this stress in check, PRDX4 prevents the cells from corroding. The researchers demonstrated that restoring PRDX4 levels or chemically reducing the stress can reverse the signs of aging in these cells. While the study was conducted in mice and human cell lines, the findings offer a clear biological pathway for how ovarian aging occurs. The work suggests that targeting this specific stress pathway could be a way to delay the aging of the ovaries, potentially extending the window of fertility and reducing the health risks associated with menopause. The researchers identified 4-PBA as a potential agent that could mimic this protective effect, though they note that further investigation is needed to see if this approach can be safely applied to humans.