Most men become infertile after spinal cord injury. Researchers are trying to find out why
A Texas A&M University study is exploring a common but little understood complication that can affect quality of life for men living with spinal cord injuries.
Doctors have known for decades that most men become infertile after a spinal cord injury. What they haven’t known is why.
Dr. Jennifer Dulin, assistant professor of biology at Texas A&M University, is working to answer that question through a project investigating the biological changes that occur after injury in hopes of laying the groundwork for future treatments.
“Most men with spinal cord injury are of reproductive age,” Dulin said. “Their lives are already profoundly disrupted. They may lose mobility and independence, and many want to build a family and live as normal a life as possible. Then they discover they may not be able to have children.”
Funded by a two-year grant from the Craig H. Neilsen Foundation, the project seeks to answer why fertility declines so dramatically after spinal cord injuries, which affect an estimated 18,000 Americans each year — with nearly 80% occurring in men. While paralysis is often the most visible consequence, fertility loss is among the condition’s most common and least understood long-term effects.
“It’s not just paralysis,” Dulin said. “The whole body is regulated by the spinal cord.”
The spinal cord acts as a communication network between the brain and the body’s organs. Dulin believes the same disruption in communication that affects other systems after spinal cord injury may also contribute to fertility loss.
“When that highway of information is disrupted, it’s like a 50-car pileup,” she said. “The normal homeostasis that keeps organs functioning properly starts to break down.”
One reason the problem has proven difficult to solve is that fertility loss after spinal cord injury does not appear to stem from an inability to produce sperm.
Men with spinal cord injuries continue producing sperm, and doctors can often retrieve those cells through medical procedures. Previous studies have documented declining sperm quality after injury, but what triggers those changes remains unclear. Dulin’s team is investigating the biological mechanisms that set that process in motion.
“We have all this clinical data showing that men’s semen has been studied extensively and that sperm quality is poor,” Dulin said. “But we don’t really know how or why this happens.”
One clue may lie in a structure called the blood-testis barrier. Similar to the blood-brain barrier, it protects developing sperm from the body’s immune system. Dulin believes changes in the nervous system after spinal cord injury may ultimately drive the breakdown of that barrier.
Dulin’s previous research found evidence that the barrier breaks down after spinal cord injury, potentially exposing developing sperm to the body’s immune system.
“This is our hypothesis — that immune cells may attack and kill the sperm, rendering them unable to do their job of fertilization,” Dulin said. “They release inflammatory compounds that create a really toxic environment within the testes.
“The encouraging part is that sperm are constantly being produced,” Dulin said. “If we can restore the regulation and restore that barrier, then fertility could, in theory, be restored.”
Dr. Akram Esfandani, a physician and doctoral candidate in Dulin’s lab, brings a clinical perspective to the project.
“Many of the men I’ve spoken with worry about marriage, parenthood and whether they’ll be able to have children,” Esfandani said. “Infertility affects their confidence, their relationships and the way they think about their future.”
Esfandani said fertility receives less attention than paralysis and mobility in spinal cord injury research, despite the profound effect it can have on patients’ quality of life.
The project builds on Dulin’s broader research program focused on improving quality of life after spinal cord injury. Earlier this year, Dulin and her collaborators identified a rare group of neurons that can help trigger leg muscle activity, advancing efforts to develop therapies that improve mobility and independence for people living with spinal cord injuries.
While treatments remain a long-term goal, Dulin hopes this work will be an essential first step toward illuminating a problem that affects countless men living with spinal cord injuries. “Fertility is a major quality-of-life issue for people living with spinal cord injury,” Dulin said. “Before we can develop solutions, we have to understand the biology.”
