According to the researchers, the effects of paternal stress can be transferred to offspring through changes in the extracellular vesicles.
Prolonged fear and anxiety owing to stressors like the novel coronavirus (COVID-19) pandemic can not only take a toll on a person's mental health but also have a lasting impact on sperm composition that could affect future offspring, warn researchers.
The study, published in the journal Nature Communications, outlines a biological mechanism for how a father's experience with stress can influence fetal brain development in the womb.
According to the researchers, the effects of paternal stress can be transferred to offspring through changes in the extracellular vesicles that then interact with maturing sperm. Extracellular vesicles are small membrane-bound particles that transport proteins, lipids, and nucleic acids between cells.
They are produced in large amounts in the reproductive tract and play an integral role in sperm maturation.
"Properly managing stress can not only improve mental health and other stress-related ailments, but it can also help reduce the potential lasting impact on the reproductive system that could impact future generations," said study researcher Tracy Bale from University of Maryland in the US.
To examine a novel biological role for extracellular vesicles in transferring dad's stress to sperm, the researchers examined extracellular vesicles from mice following treatment with the stress hormone corticosterone.
After treatment, the extracellular vesicles showed dramatic changes in their overall size as well as their protein and small RNA content.
When sperm were incubated with these previously "stressed" extracellular vesicles prior to fertilizing an egg, the resulting mouse pups showed significant changes in patterns of early brain development, and as adults these mice were also significantly different than controls for how they responded to stress themselves.
To see if similar differences occurred in human sperm, the researchers recruited students to donate sperm each month for six months, and complete questionnaires about their perceived stress state in the preceding month.
They found that students who had experienced elevated stress in months prior showed significant changes in the small RNA content of their sperm, while those who had no change in stress levels experienced little or no change.
These data confirm a very similar pattern found in the mouse study.
"Our study shows that the baby's brain develops differently if the father experienced a chronic period of stress before conception, but we still do not know the implications of these differences," said Bale.
According to the researchers, stress-induced changes in the male reproductive system take place at least a month after the stress is attenuated and life has resumed its normal patterns.
"It is important to realize that social distancing does not have to mean social isolation, especially with modern technologies available to many of us," said Joshua Gordon, Director of the National Institute of Mental Health in his web message about coping with coronavirus.
"Connecting with our friends and loved ones, whether by high tech means or through simple phone calls, can help us maintain ties during stressful days ahead and will give us strength to weather this difficult passage".
