A study published in Nature Communications proved that environmental experiences (specifically chronic stress) can transmit into men’s sperm cells and can cause their children to be more disposed to stress responses.
Caput epididymal epithelial cells (EECs) were found to be the prime suspect in facilitating the transmission by encoding stress in the tissue. Extracellular vesicles (EVs) transfer important material such as proteins and miRNA from the EECs and into the sperm cells.
One experiment involved exposing male mice to prolonged stress situations for four weeks. Then, the males bred with females after a certain amount of time. Some males were bred one week after the stress situation. The rest of the males were bred 12 weeks after the stress exposure.
The researchers found that the males bred after one week had offspring with no noticeable changes in stress response. The males bred after 12 weeks were found to have shifted stress responses in their offspring’s’ behaviour. This finding tells us that some time between the stressful event and breeding must occur before the transmission can happen.
Another test was conducted where male students from the University of Pennsylvania were selected to observe miRNA’s relation to stress levels in sperm cells. The participants returned every month for six months to give sperm samples and were evaluated for their perceived stress. In testing the samples, miRNA levels appeared to be correlated to the participants’ perceived stress and, because it is one of the cells transmitted to sperm cells, is likely to contribute to the passing on of stress levels.
More testing provided evidence that supports the idea that stress hormones, particularly corticosterone that signals stress hormones, causes effects that change the composition of the extracellular vesicles that connect to the maturing sperm.
This study presents a tremendous amount of evidence for stress being genetically transmitted to the next generation. Chronic stress exposure is bad for so many reasons right now, but the fact that it can now transcend generations should push more people to take precautions that eliminate stress in their daily lives.