Researchers have uncovered an unexpected mechanism of sperm aging that could affect male fertility and the development of future offspring. It turns out that as men age, not only does the DNA in their reproductive cells change, but so does the composition of RNA molecules. In mice, researchers observed a sharp reorganization of these molecules during midlife. This discovery is reported by ScienceAlert, citing a study published in The EMBO Journal.
The team examined small non-coding RNAs—molecules found in sperm that help regulate cellular processes—using a technique called PANDORA-seq. This method allows for the detection of RNA variants that are difficult to identify through conventional sequencing techniques.
The study revealed that the composition of these molecules shifts significantly with age. Specifically, in the sperm heads of older mice, the abundance of long ribosomal RNA fragments increased, while the number of short fragments decreased. Notably, this reorganization did not occur gradually; instead, there was a distinct, abrupt shift during the animals’ midlife.
A similar pattern was observed in humans. An analysis of sperm samples from two independent groups of donors confirmed that the ratio of long to short RNA fragments is linked to a man’s age. However, researchers have not yet been able to pinpoint a similarly sharp, age-related turning point in humans.
“It’s like finding a molecular clock that ticks as we age—in both mice and humans,” explained Qi Chen, a researcher at the University of Utah.
According to Chen, these changes may accumulate gradually until they reach a specific, critical threshold. To investigate the potential consequences of such a reorganization, scientists introduced a combination of RNA fragments—characteristic of the sperm found in older animals—into mouse embryonic stem cells. Following this, the researchers observed changes in the activity of genes associated with metabolism and neurodegenerative processes.
These findings suggest that a father’s age may influence early embryonic development through mechanisms beyond the mere accumulation of DNA mutations. Sperm also deliver RNA molecules to the egg, which may play a role in regulating gene expression in the developing organism.
However, this study does not yet prove that the observed changes directly cause infertility or disease in offspring. Further research is required to determine the causes of this RNA reorganization and to assess its implications for human reproductive health. In the future, this discovery could contribute to the development of new methods for evaluating the biological age of sperm and overall sperm quality.
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