News | Tiny RNAs in sperm are crucial to human embryo development
A Linköping University study in Sweden has found that sperm carry more than genetic material to the egg: they also contain important molecules, particularly microRNAs, that are crucial to embryo development. These sperm microRNAs can influence development for several days after fertilization. Published in Nature Communications, the findings may offer new approaches to infertility diagnosis and treatment.
"Sperm are not only carriers of genetic material; they also carry other molecules that help initiate embryo development. This means sperm play a much greater role in fertilization than we previously understood," said Anita Öst, professor of cell and molecular biology at Linköping University and one of the study leaders.
The role of microRNAs in embryo development
MicroRNAs have an important role in regulating genes within cells. Previous studies showed that sperm microRNAs affect embryo development in some animals, but human research has been limited. This Linköping University study is the first to clearly establish their role in human embryo development, with important clinical implications.
As infertility becomes more common, about one in six couples face difficulty conceiving. Some can become pregnant through in vitro fertilization (IVF), but embryo quality is a key factor in IVF success. Better assessment of early embryo quality may improve treatment outcomes.
IVF treatment generally focuses on women, using hormonal stimulation to mature several eggs before fertilization with sperm. However, sperm quality has declined in many countries in recent years for reasons that remain unclear. The Linköping researchers wanted to explore how male factors affect IVF success.
Methods and findings
The team collected surplus sperm samples from 69 couples undergoing IVF and extracted RNA for analysis. They compared different RNA types with sperm concentration, motility, fertilization capacity, embryo quality and pregnancy outcomes. Higher levels of certain sperm microRNAs were associated with a greater likelihood of embryo formation and development.
"We found that higher levels of certain microRNAs in sperm samples could predict their effect on embryo quality and even indicate how the embryo would develop several days later," added team member Signe Isacson, a postdoctoral researcher in bioinformatics at Linköping University.
Clinical significance of microRNAs
MicroRNAs are important gene-regulating molecules that have attracted broad research interest. The discoverers of microRNAs received the 2024 Nobel Prize in Physiology or Medicine for work showing their role in worm embryo development. The Linköping team found that similar microRNAs are active in human sperm and may be essential for normal embryo development.
"The microRNAs we identified belong to the same class discovered by the Nobel laureates, who first showed that they were crucial to worm embryo development. We were surprised to find that similar microRNAs in human sperm also appear to play a key role in embryo development," Professor Öst said.
Future research and challenges
Researchers still cannot fully explain why some men have higher levels of sperm microRNAs than others. It is also unclear how these microRNAs form, whether they are related to testicular or epididymal function, or whether lifestyle affects them. The team is now investigating whether diet and lifestyle influence sperm microRNA levels, particularly during IVF treatment.
The study was funded by the Swedish Research Council, Ragnar Söderberg Foundation, Knut and Alice Wallenberg Foundation and Region Östergötland.
News | Tiny RNAs in sperm are crucial to human embryo development
News | Tiny RNAs in sperm are crucial to human embryo development
A Linköping University study in Sweden has found that sperm carry more than genetic material to the egg: they also contain important molecules, particularly microRNAs, that are crucial to embryo development. These sperm microRNAs can influence development for several days after fertilization. Published in Nature Communications, the findings may offer new approaches to infertility diagnosis and treatment.
"Sperm are not only carriers of genetic material; they also carry other molecules that help initiate embryo development. This means sperm play a much greater role in fertilization than we previously understood," said Anita Öst, professor of cell and molecular biology at Linköping University and one of the study leaders.
The role of microRNAs in embryo development
MicroRNAs have an important role in regulating genes within cells. Previous studies showed that sperm microRNAs affect embryo development in some animals, but human research has been limited. This Linköping University study is the first to clearly establish their role in human embryo development, with important clinical implications.
As infertility becomes more common, about one in six couples face difficulty conceiving. Some can become pregnant through in vitro fertilization (IVF), but embryo quality is a key factor in IVF success. Better assessment of early embryo quality may improve treatment outcomes.
IVF treatment generally focuses on women, using hormonal stimulation to mature several eggs before fertilization with sperm. However, sperm quality has declined in many countries in recent years for reasons that remain unclear. The Linköping researchers wanted to explore how male factors affect IVF success.
Methods and findings
The team collected surplus sperm samples from 69 couples undergoing IVF and extracted RNA for analysis. They compared different RNA types with sperm concentration, motility, fertilization capacity, embryo quality and pregnancy outcomes. Higher levels of certain sperm microRNAs were associated with a greater likelihood of embryo formation and development.
"We found that higher levels of certain microRNAs in sperm samples could predict their effect on embryo quality and even indicate how the embryo would develop several days later," added team member Signe Isacson, a postdoctoral researcher in bioinformatics at Linköping University.
Clinical significance of microRNAs
MicroRNAs are important gene-regulating molecules that have attracted broad research interest. The discoverers of microRNAs received the 2024 Nobel Prize in Physiology or Medicine for work showing their role in worm embryo development. The Linköping team found that similar microRNAs are active in human sperm and may be essential for normal embryo development.
"The microRNAs we identified belong to the same class discovered by the Nobel laureates, who first showed that they were crucial to worm embryo development. We were surprised to find that similar microRNAs in human sperm also appear to play a key role in embryo development," Professor Öst said.
Future research and challenges
Researchers still cannot fully explain why some men have higher levels of sperm microRNAs than others. It is also unclear how these microRNAs form, whether they are related to testicular or epididymal function, or whether lifestyle affects them. The team is now investigating whether diet and lifestyle influence sperm microRNA levels, particularly during IVF treatment.
The study was funded by the Swedish Research Council, Ragnar Söderberg Foundation, Knut and Alice Wallenberg Foundation and Region Östergötland.
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