New thesis shows how oxygen levels affect embryo development during IVF
Nina Bošković from the Gastroenterology and Nutrition Unit (GUT), at the Department of Medicine, Huddinge (MedH) defends her thesis titled "Oxygen levels regulating Embryonic Genome Activation", on 13 June, 2025. Main supervisor is Juha Kere (MedH).
What is the main focus of your thesis?
My thesis focuses on understanding how environmental factors, particularly oxygen levels during embryo incubation, affect early embryo development in IVF. A key event in this process is Embryonic Genome Activation (EGA), when the embryo begins using its own DNA for the first time instead of relying on maternal genetic material.
EGA is a crucial turning point that occurs around day 3 of development, which is also when most IVF embryos tend to arrest and stop progressing. By studying how different oxygen conditions influence this stage, my goal was to better understand what contributes to developmental success and ultimately improve IVF success rates.
Which are the most important results?
We developed a highly sensitive RNA sequencing method (STRT-N seq) that can study gene activity from a single oocyte or embryo. Using this method, we confirmed the expression of key genes known to be involved in human embryonic genome activation (EGA), which had previously only been predicted, but not experimentally confirmed, in cow embryos.
Our findings showed that these genes are indeed present and active during bovine (cow) EGA. Since these same genes are absent in the mouse genome, our work supports the cow as a more suitable model than the mouse for studying human embryo development.
Finally, we found that culturing embryos in low-oxygen (hypoxic) conditions leads to better development and more successful gene activation compared to atmospheric oxygen (normoxia), supporting the use of hypoxia in IVF clinics to improve outcomes.
How can this new knowledge contribute to the improvement of people’s health?
Around 18% of people globally face infertility, and IVF offers hope, but the success rate remains low. By gaining a deeper understanding of the basic physiology of early embryo development, we can uncover clues about why some embryos stop developing and what can be done to improve IVF success rates. This knowledge can help reduce the emotional and financial burden on patients undergoing fertility treatments.
What are your future ambitions?
I am continuing my career in academia, with a focus on reproductive health and women’s health. My ambition is to carry out research that not only deepens our understanding of early human development but also translates directly into clinical improvements.
I am especially passionate about making science more accessible, both to the public and to patients, and ultimately contributing to a future where the IVF journey is more effective, less stressful, and more compassionate for everyone who needs it.
Dissertation
Friday, 13 June at 09:30, Jan-Åke Gustafsson-salen in Neo, Blickagången 16, Flemingsberg.