For many couples that are ready to start a family, infertility, which is the inability to conceive children, can be a devastating setback. In fact, according to the Mayo Clinic, about 15% of couples are infertile. Of those couples experiencing infertility, one in three are issues related to male infertility, which often involves problems with sperm development.

However, researchers at Seoul National University in South Korea have found a way to deliver an important protein to mouse testes to improve sperm development. This is the first demonstration of direct delivery of proteins into the testes to treat male infertility, which could one day help people.

Male infertility is often associated with a lack of sperm in the semen. This can occur because of damage to the blood-testis barrier (BTB), which protects reproductive cells from harm. A protein named PIN1 is important for proper BTB function.

For this study, male mice were genetically engineered to lack PIN1, making them infertile. The researchers then developed a delivery system called Fibroplex, which consists of sphere-shaped nanoparticles. The team then inserted PIN1 into the Fibroplex, which was subsequently injected into the testes of the infertile mice.

The results were remarkable. The scientists found that the treatment had restored nearly normal PIN1 levels and sperm stem cell numbers in addition to repairing the BTB. The treated mice were also able to father a similar number of pups in comparison to normal mice while untreated, infertile mice weren’t able to reproduce at all. However, the treated mice were only able to successfully reproduce until about 5 months after treatment, at which point the PIN1 was no longer present.

The full results of this study were published in ACS Nano 2020.