Researchers find pause button for mouse embryos

New York: A novel way to pause the development of early mouse embryos for up to a month in the lab has been identified, a finding that has potential implications for assisted reproduction, regenerative medicine, ageing and even cancer, researchers say.

In the study, the researchers were able to stop the development of early-stage mouse embryos -- known as blastocysts -- using drugs that inhibit the activity of mTor, a master regulator of cell growth.

"Normally, blastocysts only last a day or two, maximum, in the lab. But blastocysts treated with mTOR inhibitors could survive up to four weeks," said the study's lead author Aydan Bulut-Karslioglu, post-doctoral student at the University of California -San Francisco (UCSF).

The paused embryos could quickly resume normal growth when mTOR inhibiters were removed. When implanted back into a recipient mother, they developed into healthy mice, the researchers said.

"mTOR is this beautiful regulator of developmental timing that works by being a nutrient sensor. It doesn't just drive cells into growing willy-nilly. It tunes cell growth based on the level of nutrients that are available in the environment," added Miguel Ramalho-Santos, Associate Professor at UCSF. 

The new research could have a big impact on the field of assisted reproduction -- technology used to achieve pregnancy in procedures such as fertility medication, artificial insemination, in vitro fertilisation and surrogacy -- where practitioners are currently limited by the rapid degradation of embryos once they reach the blastocyst stage.

Further, pausing the development of early-stage embryos may also avoid the compromise of freezing embryos and give practitioners more time to test fertilised blastocysts for genetic defects before implanting them, Bulut-Karslioglu said.

Humans too may have the ability to delay implantation of fertilised embryos in some circumstances, suggested the practitioners of in vitro fertilisation, in the paper published online in the journal Nature.