New technique reveals inner structure of live embryos in 3D

Scientists have developed a way to produce three-dimensional (3D) images of live embryos, an advance that may help select most viable embryos for successful pregnancies during in vitro fertilisation (IVF).
The cost of a single IVF cycle can be USD 20,000, making it desirable to succeed in as few attempts as possible, said researchers from University of Illinois at Urbana-Champaign in the US.
Advanced knowledge regarding the health of embryos could help physicians select those that are most likely to lead to successful pregnancies, they said.
Called gradient light interference microscopy (GLIM), the new method solves a challenge that other methods have struggled with - imaging thick, multicellular samples.

In many forms of traditional biomedical microscopy, light is shined through very thin slices of tissue to produce an image.
Other methods use chemical or physical markers that allow the operator to find the specific object they are looking for within a thick sample, but those markers can be toxic to living tissue, professor Gabriel Popescu said.

"When looking at thick samples with other methods, your image becomes washed out due to the light bouncing off of all surfaces in the sample," said graduate student Mikhail Kandel, the co-lead author of the study published in the journal Nature Communications.
GLIM can probe deep into thick samples by controlling the path length over which light travels through the specimen.

The technique allows the researchers to produce images from multiple depths that are then composited into a single 3D image.
To demonstrate the new method, researchers examined cow embryos.
"One of the holy grails of embryology is finding a way to determine which embryos are most viable," professor Matthew Wheeler said.
"Having a noninvasive way to correlate to embryo viability is key; before GLIM, we were taking more of an educated guess," said Wheeler.
Those educated guesses are made by examining factors like the colour of fluids inside the embryonic cells and the timing of development, among others, but there is no universal marker for determining embryo health, Wheeler said.

"This method lets us see the whole picture, like a three-dimensional model of the entire embryo at one time," said Tan Nguyen, co-lead author of the study.