Developing human embryos less than 5 days old live imaged in real time at highest-ever resolution

Amazing stuff! Seeing the wonders of life at the very beginning!

"Researchers have captured the most-detailed images yet of human embryos developing in real time, using two common laboratory tools — fluorescent dyes and laser microscopes.

The technique ... allows researchers to study crucial events in the first few days of development without genetically altering the embryos, which has previously restricted the use of some imaging techniques in human embryos, owing to ethical concerns. ...
“This is the first time we can actually image an early human embryo at the very early stages of development with cellular resolution,” says Nicolas Plachta, a cell biologist at University of Pennsylvania in Philadelphia and a co-author of the paper. “We can see single cells and how they interact with each other as they form the pre-implantation embryo.” ...
the imaging technique could lead to the development of ways to non-invasively screen embryos conceived through in vitro fertilization (IVF). ...

The researchers were also able to compare key events in human embryos and mouse ones — which are often used as models to study embryonic development. They observed some important differences. For example, a process called compaction, which involves alterations in cell shape, starts at the 12-cell stage in human embryos compared with the 8-cell stage in mice; the process is also more asynchronous in human embryos, leading to variations in inner- and outer-cell formation. ..."

From the highlights and abstract:

"Highlights

• Fluorescent dyes enable live imaging of human embryos without genetic manipulation

• Live imaging reveals differences between human and mouse embryo morphogenesis

• Blastocyst expansion causes trophectoderm cell nuclear budding and DNA shedding

• Mechanical stress from blastocyst expansion or biopsy triggers nuclear DNA loss

Summary

Proper preimplantation development is essential to assemble a blastocyst capable of implantation. Live imaging has uncovered major events driving early development in mouse embryos; yet, studies in humans have been limited by restrictions on genetic manipulation and lack of imaging approaches. We have overcome this barrier by combining fluorescent dyes with live imaging to reveal the dynamics of chromosome segregation, compaction, polarization, blastocyst formation, and hatching in the human embryo. We also show that blastocyst expansion mechanically constrains trophectoderm cells, causing nuclear budding and DNA shedding into the cytoplasm. Furthermore, cells with lower perinuclear keratin levels are more prone to undergo DNA loss. Moreover, applying trophectoderm biopsy, a mechanical procedure performed clinically for genetic testing, increases DNA shedding. Thus, our work reveals distinct processes underlying human development compared with mouse and suggests that aneuploidies in human embryos may not only originate from chromosome segregation errors during mitosis but also from nuclear DNA shedding."

Developing human embryos imaged at highest-ever resolution Non-invasive imaging approach could lead to innovations in embryo screening.

Human embryo live imaging reveals nuclear DNA shedding during blastocyst expansion and biopsy (no public access)

Graphical abstract