Researchers are now permitted to grow human embryos in the lab for longer than 14 days. Here’s what they could learn.
In May, the International Society for Stem Cell Research (ISSCR) released new guidelines1 that relaxed the 14-day rule, taking away the hard barrier. Although only a few labs around the world have perfected the techniques needed to culture human embryos up to day 14, the science is advancing rapidly. The relaxed rule allows lab groups, in countries where it is legal, to apply to the regulators for permission to continue research past 14 days. Such studies could reveal what happens during human development after the embryo would normally have implanted in the uterus, about a week after fertilization. It then goes through a stage called gastrulation, roughly between days 14 and 22, when the body’s main pattern emerges and the foundations are laid for organ generation.
Cracking open a window on these later stages would allow scientists to better understand the nearly one-third of pregnancy losses and numerous congenital birth defects thought to occur at these points in development. In addition, these stages hold clues to how cells differentiate into tissues and organs, which could boost regenerative medicine.
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