Researchers have developed a method to make human eggs divide as if they have been fertilized, creating a potential source of embryonic stem cells that sidesteps ethical objections to existing techniques.

The University of Wales researchers made the eggs devide by injecting phospholipase C-zeta (PLC-zeta), an enzyme produced by sperm. The eggs divided for four or five days until they reached 50 to 100 cells — the blastocyst stage. These blastocysts should in theory yield stem cells.