In separate experiments reported in Nature -- one with mice, the other transplanting human stem cells into mouse bone marrow -- researchers demonstrated techniques with the potential to produce all types of blood cells.
"This step opens up an opportunity to take cells from patients with genetic blood disorders, use gene editing to correct their genetic defect, and make functional blood cells," said Ryohichi Sugimura, a doctor at Boston Children's Hospital and lead author of one of the studies.
If proven safe, the proof-of-concept methods could also lead to a "limitless supply of blood" by using cells from universal donors, he added.
Human embryonic stem cells -- generic cells which, as the embryo develops, gradually differentiate -- were first isolated in 1998.
A decade later, scientists figured out how to generate another type of all-purpose cell from human skin, known as induced pluripotent stem cells, or iPS. These were successfully used to make neurons and heart cells.
But the goal of creating blood-forming stem cells in the lab remained out-of-reach.
Sugimura and colleagues devised a three-step process to achieve that breakthrough.
They began by inducing both embryonic stems cells and iPS to morph into a form of embryonic tissue that -- in a natural process -- gives rise to blood stem cells. This had been done before.
In the second crucial step, they experimented with dozens of proteins known to control gene expression, especially during the formative process of embryo growth.
