For nearly two decades now, developmental biologist Yoshiki Sasai from Japan’s RIKEN Center for Developmental Biology has slaved away to perfect a recipe: the culture medium that could induce mouse embryonic stem cells to form organs with no additional ingredients. Disheartened by his incomplete success in generating brain tissue from stem cells, Sasai began a side project to grow early-stage mouse eyes, because they are “relatively simpler in structure than cortex” tissue, he said.
In his free time, Sasai fussed over his medium, fine-tuning the concentrations of ingredients—adding a gel containing laminin proteins essential for constructing basement membranes, decreasing growth factor levels. With his latest recipe complete, Sasai mixed in mouse embryonic stem cells—and then sat back to see what would happen, if anything.
Like most embryonic cells, aggregates of stem cells first formed hollowed spheres. But after 7 days Sasai and his colleagues noticed some “funny structures” sprouting off ...
