The team "seeded" human embryonic stem cells, which have the potential to differentiate into a variety of specialized cells, onto a biodegradable polymer scaffold. By treating the scaffold/stem cell structure with chemical cues, or growth factors, known to stimulate the formation of specific cell types, the researchers coaxed the stem cells to form tissues with characteristics of developing human cartilage, liver, nerves and blood vessels.
"Here we show for the first time that polymer scaffolds promoted proliferation, differentiation and organization of human embryonic stem cells into 3D structures," the researchers wrote in a paper to appear the week of Oct. 13 in the online edition of the Proceedings of the National Academy of Sciences.
Further, the resulting tissues continued to thrive when implanted in mice with suppressed immune systems (to eliminate rejection). They expressed human proteins, and integrated with the host's blood-vessel networks.
"For me it was very exciting to see that these [stem] cells could move around and start to 'talk' with one another, generating the different cell types common to a given tissue and organizing into that tissue," said Shulamit Levenberg, first author of the paper and a research associate in the Department of Chemical Engineering.
The technique could also have an impact on the study of cell and developmental biology. "When you give cells a three-dimensional structure [on which to grow], it's really a lot more like what's happening in the embryo," said Levenberg, a mother of four whose youngest child is seven months old.