Researchers at the University of Pennsylvania have found that adult stem cells develop and form into complex tissue structures depending on the environment they are exposed to.

They have shown for the first time that in the absence of any chemical signalling, adult bone marrow stems cells will begin to differentiate into unique cell types based solely on how tough the surrounding "tissue" is.

Adam Engler and colleagues isolated adult stem cells in a series of three different polymer gels, each of a different stiffness.

The softest corresponded roughly to the consistency of neuronal tissue; the middle to muscle tissue; and the hardest was similar to bone.

When undifferentiated stem cells were placed in each of the gels – devoid of any biochemical signals – they began differentiating down the path to becoming exactly the type of tissue the gels’ were designed to emulate.

“Cells respond extensively to their environment so this is an interesting result, but not a surprising one,” Newscientist quoted Allan Spradling, a stem cell expert at the Carnegie Institution in Baltimore, Maryland, US, as saying.

The researchers concluded by saying that further work will be necessary to test whether cells can develop and form complex tissue structures without chemical signals.

It also remains to be seen whether embryonic stem cells will display similar sensitivity to the mechanical properties of their surroundings.

Despite the incremental nature of the work, Engler said that the study’s import lies with its implications for advancing toward a successful stem cell therapy.

“A first approach to stem cell therapies has been simply injecting cells into injured tissues. We would say that’s not going to be sufficient because the cells would be entering an improper physical environment”, he said.

“That has been the dominant paradigm, but it’s naïve. We need to learn how tissues repair themselves and mimic that”, Spradling said.