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For stem cells, nurture matters

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Interaction with the environment surrounding immature embryonic stem cells is a factor in their transformation into a complex organ, even when they are outside the body in a laboratory dish, research shows.

Scientists at the University of Florida's McKnight Brain Institute found that when embryonic stem cells from mice were placed on four different surfaces in cell culture dishes, specific types of body cells were created.

Their findings, published in this week's issue of Proceedings of the National Academy of Sciences, shed light on how embryonic stem cells diversify to form various neural structures, which has been a fundamental mystery of brain development, researchers say.

"The medium and the molecular environment influence the fate of a [stem] cell. ... Ultimately, both nature and nurture influence the final identity of a stem cell. But in the early stages, it seems nurture is very important," said Dennis Steindler, executive director of the McKnight Brain Institute and lead author of the research.

Mr. Steindler said it appears a stem cell's interchange with proteins in the "extracellular matrix," a mixture that surrounds developing cells, "plays a huge part" in determining which organ the stem cells eventually become.

"This work is the first to systematically look at how components in the extracellular matrix affect the fate of these cells," said Gordon Fishell, cell biology professor at the Skirball Institute of Biomolecular Medicine at the New York University Medical Center.

Mr. Steindler said he is optimistic that the University of Florida's findings, which focused on brain cell development, will facilitate the creation of laboratory environments to grow specialized cells that can be transferred into patients to treat Parkinson's disease, Alzheimer's disease, epilepsy, Huntingdon's chorea and other brain disorders.

In experiments, the Florida scientists confirmed that a cell culture molecule called laminin activates a common developmental pathway essential for the generation and survival of particular types of brain cells.

Stem cells triggered by laminin go on to produce a brain structure known as the medial ganglionic eminence. Researchers think that particular structure gives rise to a population of early neurons in the developing cerebral cortex, the part of the brain that helps coordinate cognitive, sensory and motor functions.

Mr. Steindler said laminin is used routinely to secure cells onto culture dishes in laboratories.

"It's been known laminin is growth-supportive, but there was no reason to believe these molecules were instructive" as to the specific type of organ embryonic stem cells become, he said.

University of Florida neuroscientist Bjorn Scheffler agreed. He said this study shows that laminin "changes the fate of cells it is working with."

"When you grow [stem] cells in a culture dish, you are actually educating them to become something very special," he said.

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