Tissue engineering: The brainmaker

With his knack for knowing what stem cells want, Yoshiki Sasai has grown an eye and parts of a brain in a dish.

'He' is Yoshiki Sasai, a stem-cell biologist at the RIKEN Center for Developmental Biology in Kobe, Japan. Sasai has impressed many researchers with his green-fingered talent for coaxing neural stem cells to grow into elaborate structures. As well as the optic cup¹, he has cultivated the delicate tissue layers of the cerebral cortex² and a rudimentary, hormone-making pituitary gland³. He is now well on the way to growing a cerebellum⁴ — the brain structure that coordinates movement and balance. “These papers make for the most addictive series of stem-cell papers in recent years,” says Luc Leyns, a stem-cell scientist at the Free University of Brussels.

And is tissue formation driven by a genetic program intrinsic to cells, or shaped by external cues from neighbouring tissues? By combining intuition with patient trial and error, Sasai has found that it takes a delicate balance of both: he concocts controlled environments that feed cells physical and chemical signals, but also gives them free rein to 'do their thing' and organize themselves into issues. He sometimes refers to himself as a Japanese matchmaker who knows that, having been brought together, two strangers need to be left alone. “They know what to do,” he says. “They interact in a delicate manner, and if the external cues are too strong, it will override the internal ones.”
  
http://www.nature.com/news/tissue-engineering-the-brainmaker-1.11232