Research into the uses stem cells is at that stage where almost every month a new application is announced, typically in the replacement of damaged cells or tissues. The most recent application is the creation of pituitary gland tissue from the embryonic stem cells of mice. Researchers at the Japanese RIKEN Center for Developmental Biology under Yoshiki Sasai and published in Nature [09 November 2011, paywalled, Self-formation of functional adenohypophysis in three-dimensional culture] have succeeded in not only creating pituitary gland tissue but also in transplanting the tissue successfully into mice with damaged pituitary glands. The results show that they mice recovered all or most of their pituitary output.

The pituitary gland is tiny, about the size of a pea, but it has an extremely important set of roles in the body’s hormonal chemistry (which applies to almost all mammals including mice and men). As the key organ to the endocrine system, the pituitary glands secrete nine major hormones regulating growth, fertility, blood pressure, breast milk, temperature control and fluid management – among other things. When the pituitary gland is malfunctioning, a lot of bad things happen. The ability to repair and eventually replace pituitary glands with synthetic tissue is obviously a major achievement. But science is not there yet.

The big news from the Japanese researchers is that they have been able to culture the mice embryo stem cells into pituitary gland cells, which is no easy feat. It required that the cells be grown together with cells of the hypothalamus, a companion gland of the pituitary. These two glands have many symbiotic connections and it became obvious that functional pituitary cells could not be reproduced without the interaction of the hypothalamus. The researchers also pioneered new techniques for implanting the synthetic pituitary cells into living mice. This too was tricky and represents a future hurdle for applying the technique to human beings.

As is usually the case with breakthroughs accomplished with lab animals, mice in this case, there is always the caveat that a similar procedure for human beings may or may not work. Typically the biochemistry is compatible, but the scale change and complexity of the human brain sometimes make the transition from mice to men very difficult. Dr. Sasai at RIKEN believes that it will take about three years to produce human pituitary cells, but the technique for implanting them successfully might take much longer.

So far stem cells have been turned into synthetic liver, heart, muscle, eye, and other organs. The list grows. In some cases this has been done with embryonic stem cells, which has a controversial side, especially when it comes to humans. Most researchers try to do the same thing with pluripotent stem cells derived (through various techniques) from adult or differentiated stem cells, which gets around the controversy. The researchers at RIKEN would like to follow this path in the future.