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Stem cells used to replace part of the human brain

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Special To The Japan Times

Sometimes I imagine famous scientists and doctors from the past magically catching a glimpse of our modern world. Sure it’s fun to picture their gawping faces, but the daydream also helps remind me that we take so much for granted these days. And, in fact, it illustrates the incredible pace of discovery, because you don’t even have to go very far back in time before you are in a completely different era.

This week’s contribution is about one such discovery.

Scientists at Riken’s Center for Developmental Biology in Kobe have grown a vital part of the human brain from scratch. Well, actually, not quite from scratch. The team have coaxed human embryonic stem cells — essential cells in our body that have the capability to grow into any particular cell — into developing the cell type and structure necessary to replicate a working pituitary gland. Or, as they describe it, a functioning three-dimensional pituitary-like structure.

They then transplanted the stem-cell gland into mice without pituitary glands. The mice recovered and went on to live normal lives.

You don’t have to imagine telling this to an Edo Period doctor to appreciate what the scientists have done: They’ve grown and replaced part of the brain!

“This is an exciting step forward toward our ultimate goal, which is to be able to regrow fully functioning organs in the laboratory,” says Takashi Tsuji, leader of the Center for Developmental Biology’s Laboratory for Organ Regeneration. “We will continue to push ahead with experiments to grow other parts of the body.”

The pituitary gland is a pea-sized organ hidden deep in the brain. It produces hormones but also controls the activity of other important hormone-making glands, including the adrenal and thyroid glands. When it doesn’t work properly, people can’t make enough of the growth, sex or stress hormones humans need.

A few years ago, the same group at Riken produced a pituitary made of stem cells from mice, but now they’ve managed it with human cells. The mouse organ, produced in 2011 by biologist Yoshiki Sasai, was at the time the most complex organ made from stem cells. Back then, scientists said a human pituitary was still many years away. How wrong could they be?

It’s sad that Sasai, who committed suicide in 2014 following the STAP stem-cell scandal involving scientist Haruko Obokata, did not live to see the latest breakthrough by the lab he used to head. In a previous breakthrough in 2011, he also grew a retina — the light-sensing sheet of cells at the back of the eye — from stem cells taken from mice.

The retina was hailed as an advance that would pave the way for organ development. Who knows what Sasai would have gone on to discover, but at least his former laboratory is forging ahead following the tragedy of his death.

The mice that received the human pituitary had been given lesions on their own pituitary glands. Usually these are fatal as the mice are unable to produce enough key hormones, but the transplant worked to provide the mice with the correct balance of hormones. The mice with the transplant lived three times longer than the ones with the lesions on their pituitaries. Also, since the mice were a special strain without strong immune systems, the human pituitaries were not rejected by the body.

Hidetaka Suga, one of the authors of the new report, is reluctant to elaborate on when a lab-grown pituitary might be ready for use in human patients. When asked what other organs his group was working on, he replied, “Sorry, it’s a secret.”

That’s intriguing, I thought, wondering if they we re working on a hypothalamus.

The hypothalamus is a part of the brain near the pituitary that plays a key role in the operation of the pituitary. It is a vital component of the brain that links the brain and the rest of the nervous system to the endocrine system — the gland system in the body that produces hormones.

If the lab-grown pituitary gland is ever used in human patients, scientists will have to find some way of linking it up to the rest of the brain. To test the pituitary gland, they positioned it next to the kidneys of the mice, because it was too difficult to put it back in the brain. For a while, at least, a kidney-based pituitary can operate adequately.

However, a long-term solution is still needed to address how the organ communicates with the rest of the brain.

That’s why I wonder if the hypothalamus is the “secret” organ that Riken is working on. They might also be working on other parts of the eye, possibly a human retina. A source of synthetic human retinas would be useful in treating a range of diseases and eye conditions.

The field is known as regenerative medicine. For many years, regeneration was something we observed in animals such as lizards, which are able to regrow their tail if it falls off, and animals such as sea cucumbers, which can regenerate entire sets of internal organs. However, for the past 20 years or so it has been a branch of medicine that seeks to grow and replace damaged human organs.

The potential rewards for success in the field are huge, which is why there is such pressure on researchers to demonstrate a breakthrough.

Little by little, however, we are getting there. The pace of discovery is rapid, but not so rapid that these things will happen overnight. However, I always look forward to seeing what comes out of Kobe’s Laboratory for Organ Regeneration.

Rowan Hooper is the news editor of New Scientist magazine. The second volume of Natural Selections columns translated into Japanese is published by Shinchosha. The title is “Hito wa Ima mo Shinka Shiteru” (“The Evolving Human”). Follow Rowan on Twitter @rowhoop.