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Why I'm sure human stem cell trial will be safe


You will soon start the first ever human study using induced pluripotent stem (iPS) cells. Why is this such a big deal?

Stem cells can become any other type of cell. If we can use them to replace damaged cells it has huge implications for treating degenerative diseases. Trials of embryonic stem cells are under way, but their use can be ethically controversial. Often, too, patients need to take drugs to prevent their immune systems from rejecting this type of cell. Since iPS cells are made from a patient's own body, it removes the ethical issues as well as the need for immunosuppressant drugs.

How would treatment with iPS cells work?

You create iPS cells by injecting adult cells taken from the body with "reprogramming" genes that make them rewind to an embryonic state. Then, by injecting certain proteins, we can make iPS cells differentiate into liver, retina or any other type of cell. These can be inserted in the body to replace damaged cells. We are still 20 years from clinical treatments, but the potential is exciting.

Are there pitfalls with iPS cell treatments?

We have to be very careful because iPS cells multiply endlessly. So, if any undifferentiated iPS cells were accidentally put into someone, they could cause tumours. That's why this pilot study is so important – to confirm the safety of putting cells derived from iPS cells into humans.

Who are the participants in the study?

Six people with age-related macular degeneration in their eyes, a condition that weakens central vision. For these patients, it is caused by the deterioration of the retinal pigment epithelium (RPE) – the layer of cells that clears away debris on the retina. We aim to replace damaged parts of this layer by taking skin cells from the patients' arms, reprogramming them to iPS cells, then differentiating them into the required RPE cells.

Are you confident the pilot will be a success?

Very confident. We trialled this intervention on mice, rats and monkeys, and saw no tumours. Also, I chose to work with RPE cells because of their characteristic brown pigment. This means we can avoid injecting tumour-causing iPS cells by selecting only the clumps of pure brown RPE cells.

Another reason for optimism is that the retina is the safest place to try this as we can watch the cells closely through the participant's dilated pupil.

What does the future hold for IPS cells?

Using "auto-transplantation", in which iPS cells come from the patient, takes a lot of time, money and labour. Possible "allogeneic" treatment, in which iPS cells from one person could be used in many people, could reduce costs tenfold.

Last week, the discovery was announced that an acid bath can turn adult cells back into stem cells. How will that impact your field?

That work by my colleague Haruku Obokata is very exciting and will change many aspects of regenerative medicine. I look forward to seeing where the research leads. I feel joyful that we are both working in this wonderful area of science.


Masayo Takahashi is at the Riken Center for Developmental Biology in Kobe, Japan, where she heads the Laboratory for Retinal Regeneration. This year she will begin the first safety pilot study using induced pluripotent stem cells in humans

Issue 2955 of New Scientist magazine
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