Question: What happens when stem cells are used inside someone’s eye, and how are stem cells cultivated to perform certain actions in the body rather than mutating to form a different form of cell? Thanks

Stephen Moss answered on 13 Mar 2011:

These are such important questions, and I could give an answer that would fill a book! However, the first thing to point out is that so far, no-one has had stem cells used in their eyes. There have been lots of studies where scientists have investigated what happens when stem cells are used in the eyes of blind animals – one study a couple of years ago literally involved 3 blind mice!

What has become clear is that you can’t just stick stem cells into the eye – they will just sit there as a useless blob and do very little. So the thinking now is to turn the stem cells into the cell type you want first (such as the photoreceptors that detect light in your retina), and then do the transplant. This has the advantage that you know you’re delivering useful cells into the eye, and it also reduces the chances of the cells mutating into something either useless or dangerous.