Dr Huseyin Mehmet from Imperial College, London
Part of the show Stem Cells, Brain Repair and Tricks of the Light
Chris - So tell us a bit about how stem cells fit into the whole picture. The whole nervous system arises from a class of cells that are essentially stem cells, as they arise and divide into all the cells in the body. Is it possible to extract these things and use them to put things right in the future?
Huseyin - Well that's what we're working on and we're hoping to convince the government that we can do that. One of the things that Adrian said that I think was really interesting is that as the brain develops, cells actually die naturally as well. I think the thing that attracted us to stem cell research is that babies that are born very early actually haven't formed all their brain cells properly. If you were to look at a baby that's been born three or four months early under a special machine called an MRI scanner, it would actually look like layers of an onion in two halves. If you then imagine the picture of a brain of a normal human being with all its convoluted twists and turns, this development has to happen in a premature baby outside of mum's tummy. That's why many premature baby's have problems with their brains developing. Brains do, of course, contain some stem cells. When I was a student, we were told that the brain only had very limited powers of repair, and of course, that's true. We always thought that once brain cells have finished developing, that was it. In other words, if a patient was to damage their brain through a disease or an accident, the brain had no power to regenerate itself. We now know that that's not true. There are two areas of the brain that have small areas of stem cells in them. I think the best example to discuss is how they were discovered in the brain of a songbird. Animals that have to relearn songs, for example, have a special part of their brains where they remember the songs that they hear. These specialised brain cells develop from a very small and specialised area of stem cells. I think the problem is that in most adults, we have enough stem cells to allow us to learn a new smell or two, but not enough cells to repair a large lesion or area of damage that might happen in a stroke patient. That's where stem cells come in.
Chris - Coming back to the songbird for a minute, when the adult learns a new song, it pumps some stem cells into that area of the brain whose job it is to encode new songs, and those cells take on that new role.
Huseyin - Those cells are already there, but when the actual song is heard, they're then programmed to begin to differentiate into the memory forming cells in a specialised region of the brain.