Scientists looking for stem cells can only be so accurate when extracting stem cells from the brain, namely, in the subventricular zone. Other non-stem cells are likely to be extracted along with the stem cells. There needs to be a process where stem cells can be separated from other types of cells in order for accurate research, and successful therapy.
Biologists have devised some pretty specific and really cool ways to mark certain types of cells with stains of all different colors and even some that are fluorescent! Scientists use radioactive material as well as antibodies to visualize cells. Pictured above are neurons visualized with two different staining techniques. The one on the left is an example of Golgi staining, and the one on the right is an example of Nissl staining.
Here is a conceptual diagram that explains the molecular process of antibody staining.
I won't really get into the super-hairy details of this process, but refer to the diagram for the fluorescent antibody techniques. The Direct method uses an antibody that auto-fluoresces to bind to the cell. The indirect method entails the addition of a primary antibody to the cell before adding the fluorescent one. Both are used regularly in laboratories, depending on the color of the image desired as well as the availability and binding properties of antibodies. Click here for a protocol on immunofluorescent microscopy. Scientists have books and other resources that tell them what kinds of staining techniques work on different kinds of proteins. If the scientists know what kind of proteins they're looking for, they consult their book of spells, and find the recipe for staining that protein a certain color.
So now we have a little understanding of the process by which scientists mark and identify certain cells, and how we can use this technology to distinguish stem cells from other cells in the subventricular zone. Using the principles of cell marking, scientists have been able to find these magical multipotent neural stem cells and isolate them for the purposes of researching and culturing these cells. Here's how they isolate stem cells.