It looks like an eye. Perhaps a terrifying pink eye, like the Eye of Sauron, coming out of the darkness. It’s not an eye, but it is a bit terrifying. This is an image of a slice of the brain showing tumor cells (in green and red) surrounding a blood vessel. How does this type of image get made? How does this type of image help scientists? What does it mean that these tumor cells are near a blood vessel?
This image is created with a microscope – specifically a confocal microscope. I’m going to use a very weird analogy to explain why confocal microscopy is so cool, so stick with me. Imagine that you have a jello mold with an object it and you want to know exactly what the object looks like. Now imagine a regular microscope is like a flashlight. When you point the flashlight at the jello mold the whole thing lights up including what’s in front of the object, and if the object is translucent, the jello behind the object lights up too. This gives you an idea of what the object is, but it may be kind of fuzzy because of all the jello you see in front and behind the object. Confocal microscopy, on the other hand, is designed to turn that wide flashlight beam into a single pinpoint of light so only one part of the object is illuminated at a time. So when you move this single pinpoint around (back and forth and up and down) over the object, you can get a clear a crisp image of what is inside the jello.
To bring this analogy back into the science-verse, the jello is a cell or a piece of human tissue with layers of many cells. The objects inside the jello are certain proteins marked so that they light up in different colors (what we call fluorescence) when excited by the light from the laser (flashlight). When confocal microscopy is used to look at these proteins, you can see clear crisp images of exactly where the proteins are in the cells. And if you take enough images up and down through the cells and the tissue, you can even create a 3D image of the cell or a piece of tissue. Check out this neat video of a 3D rendering of a piece of the brain called the hippocampus.
Now back to the image above. This is a piece of tissue taken from a patient with an ependymoma, a tumor derived from brain tissue and is primarily found in younger patients. The colors you see are:
- Blue: a chemical called DAPI (or 4′,6-Diamidino-2-Phenylindole, Dihydrochloride) that binds to DNA. Since DNA is found in the nucleus of every cell, staining cells with DAPI helps you to locate each cell in the image – each blue dot is one cell.
- Red: stains a protein called GFAP (Glial Fibrillary Acidic Protein) that is found in different cells of the brain, but is also a marker of particular brain tumors, like ependymomas
- Green: stains a protein called vimentin that is also found in different cells of the brain, including cells that make up large blood vessels and brain tumors like ependoymomas
So what are we able to learn from this beautiful picture? See how there are a lot of red and green cells surrounding an empty round space. That round space is a blood vessel. Cancer cells need food and oxygen to grow, so the green and red cancer cells are clustering around the blood vessel to get the nutrients they need. Even though this is a beautiful image, it helps scientists to understand how these deadly tumors function within the brain and how they find the resources to grow.
If you want to look at more amazing images taken using confocal microscopy and fluorescently tagged proteins, check out these links
For more “What is That?”, click here.