stem cell activation and regeneration

1. CELLS IN THE NEWS If a snail can grow back its head, and a lizard can grow back its tail, why can’t a human grow back a finger?

2. Before we are born and while we are very young, humans can repair most tissue damage. After we get older, we can heal wounds and make new skin and blood, but we cannot re-grow arms or legs or even fingers. So, how is it that other animals can re-grow heads, tails, legs and even most of their bodies?

3. Beginnings As you probably know, we all begin with our lives when a male sperm fertilizes a female egg. A fertilized egg is call a zygote. The zygote begins to divide and divide and divide until all of our cells are in place, and our bodies begin to function.

4. Did you know that a human body has about10 trillion cells? That’s 10,000,000,000,000! Of course, you know that a human body has different types of cells. But, did you know that there are 200 different cell types? Look at the images of just a few: Clockwise from top left: heart muscle cells, red blood cells, skeletal muscle cells, nerve cell.

5. All of these different types of cells develop from one special type of cell called stem cells. Stem cells can become any of the cell types in our bodies.

6. Some animals have stem cells ready to replace, or regenerate, body parts and, in some cases, the whole body. Humans do not.Let’s take a look at an animal called planaria.

7. Planaria is a “cross-eyed” flatworm that lives in freshwater. It is a scavenger. When a planarian is cut as in the picture below, its stem cells reproduce and replace the parts of the body that are missing. The head can regenerate a tail, and the tail can regenerate a head. What about that?

8. Here are some other animals that can regenerate body parts. They may not be as amazing as planaria, but they are still pretty interesting.

9. Scientists are trying to figure out how to get human stem cells to “turn on” and regenerate limbs and organs. There have been some success in the laboratory, and researchers have figured out how to get muscle to re-grow in the legs of injured soldiers. Wonder if we could figure out how to re-grow nerve, bone and heart cells? This ear was grown on a mold in a laboratory. Also, bladders have been grown to replace ones that no longer work. Isn’t this amazing?

10. Scientists have also been able to grow skin, heart muscle, liver, kidney and lung cells. We’ll keep an eye on the interesting topic of regeneration. Are we closing in on planaria? For more information, look at these websites: http://www.exploratorium.edu/imaging_station/research/planaria/story_planaria3.php http://www.cbsnews.com/video/watch/?id=6711905n&tag=contentBody;housing

11. The EndThis show was prepared by Linda Moore for OCS Biology.April 2011