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									Summer 2007 Workshop
in Biology and Multimedia
for High School Teachers
Why Can’t We Grow New
An Introduction to Stem Cells and

                               Image by mila zinkov a f rom, image by Mila Zankova
Greek myth says that zeus
had prometheus chained to
  a rock for bringing fire to
  humans. Every day an
eagle would come and eat
  his liver. By the time the
 eagle came back the next
  day, the liver had grown

      Your liver can
     regenerate too!

 Will There be a day
 When your arm or leg
   will grow back?
You have probably heard that sea stars
can grow a new arm if they lose one, or
  even that a lost arm can grow into a
         whole new sea star.

Did you know that salamanders can also
         regenerate lost limbs?
   This probably makes you wonder:

    “Why can’t we grow new
    In order to answer that
  question, You will need to
 understand a little bit about
how the salamander is able to
regrow an arm and how your
   arm is formed in the first
                        Lesson Outline
  I.       What are stem cells and where do they come
  II.      How does a salamander regenerate a lost
  III.     Why can’t we grow a new arm?
  IV.      What do stem cells have to do with limb
           development and regeneration?
  V.       Can stem cells be used to grow new limbs?

These are the questions you should be able to answer by the end of
                           this lesson.
As you proceed through the lesson, click on the green links to answer the questions on
  your worksheet. As you scroll over the links, some of them have instructions as to
                where on the page you should look for the answers.
   I. What are stem cells and
   where do they come from?
A. You have
   undoubtedly heard
   of stem cells. They
   are in the news all
   the time, but what
   exactly is a stem

                                         Mouse embryonic stem cells

               Learn about stem cells
                     Answer question 1
I. What are stem cells and
where do they come from?
B. There are two types
    of stem cells,
    embryonic and
    adult. Find out
    how both are
    isolated, some
    similarities, and
    some differences.

                                 Pluripotent, embryonic stem cells originate as inner mass cells w ith in a blastocyst. The stem
                                 cells can become any tissue in the body, excluding a placenta. Only the morula's cells are
                                 totipotent, able to become all tissues and a placenta.

            Embryonic vs. Adult Stem Cells
               Where the cells are found
                         Answer question 2
  II. How Does a salamander
    Regenerate a Lost Arm?
A. Imagine if humans
   could grow new
   limbs after
   amputation. Some
   salamanders can
   do just that.
                                                                                              Photograph taken by Patrick Coin
                                       http://com m ons.wikim age:Plethodon_cylindraceusPCCA20060409-3183A.j pg

  Read about limb regeneration in salamanders
    Visual of limb regeneration in salamander
              Limb Regeneration Movie
                      Answer questions 3-6
   II. How Does a salamander
     Regenerate a Lost Arm?
B. Review the basic steps of limb regeneration
  1. An epidermal layer covers the wound.
  2. Cells in the stump become unspecialized and
     accumulate under the epidermis. This
     structuure is the blastema.
  3. The blastema elongates and flattens while cells
     are differentiating.
  4. Finally new bones form and the limb pattern is
     back to normal.
  5. The new limb grows and looks just like a normal
III. Why Can’t We Grow a New

A. First take a look at how a vertebrate
   limb develops in the first place.

        Vertebrate Limb Development
                   Answer questions 7-9
   III. Why Can’t We Grow a New
As you can see, creating an
  arm is a very complex
  process that requires a
  number of different genes.
  Each step can trigger the
  next, and more and more
  genes and environmental
  factors get involved.
                      by Peter Znamenski
III. Why Can’t We Grow a New
B. It is still unclear why salamanders can
   regenerate limbs while mammals and
   other vertebrates cannot.
C. It may have something to do with the
   complexity, but there is more to it than

 Why do we form a scar instead of a new limb?
                    Answer question 10
 IV. What do stem cells have to
  do with limb development and
Now that you know what stem cells are, how a
  limb develops and how a salamander’s limb
    can regenerate, you may be wondering…

What do stem cells have to do with limb
   development and regeneration?
IV. What do stem cells have to do
    with limb development and
A. Remember that stem cells are cells that
   can self-renew and make cells that can
                                                                               This image shows
                                                                               how a
                                                                               hematopoietic stem
                                                                               cell (an adult blood
                                                                               stem cell) can
                                                                               differentiate into all
                                                                               of the different types
                                                                               of blood cells.

 courtesy of HINcs4.asp
IV. What do stem cells have to do
    with limb development and
B. In order for limbs (or any other body part) to
   develop, the stem cells must receive the
   proper signals. Each organ requires
   different signals or a different order of
   signals. So, during development, stem cells
   for blood will receive different information
   than those for skin or neurons.

         To get a better Idea of this concept play the
          virtual stem cell laboratory from children’s
                        Hospital boston                  Answer questions 11-12
IV. What do stem cells have to do
    with limb development and
C. In salamander limb regeneration, it is
   unclear whether stem cells are
   involved, but it is known that there are
   some in the tissue that may contribute.
D. We know that when a human muscle
   is damaged stem cells are responsible
   for repair.
IV. What do stem cells have to do
    with limb development and
E. Put together all of the information you
   now have about stem cells,
   development, and regeneration to
   figure out what scientists might want to
   research in order to promote limb
   growth in humans.
           Answer question 13.
This leads us to our final
 V. Can Stem Cells Be Used to
      Grow a New Arm?                                            Image by emo_boy from /forum s/album _pic.php?pic_id=8414

A.   Many scientists are
     working on this
     problem right now.
     They are studying
     frogs, salamanders,
                              Photo Credit:US National Oc eanic and Atmospheric Administrati on

                                                                                               Image from

     sea stars, and even
     mice to figure out how
     they can regenerate
     limbs or other body

   Now find an article about
studies into limb regeneration.

       Read the Article and write down
      the source. Then, summarize the
         article and hand it in with your
        “Stem Cells and Regeneration”

end    Learn More,
Use some of the links below to answer question I. Then, write about your own opinions. Be sure to explain how you feel

                                         and give reasons for your opinion.

  I.         Why are some
             people opposed
             to stem cell
  II.        How do I feel
             about stem cell
             research and
                                  Learn More
If you would like more information on stem cells, regeneration or development, go back to any of
     the links in this presentation or check out some of the following:

     •   The book Mutants by Armand Marie Leroi discusses human development through mutation. It is full
         of interesting stories and science.

     • - article about research grant at University of Utah
     • - information about research on limb
         regeneration at Indiana University
     • - online research magazine from the
         mayo clinic
     • - McGowan Institute for Regenerative Medicine From University of

     • - International Society for Stem Cells
     • - Stanford Institute for Stem Cell biology and Regenerative Medicine
     • - Harvard Stem Cell Institute
•   Amphibian Limb Regeneration
•   Morrison, Jamie L. et al “Salamander limb regeneration involves the activation of a multipotent skeletal
    muscle satellite cell population” JCB 30 January 2006
•   Salamanders Re-grow Lost Limbs, Could Human Medicine Benefit From Understanding Regeneration?
    Science Daily 1 April 2007
•   Stem Cell Basics: What are adult stem cells? . In Stem Cell Information [World Wide Web site]. Bethesda,
    MD: National Institutes of Health, U.S. Department of Health and Human Services, 2006 [cited Wednesday,
    July 18, 2007] Available at
•   Stocum, David L. Biology and Medicine: An Overview 1 July 2004
•   Vertebrate Limb Development--an Example of the Development of Body Parts

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