A seminal paper published in 1961 by Drs. James Till and Ernest McCulloch was the first academic study to prove the existence of an exciting new type of cell, the stem cell. Since this foundational study, the promise of stem cells and their application to human disease has grown tremendously, their potential only beginning to be realized. This animated video, narrated by Dr. Till, provides a brief explanation of this early study as well as explaining the two basic concepts that define the answer to the question "What is a stem cell?".
Stem Cell Network: What are stem cells? - stemcellnetwork.ca/index.php?page=what-are-stem-cells&hl=eng
Profile of Dr. Jim Till - science.ca/scientists/scientistprofile.php?pID=467
Till & McCulloch (1961) - A direct measurement of the radiation sensitivity of normal mouse bone marrow cells - Radiation Research - tspace.library.utoronto.ca/bitstream/1807/2781/2/RadRes_1961_14_213.pdf
Bone marrow contains many different types of cells, several of which have specialized roles in the blood.
In the early 1960’s, it was shown that if bone marrow was taken from one mouse and transplanted into another; rare, unspecialized cells could travel to the spleen where they would divide and form small colonies. These colonies contained a mixture of different blood cell types. Incredibly, when the cell colonies were removed and transplanted, the rare cells formed new colonies in the spleen of a second mouse.
These experiments revealed the two defining properties of a stem cell:
First, a stem cell must be able to self-renew. That is, it must be able to divide and give rise to more cells like itself.
Second, it must be able to differentiate. In other words, it must be able to divide and give rise to specialized cells.
Since these early experiments, many different types of stem cells have been discovered and this general definition applies to all of them.
Narration by: Dr. Jim Till
Written & Directed by: Ben Paylor & Mike Long
Produced by: Infoshots - infoshots.ca
Animation by: David Murawsky - davidmurawsky.com/
Sound by: James Wallace - imdb.com/name/nm0908691/