Stem Cells: Bred in the Bone

Stem Cell Discovery

By David McLaughlin

They are a source of health that has always been with us. Stem cells in the embryo become the specialized cells that create our bones, skin, heart and brain. Throughout life, stem cells repair damage throughout the body.

In muscle, stem cells help us heal after injury.

University of Toronto researchers James Till and Ernest McCulloch found the first evidence for these building blocks of life in 1961. The breakthrough flung open a door to an astonishing series of medical breakthroughs, which continue today in the field of regenerative medicine.

Till and McCulloch were comparing the effect of radiation on healthy cells versus cancer cells at the Ontario Cancer Institute in Princess Margaret Hospital. As a byproduct of their experiments, they saw clumps of cells on the spleens of their subjects.

Then they noticed the number of these “cell colonies” matched the number of cells — stem cells they thought were just bone marrow cells — that they had injected.

The spleen nodules had arisen from a single cell. Scientists had suspected for half a century that some unknown cells must have such remarkable potential, but no one had proven it was so.

Two years later, Till and McCulloch demonstrated two key properties of stem cells — they self-renew and can become specialized cells. They became known as the “fathers of stem cell research.”

In 1971, McCulloch established a bone marrow transplantation program at Princess Margaret Hospital that has saved thousands of lives. Clinicians today use bone marrow transplants to treat blood disorders and cancers such as leukemia.

Till and McCulloch once told an interviewer:  “What made the biggest difference in our research was that we switched from focusing on what stem cells looked like to what they can do.” In the decades since, stem cell research have given us much better understanding of health and disease.

In 1993, for example, U of T Professor John Dick isolated the first cancer stem cell, offering a new explanation for how cancer grows. In 2010 Professor Derek van der Kooy used stem cells to restore sight to blind mice.

Stem cell researchers around the world are now rebuilding damaged tissue in the eye, pancreas and brain. Stem cells have shown the potential to help patients after stroke and cure multiple sclerosis, and they may even help people with spinal cord injuries walk again.

Till and McCulloch received many awards for their work, including a Gairdner Foundation International Award and the Albert Lasker Basic Medical Research Award. McCulloch passed away in 2011.