Remembering James Till, a pioneer in stem cell research

The University of Toronto and its hospital partners are celebrating the life and legacy of Professor Emeritus James Till, whose research demonstrated the existence of stem cells and fundamentally transformed the field of medical science. 

He is being remembered for pathbreaking work – conducted alongside the late Ernest McCulloch – that ultimately paved the way for bone marrow transplants and other stem cell-based therapies, and regenerative medicine approaches aimed at repairing or regenerating damaged tissues and organs.

Till died in Toronto on May 18 at the age of 94.

"The U of T community is deeply saddened by the passing of James Till, a visionary scientist whose discovery of stem cells with Ernest McCulloch revolutionized medicine and biomedical research,” said Leah Cowen, U of T’s vice-president, research and innovation, and strategic initiatives. 

“Their groundbreaking work not only laid the foundation for a new field of science but has saved and improved countless lives worldwide through stem cell-based therapies.”

Born and raised on a farm in Lloydminster, Alta., Till pursued his passion for science at the University of Saskatchewan, earning a bachelor of science degree in 1952 and a master’s degree in physics in 1954. He went on to obtain a PhD in biophysics from Yale University in 1957. Soon after, he joined U of T as a postdoctoral researcher to work with Harold Johns, a physicist at the Ontario Cancer Institute (OCI), now known as the Princess Margaret Cancer Centre at University Health Network.

At the OCI, Till began collaborating with McCulloch, then an assistant professor of medical biophysics at what is now U of T’s Temerty Faculty of Medicine, forming a partnership that would revolutionize biology. 

In 1961, the researchers conducted experiments involving the transplantation of bone marrow cells into mice that had previously received radiation. Several days later, they observed bumps on the spleens of the mice that had received transplants and discovered that each lump contained a colony of cells capable of giving rise to the multiple cell types that make up human blood.

These landmark findings provided the first description of blood-forming stem cells. 

Their 1963 study, published in the journal Nature, further demonstrated that each colony of blood-forming cells originated from a single cell. That same year, Till and McCulloch collaborated with renowned molecular geneticist and U of T researcher Louis Siminovitch to show that these bone marrow cells were capable of self-renewal, a hallmark trait of stem cells.

Till was appointed as a faculty member in the department of medical biophysics at U of T’s Faculty of Medicine (as it was then known) in 1965 and retired in 1997. During his tenure, he served in numerous leadership roles at the university and was appointed University Professor in 1984.

Following their seminal work in the 1960s, Till continued to advance stem cell research for more than 15 years, exploring the potential of stem cells to differentiate into various cell types and the feasibility of isolating viable stem cells.

In the 1980s, Till broadened his research interests to include other aspects of cancer care, such as quality of life, research ethics and the decision-making capacities of cancer patients. He also explored the internet’s role as a source of information, support and advocacy, and examined its impact on patient care.

Till received numerous honours in recognition of his work including the Canada Gairdner International Award, appointment as an Officer of the Order of Canada and induction into the Canadian Medical Hall of Fame. In 2005, he and McCulloch received the Albert Lasker Award for Basic Medical Research. 

His legacy endures through the transformative research he inspired and the many scientists he mentored – whose collective work continues to advance stem cell-science and improve lives around the world.

“Professor Till’s contributions were instrumental in establishing Toronto as a world leader in regenerative medicine and in bringing hope to patients everywhere,” Cowen said. 

“His vision, humility and dedication will inspire generations of researchers to come."

With files from the University Health Network. 

Read more about James Till in the Globe and Mail