Special Delivery: Stem Cells

Stem Cell Research

When University of Toronto scientists James Till and Ernest McCulloch accidently stumbled upon stem cells in 1961, they inadvertently opened up a brand new field of medicine. The possibilities stemming from these tiny but mighty cells were immense. Here were cells with the uncanny ability to transform into multiple specialized cell types — like biological wild cards. Almost immediately, leukemia patients began benefiting from life-saving bone marrow transplants.

Then came the discovery of “pluripotent” embryonic stem cells, with the power to become any cell type in the body. And then researchers figured out how to induce regular human cells into developing these same powers. The novel field of regenerative medicine emerged as scientists began to harness stem cells to grow new cells and tissues. Imagine, instead of waiting for a transplant donor, a custom kidney or lung could be built from one’s own cells.

While promising, the road to regenerative medicine is anything but straightforward. Researchers are still uncovering the secrets of these mysterious cells. For example, U of T’s Institute of Biomaterials & Biomedical Engineering Professor Peter Zandstra works with induced pluripotent stem cells, and builds models of different natural environ­ments they might encounter in the body. By manipulating these environments, he’s learning how to coax the stem cells into becoming heart, blood or any other type of cell.

Other U of T scientists have successfully identified and grown stem cells for the brain, spinal cord and retina. These could replenish crucial cells and tissues lost after a stroke, spinal cord injury or vision loss. But moving these new cells into the body has proven a challenge. Many are damaged in the journey and never make it to the location where they’re needed.

This is why U of T Professor Molly Shoichet turned her attention to packaging the stem cells discovered by Molecular Genetics Professor Derek van der Kooy and Anatomy Professor and Division Chair Cindi Morshead. In an attempt to deliver these vital cells safely to specific destinations in the body, the team combined the fields of engineering, stem cell science and neurobiology.

Using a hydrogel “scaffold” developed by Shoichet’s lab, they are able to help transport the cells and also keep them nourished for the trip. The cells are mixed with the hydrogel prior to injection into the spinal cord, brain or retina. The hydrogel helps the cells settle into their new environment. Then the harmless gel is reabsorbed by the body, while the cells promote tissue regeneration and repair in animal models. Mice who had suffered strokes showed improved motor coordination; rats with spinal cord injuries regained some motor function; blind mice regained partial vision. The implications for human health and rehabilitation could be immense.