A significant difference between these two trials is the type of cell being tested. (You can read more about different types of stem cells in our Stem Cell Basics.) The Geron trial uses embryonic stem cells that have been grown in large quantities then matured into a type of neuronal precursor cells. In rodents, those cells are able to restore function after a recent spinal cord injury. The Geron trials will show whether those cells are also effective in people.
By contrast, the StemCells Inc trial uses cells that are already committed to becoming a type of neuronal cell. These neuronal stem cells can repair spinal cord injuries in rodents. Like the Geron trial, StemCells Inc is first testing these cells in a small number of people to ensure that they are safe.
It's exciting to see several different approaches being tested. When I think about these early stem cell trials I often reflect on the earliest cancer trials. I don't know very much about the first chemotherapy for lymphoma, but I'm grateful to the scientists who kept trying new approaches and improving on early successes because they're the reason my mother has been cancer-free for the past 10 years.
Whether or not these first trials are successful (and honestly, more early trials fail than succeed) we are witnessing the start of what I hope will one day be a cure for all those people living with spinal cord injuries. That cure might involve embryonic stem cells, neuronal stem cells, drugs tested on stem cells in the lab, or a combination of those approaches depending on the type of injury. CIRM is funding all of those stem cell approaches in the hopes finding the quickest path to a cure.