Human Tests of Embryonic Stem Cell Treatments Planned

A California biotech company expects to begin trials of a treatment for spinal cord injuries next year.

Most of the news headlines on stem cells in recent months have focused on the political maelstrom surrounding morally charged issues.

New treatments derived from embryonic stem cells could help paralyzed patients. (Credit: Science Photo Library)

But, in the labs, scientists are making rapid progress in turning this promising research field into actual medicine. One company, in particular, Menlo Park, CA-based Geron, is taking the lead in developing experimental embryonic stem cell therapies and hopes to begin human trials next year.

Geron's clinical trial of a therapy to treat spinal cord injuries will likely be the first human test of an embryonic stem cell-based treatment. In preparation for this medical first, the company is trying to figure out how to test a therapy that's both potentially revolutionary and totally unknown to the doctors who will be carrying out the trials and government officials who will oversee the process.

Geron's lead therapy has already shown dramatic success in animal models. In 2005, Hans Keirstead, a neuroscientist at the University of California, Irvine, who developed the treatment with funding from Geron, published a paper showing that paralyzed rats injected with the cells were able to walk again.

In Geron's therapy, embryonic stem cells are the starting ingredient rather than the treatment itself. The embryonic stems cells, which are potentially able to form any human cell type, are transformed into oligodendrocytes -- a type of brain cell that wraps itself around neurons, forming a fatty insulation layer that allows electrical messages to be conducted throughout the nervous system. These cells are then injected into the site of the injury, coating neuronal projections that were damaged in the accident and restoring communication to the nervous system.

Because cells are living tissue and their behavior is somewhat unpredictable, trials of cell-based therapies are more complex than trials of conventional drugs. Scientists at Geron have spent years studying their lines of embryonic stem cells, figuring out the precise series of conditions needed to grow giant vats of embryonic stem cells and to transform them into pure populations of oligodendrocytes. The Geron researchers have also developed a way to reliably freeze and thaw the brain cells, so that they can be manufactured in a central location, and then shipped to the hospitals where they will be used. "You can use it off the shelf, just like a pill," says Thomas Okarma, Geron's chief executive officer.

Since the successful proof-of-principle experiments were published last year, both Keirstead and scientists at Geron have been running safety tests in animals. "One concern was that potential harm from the transplant was being masked by severity of injury in the animal models," says Keirstead. So researchers gave the same treatment to animals with mild injuries that usually heal on their own. In a paper published last month, Keirstead showed that the treatment caused no damage and had no negative effect on the normal healing process.