Repair work: This animation shows glial progenitor cells, made from human embryonic stem cells, repairing nerve damage. Credit: University of California, Irvine

Geron, a California-based cell-therapy company that has been working with embryonic stem cells for the last decade, finally received clearance from the U.S. Food and Drug Administration to begin clinical trials of its cell-based therapy for spinal-cord injury.

The trial is limited to eight patients with newly acquired spinal-cord injuries who will receive injections of the cell therapy, called GRNOPC1, within two weeks of their accident. GRNOPC1 is made by transforming embryonic stem cells 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. In many spinal-cord injuries, these cells are damaged, but the underlying nerve cells remain intact. These cells are then injected into the site of the injury, coating exposed nerves and restoring communication to the nervous system.

Scientists published the results of a successful study testing the therapy in animals in 2005, showing that paralyzed rats injected with the cells were able to walk again. Since then, Geron has been conducting numerous studies intended to show the safety of the cell-based therapy, as well as developing production methods that would make the cells as easy to use as more traditional treatments. Geron researchers have also developed a way to reliably freeze and thaw brain cells, so that they can be manufactured in a central location, and then shipped to the hospitals where they will be used.

Because embryonic-stem-cell-based therapies are so new, the FDA has had trouble deciding how to evaluate new drug applications. (Geron's president and CEO, Thomas Okarma, thought approval was imminent when I spoke with him in 2006. See "Human Tests of Embryonic Stem Cell Treatments Planned.") The initial trial is designed to assess safety, but doctors will also measure its effectiveness, such as improved neuromuscular control or sensation in the trunk or lower extremities.

The announcement comes amid general excitement in the stem-cell field, thanks to Barack Obama's promise to lift funding restrictions for embryonic-stem-cell research. (See "Braving Medicine's Frontier.")

Geron's Thomas Okarma said in a statement, "This marks the beginning of what is potentially a new chapter in medical therapeutics--one that reaches beyond pills to a new level of healing: the restoration of organ and tissue function achieved by the injection of healthy replacement cells. The ultimate goal for the use of GRNOPC1 is to achieve restoration of spinal cord function by the injection of hESC-derived oligodendrocyte progenitor cells directly into the lesion site of the patient's injured spinal cord."

This video illustrates how Geron's cell therapy works in rats.

I just returned from the Society for Neuroscience annual conference, where 30,000 neuroscientists swarmed into downtown San Diego to share their latest findings on everything from the teenage brain to the hedonistic synapse. There's never enough time to see everything interesting at this massive meeting, but here's a snapshot of a few things I heard about.

The neurochemistry of trust: Serotonin, that famous chemical messenger of happiness, seems to play a role in trust. Robert Rogers and his colleagues at Oxford University had undergrads play a game known as the Prisoner's dilemma, in which players must choose to cooperate with another player or look out only for themselves. About 75 percent of players chose to cooperate under normal conditions, but when they were given a diet to reduce tryptophan, a precursor of serotonin, students rated other players as less trustworthy, and their cooperation levels dropped significantly. Perhaps that tryptophan-laden Thanksgiving turkey has more significance than we realized.

Alzheimer's disease: If you want to lower your risk of Alzheimer's disease, keep your cholesterol down. Previous studies have suggested a link between Alzheimer's and cholesterol, but a new study presented by Eric Reiman at the University of Arizona found that higher cholesterol levels in middle age were linked to lower activity levels in the brain areas associated with Alzheimer's. The correlation was strongest in people with APOE4, a genetic variation known to boost Alzheimer's risk. Scientists speculate that cholesterol accelerates the molecular processes that boost risk for the disease.

A second study showed that a computer training program, previously shown to boost cognitive function in healthy old people, can also improve symptoms of mild cognitive impairment, a condition that often precedes Alzheimer's. (For more about the computer program, see "Exercising the Brain.")

Spinal cord injury: A new antibody has entered clinical tests for spinal cord injury. The antibody blocks the activity of a chemical released after spinal cord injury that blocks nerve growth. (It's not quite clear why the body releases these inhibitory factors, but they have proved to be a major hurdle in developing treatments for spinal cord injury.) In preliminary tests in monkeys presented by Martin Schwab and his colleagues at the University of Zurich, the antibody was able to restore function to the animal's damaged hand.

Stroke therapy: A simple device under development by BrainPort Technologies could help stroke patients regain their sense of balance. The device hangs around the neck and is attached to a small cord and stimulator placed under the tongue. The neck piece detects the position of the head in space and then transforms that information into electrical impulses on the tongue.