A BETTER FIX FOR CARTILAGE
Each year, approximately 750,000 people in the United States undergo surgery to replace cartilage damaged by disease or injury. Healthy cartilage acts as a cushion that prevents bone ends from rubbing together at joints. But once damaged, cartilage can't repair itself.
As a former marathon runner, Stanford associate professor of radiology Garry Gold, MS '88, MD '92, knows firsthand how painful that can be. "I know what the impact of having an injury like this can be on your life and on doing the things you want to do," he told the San Jose Mercury News.
Existing interventions provide only a temporary fix. The standard method—called microfracture—involves perforating the bone with tiny holes in the hope that the stem-cell-rich marrow and blood will stimulate cartilage growth. However, cartilage produced in this manner is less durable and breaks down quickly.
Gold and his colleague Jennifer Elisseeff, an associate professor of biomedical engineering at Johns Hopkins, have devised a potential solution to this problem by modifying the microfracture technique. A flexible material called hydrogel is inserted into the surgery site to form a scaffold for the growing cartilage cells, which improves the integrity of the resulting tissue.
In a pilot clinical study, 15 patients with cartilage damage in their knees received the microfracture plus hydrogel surgery, while another three had microfracture only. After six months, MRI showed 34 percent more new cartilage growth, on average, in patients who received the hydrogel versus those who had microfracture alone. Patients who got hydrogel also reported less knee pain. The results were published in Science Translational Medicine in January.
A company called BioMet, which acquired the technology, will oversee ongoing trials to ensure the long-term safety and efficacy of hydrogel for cartilage repair.
EXPLORING MARS BY PROXY
Mars has loomed large in the human imagination for centuries. Since the 1960s, NASA has launched more than a dozen spacecraft to explore Earth's closest planetary neighbor—with varying degrees of success. A manned mission poses daunting challenges, mainly due to Mars's high gravity. But what if there were another way to learn the red planet's secrets?
Marco Pavone, an assistant professor in Stanford's department of aero/astronautics, is developing a hybrid spacecraft-rover platform to investigate the Martian moon Phobos. If, as some scientists believe, Phobos is a piece of Mars knocked loose by an asteroid impact (as opposed to a space rock captured by the planet's gravity), scientists could study the moon as a proxy, or use it as a test bed for Mars-bound technologies.
The proposed Phobos Surveyor system comprises an orbiting mothership, powered by two umbrella-shaped solar panels, and a half dozen roughly spherical, beach ball-size probes. Dubbed "hedgehogs" for the spikes protruding from their surface, these probes are designed to exploit the microgravity environments of the solar system's smaller bodies. Three rotating discs inside each hedgehog create inertial forces that allow the probes to tumble, hop or bound on a variety of terrain without getting stuck or losing traction.
Pavone's group envisions parking the mothership near Stickney Crater where it can stably hover between Mars and Phobos. The hedgehogs would be released one at a time, several days apart, to take measurements of the moon's exposed layers while reporting their position to the mothership, which would relay the data to scientists on Earth.
The team has built and tested two generations of a hedgehog prototype and are at work on a third, which they plan to test this summer. However, a Phobos Surveyor mission is a long way off; just getting the mothership to the moon would take two years. Still, Pavone is optimistic that the system, which he sees as an important step toward a human mission to Mars, could be launched within the next two decades.
