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Science, Medicine, Technology
  Columbia geneticists have discovered that osteoporosis, which occurs when bone tissue becomes too porous, as seen in this picture, can be reversed in mice by slowing down production of the hormone serotonin.
Bone-building solution

Bones are constantly regenerating: as their cells deteriorate and are absorbed back into the bloodstream, new cells replace the old ones. In people who suffer from osteoporosis, the body can’t produce new bone fast enough, leaving the skeleton porous and brittle.

Until now, scientists thought they had identified all of the major hormones that control this regeneration process. But Columbia geneticist Gerard Karsenty says that a type of serotonin known for its role in heart development also instructs the skeleton to slow production of new bone cells. Karsenty and his research team say that by shutting down production of this serotonin, which is made in the small intestine, they’ve been able to reverse osteoporosis in mice. The study appeared in the November 28 issue of the journal Cell.

“It’s a groundbreaking paper,” said Christopher Gallagher, an osteoporosis specialist and professor of medicine at Creighton University, in the New York Times on November 27. Ronald N. Margolis, an endocrinologist at the National Institute of Diabetes and Digestive and Kidney Diseases, added: “I was astonished. My jaw was dropping.”

Karsenty’s research team made the discovery while studying the gene LRP5, which scientists have known for years influences bone production. Karsenty assumed, as had most scientists, that a dangerous LRP5 mutation that stops bone from growing originates inside the skeleton. But when Karsenty’s team extracted bone cells from osteoporosis-afflicted mice and grew new bone mass in a petri dish, the bone developed healthfully. This suggested that the LRP5 mutation was coming from somewhere else in the animal’s body, not from within the bone. The scientists then detected very high levels of serotonin in the sick mice. When they injected the serotonin into the bone in the petri dish, the bone stopped growing. They soon confirmed that LRP5 in the gut was affecting serotonin levels.

Karsenty hopes this discovery will lead to the development of osteoporosis treatments that generate new bone. Most osteoporosis drugs today simply prevent the breakdown of old bone; only one drug creates new bone and it’s suspected to cause cancer and so is administered only to people with the most severe forms of osteoporosis. “We need something to build bone, not just prevent or repair its loss,” says Karsenty, who chairs the department of genetics and development at Columbia University Medical Center. “Osteoporosis is often diagnosed when the damage to bone is already significant, and fracture risk is high.”

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— David J. Craig

Columbia geologist Peter Kelemen, at right, and Brown University geologist Greg Hirth sample carbonate minerals that have accumulated on a rock formation in Oman.
Rock-solid CO2 storage

Columbia scientists say they’ve devised a new method to store carbon dioxide underground so that it doesn’t linger in the atmosphere and contribute to global warming. They envision that hot water containing huge quantities of pressurized CO2 could be poured into holes drilled in peridotite, a dense rock that makes up the earth’s mantle.

Scientists have long known that peridotite reacts with CO2 to form a solid similar to limestone. The new insight of geologist Peter Kelemen, the Arthur D. Storke Memorial Professor in the department of earth and environmental sciences, and geochemist Juerg Matter, a research scientist at Lamont-Doherty Earth Observatory, is that peridotite reacts with CO2 at a faster rate than previously believed. This means that it might be economically feasible to store CO2 in the rock.

They made their discovery in Oman, one of a handful of places where the collision of tectonic plates has forced peridotite aboveground. Peridotite typically rests 20 kilometers underground, but a mountainous section of Oman roughly the size of Massachusetts is covered in it. Cracks in the peridotite are laced with the chalky white carbonate that forms wherever CO2-laden air or water comes into contact with the rock’s rich minerals.

Kelemen and Matter demonstrated that the carbonate in the region isn’t nearly as old as the peridotite, as most scientists had assumed. Using carbon isotope dating, they found that carbonate in the region is just 26,000 years old, on average, whereas the peridotite formed 96 million years ago. This indicated that the peridotite is absorbing up to 100,000 tons of carbon annually, far more than anyone thought. The scientists say that if deep holes were drilled, this region could absorb 20 percent of the CO2 humans spew into the air each year.

Petroleum Development Oman, the state oil company, is interested in a pilot program that would pump below the surface CO2 generated at nearby power plants. “This would afford a low-cost, safe, and permanent method to store CO2,” says Kelemen, the lead author of the study in the November issue of the Proceedings of the National Academy of Sciences. “We see this as just one of a whole suite of methods to trap carbon. It’s a big mistake to think that we should be searching for one method that will take care of it all.”


  Raimondo Betti has invented a system to monitor corrosion in suspension bridge cables remotely.
Mending bridges

Bridge inspectors today evaluate the integrity of suspension cables in much the same way they did when the Brooklyn Bridge opened to traffic back in 1883: they climb on top of the gigantic wire bundles and look for visual signs of deterioration. Needless to say, engineers would prefer a more scientific approach.

Raimondo Betti, a Columbia professor of civil engineering, is developing a new method for detecting corrosion in the cables. To fine-tune his technique, he has built a replica of a suspension bridge cable in the basement of the Mudd Building. Composed of some 9000 steel wires, just like the real thing, the 20-foot-long replica is suspended by a huge steel frame that exerts more than one million pounds of force. The cable withstands a constant barrage of acid rain, extreme cold, heat, and humidity inside an acrylic encasement. Betti has squeezed between the cable’s outermost wires tiny sensors that measure temperature, acidity, and humidity and transmit the information to a remote computer that calculates how much corrosion likely has occurred.

Betti is working with the city’s department of transportation (DOT) in hopes of installing his sensor system on the Manhattan Bridge within 10 years to help bridge inspectors work more efficiently. Today, when inspectors spot signs of corrosion on a cable they must decide whether or not to loosen the outermost wires and look underneath. That’s an expensive and time-consuming operation, even if no wires ultimately need to be replaced.

“Sometimes one or two wires need to be replaced and sometimes hundreds need to be replaced — as occurred on the Williamsburg Bridge when it was shut down for repairs about 20 years ago,” says Bojidar Yanev, the head of bridge inspection for the city’s DOT. He says that during the past two decades, authorities have spent nearly $1 billion maintaining the Williamsburg Bridge, about $900 million on the Manhattan Bridge, and $600 million on the Brooklyn. “Dr. Betti’s work will have applications for suspension bridges around the world.”

— Erica Westly

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