BY MEGHAN ROSEN To rebuild teeth, just add laser light. Zaps from a low-power laser boosted tooth growth in rodents, researchers report in the May 28 Science Trans lational Medicine. The beams of light set off a molecular chain reaction that ended with the regeneration of dentin, the tough inner material of teeth. The findings may change the way den tists think about treating patients, says stem cell researcher Peter Murray of Nova Southeastern University in Fort Lauderdale, Fla. Dentists can use lasers as high-tech scalpels to carve out damaged tissue, slice away overgrown gums or burn off tumors. But scientists have had hints that turning down a laser's power could actually get cells growing. Light from a low-power laser can spark new growth of heart, skin and nerve tissue, and researchers have speculated that the regeneration involves stem cells, says study coauthor David Mooney, a bioengineer at Harvard University. "But certainly people did not understand how it worked," he says. "We wanted to put all the pieces of the puzzle together." Mooney and colleagues drilled holes into two molars each in seven rats—down past the enamel and through the tough dentin — to expose the spongy, sensitive pulp at each tooth's core. The team hit the pulp of one tooth in each rat with a five minute blast from a handheld near-infra red laser and left the other tooth alone. After filling both drilled teeth and waiting 12 weeks, the team saw knobs of dentin growing in and around the pulps of both teeth. dental laser manufacturer
About 20 percent more dentin grew in the laser-treated tooth than in the untreated one. "It's not re-forming the tooth per fectly," Mooney says. But teeth could benefit from having extra dentin. Dam age to dentin by cavity-causing bacteria can leave the pulp vulnerable to micro A brief blast of laser light might spur mouse dental cells, shown here in false color growing in a 3-D scaffold, to make dentin, the tough stuff inside teeth. bial attack, which can kill the tooth. The laser treatment may work by activating stem cells. In lab tests, dental stem cells from human teeth and dental cells from mice showed signs of turn ing into dentin-making cells when hit with low-power laser light. Chemicals in the cells absorb the light's energy and morph into reactive molecules that rev up a growth factor protein. The protein spurs dental stem cells into action, which appear to turn into dentin-forming cells, Mooney says
BY LAURA SANDERS Mice with less pain live longer. When the animals lack a certain pain-sensing pro tein, their life span increases by an aver age of 10 to 15 percent, scientists report in the May 22 Cell. With age, many people suffer more frequent bouts of pain, says study coau thor Andrew Dillin of the University of California, Berkeley. He and his team wondered about pain's connection to getting older. "We simply just asked, is pain actually driving the aging process or is it part of the process, just going along for the ride?" Dillin says. The team studied mice genetically engineered to lack the protein Trpvl, a molecule important for sensing pain. Perched on the outsides of nerve cells, Trpvl senses scalding heat and spicy chili peppers, among other things. It also helps maintain body temperature and influences insulin-producing cells. Mice lacking Trpvl appeared normal, except that males fought one another viciously. But the team uncovered a big difference in metabolic health. Mice without Trpvl processed sugar more effectively than mice with Trpvl. This benefit remained even as the animals aged. Old mice lacking Trpvl also had more insulin-producing cells, which help metabolize sugar, in their pancreas than older mice with Trpvl. This link between pain sensation, metabolism and life span is exciting because the same connection may occur in other animals, says molecular physi ologist Rochelle Buffenstein of the Uni versity of Texas Health Science Center at San Antonio. Evidence from studies on a small subterranean rodent supports the link between pain sensing and life span. Buffenstein and others have found that the naked mole-rat, which lives to the unusually old age of 30 years, lacks a typical pain response. Favorable metabolic changes that come with a reduced-pain existence might drive life span extension. Male mice that lack Trpvl lived about 10.6 per cent longer than males with the protein, from an average of 937 to 1,036 days. In females, the average increase was about 15.6 percent, from 828 to 957 days. It's unclear whether metabolic effects alone alter life span or if the experience of pain, and the stress and anxiety that come with it, also contribute. "All we know is that when we reduce pain," Dillin says, "we increase metabolic health.