Every year, like clockwork, DISCOVER digs through reams of newspapers and gigabytes of Web sites to find the 100 most important and interesting science stories of the year. We're unveiling the top stories from 2006 over the next couple of weeks, one subject at a time. Here's the whole list (only subscribers get access to the whole special package immediately).
Also check out the results of our year-in-science poll, in which readers chose Pluto Demoted as the biggest story of the year.
2 Tissue Engineering Triumph: Lab-Grown Bladders
Artificial bladders can be grown from a patient's own cells and successfully implanted...
14 Fast-Food Fats Prove Health Hazard
Small daily amounts of trans fats cause weight gain, atherosclerosis, and insulin resistance...
18 Drugs Aim to Silence Bad Genes
RNA interference helped launch an entirely new class of drugs into trials...
19 World Trade Center Fallout Fails Health Test
A report revealed widespread, persistent respiratory illness among rescue and recovery workers...
23 Mouse Breast Grown in Lab
To make a breast, all you need is a single cell...
24 Bird Flu Risk Explained
The deep infection makes it difficult to spread the avian flu virus...
25 First Face Transplant
Attaching the nose, chin, cheeks, and lips of a 46-year-old brain-dead woman...
28 New HIV Drugs
Three new categories of anti-HIV drugs are in the pipeline...
31 British Clinical Drug Trial Goes Spectacularly Awry
Six of the test subjects wound up with massive organ failure...
44 Stem Cells Reverse Parkinson's in Rats
Embryonic stem cells helped rats suffering from Parkinson's-like symptoms...
49 Power of Hallucinogenic Mushrooms Revealed
People who tripped ranked the experience as one of the most meaningful in their life...
53 Low-Fat Diet A Bust?
Cutting fat from the diet doesn't significantly reduce the incidence of breast or colorectal cancer, heart disease, or stroke...
98 Fat Vaccine Works in Rats
In August, immunologist Kim Janda grabbed headlines with reports of a vaccine against obesity...
2 Tissue Engineering Triumph: Lab-Grown Bladders
On April 15, the British medical journal The Lancet carried a landmark article showing that it is now possible to engineer a complex organ to replace one ravaged by disease. Anthony Atala, a surgeon and director of the Institute for Regenerative Medicine at Wake Forest University School of Medicine in Winston-Salem, North Carolina, reported that artificial bladders can be grown in the lab from a patient's own cells and successfully implanted. Over the past six years, seven children have received the organs, which are functioning well.
Atala's quest to build an artificial bladder began about 16 years ago when he was honing his skills as a pediatric surgeon at Harvard University. He became increasingly unsettled by a routine century-old procedure he was performing in young children: replacing damaged or diseased bladders with sections of the bowel or the stomach. Because the role of these tissues is to absorb chemicals (whereas the role of the bladder is to store and eliminate them), patients, especially young children, who underwent the procedure were often saddled with a suite of inescapable side effects. "When you replace bladder with intestine, you absorb chemicals you should get rid of, creating lots of problems," says Atala. Among them is a higher risk of cancer, stone formation within the walls of the transplanted tissue, and bone deformities due to calcium reabsorption by the tissue.
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A red solution of a patient's cells is placed on |
Atala wondered whether it would instead be possible to remove bladder cells from a patient and use them to grow a replacement organ, thus eliminating the risk of transplant rejection. "I had no idea how difficult it would be," says Atala. It took about a decade, but in 1999 he and his colleagues began implanting these engineered organs in spina bifida patients aged 4 to 19 who, in addition to spinal cord defects and nerve damage, had abnormal bladders.
For patient Kaitlyne McNamara of Middletown, Connecticut, who received her implant in 2001 at age 12, the timing could not have been more crucial, says her mother, Tracy McNamara. She had the "bladder capacity of a thimble," was wet all the time, and was forced to wear diapers. More critical was that her tiny, rigid bladder would spasm frequently, forcing urine back into her kidneys, where it triggered severe infections that were slowly destroying them. Her bladder condition disqualified her for a kidney transplant.
Six weeks prior to Kaitlyne's surgery, Atala and his team harvested a dime-size piece of tissue from her bladder, using this as the source of cells to create a new organ. A normal bladder has three layers: On the outside is muscle, in the middle is collagen, and the innermost layer consists of specialized urothelial cells that are impermeable to urine and protect the body from waste fluids. After a biopsy, Atala teased apart the three layers, cultivating the muscle and urothelial cells separately and discarding the collagen. Four weeks of cell division produced enough cells to build a new bladder. "The key to these technologies is, first and foremost, getting the cells to grow outside the body," says Atala. "Then you need to figure out how to attach them to a biodegradable scaffold."
Atala's method involved painting several coats of Kaitlyne's muscle cells on the outer surface of a bladder-shaped mold made of collagen. The inside of the scaffold was covered with her urothelial cells. The whole structure was then immersed in a nutrient bath and put in an incubator at 90 degrees Fahrenheit. Ten days later the bladder, looking like a shiny pink ball, was ready for implantation. Once in the body, if all went well, natural processes would take over and allow the tissue to mature. Five years after her implant, Kaitlyne lives without diapers, has normal bladder capacity, no longer suffers from kidney or urinary tract infections, and has a dramatically improved quality of life.
Critics caution that this is a small trial and that the implants need a longer follow-up. And technically, Atala has yet to create and implant an entire bladder; the ureters at the top and the sphincters at the base are still the originals. He is expanding clinical trials for the artificial bladder to include more populations who could benefit, such as bladder cancer patients. He is also working on engineering other body parts—the liver, nerves, heart valves, and pancreas. Next in line for clinical trials: blood vessels.
Bijal Trivedi
More on tissue engineering; it's not easy to grow new organs.
Anthony Atala strives to eliminate the problem of urinary incontinence.
14 Fast-Food Fats Prove Health Hazard
The dangers of trans-fatty acids—a cornerstone of fast-food cooking—were confirmed in June, when a study at Wake Forest University in Winston-Salem, North Carolina, revealed that even small daily amounts of trans fats led to alarming patterns of weight gain, atherosclerosis, and insulin resistance in monkeys.
Trans fats are the partially hydrogenated vegetable oils in the fryers at most fast-food chains; they are also used in many commercial cookies, pies, and crackers. These fats are commercially popular because they are shelf-stable and resistant to high heat. In recent years, though, they've become public health enemy number one, as evidence mounted that they contribute to heart disease, high cholesterol, and type 2 diabetes. In early 2006 new Food and Drug Administration rules went into effect requiring food labels to show trans fat content; in September the city of New York proposed severely limiting the use of trans fats in local restaurants.
Led by biochemist and pathologist Lawrence Rudel, the Wake Forest study set out to document the effects of a high trans-fat diet on atherosclerosis. But the results showed an impact far beyond hardened arteries. Two groups of male vervet monkeys were fed on different regimens for six years. Although the total calories and total dietary fat were the same for each group, the type of fat was not. One group received trans fats; the other received traditional monounsaturated fats. Over the six years, monkeys on the trans-fat diet added an average of 7.2 percent of their body mass, while the other group averaged just a 1.8 percent increase. Worse, the new weight from trans fats showed up mostly around the abdomen, a pattern strongly associated with cardiovascular disease in humans.
Ominously, the obesity-inducing monkey grub was not so different from a mainstream American diet. "The trans-fatty acids were roughly 8 percent of total energy," Rudel says. "That's high, but not outside the reported range for people who eat a lot of french fries and Krispy Kremes."
Commenting in the New England Journal of Medicine, Walter Willett, a nutritional epidemiologist at the Harvard School of Public Health, proclaimed that trans fats are probably a bigger public health problem than either food contamination or pesticides. Biochemists don't know exactly why they are so damaging, but the monkey study has one clear implication, Willett wrote: "Trans fats are clearly toxic to humans and have no place in human diets."
Kathleen McGowan
Nutritionist and physician Walter Willett, a voice of reason on diet.
