Liver delivery

Will the future of medicine involve replacement organs for livers, kidneys, or even hearts? New research from Japan increases the likelihood. For the first time, scientists say they’ve grown three-dimensional, functional pieces of human liver.

The Japanese team believes its miniature livers are also the first functional organs grown using induced pluripotent stem cells. That’s good because “iPS” cells, taken from adult tissue, don’t require the destruction of an embryo, and don’t have the problem of immune system rejection that troubles most organ transplants.

Reporting in Nature, the researchers said they grew their bits of human liver not in humans but mice: Through trial and error, they discovered that the right combination of human iPS cells, blood stem cells, and bone stem cells will grow into liver tissue, mimicking how a liver grows inside a developing embryo. They began the growth process in petri dishes, then implanted the “liver buds” into the brains of mice whose skulls had been cut open and fitted with glass slides, giving scientists a window to observe the growth. (Yes, it’s all quite bizarre.)

The liver buds grafted into the brain tissue, growing new, working blood vessels. Although only a fraction of an inch in size, the buds behaved like actual livers—producing proteins and metabolizing drugs. When the researchers implanted the liver buds into the abdomens of mice with liver failure, their survival odds increased, proving the lab-grown livers really worked.

Behind kidneys, livers are the second most in-demand organ in the United States. As of early July, nearly 16,000 people were on the U.S. liver transplant waiting list. An organ regrowth treatment, if it existed, could help them.

However, a lead researcher on the Japanese team said using the “liver bud” approach in a human—to seed a dying organ with billions of iPS cells—would require an automated technique that might take five years or more to develop. Because of safety concerns, starting a human trial would probably take a decade.

Don’t write it off as far-fetched, though: Doctors have already “grown” simpler organs—windpipes—in labs and implanted them in patients. With some technical advances, liver regeneration might be just a few labs experiments away.

Report card

Stimulants that treat attention deficit hyperactivity disorder in children and teens, such as Ritalin and Adderall, may decrease fidgety behavior in the classroom, but don’t expect them to improve your child’s grades. According to a Wall Street Journal report, in recent studies ADHD drugs appeared to reduce math scores in boys and increase unhappiness in girls, and didn’t improve any level of academic achievement over the course of several years. Kids who take ADHD drugs may be easier for parents and teachers to handle, but the idea that calmer moods will translate into better study habits seems merely wishful.

At last count (in 2007), the government estimated 2.7 million American children under 18 were taking ADHD medications. Prescriptions have surged since then, with spending on the drugs more than doubling, to $9 billion from $4 billion. —D.J.D.