Developments in Adult-Stem-Cell Research, HIV Prevention, and C-Section Guidelines Top the Week's Medical News

Medical news never takes a vacation, summer or not. This week alone, there is a slew of important developments—so many that we decided to create a checklist of three big ones you should know about.

1. Adult stem cells have memories. Four years ago, a breakthrough in stem-cell science accomplished the impossible by making both sides of the embryonic-stem-cell debate happy: those who support the research and those who oppose it. How? A group of scientists in Japan managed to genetically reprogram adult-mouse skin cells, turning back the clock on their biological destiny. In their new incarnation, these induced pluripotent stem cells (iPS cells), which scientists later made from human cells as well, looked like embryonic stem cells, which have the unique capacity to turn into any kind of cell in the body. Critics of embryonic-stem-cell research hailed them as an ethically acceptable alternative; scientists hailed them as a major advance in the field, moral controversies aside. But, from the start, major questions remained: Would iPS cells have the same properties as their embryonic counterparts? Would they not just look like embryonic stem cells but act like them too?

Not exactly, it turns out. This week Dr. George Daley, director of the Stem Cell Transplantation Program at Children's Hospital Boston and a Howard Hughes Medical Institute investigator, and colleagues reported in the journal Nature that iPS cells retain an "epigenetic memory" of their origins; they remember whether they came from skin or muscle or blood. When Daley's team tried to make mouse blood cells out of reprogrammed mouse skin cells, they weren't hugely successful. But "blood-originated" iPS cells made plenty of blood cells. This means iPS cells could be self-limiting, but it by no means makes them moot. Another Harvard team, reporting in Nature Biotechnology, found that when iPS cells are cultured multiple times, their genetic memory fades. Stay tuned.

2. A weapon against HIV. It's been 15 years since the first powerful protease inhibitors were approved to fight HIV, launching a new era of powerful drug cocktails that have allowed patients to live with the virus for decades instead of dying from it. But prevention, not treatment, is the ultimate goal. Researchers have been trying to manufacture an effective HIV vaccine for a very long time, but it has proved to be a painstaking and arduous task. Earlier this month there was some potentially exciting news when U.S. government scientists reported that they'd identified three promising antibodies, one of which neutralizes 91 percent of HIV strains. But crafting those findings into a vaccine will take time. As Gary Nabel, director of the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases, said here, "We're going to be at this awhile."

What the world needs now is immediate protection, and this week came some significant progress on that front. Researchers at the Centre for the AIDS Programme of Research in South Africa reported that a vaginal gel containing the antiretroviral drug tenofovir reduced the risk of HIV infection by 39 percent in women who applied it 12 hours before and 12 hours after sex. "High adherers"—women who used the gel at least 80 percent of the time—saw an even greater benefit: their risk was slashed by 54 percent. The gel also cut the risk of genital herpes infection by 51 percent—a major boon, since women who have herpes are twice as likely to be infected with HIV. The news was reported in the online edition of Science and at the 18th International AIDS Conference in Vienna, where "hearty applause" broke out in response.

3. New guidelines on Caesareans. Many women who deliver a baby by C-section want to try natural labor and delivery the next time around. But a vaginal birth after Caesarean, or VBAC, isn't always an option, in part because of guidelines issued by the American College of Obstetricians and Gynecologists(ACOG) in 1999, which stated that medical specialists be immediately available during a "trial of labor" to provide emergency care for women who'd had a prior C-section—a standard that doesn't exist for routine labor. Some hospitals that didn't have adequate emergency staff (and were wary of lawsuits) stopped offering VBAC altogether.

At the same time, the population of women considering a VBAC is up because the rate of C-sections has spiked dramatically, increasing 53 percent between 1996 and 2007. As a result, some women have succumbed to a second or third C-section against their wishes or have sought out VBAC-friendly doctors and hospitals. The VBAC issue has received national attention this year. As we reported here, the National Institutes of Health held a conference in March in which experts defined the barriers women were up against if they wanted a natural delivery and explored the risks and benefits of labor versus VBAC. The risk of uterine rupture during labor in women who've had a prior C-section—which is often cited as a warning against VBAC—is less than 1 percent. Multiple C-sections, for their part, carry significant risk, including abnormal placenta growth, which can lead to hemorrhaging.

The big news this week: ACOG is releasing revised and less restrictive VBAC guidelines. ACOG now says a trial of labor is safe and appropriate for most women, including those who've had two previous C-sections and those carrying twins. The new guidelines also state that when emergency personnel aren't immediately available during labor, doctors should discuss the situation with their patients, who "should be allowed to accept increased levels of risk" as long as they are clearly informed.

This is good news to Dr. Howard Minkoff, chair of obstetrics and gynecology at Maimonides Medical Center in Brooklyn, N.Y. "Something had to be done," he says. "We need to make sure this is a choice left in the hands of women and their doctors." Now that the guidelines are out, a cultural shift—away from repeat Caesareans and toward VBAC—must begin to take place. If that happens, the number of repeat C-sections will start to drop. Dr. Jeffrey Ecker, a high-risk OB at Massachusetts General Hospital in Boston and coauthor of the new guidelines, says it's hard to define an appropriate Caesarean rate. But "I and probably many others hope the C-section rate will be lower," he says. So do plenty of women.