Modern biology needs tools. One of the most controversial of those tools has proven to be crucial to explaining how the Zika virus causes brain damage in newborns.
Zika is poised to dwarf the threat of Ebola, which was never a significant danger to the United States in spite of the cable news-induced hysteria. But Zika is a different story. Public health officials expect the virus to spread in the southern states this spring partly owing to extensive travel to and from South America. It is already a serious problem in Puerto Rico. With the disease-carrying mosquito likely to be seen in the U.S. mainland soon, the White House will hold a one-day summit on the problem this spring.
Understanding the mechanism of Zika could open a pathway to preventing the condition in infants. Working together in an important experiment, scientists at several universities have found that the virus attacks stem cells early in pregnancy. Some of these stem cells will become neurons and form the cortex, the outer layer of the brain. It seems that the virus invades these cells, killing some and preventing others from dividing, which they must do to populate the fetal brain.
The cells that the scientists used to achieve this understanding would not have been available just ten years ago. In 2007 a Japanese team found that it was possible to turn adult cells into highly potent stem cells that resemble embryonic stem cells, which have the ability to turn into all of the more than-200 kinds of cell in the adult human. These induced pluripotent stem cells were the essential ingredients in the Zika virus experiment.
But the debt to stem cell biology goes back still further, to 1998 when American scientists isolated human embryonic stem cells in the laboratory for the first time. These embryonic stem cells then became the gold standard that allowed later investigators to see what they were aiming for in creating cells that did not need to be taken from an embryo. Although the lab-grown cells don't seem to be perfectly similar to the ones from embryos, they have made it easier to do a wide range of experiments.
Unfortunately, the road to the science behind the pluripotent cells was a painful one. Before they were developed, the fact that a six-day old embryo was destroyed in the course of obtaining its stem cells led to a furious ethical and political battle. Advocates noted that the few embryos required were in fertility clinics and were donated by couples who would never have used them. Opponents found such reasoning grotesquely utilitarian and disrespectful of incipient human life. This esoteric laboratory technique became a political issue in several presidential campaigns and numerous congressional races.
Emotions on both sides ran high as the issue symbolized a struggle between the freedom of scientific inquiry and the value of even the smallest human being.
At the time it was easy to miss the fact that support for at least some stem cell research was bipartisan. President Bill Clinton was in favor of it before his term ended. President George W. Bush continued to fund embryonic stem cell research, albeit with severe limitations, and Senator John McCain refused to disavow it when he ran for president, which probably cost him the votes of some social conservatives. Then President Obama expanded the list of stem cells that could be used in federally supported studies.
With some distance from that controversy it is possible to acknowledge both that induced pluripotent stem cells were an advance and that cells from embryos made it possible to get there. No one could have predicted that stem cells would be so important for a crisis like this. If the recent experiments do lead to a treatment for the brain damage caused by the Zika virus, we will have learned an important lesson about the way that modern biology needs to progress.