Many conditions, such as sickle cell and heart disease, are caused by genetic mutations. Over the past few years, scientists have learned how to treat some of those conditions by introducing cells that have been edited with bioengineering tools like CRISPR. But in the future, doctors could treat those conditions by editing patients’ cells while they’re still in their bodies—an approach called in vivo gene editing. Cordilia James spoke with WSJ senior writer Betsy McKay about how the approach works and its potential risks. Alex Ossola hosts. Learn more about your ad choices. Visit megaphone.fm/adchoices