Paul Knoepfler is an unlikely watchdog for the therapeutic stem cell industry. His University of California, Davis, lab mostly uses stem cells to study cancer-causing gene mutations—not to develop potential therapies. But thanks to The Niche, a blog he has run since 2010, Knoepfler has become an international authority—and a dogged voice of caution—on the clinical use of stem cells. For years, he has sounded the alarm on hundreds of U.S. physicians and clinics advertising stem cells to treat everything from sore knees to spinal cord injury without oversight from the U.S. Food and Drug Administration or support from randomized clinical trials. The blog, which now averages more than 4000 daily visits, has elevated him from an obscure bench scientist into a divisive figure.
