This week in science, we featured a new study showing that injections of an experimental drug can repair cartilage to relieve osteoarthritis within weeks. The study also revealed a pattern in whale communication that appears similar to human speech. A Norwegian man is in long-term HIV remission after a stem cell transplant from his brother, who carries a rare, beneficial genetic mutation, four years after the transplant. A large reservoir of magma has been discovered beneath Tuscany in Italy, at a volume similar to that of the Yellowstone supervolcano. Higher levels of vitamin D in midlife have been linked with lower levels of tau protein tangles in the brain later, potentially a risk factor that could be modified to reduce dementia. The most pure star ever detected was found in the Milky Way.