Here is a snapshot of what they said in the above article: “Your body is equipped with something called progenitor stem cells. These cells are in charge of repairing and replenishing specific organs in the body. For example, a mesenchymal stem cell of the osteoblast lineage can go in and repair bone that’s damaged. That process has something to do with the WNT pathway, a set of proteins that tell these stem cells to spring into action.”
The article, although a bit ‘technical’ will give you the flavor of what is happening with new hair growth in their hands.