Fresh clues to what makes hair follicles go dormant are pointing toward potential cures for baldness.

Several research teams are working to figure out ways to spur existing follicles—the tiny organs in the skin that give birth to hair—back into action, or to make new, active follicles. New treatments based on this work likely are many years from the market, but these approaches could lead to the significant breakthrough of helping people who are already bald. By contrast, topical...