Researchers have developed a protein-based injection that can regrow blood vessels in the human heart. By sparking the growth of new tiny blood vessels, the injection could help millions avoid bypass surgery and have a new lease on life. In animal tests, the injection has regrown blood vessels in the legs within a few weeks with no side effects or inflammation. The researchers hope to complete toxicity studies and begin phase 1 trials in humans within two years, which could eventually replace bypass surgeries altogether through regrowing blood vessels in the heart.