In a study on the mechanism of accelerating fracture healing in traumatic brain injury, it was found that noradrenergic signal regulation of M2 macrophage infiltration played a role in the healing tissue, and the addition of ADRB2 agonists accelerated tissue healing,43 indicating that the ADRB2 signal had a regulatory role in the polarization of M2 macrophages. The gene discussed is ADRB2; the disease is injury.