Blinded by old macrophages

As they age, some cells simply fail to perform their jobs, but macrophages become troublemakers. According to Jennifer Kelly, Rajendra Apte (Washington University, St. Louis, MO), and colleagues, old macrophages promote abnormal blood vessel growth that can lead to diseases such as age-related macular degeneration (AMD).

Ample evidence suggests that macrophages check angiogenesis. Apte and colleagues previously reported that macrophages with Fas ligand (FasL) on their surface spur blood vessel cells to commit suicide, thus pruning new capillaries. But other work indicates that macrophages encourage vessel growth. The researchers wanted to pin down macrophages' effects on angiogenesis during AMD.

The team replicated AMD's key defect—growth of numerous vessels beneath the retina—by zapping the eyes of mice with a laser. Fewer vessels sprouted in young mice...