Under normal conditions, OPN expression is weak in the brain, while under pathological conditions including Alzheimer's disease, Parkinson's disease, TBI, stroke and hypoxia‐ischaemia brain injury, it is significantly increased in macrophages/microglia and astrocytes and exerts neuroprotective effects.26, 27, 28, 29, 30. The gene discussed is SPP1; the disease is stroke disorder.