There is evidence for both local and systemic sources of OPN based on studies of a variety of tissues and cells including macrophages, activated microglia, astrocytes and epithelial cells33,87–92, as well as neurodegenerative diseases such as multiple sclerosis, Alzheimer’s disease, Parkinson’s disease, and ischemic stroke53,91,93–97. The gene discussed is SPP1; the disease is neurodegenerative disease.