SPP1 and Alzheimer disease: Since OPN is an extracellular matrix protein that mediates its effects through binding to integrin β1 or CD44,22–24 to further investigate the mechanism of OPN regulation of AD differentiation, hBMSC were treated with an integrin β1 blocking antibody and we observed enhanced AD differentiation and abolishing the impaired AD differentiation in siRNA-KIAA1199 (Fig. 7c, d).