Osteopontin increases the proliferation of neural progenitor cells.

We examined the role of osteopontin in the proliferation of neural progenitor cells in vitro. Osteopontin increased the proliferation of neural progenitor cells in the presence of FGF2 as measured by cell proliferation assay and bromodeoxy uridine incorporation studies. In addition, immunoblot analysis demonstrated an increase in the phosphorylation of retinoblastoma protein with a concurrent increase in the content of phospho-Akt and cyclin D1. These results indicate that osteopontin can upregulate the content of phospho-Akt, cyclin D1 and phospho-Rb to subsequently enhance the proliferation of neural progenitor cells in the presence of FGF2.