Osteopontin is upregulated after mechanical brain injury and stimulates neurite growth from hippocampal neurons through β1 integrin and CD44.

Brain trauma induces a multitude of reactions at molecular, cellular, and tissue levels, some of which are beneficial to recovery, whereas others are detrimental. Osteopontin (OPN), a glycosylated phosphoprotein, can be found in both the soluble form and as an extracellular matrix constituent in several tissues in the vertebrate body, but its function after brain injury is largely unknown. In this study, the expression of OPN after an experimental traumatic brain injury in rats was examined and its effects on hippocampal neurons and cortical astrocytes were studied using cell-culture techniques. OPN had no influence astrocyte behavior in a scratch assay. However, hippocampal neurons grew well on an OPN substrate with growth comparable to that seen on laminin, but showed a higher degree of primary neurites. Finally, growth on OPN was mediated through β1 intregrins and CD44. These findings indicate that injury-induced OPN may support neurite sprouting, suggesting a role for this molecule in recovery from central nervous system trauma.