SPP1 and injury: In the immature brain, OPN is one of the most highly regulated molecules in perinatal brain injury [26, 68], where a neuroprotective role has been suggested in neonatal brain injury in rodent models equivalent to term infants [16, 68], while in younger mouse brains administration of OPN peptides exacerbated brain injury in a mouse model of hypoxia-ischemia-induced preterm brain injury [1].