Moderate growth restriction: deleterious and protective effects on white matter damage.

The role for growth restriction in the multifactorial pathophysiology of developing white-matter damage remains debated. We studied rat pups with prenatal growth restriction (GR) induced by unilateral ligation of the uterine artery. Pups with severe GR exhibited white-matter damage that persisted to adulthood [Olivier, P., Baud, O., Evrard, P., Gressens, P.,Verney, C., 2005. Prenatal ischemia and white matter damage in rats. J. Neuropathol. Exp. Neurol. 64, 998-1006]. Moderate GR was associated with diffuse white-matter lesions, microglial activation, and astrogliosis. Loss of pre-oligodendrocytes on postnatal day 7 was followed by a delay in myelination. Following a cortical excitotoxic insult on postnatal day 5, the size of the induced white-matter lesion was smaller in pups with moderate GR and larger in pups with severe GR, compared to normal pups. The increased pre-oligodendrocyte proliferation seen in the white matter of pups with moderate GR subjected to this "double-hit" injury may constitute a heretofore-undescribed neuroprotective mechanism of immature white matter.