Strain differences in behavioral and cellular responses to perinatal hypoxia and relationships to neural stem cell survival and self-renewal: Modeling the neurovascular niche.

Premature infants have chronic hypoxia, resulting in cognitive and motor neurodevelopmental handicaps caused by suboptimal neural stem cell (NSC) repair/recovery in neurogenic zones (including the subventricular and the subgranular zones). Understanding the variable central nervous system repair response is crucial to identifying "at risk" infants and to increasing survival and clinical improvement of affected infants. Using mouse strains found to span the range of responsiveness to chronic hypoxia, we correlated differential NSC survival and self-renewal with differences in behavior. We found that C57BL/6 (C57) pups displayed increased hyperactivity after hypoxic insult; CD-1 NSCs exhibited increased hypoxia-induced factor 1alpha (HIF-1alpha) mRNA and protein, increased HIF-1alpha, and decreased prolyl hydroxylase domain 2 in nuclear fractions, which denotes increased transcription/translation and decreased degradation of HIF-1alpha. C57 NSCs exhibited blunted stromal-derived factor 1-induced migratory responsiveness, decreased matrix metalloproteinase-9 activity, and increased neuronal differentiation. Adult C57 mice exposed to hypoxia from P3 to P11 exhibited learning impairment and increased anxiety. These findings support the concept that behavioral differences between C57 and CD-1 mice are a consequence of differential responsiveness to hypoxic insult, leading to differences in HIF-1alpha signaling and resulting in lower NSC proliferative/migratory and higher apoptosis rates in C57 mice. Information gained from these studies will aid in design and effective use of preventive therapies in the very low birth weight infant population.