Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA295

Poster Communications

Common denominators of Hypoxia-inducible Factor activation in brain to regenerate from ischemia/reperfusion

T. Leu1, J. Fandrey1, T. Schreiber1

1. Institute of Physiology, University of Duisburg-Essen, Essen, Germany.

Ischemic hypoxia results from insufficient blood flow to supply adequate amounts of oxygen and nutrients and causes ATP depletion and rapid cell death. It was long thought that the mammalian brain is a post-mitotic organ and incapable of regeneration following cellular loss, which underpins the devastating impact of cerebral ischemia. Recently, it has become clear that the brain is capable of modest regeneration. Moreover, it was shown that hypoxia and the hypoxia-inducible factor (HIF) are key factors in neural regeneration1. Endogenous sensors of hypoxia and their downstream effectors are prime targets for therapeutic manipulation. Key among these targets is the transcription activator HIF, an oxygen-responsive member of the basic helix-loop-helix PAS (PER-ARNT-SIM) family2. Especially HIF-2α is distributed tissue specific and expressed in the developing brain. It modulates gene activity in response to low oxygen and protects neural progenitor cells and neural differentiation processes3,4. But in general, the role of HIF-2α during neural development is not well understood. To investigate the impact of HIF on neural regeneration, we established a murine neurosphere culture for wildtypic (Wt) and Hif-2α-knockout (KO) cells. Neurospheres are heterogeneous cell clusters based on neural stem cells (NSCs). Using this 3D model we were able to mimic basic processes of brain development: neural progenitor cell proliferation, migration, differentiation and apoptosis. Here, we focused on the signaling pathway of HIF by challenging the proliferating and differentiating neurospheres with up to 4h oxygen/glucose-deprivation (OGD: 0.2% O2; glucose free medium). Afterwards, we analyzed the migration capability by measuring the migration distance of the cells after 24h, 48h and 72h. Before OGD, Wt cells had significantly better abilities to migrate than to the KO. After OGD, neurospheres migrated significantly less than the control and did not differ between Wt and KO (n = 3). Additionally mRNA analysis showed a strong effect on the expression of genes involved in neurogenesis. Here, genes like Nrg1, which has a protective function against astrogliosis, or Grin1, which is critical for neuronal connectivity and survival, significantly differ between Wt and KO cells after challenging the spheres with OGD (n = 5). These data suggest a restricted capability to regenerate from ischemia without HIF-2α and decode its role in (re)modeling the CNS.

Where applicable, experiments conform with Society ethical requirements