Stanniocalcin 1 is important for poststroke functionality, but dispensable for ischemic tolerance

Stanniocalcin 1 (STC1), originally described as an antihypercalcemic hormone in fish, is highly expressed in differentiated mammalian neurons. Mild hypoxic treatment and focal cerebral ischemia induce upregulation of STC1 in the brain. These findings prompted us to investigate whether STC1 contributes to neuroprotection after ischemia and whether STC1 is required for development of ischemic tolerance. We induced 60 minutes of temporary middle cerebral artery occlusion in wild type (WT) and STC1-deficient mice (STC1(-/-)) with or without prior hypoxic preconditioning (HPC, 8% oxygen for 6 hours followed by reoxygenation for 24 hours). Infarct sizes, neurological scores, and Stc1, Stc2, and Il-6 mRNA brain levels were measured 24 hours after ischemia. Additionally, we examined blood-brain barrier (BBB) integrity (Evans Blue fluorescence) under normal conditions and 0 and 24 hours after hypoxia. STC1(-/-) and WT mice developed brain infarcts of similar size. In both strains, HPC triggered ischemic tolerance with similar reduction in infarct size. However, STC1(-/-) mice had worse neurological scores in both scenarios. HPC induced upregulation of STC1 and STC2 in WT mice and of STC2 in STC1(-/-) mice. Ischemic STC1(-/-) mice showed significantly lower Il-6 mRNA expression than ischemic WT mice. Evans Blue fluorescence levels showed no difference in between WT and STC1(-/-) mice under evaluated conditions, thus BBB integrity is preserved despite STC1 deficiency. STC1 was not crucial for the development of ischemic tolerance triggered by HPC or for preserving BBB integrity but may be involved in functional recovery after stroke.