Elevated Mir-9 In Cerebrospinal Fluid Is Associated With Poor Functional Outcome After Subarachnoid Hemorrhage

Background: Aneurysmal subarachnoid hemorrhage (SAH) has a lower incidence than ischemic stroke but affects younger individuals with a high mortality and a high frequency of complications in survivors. The underlying pathways that contribute to poor functional outcome are poorly understood. This study evaluated microRNA (miRNA) changes in cerebrospinal fluid (CSF) and their association with the occurrence of delayed cerebral ischemia (DCI) and poor functional outcome after SAH. Methods: Using real-time quantification polymerase chain reaction, 43 selected miRNAs were measured in daily CSF samples from a discovery cohort of SAH patients admitted to Rigshospitalet, Copenhagen, Denmark, and compared to neurologically healthy patients. Findings were validated in CSF from a replication cohort of SAH patients admitted to Massachusetts General Hospital, Boston, Massachusetts. The CSF levels of miRNA over time were compared to the occurrence DCI, and functional outcome three months after ictus measured by the modified Rankin Scale (mRS) score. Findings: MiRNAs were quantified in 427 CSF samples from 63 SAH patients in the discovery cohort, in 104 CSF samples from 63 SAH patients in the replication cohort and in 11 CSF samples from 11 neurologically healthy patients. The miRNA profile changed remarkably immediately after SAH. Elevated miR-9-3p was associated with a poor functional outcome in the discovery cohort (p < 0·0001) after correction for multiple testing (q < 0·01) and in the replication cohort (p < 0·01). Furthermore, elevated miR-9-5p was associated with a poor functional outcome in the discovery cohort (p < 0·01) after correction for multiple testing (q < 0·05). No miRNA was associated with DCI in both cohorts. Interpretation: MiR-9-3p is elevated in the CSF following SAH and this elevation is associated with a poor functional outcome. Clinical Registration Number: clinicaltrials.gov (file # NCT02320539 & NCT01791257). Funding Statement: S.B. was salaried by grants from the Research Board at Rigshospitalet, Copenhagen, Denmark and The Lundbeck Foundation. Reagents for miRNA profiling were funded by Grosserer Jakob Ehrenreich & Hustru Grete Ehrenreichs Fond, Brodrene Hartmanns Fond, Torben & Alice Frimodts Fond, Grosserer L.F.Foghts Fond and Aase & Ejnar Danielsens Fond. Declaration of Interest: The authors have no conflict of interest. Ethical Approval Statement: The first two protocols were approved by the Danish Scientific Ethics Committee of the Capital Region (file # H-3-2013-009 & H-6-2014-073) and the Danish Data Protection Agency (file # RH-2013-30-0935 & RH-2013- 30-1386). The protocol for the replication cohort was approved by the Massachusetts General Hospital Institutional Review Board (file # 2010P002749). According to Danish and U.S. law, informed consent was obtained from either the patient or by their next of kin and general practitioner