Paper Title
Mirnaprofiling of Cerebrospinal Fluid: Isolation Method Matters

Abstract
Introduction - Microrna expression profiles of bodily fluids are exploited for the discovery of biomarkers implicating the importance of microRNA extraction techniques. Cerebrospinal fluid (CSF) is a mirror of central nervous system and has been interrogated for identification of biomarkers of neurodegenerative diseases, cancer and traumatic brain injury. However, there is poor correlation between different reports indicating interlaboratory differences and the need to standardize miRNA isolation method for CSF. Methods: RNA isolation methods can be broadly classified as phenol-based and phenol-free techniques. Two commonly used RNA isolation kits from both categories were compared for their efficiency to isolate miRNAs from CSF. CSF was collected from healthy pregnant women between the age of 20 – 29 years old and 30 – 39 years old. miRNA profiles of young and old pregnant women were analysed for miRNA differences using aforementioned RNA isolation methods. Microfluidic gene expression system was used to identify differential miRNAs. Results - Phenol-based technique was performant over the phenol-free technique. Out of seventy seven miRNAs, none was found significant in the case of phenol-free method. However, two miRNAs were found significantly altered in phenol-based method. Conclusion - The choice ofRNA isolation method is critical in order to avoid masking effects due to the poor techniques employed by the commercially available kits. In our hands, phenol-based technique allowed identification of age related miRNA differences in the CSF of a healthy cohort of pregnant women. Therefore, for miRNA expression studies in bodily fluids like CSF, phenol-based RNA isolation methods are recommended. Keywords: Cerebrospinal fluid, RNA isolation, microRNA, aging