Examination and comparison of the RNA extraction methods using mouse serum.

Serum microRNAs (miRNAs) are considered useful as non-invasive biomarkers for different diseases. However, the optimal method for extracting RNAs from serum is currently unknown. In the present study, several RNA extraction kits were used to examine the optimal kit. RNAs were extracted from the serum of 8-week-old C57BL/6NJcl male mice following the protocol of each RNA extraction kit. The yield of the extracted RNA samples was calculated, and an Agilent Bioanalyzer was used to assess the electrophoretic patterns. An Agilent mouse miRNA microarray was utilized to confirm the expression patterns of the extracted RNA samples. The results revealed significant differences in RNA yields from the miRNeasy Serum/Plasma Advanced kit and mirVana™ PARIS™ RNA and Native Protein Purification Kit compared with almost all other samples. Further, two peaks were determined in the miRNeasy Serum/Plasma Advanced kit using a small RNAs kit of Agilent Bioanalyzer, including one at 20-40 nucleotides (nt) and another at ~40-100 nt, whereas the other reagents had a single peak. This revealed that the extracted RNAs may differ in composition based on the RNA extraction method. Some types of miRNAs were only detected with certain RNA extraction reagents. This suggested that different RNA extraction reagents may cause differences in the types of miRNAs detected. On the other hand, the miRNAs commonly expressed by the three RNA extraction reagents are highly correlated in expression levels.