Background: MicroRNAs have recently taken center stage as short noncoding RNAs that regulate mRNA expression.
Aim/Methods: To assess the feasibility of microRNA techniques in routinely processed tissues, we examined the accessibility of two representative microRNAs by real-time quantitative PCR in 86 human formalin-fixed paraffin-embedded (FFPE) samples from liver, breast, bone marrow, lymphatic tissues and colon. Murine liver was used to analyze the influence of fixation time and different fixatives.
Results: High quality microRNA was successfully extracted from routinely processed formalin-fixed tissues, resembling PCR amplification results from snap-frozen material analyzed in parallel. While fixation time does not affect microRNA accessibility, non-buffered formalin or fixative supplements like glutaraldehyde influence PCR results. Storage of human tissues for up to seven years did not deteriorate microRNA significantly. However, microRNA quality in human archival material following routine processing 10 to 20 years ago was decreased. Oxidation by ambient air during storage and fixation in unbuffered formalin are possible reasons for loss of microRNA quality.
Conclusion: The assessment of microRNAs in readily obtained FFPE samples is a highly promising tool in molecular pathology when similarly treated samples are analyzed. Therefore, microRNA analyses will gain wider acceptance as an adjunct to morphological tissue assessment in routine pathology and retrospective studies.