miRNA in situ hybridization in mammalian tissues fixed with formaldehyde and EDC

MicroRNAs (miRNAs) are small regulatory RNAs with many biological functions and disease associations. We showed that in situ hybridization (ISH) using conventional formaldehyde fixation results in significant miRNA loss from mouse tissue sections, which can be prevented by fixation with 1–ethyl–3–(3–dimethylaminopropyl) carbodiimide (EDC) that irreversibly immobilizes the miRNA at its 5' phosphate. We determined optimal hybridization parameters for 130 locked nucleic acid (LNA) probes by recording nucleic acid melting temperature during ISH.