RNA Extraction from Formalin-Fixed and Paraffin-Embedded Tissues

Fixed and paraffin-embedded tissues from pathology department archives can be available for RNA expression analysis. We have already shown that RNA isolated from biopsy, surgical, or autopsy tissue, routinely processed by fixation and paraffin embedding, is not completely degraded. RNA fragments of around 100 bases in length or more are still present even in organs fixed at later stages after removal and very rich in RNase, such as pancreas (1 ). Analysis of RNA from paraffin-embedded tissues allows us to use a large quantity of human tissues with any type of lesions collected in the pathology departments of any hosprtal. Thus method can be used to study the persistence in tissues of RNA virus genome or cell expression. Some procedures have been proposed to study this type of tissue (1 –3 ). Here is described a general method for RNA extraction from single 6–8 μm human tissue histological sections cut from paraffin blocks that can give constant and reproducible results.