Effect of preservation time of formalin-fixed paraffin-embedded tissues on extractable DNA and RNA quantity

Abstract

Objectives: This study aimed to investigate the factors affecting the quantity of DNA and RNA extractable from human formalin-fixed paraffin-embedded (FFPE) tissues stored for different lengths of time. Methods: We randomly selected 20 FFPE specimens harvested from hysteromyoma patients with uterine fibroids during 2010, 2015, and 2017 at the Department of Pathology, Jiading District Central Hospital Affiliated Shanghai University of Medicine and Health Sciences. DNA and RNA extractions were performed using a DNA/RNA FFPE kit. DNA and RNA concentrations and their OD260/OD280 ratios were determined by a NanoDrop 2000 spectrophotometer. The human β-globin gene and aldehyde dehydrogenase-2 (ALDH2) gene were amplified from nucleic acids using a LightCycler 480 Real-Time PCR System, and PCR amplification products were electrophoresed on 1% agarose gels. Results: Specimens that were stored for longer showed more degradation and a reduced concentration of DNA and RNA after nucleic acid extraction. However, there was no significant difference in DNA or RNA purity. β-globin and ALDH2 genes could be amplified from more than 99% of specimens. Conclusion: We found that FFPE tissues stored for longer had a reduced quantity of extractable DNA and RNA. However, these tissues could be used for the analysis of some small target genes.