Non-destructive extraction of DNA from preserved tissues in medical collections

Museum specimens and histologically fixed material are valuable samples for the study of historical soft tissues and represent a possible pathogen-specific source for retrospective molecular investigations. However, current methods for molecular analysis are inherently destructive, posing a dilemma between performing a study with the available technology, thus damaging the sample, and conserving the material for future investigations. Here the authors present the first tests of a non-destructive alternative that facilitates genetic analysis of fixed wet tissues while avoiding tissue damage. The authors extracted DNA from the fixed tissues as well as their embedding fixative solution, to quantify the DNA that was transferred to the liquid component. The results show that human historical DNA can be retrieved from the fixative material of medical specimens and provide new options for sampling valuable collections. METHOD SUMMARY The authors compared the metagenomic content of historical tissues and their embedding liquid to retrieve DNA from the host and specified pathogens based on the diagnosis of the sample. They applied ancient DNA research techniques, including in-solution hybridization capture with DNA baits for human mitochondrial DNA, Mycobacterium tuberculosis, Mycobacterium leprae and Treponema pallidum.