Long-term room temperature preservation of corpse soft tissue: an approach for tissue sample storage

Abstract

BackgroundDisaster victim identification (DVI) represents one of the most difficult challenges in forensic sciences, and subsequent DNA typing is essential. Collected samples for DNA-based human identification are usually stored at low temperature to halt the degradation processes of human remains. We have developed a simple and reliable procedure for soft tissue storage and preservation for DNA extraction. It ensures high quality DNA suitable for PCR-based DNA typing after at least 1 year of room temperature storage.MethodsFragments of human psoas muscle were exposed to three different environmental conditions for diverse time periods at room temperature. Storage conditions included: (a) a preserving medium consisting of solid sodium chloride (salt), (b) no additional substances and (c) garden soil. DNA was extracted with proteinase K/SDS followed by organic solvent treatment and concentration by centrifugal filter devices. Quantification was carried out by real-time PCR using commercial kits. Short tandem repeat (STR) typing profiles were analysed with 'expert software'.ResultsDNA quantities recovered from samples stored in salt were similar up to the complete storage time and underscored the effectiveness of the preservation method. It was possible to reliably and accurately type different genetic systems including autosomal STRs and mitochondrial and Y-chromosome haplogroups. Autosomal STR typing quality was evaluated by expert software, denoting high quality profiles from DNA samples obtained from corpse tissue stored in salt for up to 365 days.ConclusionsThe procedure proposed herein is a cost efficient alternative for storage of human remains in challenging environmental areas, such as mass disaster locations, mass graves and exhumations. This technique should be considered as an additional method for sample storage when preservation of DNA integrity is required for PCR-based DNA typing.

Preservation and rapid purification of DNA from decomposing human tissue samples

“…These treatments range from dehydration and desiccation [3,9,12] to storage in various chemical preservatives in order to inhibit the nuclease activity that leads to DNA degradation [2,9,[11][12][13][14]. Several preservative solutions have been shown to effectively preserve fresh human tissue [2,3,9,11].…”

“…Prolonged exposure to heat, humidity, ultraviolet (UV) radiation, and microorganisms further increases the rate of DNA damage and degradation resulting in fragmentation of the DNA molecule into smaller lengths [4,6,7]. Although DNA typing using short tandem repeats (STRs) is currently the gold standard for human identification purposes [3], highly degraded samples often result in partial STR profiles because the larger loci (>250bp) commonly fail to amplify due to fragmentation of the DNA structure [4][5][6][7][8].…”

“…Several studies have investigated the potential for room temperature storage of biological samples for DNA analysis [2,3,9,[11][12][13][14]. These treatments range from dehydration and desiccation [3,9,12] to storage in various chemical preservatives in order to inhibit the nuclease activity that leads to DNA degradation [2,9,[11][12][13][14].…”

“…In hot and humid climates, rapid decomposition and putrefaction of bodies create a public health risk, and also makes human identification more difficult [3]. As bodies decompose, DNA starts its degradation process.…”

“…However, after a mass fatality event, the loss of electricity and lack of adequate storage facilities often prevent this action [2,3,9]. Recommendations published by the DNA Commission of the International Society for Forensic Genetics state that tissue samples may be stored in a chemical preservative at room temperature (with the exception of formalin) [1].…”