Evaluation of acetic acid solution for rehydration of mummified skin tissues

Histological characteristics such as transverse striation of skeletal muscle are preserved in mummified tissues compared with autolyzed or putrefied tissues, providing histological or forensic information upon histological analysis. However, processing dried tissue for histological examination is difficult due to its hardness. In addition, the histological architecture may be altered during the dehydration process, leading to alternation of the staining appearance. To overcome these problems, rehydration solutions such as Sandison's solution have been utilized in both paleohistological and forensic contexts. In this study, we introduce another procedure utilizing acetic acid to rehydrate dried tissue for forensic trace evidence analysis. We prepared mock mummified tissue specimens by drying sliced animal skin tissues to simulate fragmented tissue specimens found at crime scene investigations. Acetic acid treatment improved the staining results efficiently for both hematoxylin-eosin staining and connective tissue staining compared with specimens without rehydration treatments. Notably, even 2-h treatment with acetic acid solution sufficiently improved the staining results, suggesting that acetic acid solution can be used to rapidly analyze fragmented and dried tissues for criminal investigations.