Differential expression of bone microRNAs for post-mortem interval estimation in buried and exposed remains

Forensic science can benefit from microRNAs due to their stability and in estimating post-mortem interval (PMI). The study evaluated microRNA expression in post-mortem bone tissues under two distinct environmental conditions – surface-exposed and buried. Forty bone samples from pigs were purchased, all adhering to soft tissues carefully removed before analysis and divided into control (PMI Day 0) and experimental groups (PMI Days 30, 45, and 60 respectively). Five bone-specific miRNAs, namely: miR-144, miR-126, let-7e, miR-133a, and miR-1 were studied with GAPDH as the reference gene. Relative gene expression was evaluated using the 2−ΔΔCt method, predictive modelling was used to estimate PMI using the expression levels of the microRNAs of interest. The exposed condition showed a sharp increase in relative fold change for the miR-144 miRNA. The expression levels of let-7e decreased significantly by Day 60 under buried and exposed conditions. For the miR-1 miRNA, both exposed and buried conditions showed increased fold change values which were more evident under exposed condition. The expression appeared to be stable in the miR-126 with slight changes observed across the different days, maintaining a lower ΔCt value. Among the evaluated biomarkers, miR-126 and let-7e demonstrated strong association with PMI.