Recognition of the Presence of Bone Fractures Through Physicochemical Changes in Diagenetic Bone.

Much research has focused on attempting to understand the drivers of bone diagenesis. However, this sensitive process is easily influenced by various factors, particularly the condition of the remains (i.e., whether they have been subjected to trauma). Previous research demonstrates that trauma can influence soft tissue decomposition, yet to date, no studies have looked at how bone fractures could affect bone diagenesis. To address this gap, two short timescale studies were conducted to investigate the influence of bone fractures on the physicochemical composition of disarticulated, partially fleshed animal remains. Disarticulated porcine bones were either fractured using blunt force or sharp force whilst fresh (producing perimortem damage), at 60 days producing postmortem damage (postmortem interval (PMI)), or left intact and left outside for up to 180 days post-fracture/240 days PMI. Retrieved bone sections were then analyzed for physicochemical differences using non-destructive methods, i.e., scanning electron microscopy energy dispersive spectroscopy and Fourier transform infrared spectroscopy with attenuated total reflectance. It was hypothesized that differences would be found in the physicochemical composition between the bones with fractures and those without after undergoing diagenetic change. The bone fractures significantly affected the elemental composition of bone over time, but structural composition initially remained stable. It was also possible to distinguish between perimortem and postmortem fractures using these two analytical techniques due to physicochemical differences. This research shows bone fractures can significantly alter the physicochemical composition of the bone during the postmortem period and have the potential to facilitate more accurate PMI estimations in forensic contexts.

Bone Diagenesis in Short Timescales: Insights from an Exploratory Proteomic Analysis.

The evaluation of bone diagenetic phenomena in archaeological timescales has a long history; however, little is known about the origins of the microbes driving bone diagenesis, nor about the extent of bone diagenesis in short timeframes-such as in forensic contexts. Previously, the analysis of non-collagenous proteins (NCPs) through bottom-up proteomics revealed the presence of potential biomarkers useful in estimating the post-mortem interval (PMI). However, there is still a great need for enhancing the understanding of the diagenetic processes taking place in forensic timeframes, and to clarify whether proteomic analyses can help to develop better models for estimating PMI reliably. To address these knowledge gaps, we designed an experiment based on whole rat carcasses, defleshed long rat bones, and excised but still-fleshed rat limbs, which were either buried in soil or exposed on a clean plastic surface, left to decompose for 28 weeks, and retrieved at different time intervals. This study aimed to assess differences in bone protein relative abundances for the various deposition modalities and intervals. We further evaluated the effects that extrinsic factors, autolysis, and gut and soil bacteria had on bone diagenesis via bottom-up proteomics. Results showed six proteins whose abundance was significantly different between samples subjected to either microbial decomposition (gut or soil bacteria) or to environmental factors. In particular, muscle- and calcium-binding proteins were found to be more prone to degradation by bacterial attack, whereas plasma and bone marrow proteins were more susceptible to exposure to extrinsic agents. Our results suggest that both gut and soil bacteria play key roles in bone diagenesis and protein decay in relatively short timescales, and that bone proteomics is a proficient resource with which to identify microbially-driven versus extrinsically-driven diagenesis.