Collagen degradation as a possibility to determine the post-mortem interval (PMI) of animal bones: a validation study referring to an original study of Boaks et al. (2014)

Abstract

Estimation of the post-mortem interval (PMI) of unknown skeletal remains is a common forensic task. Boaks and colleagues demonstrated a new method for PMI estimation in showing a reduction of the collagen to non-collagen content (Co/NCo ratio) in porcine bones after a PMI of 12 months using the Sirius Red/Fast Green Collagen Staining Kit from Chondrex in 2014 (Boaks et al. Forensic Sci Int 240: 104-110, 2014). The aim of our study was to reproduce this method and to investigate if the method could be used for forensic issues. Sixteen fresh porcine bones were placed in prepared boxes where they were treated regularly with distilled water or with water from hay infusions. For determining the Co/NCo ratio, we used the Sirius Red/Fast Green Collagen Staining Kit from Chondrex, which stains collagenous (Co) proteins red and non-collagenous (NCo) proteins green Chondrex Inc. (2008). After a PMI of 1-3 months, an analysis of porcine bone thin sections was performed on the one hand with spectrophotometry, on the other hand with stereomicroscopy. Using spectrophotometry, we go low and partially negative Co/NCo ratios which were up to 100-fold lower than the results we expected to get. The data we got by stereomicroscopy and calculating the Co/NCo ratio from extracting the red and green content with the software MATLAB and so calculating the Co/NCo ratio showed a correlation between PMI and the Co/NCo ratio in the porcine bone samples. Regular addition of distilled water or water from a hay infusion did not produce any significant differences so that an increased presence of microorganisms had obviously no influence on collagen degradation.

The impact of burial period on compact bone microstructure: Histological analysis of matrix loss and cell integrity in human bones exhumed from tropical soil

“…Intra-group analysis showed that the period of burial was inversely correlated with the bone integrity index, showing that the longer bone remains interred, the lower its integrity ( Table 1). Similar findings were reported in studies that correlated post mortem interval (PMI) and loss of collagen in human and non-human bones [60,61]. While the number of osteocyte lacunae present in the exhumed bone group showed no difference in comparison to the control group, the number of osteocytes was significantly lower.…”

Determination of postmortem interval through histopathological alterations and collagen evaluation in the prostate of Wistar albino rats

“…However, collagen considered as an ultimate parameter for determination of PMI because it degraded slowly by the time after death if compared to other functional or structural proteins (Mazzotti et al, 2019). Until now, histochemical studies on degradation of collagen have been done in skeletonized human remains for the determination of PMI (Boaks et al, 2014;Jellinghaus et al, 2018;Jellinghaus et al, 2019). Moreover, immunohistochemistry for collagen proteins in gingival tissue was only done by Mazzotti et al (2019).…”

Aquatic Decomposition of Mammalian Corpses: A Forensic Proteomic Approach

“…They collected bone samples from pigs deposited on the ground surface at zero-, two-, four-, six-, ten-and twelvemonths post mortem and observed that the ratio of collagen proteins to NCPs significantly decreased at 10 months. Later, Jellinghaus et al 50 conducted a similar study and suggested that bone protein degradation could be used as means to estimate PMI. More recently, Procopio et al 51 performed LC-MS/MS analysis on bone samples of buried pigs allowed to decompose for time interval ranging from one month to one year post mortem to evaluate linkages between protein survival and PMI, i.e., the amount and variety of proteins after several PMIs.…”