EVALUATING DIFFERENTIAL NUCLEAR DNA YIELD RATES AMONG HUMAN BONE TISSUE TYPES: A SYNCHROTRON MICRO-CT APPROACH

Molecular human identification has conventionally focused on DNA sampling from dense, weight-bearing cortical bone tissue from femora or tibiae. A comparison of skeletal elements from three contemporary individuals demonstrated that elements with high quantities of cancellous bone yielded nuclear DNA at the highest rates, suggesting that preferentially sampling cortical bone is suboptimal (Mundorff & Davoren, 2014). Despite these findings, the reason for the differential DNA yields between cortical and cancellous bone tissues remains unknown.

The primary goal of this research is to ascertain whether differences in bone microstructure can be used to explain differential nuclear DNA yield among bone tissue types, with a focus on osteocytes and the 3D quantification of their associated lacunae. Osteocytes and other bone cells are recognized to house DNA in bone tissue, thus examining the density of their lacunae may explain why nuclear DNA yield rates differ among bone tissue types. Methods included: (1) quantifying cortical and cancellous bone volume from each bone-sampling site using Computed Tomography (CT), and (2) visualizing and quantifying osteocyte lacunae using synchrotron radiation micro-Computed Tomographic imaging (SR micro-CT). Regions of interest (ROIs) from cortical and cancellous bone tissues (n=129) were comparatively analyzed from the three skeletons sampled for Mundorff and Davoren’s (2014) study. Analyses tested the primary hypothesis that the abundance and density of bone’s cellular spaces vary between cortical and cancellous bone tissue types.

Results demonstrated that osteocyte lacunar abundance and density vary between cortical and cancellous bone tissue types, with cortical bone ROIs containing a higher lacunar abundance and density. The osteocyte lacunar density values are independent of nuclear DNA yield, suggesting an alternative explanation for the higher nuclear DNA yields from predominantly cancellous bones. It is hypothesized that soft tissue remnants within the medullary cavities of primarily cancellous skeletal elements are driving the high nuclear DNA yields.

These findings have significant implications for bone-sample selection for nuclear DNA analysis in a forensic context. The procurement of small, primarily cancellous bones with associated soft tissues should be preferentially sampled, and no longer dismissed as potential DNA sources in favor of cortical bone tissue.