Exploring Microstructural Signatures of Physiological Stress through Cross-Sectional Geometry and Cortical Bone Histology

Unidentified human remains present particular difficulties for forensic practitioners, particularly in contexts where limited antemortem data are available. Forensic anthropologists assess postmortem information from skeletal remains (e.g., biological profile demographics), but this data will only confirm identification if there is sufficient antemortem data available for comparison. Thus, the development of methods that can extract additional antemortem data from unidentified skeletal remains would benefit ongoing identification efforts. In specific settings, such as along the U.S.-Mexico border, macroscopic indicators of stress have been used to infer lived experiences from skeletal remains consistent with various forms of structural inequality, informing investigative efforts and improving identification rates. Microscopic assessments of stress and health in cortical bone may allow for similar approaches at less severe presentations (i.e., prior to macroscopic lesion formation). However, the specific mechanisms of microstructural responses to physiological stress are unclear. This dissertation explores the variation in cortical bone microstructure in relation to known individual demographics and documented medical histories in a sample of 70 femora from modern individuals. Histological sections were mounted, imaged in both polarized and brightfield light, and analyzed in ArcGIS Pro and ImageJ software programs. For each individual, anteromedial, anterior, and anterolateral octants were assessed, accounting for variation across periosteal, intracortical, and endosteal membranes. ArcGIS Pro was used to manually annotate remodeling events (including osteon morphotype) and ImageJ was used to automate osteocyte lacunae counts, allowing for histomorphometrics osteon morphotype and osteocyte lacunae densities to be derived. Cross-sectional properties for each individual were also collected in ImageJ. Individual medical histories were recoded using the International Classification of Diseases 11th Revision for Mortality and Morbidity Statistics. In total, data collected from 70 individuals yielded 280 cross-sectional geometric measurements, 630 ROIs, 4,297 histomorphometric parameters, as well as 2,169 demographic datapoints. More specifically, this dataset included 204,500 manually annotated osteon morphotypes and over 5 million automatically enumerated osteocyte lacunae. In addition to traditional statistical analyses, a novel approach in histological research (multilevel structural equation modeling) was applied to allow for the effects of health to be considered as a latent (unobservable) variable. Histomorphology and intracortical remodeling distributions were also qualitatively assessed using kernel density maps generated in ArcGIS Pro, resulting in a holistic consideration of microstructural variation. Results suggest that fragmentary osteon population density may be sensitive to stress related changes, particularly at the anteromedial endosteum where there may be relatively lower biomechanical and age-related constraints in the femur. However, this relationship requires further consideration and testing in relation to known stressors. The overall influence of age and biomechanically related influences likely constrains histomorphometric variation such that microstructural reactions to physiological stress are largely masked, however, collective results from latent variable modeling, traditional statistical analyses, and qualitative assessments suggest that the effects of parasitic and/or infectious diseases on cortical bone should be further explored. The exploratory nature of this dissertation not only yields promising results for future histological work analyzing the impact of physiological stress on bone, but also formulates practical recommendations for potential model improvements, novel variable developments and expansions, and technical practices.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Applied Anthropology

Grantor

Texas State University

Year dc:date.issued

2023

Author dc:creator

• Goldstein, Justin

Advisors dc:contributor.advisor

• Gocha, Timothy P.
• Herrmann, Nicholas P.

Committee members dc:contributor.committeemember

• Wescott, Daniel J.
• Agnew, Amanda M.
• Maggiano, Corey M.

• histology
• bone biology
• forensic anthropology
• stress

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10877/20097

OAI identifier oai:identifier

oai:digital.library.txst.edu:10877/20097