Differential response of skeletal microstructure to locomotor loading in a bipedal rodent model (Rattus norvegicus)

Open Access
- Author:
- Campillo, America
- Graduate Program:
- Anthropology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 31, 2024
- Committee Members:
- Tim Ryan, Chair & Dissertation Advisor
Jonas Rubenson, Outside Unit & Field Member
Joan Richtsmeier, Major Field Member
George Milner, Major Field Member
Tim Ryan, Program Head/Chair - Keywords:
- Locomotion
Human Evolution
Bone biology
Trabecular Bone
Cortical Bone
Subchondral Bone
Experimental Animal Model
Bipedalism - Abstract:
- The evolution of bipedalism in humans has been a long-standing topic of research in anthropology, as it marks a pivotal transition in our evolutionary history. Understanding the skeletal adaptations associated with bipedal locomotion is critical for comprehending the timing and progression of this locomotor transition, especially considering that bone is frequently the sole material preserved in fossil contexts. Delving into the details of these adaptations is essential for gaining deeper insights into the evolutionary process. However, it is difficult to understand the nuances of skeletal adaptation to bipedalism when locomotor behavior is not explicitly known. Additionally, previous research has often focused on solely one level of bone, rather than comprehensively investigating the functional response of all three levels of bone tissue – cortical, trabecular, and subchondral bone – to alterations in locomotion. Therefore, this dissertation uses a previously executed rat model that induced bipedal gait, in which all locomotor behaviors are known, and other extraneous variables that contribute to skeletal phenotype are controlled for. In the following chapters, this dissertation will investigate the influence of locomotor behavior to skeletal morphology, focusing on the effects of bipedal posture and increased activity levels. Employing an integrative approach, the trabecular, cortical, and subchondral bone of the femur from this rat sample are analyzed. High-resolution microcomputed tomography image data of the femoral diaphysis and distal femur are used, alongside novel quantification techniques, to attain a comprehensive understanding of bone functional adaptation to locomotor loading. The results find a differential response of bone compartments to alterations in locomotor behavior, with trabecular and subchondral bone demonstrating the greatest sensitivity to the adoption of bipedal posture and an increase in locomotor activity, and cortical bone being indicative only to alteration of activity level. As such, the results of this dissertation serve to strengthen our current understanding of skeletal adaptation to bipedalism and will inform future studies in skeletal biomechanics and evolutionary anthropology.