Browsing by Subject "Mechanical testing"

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    Even With Rehydration, Preservation in Ethanol Influences the Mechanical Properties of Bone and How Bone Responds to Experimental Manipulation
    (Elsevier, 2017-04) Vesper, Evan O.; Hammond, Max A.; Allen, Matthew R.; Wallace, Joseph M.; Biomedical Engineering, School of Engineering and Technology
    Typically, bones are harvested at the time of animal euthanasia and stored until mechanical testing. However, storage methods are not standardized, and differential effects on mechanical properties are possible between methods. The goal of this study was to investigate the effects that two common preservation methods (freezing wrapped in saline-soaked gauze and refrigerating ethanol fixed samples) have on bone mechanical properties in the context of an in vitro ribosylation treatment designed to modify mechanical integrity. It was hypothesized that there would be an interactive effect between ribose treatment and preservation method. Tibiae from twenty five 11week old female C57BL/6 mice were separated into 2 preservation groups. Micro-CT scans of contralateral pairs assessed differences in geometry prior to storage. After 7weeks of storage, bones in each pair of tibiae were soaked in a solution containing either 0M or 0.6M ribose for 1week prior to 4 point bending tests. There were no differences in any cortical geometric parameters between contralateral tibiae. There was a significant main effect of ethanol fixation on displacement to yield (-16.3%), stiffness (+24.5%), strain to yield (-13.9%), and elastic modulus (+18.5%) relative to frozen specimens. There was a significant main effect of ribose treatment for yield force (+13.9%), ultimate force (+9.2%), work to yield (+22.2%), yield stress (+14.1%), and resilience (+21.9%) relative to control-soaked bones. Postyield displacement, total displacement, postyield work, total work, total strain, and toughness were analyzed separately within each preservation method due to significant interactions. For samples stored frozen, all six properties were lower in the ribose-soaked group (49%-68%) while no significant effects of ribose were observed in ethanol fixed bones. Storage in ethanol likely caused changes to the collagen matrix which prevented or masked the embrittling effects of ribosylation that were seen in samples stored frozen wrapped in saline-soaked gauze. These data illustrate the clear importance of maintaining hydration if the eventual goal is to use bones for mechanical assessments and further show that storage in ethanol can alter potential to detect effects of experimental manipulation (in this case ribosylation).
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    Iron deficiency and high-intensity running interval training do not impact femoral or tibial bone in young female rats
    (Cambridge University Press, 2022) Scott, Jonathan M.; Swallow, Elizabeth A.; Metzger, Corinne E.; Kohler, Rachel; Wallace, Joseph M.; Stacy, Alexander J.; Allen, Matthew R.; Gasier, Heath G.; Anatomy, Cell Biology and Physiology, School of Medicine
    In the US, as many as 20% of recruits sustain stress fractures during basic training. In addition, approximately one-third of female recruits develop iron deficiency upon completion of training. Iron is a cofactor in bone collagen formation and vitamin D activation, thus we hypothesized iron deficiency may be contributing to altered bone microarchitecture and mechanics during 12-weeks of increased mechanical loading. Three-week old female Sprague Dawley rats were assigned to one of four groups: iron adequate sedentary, iron deficient sedentary, iron adequate exercise, and iron deficient exercise. Exercise consisted of high-intensity treadmill running (54 min 3×/week). After 12-weeks, serum bone turnover markers, femoral geometry and microarchitecture, mechanical properties and fracture toughness, and tibiae mineral composition and morphometry were measured. Iron deficiency increased the bone resorption markers C-terminal telopeptide type I collagen and tartate-resistant acid phosphatase 5b (TRAcP 5b). In exercised rats, iron deficiency further increased bone TRAcP 5b, while in iron adequate rats, exercise increased the bone formation marker procollagen type I N-terminal propeptide. In the femur, exercise increased cortical thickness and maximum load. In the tibia, iron deficiency increased the rate of bone formation, mineral apposition, and zinc content. These data show that the femur and tibia structure and mechanical properties are not negatively impacted by iron deficiency despite a decrease in tibiae iron content and increase in serum bone resorption markers during 12-weeks of high-intensity running in young growing female rats.
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    Metabolic and Skeletal Characterization of the KK/Ay Mouse Model – a Polygenic Mutation Model of Obese Type 2 Diabetes
    (Springer, 2024) Chowdhury, Nusaiba N.; Surowiec, Rachel K.; Kohler, Rachel K.; Reul, Olivia N.; Segvich, Dyann M.; Wallace, Joseph M.; Radiology and Imaging Sciences, School of Medicine
    Type 2 diabetes (T2D) increases fracture incidence and fracture-related mortality rates (KK.Cg-Ay/J. The Jackson Laboratory; Available from: https://www.jax.org/strain/002468 ). While numerous mouse models for T2D exist, few effectively stimulate persistent hyperglycemia in both sexes, and even fewer are suitable for bone studies. Commonly used models like db/db and ob/ob have altered leptin pathways, confounding bone-related findings since leptin regulates bone properties (Fajardo et al. in Journal of Bone and Mineral Research 29(5): 1025-1040, 2014). The Yellow Kuo Kondo (KK/Ay) mouse, a polygenic mutation model of T2D, is able to produce a consistent diabetic state in both sexes and addresses the lack of a suitable model of T2D for bone studies. The diabetic state of KK/Ay stems from a mutation in the agouti gene, responsible for coat color in mice. This mutation induces ectopic gene expression across various tissue types, resulting in diabetic mice with yellow fur coats (Moussa and Claycombe in Obesity Research 7(5): 506-514, 1999). Male and female KK/Ay mice exhibited persistent hyperglycemia, defining them as diabetic with blood glucose (BG) levels consistently exceeding 300 mg/dL. Notably, male control mice in this study were also diabetic, presenting a significant limitation. Nevertheless, male and female KK/Ay mice showed significantly elevated BG levels, HbA1c, and serum insulin concentration when compared to the non-diabetic female control mice. Early stages of T2D are characterized by hyperglycemia and hyperinsulinemia resulting from cellular insulin resistance, whereas later stages may feature hypoinsulinemia due to β-cell apoptosis (Banday et al. Avicenna Journal of Medicine 10(04): 174-188, 2020 and Klein et al. Cell Metabolism 34(1): 11-20, 2022). The observed hyperglycemia, hyperinsulinemia, and the absence of differences in β-cell mass suggest that KK/Ay mice in this study are modeling the earlier stages of T2D. While compromised bone microarchitecture was observed in this study, older KK/Ay mice, representing more advanced stages of T2D, might exhibit more pronounced skeletal manifestations. Compared to the control group, the femora of KK/Ay mice had higher cortical area and cortical thickness, and improved trabecular properties which would typically be indicative of greater bone strength. However, KK/Ay mice displayed lower cortical tissue mineral density in both sexes and increased cortical porosity in females. Fracture instability toughness of the femora was lower in KK/Ay mice overall compared to controls. These findings indicate that decreased mechanical integrity noted in the femora of KK/Ay mice was likely due to overall bone quality being compromised.