Researcher(s)
- Hailey Bonelli, Biomedical Engineering, University of Delaware
Faculty Mentor(s)
- Dawn Elliott, Biomedical Engineering, University of Delaware
Abstract
Introduction:
Tendon overload and overuse result in degeneration. Clinically, degeneration presents as rupture, acute injury from overload with no prior pain, or tendinopathy, chronic pain from overuse. Achilles tendon ruptures are more common in males, while females more often develop tendinopathies. These differences persist despite similar ages and activity levels, suggesting development of these outcomes may be sex dependent. Animal models enable mechanical in vivo loading while allowing tissue-level analysis. Prior studies have shown sex-dependent differences in healthy and healing tendons that may explain increased male risk for overload and overuse disorders. However, the tendon response to overload in males has yet to be investigated. A prior study using a synergistic ablation (SynAb) model, where the Achilles is resected to overload the plantaris, showed adaptive structural and functional changes after 8 weeks in females. It is unclear if males show a similar response. This study aims to compare male versus female tendon structure and function following 8 weeks of overload using the SynAb model. We hypothesize that males will exhibit inferior structural and mechanical properties than females, including increased cross-sectional area (CSA), reduced stiffness/modulus, and lower collagen type I/type III ratio reflecting a reduced reparative response.
Materials and Methods:
Three-month-old male and female rats (n=7/group) were assigned to intact control, sham (skin incision with Achilles intact), or SynAb (bilateral Achilles resection). Animals were euthanized 8 weeks post-surgery. Each limb was randomly assigned to mechanical testing or histology/immunohistochemistry. A subset also underwent MRI for tissue-scale structure. Mechanical outcomes included stiffness, modulus, and failure/yield/transition stress and strain. Structural outcomes included CSA, collagen organization, and collagen type I/type III ratio.
Expected Results:
We expect male rats will show greater CSA, decreased mechanical properties, and lower type I/type III collagen ratio compared to females. Inferior properties in males may indicate underlying sex differences.