Age-dependent effects of systemic administration of oxytetracycline on the viscoelastic properties of rat tail tendons as a mechanistic basis for pharmacological treatment of flexural limb deformities in foals.

This research evaluates the impact of oxytetracycline, a type of antibiotic, on the flexibility and elasticity of tendons in young and older rats. The results suggest that oxytetracycline reduces these properties in younger rats, but not in older ones, potentially giving clues for better pharmacological treatments of limb deformities in young horses.

Introduction

• The study is primarily focused on understanding how the antibiotic oxytetracycline impacts the viscoelastic characteristics of tendon tissues in rats, and to use this knowledge to suggest mechanisms for treating flexural limb deformities in foals.
• Flexural limb deformities are common pathological conditions observed in neonatal and young horses, where the digit axis gets deviated due to abnormal tendon growth or changes in tendon properties.

Methods

• The subjects of the study were 20 male Sprague-Dawley rats, half of them 1-month-old and the other half 6-month-old.
• In each age group, 5 rats were treated with oxytetracycline over a period of 4 days, while the remaining 5 served as untreated controls.
• Five days after the start of treatment, tendon tissues were collected from the rats’ tails, and their viscoelastic properties were examined and compared using a stress-relaxation protocol.
• In addition, the size, density, and orientation of collagen fibrils in the tendon tissues were analyzed and compared between the treated and untreated rats.

Results

• The results revealed a significant decrease in the viscoelastic properties in tendons of 1-month-old rats treated with oxytetracycline, compared to the untreated group.
• In contrast, no changes were observed in the viscoelastic properties of tendons from the 6-month-old rats following the treatment.
• Further, no noticeable changes were found in the collagen fibril size, density, or orientation in tendon tissues between the treated and untreated 1-month-old rats.

Conclusions

• The research hence concludes that oxytetracycline has an age-dependent impact on the viscoelastic properties of tendon tissues, decreasing these properties in younger rats but not affecting older ones.
• The changes in viscoelastic properties do not appear to be because of any alterations in the size or organization of collagen fibrils.
• It is suggested that the age-dependent effects of oxytetracycline might be related to its impact on the development and maturation of extracellular matrix within the tendons.