Evaluation of Autologous Protein Solution Injection for Treatment of Superficial Digital Flexor Tendonitis in an Equine Model.
Authors: Gaesser Angela M, Underwood Claire, Linardi Renata L, Even Kayla M, Reef Virginia B, Shetye Snehal S, Mauck Robert L, King William J, Engiles Julie B, Ortved Kyla F
Journal: Frontiers in veterinary science
Summary
# Editorial Summary: Autologous Protein Solution for Equine Tendon Repair Autologous protein solution (APS) has gained traction in equine practice for treating tendon injuries, yet robust evidence supporting its efficacy remained absent until this controlled study. Researchers induced superficial digital flexor tendonitis in both forelimbs of eight horses via collagenase injection, then treated one limb with intralesional APS and the contralateral with saline, evaluating outcomes over 12 weeks using ultrasonography, histology, biomechanical testing, and molecular analysis. Whilst APS-treated tendons showed a trend towards superior biomechanical properties (higher elastic modulus) and importantly displayed normalised expression of type III collagen—compared to saline controls where COL3A1 expression remained significantly elevated—histological and ultrasonographic appearance showed no significant differences between treatments, and both groups healed substantially. The apparent normalisation of inflammatory gene expression in APS-treated tissue may indicate accelerated progression towards mature healing rather than prolonged inflammatory remodelling, though the short study window and variable lesion severity limit definitive conclusions. These findings suggest APS warrants further investigation as an adjunctive therapy, yet practitioners should recognise that standard management (rest, controlled rehabilitation) produces comparable structural repair, and any superiority of APS appears modest rather than transformative.
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Practical Takeaways
- •APS injection shows promise for SDF tendonitis with potential benefits in biomechanical properties and healing progression, though structural improvements are modest at 12 weeks
- •APS-treated tendons may progress to more mature healing phases faster than controls, based on gene expression patterns
- •This study was limited by short follow-up (12 weeks) and variable lesion sizes—longer-term clinical outcome data in field cases is still needed before changing current treatment protocols
Key Findings
- •APS-treated tendons showed reduced COL3A1 expression compared to saline controls, suggesting more advanced healing stage
- •Total DNA content was significantly higher in saline-treated tendons than normal tendons (p=0.024), but not different between APS-treated and normal tendons
- •Elastic modulus was numerically higher in APS-treated tendons but the difference was not statistically significant
- •No significant differences in histologic or ultrasonographic scores between APS and saline treatment groups at 12 weeks