Effect of Tendon-Derived Progenitor Cells on a Collagenase-Induced Model of Tendinitis in Horses

Cell-based therapies with tendon-derived progenitor cells may be warranted in clinical cases of tendinitis. Authors’ address: Department of Veterinary Clinical Medicine, University of Illinois, 1008 West Hazelwood Drive, Urbana, IL 61802; e-mail: [email protected]. *Corresponding author. © 2011 AAEP.

1. Introduction

Tendon and ligament injuries are a common cause of lameness in performance horses. Stem cell-based treatments for tendon injuries show promise and are increasingly used. Our hypothesis was that autogenous tendon-derived progenitor cells promoted healing in a tendinitis model.

2. Materials and Methods

Collagenase-induced tendinitis was created in the superficial digital flexor tendons of the forelimbs of eight horses. Autogenous tendon-derived progenitor cells were isolated by pre-plating technique; 10 million cells were injected 4 wk post-collagenase injection, and the opposite control tendon was injected with saline. Horses were euthanized 12 wk post-treatment, and the superficial digital flexor tendons were harvested for mitochondrial RNA (mRNA), biochemical analyses, collagen and proteoglycan syntheses, and histological quantification. 

3. Results

Tendon-derived progenitor cells yielded clinically relevant numbers within a short duration for autogenous treatment (mean  21 ± 2 days). Both of the treated tendons had a significant increase in total DNA content (p = 0.021) and proteoglycan synthesis (p = 0.01) compared with a normal hindlimb tendon. mRNA expression of collagen type I (p = 0.003), collagen type III (p = 0.007), cartilage oligomeric matrix protein (COMP) (p < 0.001), and tenomodulin (p = 0.017) were significantly higher in both the treated tendons compared with the normal tendon.

4. Discussion

Collagen remodeling after tendinitis is a long-term process, and increased mRNA levels at 12 wk post-treatment may not accurately reflect the matrix synthesis during that period. Additional analyses of the protein composition and biomechanical properties are important to assess the effects of progenitor cell treatment.

The authors would like to thank the American Quarter Horse Association (AQHA) for funding this project.