Fetal-Derived "Embryonic" Stem Cells Improve Equine Tendonitis Repair

1. Introduction

Stem cells with greater potency may better contribute to tenocyte regeneration and tendon fiber deposition within the core lesion of tendonitis. The goal of this study was to examine the effects of fetalderived embryonic-like stem cells (fdESCs; OK100™) on tendon healing in vivo.

2. Materials and Methods

Early fetal cells were harvested, propagated, karyotyped, and tested for markers of pluripotency. Eight mares had collagenase tendonitis induction in the mid-metacarpal superficial digital flexor tendon (SDFT) in one forelimb. One week later, four lesions were implanted with 3 x 106 male fdESCs in 1.5 ml growth media and four were implanted with 1.5 ml of media alone (CONT). Investigators were blinded to treatment group. Ultrasound examinations were performed every 2 wk, limbs were bandaged for 4 wk, and horses were confined to box stalls for the study duration. Horses were euthanized at 8 wk. Post-mortem magnetic resonance imaging (MRI) was performed, and SDFTs were harvested for histological, molecular, and biochemical assays. 

3. Results

There were no significant differences in post-injection swelling or lameness or in selected gene expression, collagen, DNA, or proteoglycan. fdESC tendon architecture was statistically improved at 8 wk: ultrasonographically, there was better longitudinal fiber alignment and a return to preinjury tendon cross-sectional area, MRI lesions were smaller, and, histologically, tendons were more normal in several parameters.

4. Discussion

Improved tendon architecture may lead to reduced re-injury rate.

This protocol was approved by the university’s Institutional Animal Care and Use Committee.