Mesenchymal stem cells and insulin‐like growth factor‐I gene‐enhanced mesenchymal stem cells improve structural aspects of healing in equine flexor digitorum superficialis tendons

Abstract

Tendinitis remains a catastrophic injury among athletes. Mesenchymal stem cells (MSCs) have recently been investigated for use in the treatment of tendinitis. Previous work has demonstrated the value of insulin‐like growth factor‐I (IGF‐I) to stimulate cellular proliferation and tendon fiber deposition in the core lesion of tendinitis. This study examined the effects of MSCs, as well as IGF‐I gene‐enhanced MSCs (AdIGF‐MSCs) on tendon healing in vivo. Collagenase‐induced bilateral tendinitis lesions were created in equine flexor digitorum superficialis tendons (SDFT). Tendons were treated with 10 × 10 6 MSCs or 10 × 10 6 AdIGF‐MSCs. Control limbs were injected with 1 mL of phosphate‐buffered saline (PBS). Ultrasound examinations were performed at t = 0, 2, 4, 6, and 8 weeks. Horses were euthanized at 8 weeks and SDFTs were mechanically tested to failure and evaluated for biochemical composition and histologic characteristics. Expression of collagen types I and III, IGF‐I, cartilage oligomeric matrix protein (COMP), matrix metalloproteinase‐3 (MMP‐3), matrix metalloproteinase‐13 (MMP‐13), and aggrecanase‐1 (ADAMTS‐4) were similar in MSC and control tendons. Both MSC and AdIGF‐MSC injection resulted in significantly improved tendon histological scores. These findings indicate a benefit to the use of MSCs and AdIGF‐MSCs for the treatment of tendinitis. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1392–1398, 2009