Insulin-like growth factor-I improves cellular and molecular aspects of healing in a collagenase-induced model of flexor tendinitis

J Orthop Res. 2002 Sep;20(5):910-9. doi: 10.1016/S0736-0266(02)00009-8.


Flexor tendinitis is a common and debilitating injury of elite and recreational athletes. Healing may be improved through intratendinous injection of insulin-like growth factor-I (IGF-I), which has been shown in vitro to stimulate mitogenesis and enhance tendon matrix production. This study investigated the effects of intratendinous injection of IGF-I on tendon healing in an equine model of flexor tendinitis. Collagenase-induced lesions were created in the tensile region of theflexor digitorum superficialis tendon of both forelimbs of eight horses. Treated tendons were injected with 2 microg rhlGF-I intralesionally every other day for 10 injections, while controls received 0.9% NaCl. Tendon fiber deposition and organization were evaluated serially using ultrasonography throughout the 8 week trial period. Following euthanasia, the tendons were harvested and DNA, hydroxyproline, and glycosaminoglycan content determined, mechanical strength and stiffness evaluated, gene expression and spatial arrangement of collagen types I and III assessed by northern blot and in situ hybridization, and tendon fiber architecture assessed by polarized light microscopy. Local soft tissue swelling was reduced in the IGF-I treated limbs. Similarly, lesion size in IGF-I treated tendons was smaller 3 and 4 weeks after initiation of treatment. Cell proliferation and collagen content of the IGF-I treated tendons were increased compared to controls. Mechanically, IGF-I treated tendons showed a trend toward increased stiffness compared to saline treated controls. Considered together with the decreased soft tissue swelling and improved sonographic healing, these data support the potential use of intralesional IGF-I for treatment of debilitating tendon injuries.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Northern / veterinary
  • Collagen / genetics
  • Collagen / metabolism
  • Collagenases / adverse effects
  • Disease Models, Animal
  • Female
  • Horse Diseases / chemically induced
  • Horse Diseases / drug therapy*
  • Horse Diseases / pathology
  • Horses
  • In Situ Hybridization / veterinary
  • Injections, Intralesional
  • Insulin-Like Growth Factor I / administration & dosage*
  • Male
  • RNA, Messenger / metabolism
  • Stress, Mechanical
  • Tendinopathy / chemically induced
  • Tendinopathy / drug therapy
  • Tendinopathy / pathology
  • Tendinopathy / veterinary*
  • Tendon Injuries / chemically induced
  • Tendon Injuries / drug therapy
  • Tendon Injuries / pathology
  • Tendon Injuries / veterinary*
  • Tendons / diagnostic imaging
  • Tendons / drug effects
  • Tendons / pathology
  • Tendons / physiopathology
  • Ultrasonography
  • Wound Healing / drug effects*
  • Wound Healing / physiology


  • RNA, Messenger
  • Insulin-Like Growth Factor I
  • Collagen
  • Collagenases