Somatomedin C immunoreactivity in the Achilles tendon varies in a dynamic manner with the mechanical load.
Distribution of the trophic peptide somatomedin C (Sm-C; insulin-like growth factor I; IGF-I) immunoreactivity was mapped in normal Achilles and tibialis anterior tendons. The spindle-shaped tendon fibroblasts showed faint perinuclear staining. Fibroblasts in the paratenon mostly had a more intense IGF-I immunoreactivity, i.e. faint to moderate. When analysing either tendon in detail, areas with more intense IGF-I immunoreactivity could be recognized and seemed to correlate with areas of high mechanical stress. Increased mechanical load induced over 3 days elevated IGF-I immunoreactivity throughout the cytoplasm of tendon fibroblasts. Peak intensity was reached in 7 days, and thereafter the IGF-I immunoreactivity seemed to decrease irrespective of persistent high mechanical load. Training the animals on a treadmill for from 20 up to 60 min per day for 5 days induced after 3-5 days increased IGF-I immunoreactivity throughout the cytoplasm of the tendon and paratenon fibroblasts. Sudden curtailment of loading the Achilles tendon resulted in a marked reduction of the IGF-I immunoreactivity in most fibroblasts within 3 days. After a week only a small number of tendon fibroblasts showed any IGF-I immunoreactivity. The IGF-I immunoreactivity of tendon fibroblasts thus correlates to mechanical loading of the tendon. It is proposed that IGF-I may have a trophic influence on tendon and paratenon cells by autocrine and/or paracrine mechanisms.
Hansson
H A
HA
Department of Histology, University of Gothenburg, Sweden.
Engström
A M
AM
Holm
S
S
Rosenqvist
A L
AL
D000125:Achilles Tendon / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D001696:Biomechanical Phenomena; D005260:Female; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013002:Somatomedins / Q000378:metabolism*; D013314:Stress, Mechanical; D013710:Tendons / Q000378:metabolism / Q000502:physiology; D013977:Tibia
D013002:Somatomedins; D007334:Insulin-Like Growth Factor I