Age-related changes in serum insulin-like growth factor-I, insulin-like growth factor-I binding protein-3 and articular cartilage structure in Thoroughbred horses.
BACKGROUND
Structural changes in articular cartilage associated with the ageing process require definition for investigators performing developmental and age-related studies, for which information is lacking.


OBJECTIVE
To 1) determine the onset and end of puberty as defined by serum insulin like growth factor (IGF-I) and IGF-binding protein-3 (IGFBP-3) concentrations and 2) correlate articular-epiphyseal cartilage complex structural changes with the onset and end of puberty.


METHODS
IGF-I and IGFBP-3 were measured in serum samples from normal female and male horses age 9-715 days to determine peak and steady-state values for horses transitioning through puberty. Osteochondral tissue sections were obtained from horses age 120-840 days (4-28 months) and examined histologically for cartilage canals and tidemark formation.


RESULTS
In male and female horses, serum IGF-I/IGFBP-3 concentrations peaked at approximately 225 days, defining the onset of puberty. Cartilage canals were absent from articular cartilage just prior to this time point. IGF-I/IGFBP-3 concentrations declined to steady-state levels at approximately age 450 days, signalling exit from puberty and therefore the beginning of ageing. This time point correlated to initial formation of a tidemark in the osteochondral tissue sections.


CONCLUSIONS
Horses may be considered pubescent at age 225-450 days, and post pubescent and ageing after age 450 days.


CONCLUSIONS
Defining the normal post natal to post pubescent concentrations for serum IGF-I and serum IGFBP-3 establishes subsets of animals for age-related studies and may be used to monitor horses for abnormally high IGF-I concentrations due to natural disease or subsequent to systemic growth hormone administration.
Fortier
L A
LA
Department of Clinical Sciences, Cornell University, Ithaca, New York 14853, USA.
Kornatowski
M A
MA
Mohammed
H O
HO
Jordan
M T
MT
O'Cain
L C
LC
Stevens
W B
WB
D000367:Age Factors; D000375:Aging / Q000097:blood / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D015415:Biomarkers / Q000097:blood / Q000378:metabolism; D002358:Cartilage, Articular / Q000254:growth & development* / Q000473:pathology; D003430:Cross-Sectional Studies; D005260:Female; D006736:Horses / Q000097:blood / Q000378:metabolism / Q000502:physiology*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D012741:Sexual Maturation / Q000502:physiology
D015415:Biomarkers; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I