Study of cartilage and bone layers of the bearing surface of the equine metacarpophalangeal joint relative to different timescales of maturation.
BACKGROUND
A detailed and comprehensive insight into the normal maturation process of the different tissues that make up functional units of the locomotor system such as joints is necessary to understand the influence of early training on musculoskeletal tissues.


OBJECTIVE
To study simultaneously the maturation process in the entire composite structure that makes up the bearing surface of a joint (cartilage, subchondral and trabecular bone) in terms of biochemical changes in the tissues of juvenile horses at 2 differently loaded sites of the metacarpophalangeal joint, compared to a group of mature horses.


OBJECTIVE
In all the structures described above developmental changes may follow a different timescale.


METHODS
Age-related changes in biochemical characteristics of the collagen part of the extracellular matrix (hydroxylysine, hydroxyproline, hydroxypyridinum crosslinks) of articular cartilage and of the underlying subchondral and trabecular bone were determined in a group of juvenile horses (n = 13) (Group 1, age 6 months-4 years) and compared to a group of mature horses (n = 30) (Group 2, >4 years). In both bony layers, bone mineral density, ash content and levels of individual minerals were determined.


RESULTS
In cartilage, subchondral bone and trabecular bone, virtually all collagen parameters in juvenile horses were already at a similar (stable) level as in mature horses. In both bony layers, bone mineral density, ash- and calcium content were also stable in the mature horses, but continued to increase in the juvenile group. For magnesium there was a decrease in the juvenile animals, followed by a steady state in the mature horses.


CONCLUSIONS
In horses age 6 months-4 years, the collagen network of all 3 layers within the joint has already attained a mature biochemical composition, but the mineral composition of both subchondral and trabecular bone continues to develop until approximately age 4 years.


CONCLUSIONS
The disparity in maturation of the various extracellular matrix components of a joint can be assumed to have consequences for the capacity to sustain load and should hence be taken into account when training or racing young animals.
van der Harst
M R
MR
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
van de Lest
C H A
CH
Degroot
J
J
Kiers
G H
GH
Brama
P A J
PA
van Weeren
P R
PR
D000367:Age Factors; D000375:Aging / Q000502:physiology*; D000818:Animals; D015519:Bone Density / Q000502:physiology; D001842:Bone and Bones / Q000737:chemistry* / Q000378:metabolism; D002118:Calcium / Q000032:analysis; D002358:Cartilage, Articular / Q000737:chemistry* / Q000378:metabolism; D003094:Collagen / Q000032:analysis; D005109:Extracellular Matrix / Q000737:chemistry; D006736:Horses / Q000033:anatomy & histology* / Q000254:growth & development / Q000502:physiology; D007596:Joints / Q000033:anatomy & histology* / Q000502:physiology*; D008274:Magnesium / Q000032:analysis; D008903:Minerals / Q000032:analysis
D008903:Minerals; D003094:Collagen; D008274:Magnesium; D002118:Calcium