Ke. Gregory et al., Developmental distribution of collagen type XII in cartilage: Association with articular cartilage and the growth plate, J BONE MIN, 16(11), 2001, pp. 2005-2016
Collagen type XII is a member of the fibril-associated collagens and is cha
racterized by a short triple-helical domain with three extended noncollagen
ous NC3 domains. Previous studies suggested that collagen XII is a componen
t of cartilage but little is known about its spatial-temporal distribution.
This study uses a polyclonal antibody to the purified NC3 domain to invest
igate its developmental distribution in rat forelimb. Collagen XII was pres
ent at the joint interzone on embryonic day 16 (E16d) and restricted to the
presumptive articular cartilage by E18d. Labeling of the articular surface
intensified as development progressed postnatally (day I [1d] to 28d) and
extended approximately six cell diameters deep. In juvenile rats, collagen
XII antibodies also labeled the longitudinal and transverse septa of stacke
d chondrocytes in the growth plate. However, collagen XII was not associate
d at any developmental stage with the cartilaginous secondary ossification
center and was only weakly expressed in epiphyseal cartilage. Ultrastructur
al localization of the NC3 domain epitope showed labeling of the surface of
collagen II fibrils, both in tissue and in isolated fibrils. The results p
resented provide further evidence that articular cartilage differs substant
ially from the underlying epiphyseal cartilage and that different chondrocy
tic developmental fates are reflected in the composition of their extracell
ular matrix starting early in development. In addition, collagen XII was di
stributed in areas of cartilage with more organized fibril orientation and
may have a role in promoting alignment or stabilizing such an organization,
thereby creating a matrix capable of withstanding load-bearing forces.