Ca. Poole et al., IMMUNOLOCALIZATION OF TYPE-IX COLLAGEN IN NORMAL AND SPONTANEOUSLY OSTEOARTHRITIC CANINE TIBIAL CARTILAGE AND ISOLATED CHONDRONS, Osteoarthritis and cartilage, 5(3), 1997, pp. 191-204
Objective: The pericellular localization of type IX collagen in avian
and mammalian hyaline cartilages remains controversial, while its dist
ribution during osteoarthritic degeneration is poorly understood. This
study aimed to compare and contrast the immunohistochemical distribut
ion of type IX collagen in normal mature and spontaneously osteoarthri
tic canine tibial cartilage. Design: Thick vibratome sectioning techni
ques were evaluated and compared with isolated chondrons using a range
of streptavidin-linked probes in combination with light, confocal and
transmission electron microscopy. Results: In normal intact samples,
type IX collagen was concentrated in the pericellular microenvironment
, while a weaker extracellular reaction around each chondron separated
the territorial matrix from the unstained interterritorial matrix. Fu
rther differentiation was evident in isolated chondrons where the fibr
ous pericellular capsule stained more intensely than the tail and inte
rconnecting segments between columnated chondrons. Two regions of type
IX reactivity were identified in osteoarthritic tissue: an intensely
stained superficial reactive region below the eroding margins, and nor
mal deep layer cartilage where pericellular staining persists. The sup
erficial reactive region was characterized by chondron swelling and ch
ondrocyte cluster formation, a loss of pericellular type IX staining,
and a significant increase in matrix staining between clusters. Disint
egration and loss of fibrillar collagens was evident in both the swoll
en microenvironment and adjacent territorial matrices. Conclusions: Th
e results suggest that changes in type IX distribution, expansion of t
he pericellular microenvironment and chondrocyte proliferation represe
nt key elements in the chondron remodeling and chondrocyte cluster for
mation associated with osteoarthritic degeneration.