Spatial organization of types I and II collagen in the canine meniscus

Abstract

The meniscus of the knee joint is a fibrocartilage mainly composed of type I collagen and smaller amounts of type II collagen. The distribution of type II collagen in the canine meniscus and its spatial relationship to type I collagen was examined by immunohistochemistry and confocal microscopy. Dorsal and coronal slices of the mid-section of medial and lateral menisci from the knee joints of skeletally mature dogs were predigested with Streptomyces hyaluronate lyase and bacterial Protease enzyme XXIV. Monoclonal antibodies against type I collagen (CP17L) and type II collagen (II-II6B3) and an anti-type II collagen polyclonal antibody (AB759) were employed. The staining for type II collagen in the extracellular matrix of hyaline articular cartilage was diffuse without any identifiable spatial organization. In striking contrast, type II collagen in the fibrocartilage of the meniscus stained as an organized network. Type II collagen was distributed throughout the meniscus with the exception of the outer zone containing the blood vessels. Coronal and dorsal staining of the meniscus showed bundles of circumferential fibrils of type I that colocalized with type II collagen in specific sites. These bundles were enwrapped in a second organizational fibrillar system of types I and II collagen that also colocalized. Bundles of circumferential fibrils appeared in cross-section in coronal sections as dots within the interstitial spaces framed by the network of types I and II collagen of the second system. Confocal overlays showed that types I and II collagens were superimposed, suggesting a close spatial proximity between the two collagens. The cells were confined to the types I and II collagen fibrils that enwrapped the bundles. A striking feature of the radial tie fibers was patches of type II collagen without colocalized type I collagen. Our study reveals a unique network of type II collagen in fibrocartilage of the meniscus that serves as a morphological distinction between fibro- and hyaline cartilage.

Meniscus structure in human, sheep, and rabbit for animal models of meniscus repair

“…It has previously been reported in the rabbit that collagen I and II overlap in younger animals while discrete areas of collagen I or II appear with age. 27 Interestingly, some collagen II fibers were organized into a network similar to that described in the dog meniscus 28 and quite distinct from that observed in articular cartilage. The ability of fibrochondrocytes to form fibrillar networks of collagen II and collagen I appears to be specific to the meniscus.…”

Mechanical stretch enhances COL2A1 expression on chromatin by inducing SOX9 nuclear translocalization in inner meniscus cells

“…3 Cartilaginous tissuespecific type II collagen co-localizes with type I in the canine meniscus, except for the outer peripheral zone. 4 However, the distributions of types I and II collagen and proteoglycan in human menisci are different from those in rabbit and sheep menisci. 5 In the human meniscus, a perimeniscal capillary plexus supplies the outer 10-25% of the meniscus, whereas the inner 70-80% is composed of avascular tissue.…”

Comparison of osmotic swelling influences on meniscal fibrocartilage and articular cartilage tissue mechanics in compression and shear

“…8 While the functional importance of this secondary network has not been widely studied, it appears to facilitate rearrangement of the primary collagen bundles under load. 9 This secondary network is a compositionally distinct matrix compartment, containing colocalized collagens I, II, and VI, 10,11 as well as aggrecan and other proteoglycans. 5,12 Consequently, the majority of sulfated glycosaminoglycans (sGAG) in the middle and outer regions are concentrated in this compartment.…”