Absence of collagen IX accelerates hypertrophic differentiation in the embryonic mouse spine through a disturbance of the Ihh-PTHrP feedback loop.

Collagen IX (Col IX) is a component of the cartilage extracellular matrix and contributes to its structural integrity. Polymorphisms in the genes encoding the Col IX ɑ2- and ɑ3-chains are associated with early onset of disc degeneration. Col IX-deficient mice already display changes in the spine at the newborn stage and premature disc degeneration starting at 6 months of age.

COMP-assisted collagen secretion--a novel intracellular function required for fibrosis.

Cartilage oligomeric matrix protein (COMP) is an abundant component in the extracellular matrix (ECM) of load-bearing tissues such as tendons and cartilage. It provides adaptor functions by bridging different ECM structures. We have previously shown that COMP is also a constitutive component of healthy human skin and is strongly induced in fibrosis.

Early changes in morphology, bone mineral density and matrix composition of vertebrae lead to disc degeneration in aged collagen IX -/- mice.

Collagen IX (Col IX) is an important component of the cartilage extracellularmatrix and has been associated with degenerative cartilage disorders and chondrodysplasias in humans. Further, polymorphisms in Col IX are known risk factors for the development of early intervertebral disc (IVD) degeneration. To understand the role of Col IX in the pathogenesis of IVD disorders, the spine of newborn and older Col IX deficient mice was systematically analyzed and compared to C57BL/6N controls.

COMP does not directly modify the expression of genes involved in cartilage homeostasis in contrast to several other cartilage matrix proteins.

Objective: We investigated whether COMP may modify cartilage metabolism and play a role as an endogenous disease aggravating factor in OA.

Materials And Methods: Full-length and momomeric COMP was recombinantly expressed in human embryonic kidney cells and purified it via affinity chromatography. Purified COMP was used to stimulate either primary human chondrocytes or cartilage explants.