Review Question - QID 5647

A reduction in proteoglycan content represents one of the pathological processes taking place in the degenerative pathway of intervertebral disc disease (IVD).

The intervertebral disc is composed of the outer annulus fibrosis and the inner nucleus pulposus. The annulus is composed of type I collagen and is characterized by high tensile strength due to its high collagen:proteoglycan ratio. The inner nucleus pulposus is composed of more type II collagen, water and proteoglycans and serves to increase the compressibility of the intervertebral disc to resist compression forces. As aging of the intervertebral discs occur, they tend to decrease in water and proteoglycan content, while increasing the amount of degradative enzymes present. This leads to an environment where they are less functional in resisting compression forces and can contribute to discogenic back pain.

Yaltrik et al evaluated the use of proteoglycan gene markers to predict lumbar disc degeneration. They noted that proteoglycan levels were significantly lower in the group with lumbar degenerative disease compared to a control group. They emphasize that biomarkers for proteoglycan genes may provide a useful tool in predicting disc disease in the future.

Wei et al. discuss the role of proteoglycans in intervertebral disc degeneration and potential therapies. They note that aggrecan is the major structural proteoglycan in the disc and is important for maintaining a hydrated state that allows for disc compression. They note that these proteoglycan molecules play a central role in intervertebral disc degeneration and there may be potential therapies that can target the loss of aggrecan to improve disc degeneration.

Incorrect Answers:
Answer 1: Water content has been shown to decrease in intervertebral disk disease.
Answer 2: There is an increase in the keratin sulfate-to-chondroitin sulfate ratio in intervertebral disk disease.
Answer 3: The activity of degradative enzymes has been shown to increase in association with degeneration of the intervertebral disc.
Answer 5: There is not thought to be an obvious change in the absolute quantity of cartilage with IVD. Regardless, levels of type II cartilage certainly do not increase in this setting.