Question

Which of the following statements about changes in articular cartilage with aging is not true?

• A. Total proteoglycan content is decreased
• B. Synthesis of proteoglycans is decreased
• C. Enzymatic degradation of proteoglycans is increased
• D. Total water content of cartilage is decreased

Hint:

Separate aging from osteoarthritis. Surging enzymatic breakdown belongs to the disease, not to normal aging.

Answer 1

The Correct Option is C

Step 1: It helps to separate normal aging of cartilage from the disease process of osteoarthritis. The two are not the same, and exam stems about aging want the changes seen in healthy senescent cartilage.

Step 2: With normal aging the chondrocytes become less active, so synthesis of proteoglycans falls and the total proteoglycan content of the matrix declines. Options A and B are therefore true features of aging.

Step 3: Because proteoglycans are responsible for holding water in the matrix through their hydrophilic charge, a drop in proteoglycan content leads to a fall in the total water content. So with aging the cartilage becomes drier, making option D true. This is the opposite of early osteoarthritis, where water content actually rises.

Step 4: Increased enzymatic degradation of proteoglycans by matrix metalloproteinases is a hallmark of osteoarthritis, an active catabolic disease, rather than of simple aging. In aging the loss is mainly from reduced synthesis, not from a surge in enzymatic breakdown. Hence the statement that enzymatic degradation is increased is the one that does not fit aging.

Answer: C. Enzymatic degradation of proteoglycans is increased.