Question

Physiologically, why does cartilage regeneration decrease as adults compared to our teen years? Please explain in detail.

Answer 1

Bones and cartilages continue to develop till the age of 18-21 rapidly and then gradually till the age 30, after that the bones and cartilages start to deteriorate. In women it’s even more gradual after the menopause. There are following factors which may contribute in the late healing in old age.

• Low Chondrocytes reactivity to growth factors
• Mitochondrial dysfunction, oxidative stress and abnormal accumulation of advanced glycation end products (AGEs).
• Age-related changes in cartilage extracellular matrix proteins like collagen or proteoglycans could induce nonenzymatic collagen cross-linking and shorten aggrecan molecules.
• Extreme collagen cross-linking affects the biomechanical properties of cartilage, causing increased stiffness, and makes cartilage more brittle and vulnerable to fatigue and failure.
• Shortening and degradation of aggrecan leads to substantial loss of sugar side chains and water-binding ability.
• Cartilage covers and cushions the ends of bones where they come together in the joints. Synovial fluid lubricates the joint and also supplies nutrients and oxygen to the cartilage. As one age, the synovial fluid may begin to dry up, and the stress put on the cartilage by passing years and injuries can cause it to wear out. When this happens, the bones in the joints rub together and become inflamed, and develop a condition known as osteoarthritis.
• Some bones are entirely or partly made of cartilages, but as one grows, the cartilage grows and is slowly replaced by bone, and in old age the bones are harder to heal because of stiffness and tight space caused by bone calcination.