A 49-year-old patient undergoing evaluation for chronic low-back pain has reduced T2 signal and loss of height at the L4–L5 intervertebral disc. Which extracellular matrix change most directly reduces the nucleus pulposus’s ability to retain water and resist compression?

Increased type I collagen deposition within the nucleus

Reduced elastin content within the outer annulus

Loss of aggrecan proteoglycan and its sulfated glycosaminoglycan chains

Disorganization of collagen lamellae in the outer annulus

Reduced type II collagen network density within the nucleus