FIBRILLIN-RICH MICROFIBRILS - STRUCTURAL MODIFICATIONS DURING AGING IN NORMAL HUMAN ZONULE

Ageing is marked by ultrastructural and functional changes in most tis sues. In part, these changes are caused by a loss of elasticity in the elastic fibers of the extracellular matrix. These fibers are composed of the protein elastin associated with microfibrils of 8 to 12 nm in diameter. Microfibrils contain fibrillins as major constituents. Mutat ions in fibrillin genes are considered as primary causes of Marfan syn drome, a genetic disorder with pathological manifestations in the card iovascular and skeletal systems, in addition to dysfunctions in the ey e. Fibrillin is also the major protein of the ciliary zonule fibers. D uring ageing, these fibers become more fragile, and concomitantly, an increased risk for ocular pathologies is observed. We have investigate d structural modifications in fibrillin-rich microfibrils during agein g of human ciliary zonule. Observations using light microscopy and tra nsmission electron microscopy after rotary shadowing allowed us to des cribe the organization of the zonule fibers and their insertion into t he ciliary body. Our results emphasize qualitative differences between young and old zonules, which are likely due to modifications in the s tructure of microfibrils.