Composition and structure of human cartilage extracellular matrix: unravelling changes during osteoarthrosis at the nanoscale

Abstract

Purpose: The articular cartilage is a 2-4 mm thick smooth tissue covering the ends of long bones in the joints. Its extracellular matrix (ECM) contains a significant amount of water (65-75 %wt.), type II collagen fibrils (ca. 20-30 %wt.) and negatively charged aggrecans (ca. 10 %wt.) organized in a peculiar three-dimensional network. Aggrecans only exist as an aggregate within the extracellular matrix (ECM): they are noncovalently attached to another long GAG chain, hyaluronic acid (HA) to form larger aggrecan aggregate.