ACAN

ACAN Full Name

aggrecan

ACAN Introduction

Aggrecan, encoded by the ACAN gene, is the most abundant structural proteoglycan found within the extracellular matrix of articular cartilage. Structurally, it consists of a central protein core that is heavily modified with negatively charged glycosaminoglycan (GAG) side chains, primarily chondroitin sulfate and keratan sulfate. Within the cartilage matrix, hundreds of these monomeric aggrecan core proteins non-covalently bind to a central hyaluronic acid backbone—a linkage stabilized by specific link proteins—to form massive, supramolecular aggregates. The extraordinarily high density of negative charges from the GAG chains draws a tremendous amount of osmotic water into the tissue. This unique hydration mechanism swells the proteoglycan network against the surrounding rigid collagen fibrils. This swelling pressure confers articular cartilage with its exceptional load-bearing capacity, resilience, and shock-absorbing properties, which are absolutely essential for smooth and pain-free joint articulation.

Figure 1. Schematic representation of the aggrecan structure. (Source: Jerosch J. 2011)

Clinically, the structural integrity of aggrecan is central to both joint longevity and proper skeletal development. The progressive enzymatic degradation of aggrecan—primarily driven by ADAMTS aggrecanases and matrix metalloproteinases (MMPs)—is the critical initiating event in the pathogenesis of osteoarthritis (OA). As aggrecan is irreversibly cleaved and lost from the matrix, the cartilage loses its hydration and compressive stiffness, ultimately leading to mechanical failure and bone-on-bone friction. Beyond age-related mechanical wear, inherited heterozygous mutations in the ACAN gene result in a spectrum of severe congenital skeletal dysplasias. These genetic disorders manifest clinically as idiopathic short stature, early-onset multiple joint osteoarthritis, osteochondritis dissecans, and spondyloepiphyseal dysplasia. Consequently, preserving aggrecan synthesis and therapeutically inhibiting its pathological cleavage remain primary targets for treating degenerative joint diseases and managing growth disorders.

Alternate Names for ACAN

ACAN; aggrecan; AGC1; SEDK; AGCAN; CSPG1; MSK16; CSPGCP; aggrecan core protein; large aggregating proteoglycan; cartilage-specific proteoglycan core protein; chondroitin sulfate proteoglycan core protein 1;

• 1. Jerosch J. Effects of Glucosamine and Chondroitin Sulfate on Cartilage Metabolism in OA: Outlook on Other Nutrient Partners Especially Omega-3 Fatty Acids. Int J Rheumatol. 2011;2011:969012.
  2. Dateki S. ACAN mutations as a cause of familial short stature. Clin Pediatr Endocrinol. 2017;26(3):119-125.