Chondroitin sulphate sulphation motif expression in the ontogeny of the intervertebral disc

Abstract

Chondroitin sulphate chains on cell and extracellular matrix proteoglycans play important regulatory roles in developing systems. Specific, developmentally regulated, sulphation motifs within the chondroitin glycosaminoglycan structure may help bind, sequester or present bioactive signalling molecules to cells thus modulating their behaviour. Using monoclonal antibodies 3B3(-), 4C3, 6C3 and 7D4, we have mapped the distribution of different chondroitin sulphation epitopes in a rat intervertebral disc developmental series. The sulphation epitopes had complex, dynamic and specific distributions in the disc and vertebral tissues during their differentiation, growth and ageing. At embryonic day [E]15, prior to disc differentiation, 4C3 and 7D4 occurred within the cellular disc condensations whilst 6C3 was present in the notochordal sheath. At E17, post disc differentiation, 4C3 and 7D4 occurred within the nucleus pulposus, inner annulus and vertebral bodies; 3B3(-) in the nucleus, inner annulus, annulus/vertebral body interface and perichondrium; and 6C3, ventrally, within the perichondrium. At E19, 3B3(-), 4C3 and 7D4 became further restricted to the nucleus, inner annulus, annulus/vertebral body interface and perichondrium. Prior to birth, all four epitopes occurred within the inner annulus and nucleus, with 6C3 and 7D4 also occurring within the future end-plate. Postnatal expression of the sulphation epitopes was more widespread in the disc and also within the growth plate. At 4 months, the epitopes were associated with chondrocyte clusters within the nucleus; and at 24 months, with annular lesions. Overall, our data suggests that differential sulphation of chondroitin correlates with significant events in development, growth and aging of the rat intervertebral disc.