ON THE EXISTENCE OF A CARTILAGE-LIKE PROTEOGLYCAN AND LINK PROTEINS IN THE CENTRAL-NERVOUS-SYSTEM

Monoclonal antibodies (mAbs) against the major constituents of cartila ge extracellular matrix, aggrecan and link protein, were screened by i ndirect immunefluorescence on frozen sections of bovine spinal cord. A ntibodies against aggrecan and link protein gave rise to very similar perineuronal labeling in spinal cord gray matter. Aggrecan and Link pr otein reactivities were seen in other regions of the central nervous s ystem(CNS), although their distributions were not always coincident. P retreatment of the tissue section with Streptomyces hyaluronidase, whi ch is hyaluronate-specific, led to the loss of both reactivities. On W estern blots, anti-aggrecan mAbs reacted with a large chondroitin sulf ate proteoglycan. The chondroitinase-treated CNS proteoglycan co-migra ted with the chondroitinase- and keratanase-treated cartilage proteogl ycan. In CNS tissue homogenates, the addition of Streptomyces hyaluron idase brought about the release of the proteoglycan from the tissue. A nti-Link protein mAbs were reactive with two species in the bovine CNS , the mobilities of which were very similar to those of the cartilage link proteins. The release of these species from the tissue required h yaluronidase. A rabbit antiserum against aggrecan was used to identify a similar proteoglycan in the rat CNS. In spinal cord-derived cell cu ltures, the labeled material was associated with astrocytes. An aggrec an cDNA hybridized to a 9.5 kb mRNA in the rat CNS. We conclude that t he perineuronal matrix consists, in part, of a hyaluronate-bound aggre can-like proteoglycan and link proteins, and that the former is produc ed by astrocytes. (C) 1995 Wiley-Liss, Inc.