Einfluss des Differenzierungszustandes auf die Heparansulfat-Proteoglycan-Synthese humaner Chondrozyten

Abstract

Chondrocytes are well known to change their phenotype in monolayer cultures. Morphologic transformation to a fibroblastoid appearance is accompanied by downregulation of cartilage-specific macromolecules (e.g. collagen type II) and upregulation of collagen type I. Concomitantly, mitogenic activity is increased. This latter change allows the preparation of large amounts of cells from small samples, potentially of interest for tissue engineering applications. Apart from cell shape and cell-matrix interactions, phenotypic expression depends on the presence and signaling activity of soluble factors, e.g. growth factors and cytokines. As most of these factors bind to heparan sulfate, heparan sulfate proteoglycans can be expected to have an influence on the signaling status of the cell. However, information on the expression of heparan sulfate proteoglycans by chondrocytes is still very limited. We therefore studied the expression of the known heparan sulfate proteoglycan core proteins in human articular Chondrocytes directly after isolation, after a period of dedifferentiation in monolayer culture and after a period of redifferentiation in alginate bead culture by means of RT-PCR and semi-quantitative RT-PCR. The chondrocytes were isolated from the tibia plateau of osteoarthritic patients who underwent joint replacements. In addition to the already published expression of syndecan 1-4, glypican-1, CD44, betaglycan, perlecan, testican-1 and collagen-XVIII, we here describe for the first time expression of glypican-4, -5, -6, agrin, testican-2, -3 and adlican in human Chondrocytes. Whereas expression of some of the heparan sulfate proteoglycan core proteins remained essentially constant during extended culture in monolayer and alginate beads, others exhibited remarkable changes and it can be anticipated that changes in the expression profile of these proteoglycans will have an influence on the signaling status of the cell.