Matrix Biology 22 (2003) 153–161 0945-053X/03/$30.00  2003 Elsevier Science B.V. yInternational Society of Matrix Biology. All rights reserved. doi:10.1016/S0945-053X(03)00019-2 Changing profiles of proteoglycans in the transition of predentine to dentine R.J. Waddington *, R.C. Hall , G. Embery , D.M. Lloyd a, b b a Department of Basic Dental Science, Dental School, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XY, UK a Department of Clinical Dental Sciences, Edwards Building, The University of Liverpool, Liverpool L69 3GN, UK b Received 25 July 2002; received in revised form 5 March 2003; accepted 7 March 2003 Abstract Proteoglycans and their constituent glycosaminoglycans have been proposed to play important roles in matrix mediated formation of mineralised tissues, such as dentine. This study has examined the changing profile of proteoglycan species during the transition of unmineralised predentine to mineralised dentine. Three-week-old calves teeth were collected and proteoglycans purified from the predentine, the predentineydentine interface and dentine. Decorin and biglycan, together with related degradation products, were identified in the predentine fraction, alongside degradation products of versican, indicating metabolism of the proteoglycan components within this tissue. Decorin and biglycan were also identified as major proteoglycan species within extracts from the predentineydentine interface and dentine. Analysis of the glycosaminoglycan constituents within each fraction demonstrated significant changes in their composition. Predentine contained a high proportion of dermatan sulfate (DS)(51.5%), with chondroitin sulfate (CS)(17.8%) and hyaluronan (HA)(30.7%) additionally identified. Within the predentineydentine interface the proportion of CS increased greatly (62.5%), with corresponding decrease in the proportion of DS (21.4%) and HA (16.1%) also evident. CS only was identifiable within the dentine matrix. A four-fold increase in the level of sulfation was identified for glycosaminoglycans extracted from the predentineydentine interface compared with the predentine and dentine fraction. The ratio of DDi4S:DDi6S was higher for glycosaminoglycans isolated from the predentine fraction. Glycosaminoglycans extracted from the dentine fraction possessed longer chain lengths than those present in the predentine and predentineydentine fractions. The results indicate that the proteoglycans within each fraction undergo subtle structural modification, particularly at the onset of mineralisation, indicating an active involvement of these macromolecules in the overall mineralisation process.  2003 Elsevier Science B.V.yInternational Society of Matrix Biology. All rights reserved. Keywords: Proteoglycans; Mineralisation; Dentine; Dentinogenesis 1. Introduction Recent studies on the transition of predentine to dentine have suggested that the process is accompanied by structural modification of the extracellular compo- nents prior to the onset of mineralisation (Embery et al., 2001). Current views imply a change in the proteo- glycan content of predentine with subsequent influence on type I collagen fibrillogenesis, as a prelude to the expression and interaction of phosphoproteins (Embery et al., 2001; Limeback, 1991) or phospholipids (Gold- berg and Boskey, 1996). The phosphoproteins are selec- tively secreted at the predentine–dentine interface with *Corresponding author. Tel.: q44-2920-742609; fax: q44-2920- 744509. E-mail address: waddingtonrj@cardiff.ac.uk (R.J. Waddington). the final molecular complex acting as a template for calcium capture (Embery et al., 2001). Most attention on this transitional phase has been directed at the small leucine-rich proteoglycans (SLRPs), which in predentine–dentine have been shown to include the chondroitin sulfate (CS)-rich, decorin and biglycan and the keratan sulfate-rich (KS) lumican and fibromodulin (Embery et al., 2001; Waddington et al., 1993; Hall et al., 1996). Previously held views, which have implicated a uniform steady state of such mole- cules, have been modified by the studies of Septier et al. (1998) and Hall et al. (1999) showing gradients of CSydermatan sulfate (DS) decreasing in a sequential fashion from the pulpal aspect towards the mineralisation front. Converse gradients of KS are also evident, although the significance of this finding is not apparent.