ELSEVIER Biochimica et Biophysica Acta 1290 (1996) 18-28 BR Biochi ~mic~a et Biophysica A~ta Proteoglycans and glycosaminoglycans synthesized in vitro by mesangial cells from normal and diabetic rats Semiramis J. Hadad a, Yara M. Michelacci b,,, Nestor Schor a " Disciplina de Nefrologia, Universidade Federal de SSo Paulo, Escola Paulista de Medicina, Sglo Paulo, Brazil b Disciplina de Biologia Molecular, Unicersidade Federal de SSo Paulo, Escola Paulista de Medicina, UNIFESP, Unit,ersidade Federal de SSo Paulo, EPM, Escola Paulista de Medicina Rua Trgs de Maio, 100, 04023-020 Sglo Paulo SP, Brazil Received 30 June 1995; revised 3 November 1995; accepted 7 December 1995 Abstract In the renal glomerulus, two extracellular matrices have been identified, the glomerular basement membrane and the mesangial matrix. Accumulation of glomerular extracellular matrix is a conspicuous feature of most forms of progressive glomerular disease, including diabetic nephropathy. Since proteoglycans are prominent components of the extracellular matrix, we examined the glycosaminoglycans and proteoglycans synthesized in vitro by mesangial cells from normal and diabetic rats. A mixture of dermatan sulfate and heparan sulfate was recovered. Dermatan sulfate was the predominant glycosaminoglycan synthesized and most of it was released to the culture medium, in contrast to heparan sulfate which was found to be cell associated to a higher degree. The dermatan sulfate chains are composed by D-glucuronic and L-iduronic acid-containing disaccharides and are highly sulfated. Mesangial cells from diabetic rats produce much more glycosaminoglycans than mesangial cells from normal rats, especially dermatan sulfate and this increase was proportional to the duration of diabetes. In contrast, exposure of mesangial cell from normal rats to elevated glucose did not lead to any changes in glycosaminoglycan synthesis, indicating that this short-term culture conditions may not adequately simulate diabetes mellitus. Other factors related to diabetes environment may be responsible for the observed alterations. The dermatan sulfate was secreted to the medium as proteoglycan. Two dermatan sulfate proteoglycans were identified, with molecular weights of 120 and 85 kDa respectively. The proteoglycan core protein M r was 45 kDa and the dermatan sulfate chains were 35 kDa. It is possible that the two proteoglycans represent two populations, one with two dermatan sulfate side chains (120 kDa) and the other with only one side chain (85 kDa), presumably fitting in the decorin/biglycan family of small proteoglycans. Keywords: Proteoglycan; Glycosaminoglycan; Mesangial cell; Diabetic; (Rat) 1. Introduction Proteoglycans are a heterogeneous and complex family of macromolecules composed of a core protein to which complex linear heteropolysaccharides called glycosamino- glycans are covalently linked. The glycosaminoglycans are made up of a characteristic repeating disaccharide unit containing a hexuronic acid, either D-glucuronic or L- iduronic acid, and an amino sugar, either o-glucosamine or D-galactosamine. The sugars are variably N- and O- sulfated, which further adds to their heterogeneity. Six classes of glycosaminoglycans have been identified: * Corresponding author. Fax: + 55 11 5736407. 0304-4165/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved SSDI 0304-41 65(95)001 83-2 hyaluronic acid, keratan sulfate, heparan sulfate, chon- droitin sulfate, dermatan sulfate and heparin. Many distinct core proteins may be substituted with the same type of glycosaminoglycan chain. The proteoglycans identified to date can be classified into five groups, based largely on topographical distribu- tion, but also incorporating familial relationships of core protein structure. These classes are the cell surface proteo- glycans, the secretory granule proteoglycans and three classes of extracellular matrix proteoglycans, the large aggregating proteoglycans interacting with hyaluronic acid, the small leucine-rich proteoglycans, also named 'fibrilar proteoglycans' because some members of the family inter- act with fibrilar collagen, and the basement membrane proteoglycans, recently named 'perlecans'. The large proteoglycans of the versican/aggrecan fam- ily and the small proteoglycans of the decorin/biglycan