The small proteoglycans fibromodulin and decorin may play an important role in regulating collagen fibrillogenesis and interactions with growth factors. Here, we describe the presence of these proteoglycans in cartilage submitted to different biomechanical forces. Fibromodulin from chicken and bovine articular cartilage was shown to self-associate. The different states of fibromodulin aggregation due to disulfide bonding demonstrable in different regions of the same joint suggest that the presence of different biomechanical forces results in the differential expression of small proteoglycans. A 250-kDa complex found in chicken tibiotarsal cartilage, which migrates as a 59-kDa component in SDS-PAGE under reducing conditions, and which was recognized by anti-fibromodulin antibodies, was not demonstrable in tarsometatarsal cartilage where a different fibromodulin complex has been recently demonstrated. Biglycan and decorin were not expressed in the same way in different regions of the bovine knee joint, suggesting that there is a relationship between the expression of small proteoglycans and the different biomechanical properties of a tissue.29912431246Sajdera, S.W., Hascall, V.C., Protein polysaccharide complex from bovine nasal cartilage (1969) Journal of Biological Chemistry, 244, pp. 77-87Hascall, V.C., Sajdera, S.W., Physical properties and polydispersity of proteoglycan from bovine nasal cartilage (1970) Journal of Biological Chemistry, 245, pp. 4920-4930Hascall, V.C., Sajdera, S.W., Proteinpolysaccharide complex from bovine nasal cartilage (1969) Journal of Biological Chemistry, 244, pp. 2384-2396Heinegård, D., Pimentel, E.R., Cartilage matrix proteins (1992) Articular Cartilage and Osteoarthritis, , Kuettner KE (Editor), Raven Press, New YorkStanescu, V., The small proteoglycans of cartilage matrix (1990) Seminars in Arthritis and Rheumatism, 20, pp. 51-64Scott, J.E., Proteoglycan - fibrillar collagen interactions (1988) Biochemical Journal, 252, pp. 313-323Vogel, K.G., Paulsson, M., Heinegård, D., Specific inhibition of type I and type II collagen fibrillogenesis by the low molecular mass proteoglycan of tendon (1984) Biochemical Journal, 223, pp. 587-597Brown, D.C., Vogel, K.G., Characterization of the in vivo interaction of a small proteoglycan (PG II) of bovine tendon with type I collagen (1989) Matrix, 9, pp. 468-478Hedbon, E., Heinegård, D., Interactions of a 59-kDa connective tissue matrix protein with collagen I and collagen II (1989) Journal of Biological Chemistry, 264, pp. 6898-6905Wight, T.N., Heinegård, D., Hascall, V.C., Proteoglycans: Structure and functions (1991) Cell Biology of Extracellular Matrix, , Hay ED (Editor), Plenum Press, New YorkYamaguchi, Y., Mann, D.M., Ruoslahti, E., Negative regulation of transforming growth factor beta by the proteoglycan decorin (1990) Nature, 336, pp. 281-284Hildebrand, A., Romaris, M., Rasmussen, L.H., Heinegård, D., Twardzik, D.R., Border, W.A., Ruoslahti, E., Interactions of the small interstitial proteoglycans biglycan, decorin and fibromodulin with transforming growth factor ß (1994) Biochemical Journal, 302, pp. 527-534Johnstone, B., Markopoulos, M., Neame, P., Caterson, B., Identification and characterization of glycanated and non-glycanated forms of biglycan and decorin in the human intervertebral disc (1993) Biochemical Journal, 292, pp. 661-666Roughley, P.J., White, R.J., Magny, M.C., Liu, J., Pearce, R.H., Mort, J.S., Non-proteoglycan forms of biglycan increase with age in human articular cartilage (1993) Biochemical Journal, 295, pp. 421-426Liu, J., Laue, T.M., Choi, H.U., Tang, L.H., Rosenberg, L., The self-association of biglycan from bovine articular cartilage (1994) Journal of Biological Chemistry, 269, pp. 28366-28373Gomes, L., Pimentel, E.R., Detection of a small proteoglycan present in xiphoid cartilage regions submitted to different biomechanical forces (1994) Brazilian Journal of Medical and Biological Research, 27, pp. 2117-2124Roughley, P.J., White, R.J., Dermatan sulfate proteoglycans of human articular cartilage. The properties of dermatan sulfate proteoglycan I and II (1989) Biochemical Journal, 262, pp. 823-827Bidanset, D.J., Guidray, C., Rosenberg, L.C., Choi, H.U., Timpl, R., Hook, M., Binding of the proteoglycan decorin to collagen type VI (1992) Journal of Biological Chemistry, 267, pp. 5250-5256