Anionic glycoconjugates from differentiated and dedifferentiated cultures of bovine articular chondrocytes: Modulation by TGF-β

Summary

Primary, high density bovine articular chondrocyte (BAC) cultures, stimulated with transforming growth factor-β-1, elaborated a high molecular weight anionic glycoconjugate, kDa 540, which does not contain glycosaminoglycan chains (Chan and Anastassiades, 1996). The effect of exogenously added transforming growth factor-β-1 on the elaboration of the high molecular weight glycoconjugate and of proteoglycans was studied during dedifferentiation of the chondrocytes, utilizing a serial subculture technique under anchorage-dependent conditions, up to four subcultures. The high molecular weight glycoconjugate was detected in the media of all growth-factor-stimulated chondrocyte subcultures, as well as stimulated primary cultures, but not in unstimulated primary cultures or subcultures. By contrast, a large proteoglycan, was only secreted by primary cultures and first subcultures, whether treated with transforming growth factor-β-1 or untreated. This proteoglycan contained mostly chondroitin sulfate chains, whose hydrodynamic size was increased by the addition of transforming growth factor-β-1. Further, the pattern of the proteoglycans appearing in the media of subcultures 2–4 was influenced by the addition of transforming growth factor-β-1, so that while these control subcultures elaborated both the large and small chondroitin sulfate proteoglycans, the equivalent stimulated subcultures elaborated only intermediate sized chondroitin sulfate proteoglycan(s). These results suggest that while dedifferentiation of articular chondrocytes, achieved by subculturing, strongly modulates the effect of exogenously added transforming growth factor-β-1 on the type of proteoglycan elaborated, the process of dedifferentiation does not influence the transforming-growth-factor-β-dependent synthesis of the high molecular weight anionic glycoconjugate.